Contents

Nocash PSXSPX Playstation Specifications
Memory Map
I/O Map
Graphics Processing Unit (GPU)
Geometry Transformation Engine (GTE)
Macroblock Decoder (MDEC)
Sound Processing Unit (SPU)
Interrupts
DMA Channels
Timers
CDROM Drive
CDROM File Formats
Controllers and Memory Cards
Pocketstation
Serial Port (SIO)
Expansion Port (PIO)
Memory Control
Unpredictable Things
CPU Specifications
Kernel (BIOS)
Arcade Cabinets
Cheat Devices
PSX Dev-Board Chipsets
Hardware Numbers
Pinouts
About & Credits

Latest Research
GPU Rendering Timings
GPU Texture Caching
Controllers - I-Mode Adaptor (Mobile Internet)
Controllers - Fishing Controllers
CDROM File Formats

Nocash PSX Emulator/Debugger
No$psx Emulation Controls
No$psx Emulation Files
No$psx Emulation Notes
No$psx Debugger - Hotkeys in Debug Mode
No$psx Debugger - Breakpoints
No$psx Debugger - General Debug Features



Memory Map

Memory Map
  KUSEG     KSEG0     KSEG1
  00000000h 80000000h A0000000h  2048K  Main RAM (first 64K reserved for BIOS)
  1F000000h 9F000000h BF000000h  8192K  Expansion Region 1 (ROM/RAM)
  1F800000h 9F800000h    --      1K     Scratchpad (D-Cache used as Fast RAM)
  1F801000h 9F801000h BF801000h  8K     I/O Ports
  1F802000h 9F802000h BF802000h  8K     Expansion Region 2 (I/O Ports)
  1FA00000h 9FA00000h BFA00000h  2048K  Expansion Region 3 (whatever purpose)
  1FC00000h 9FC00000h BFC00000h  512K   BIOS ROM (Kernel) (4096K max)
        FFFE0000h (KSEG2)        0.5K   I/O Ports (Cache Control)
Additionally, there are a number of memory mirrors.

Additional Memory (not mapped to the CPU bus)
  1024K   VRAM (Framebuffers, Textures, Palettes) (plus 2.5KB GPU Cache)
  512K    Sound RAM (Capture Buffers, ADPCM Data, Reverb Workspace)
  0.5K    CDROM controller RAM (see CDROM Test commands)
  16.5K   CDROM controller ROM (Firmware and Bootstrap for MC68HC05 cpu)
  32K     CDROM Buffer (IC303) (32Kx8) (BUG: only two sectors accessible?)
  128K    External Memory Card(s) (EEPROMs)

KUSEG,KSEG0,KSEG1,KSEG2 Memory Regions
  Address   Name   Size   Privilege    Code-Cache  Data-Cache
  00000000h KUSEG  2048M  Kernel/User  Yes         (Scratchpad)
  80000000h KSEG0  512M   Kernel       Yes         (Scratchpad)
  A0000000h KSEG1  512M   Kernel       No          No
  C0000000h KSEG2  1024M  Kernel       (No code)   No
Kernel Memory: KSEG1 is the normal physical memory (uncached), KSEG0 is a mirror thereof (but with cache enabled). KSEG2 is usually intended to contain virtual kernel memory, in the PSX it's containing Cache Control I/O Ports.
User Memory: KUSEG is intended to contain 2GB virtual memory (on extended MIPS processors), the PSX doesn't support virtual memory, and KUSEG simply contains a mirror of KSEG0/KSEG1 (in the first 512MB) (trying to access memory in the remaining 1.5GB causes an exception).

Code Cache
Works in the cached regions (KUSEG and KSEG0).
There are reportedly some restrictions... not sure there... eventually it is using the LSBs of the address as cache-line number... so, for example, it couldn't simultaneously memorize opcodes at BOTH address 80001234h, AND at address 800F1234h (?)

Data Cache aka Scratchpad
The MIPS CPU usually have a Data Cache, but, in the PSX, Sony has misused it as "Scratchpad", that is, the "Data Cache" is mapped to a fixed memory location at 1F800000h..1F8003FFh (ie. it's used as Fast RAM, rather than as cache).
There <might> be a way to disable that behaviour (via Port FFFE0130h or so), but, the Kernel is accessing I/O ports via KUSEG, so activating Data Cache would cause the Kernel to access cached I/O ports.
Not tested yet, but most probably the Scratchpad can be used only for Data (ie. NOT for program Code?).

Memory Mirrors
As described above, the 512Mbyte KUSEG, KSEG0, and KSEG1 regions are mirrors of each other. Additional mirrors within these 512MB regions are:
  2MB RAM can be mirrored to the first 8MB (strangely, enabled by default)
  512K BIOS ROM can be mirrored to the last 4MB (disabled by default)
  Expansion hardware (if any) may be mirrored within expansion region
  The seven DMA Control Registers at 1F8010x8h are mirrored to 1F8010xCh
The size of the RAM, BIOS, Expansion regions can be configured by software, for Expansion Region it's also possible to change base address, see:
Memory Control
The Scratchpad is mirrored only in KUSEG and KSEG0, but not in KSEG1.

Memory Exceptions
  Memory Error ------> Misalignments
               (and probably also KSEG access in User mode)
  Bus Error    ------> Unused Memory Regions (including Gaps in I/O Region)
               (unless RAM/BIOS/Expansion mirrors are mapped to "unused" area)

More Memory Info
For Info on Exception vectors, Unused/Garbage memory locations, I/O Ports, Expansion ROM Headers, and Memory Waitstate Control, etc. see:
I/O Map
Memory Control
EXP1 Expansion ROM Header
BIOS Memory Map
BIOS Memory Allocation
COP0 - Exception Handling
Unpredictable Things


I/O Map

Expansion Region 1
  1F000000h 80000h Expansion Region (default 512 Kbytes, max 8 MBytes)
  1F000000h 100h   Expansion ROM Header (IDs and Entrypoints)
Scratchpad
  1F800000h 400h Scratchpad (1K Fast RAM) (Data Cache mapped to fixed address)
Memory Control 1
  1F801000h 4    Expansion 1 Base Address (usually 1F000000h)
  1F801004h 4    Expansion 2 Base Address (usually 1F802000h)
  1F801008h 4    Expansion 1 Delay/Size (usually 0013243Fh; 512Kbytes 8bit-bus)
  1F80100Ch 4    Expansion 3 Delay/Size (usually 00003022h; 1 byte)
  1F801010h 4    BIOS ROM    Delay/Size (usually 0013243Fh; 512Kbytes 8bit-bus)
  1F801014h 4    SPU_DELAY   Delay/Size (usually 200931E1h)
  1F801018h 4    CDROM_DELAY Delay/Size (usually 00020843h or 00020943h)
  1F80101Ch 4    Expansion 2 Delay/Size (usually 00070777h; 128-bytes 8bit-bus)
  1F801020h 4    COM_DELAY / COMMON_DELAY (00031125h or 0000132Ch or 00001325h)
Peripheral I/O Ports
  1F801040h 1/4  JOY_DATA Joypad/Memory Card Data (R/W)
  1F801044h 4    JOY_STAT Joypad/Memory Card Status (R)
  1F801048h 2    JOY_MODE Joypad/Memory Card Mode (R/W)
  1F80104Ah 2    JOY_CTRL Joypad/Memory Card Control (R/W)
  1F80104Eh 2    JOY_BAUD Joypad/Memory Card Baudrate (R/W)
  1F801050h 1/4  SIO_DATA Serial Port Data (R/W)
  1F801054h 4    SIO_STAT Serial Port Status (R)
  1F801058h 2    SIO_MODE Serial Port Mode (R/W)
  1F80105Ah 2    SIO_CTRL Serial Port Control (R/W)
  1F80105Ch 2    SIO_MISC Serial Port Internal Register (R/W)
  1F80105Eh 2    SIO_BAUD Serial Port Baudrate (R/W)
Memory Control 2
  1F801060h 4/2  RAM_SIZE (usually 00000B88h; 2MB RAM mirrored in first 8MB)
Interrupt Control
  1F801070h 2    I_STAT - Interrupt status register
  1F801074h 2    I_MASK - Interrupt mask register
DMA Registers
  1F80108xh      DMA0 channel 0 - MDECin
  1F80109xh      DMA1 channel 1 - MDECout
  1F8010Axh      DMA2 channel 2 - GPU (lists + image data)
  1F8010Bxh      DMA3 channel 3 - CDROM
  1F8010Cxh      DMA4 channel 4 - SPU
  1F8010Dxh      DMA5 channel 5 - PIO (Expansion Port)
  1F8010Exh      DMA6 channel 6 - OTC (reverse clear OT) (GPU related)
  1F8010F0h      DPCR - DMA Control register
  1F8010F4h      DICR - DMA Interrupt register
  1F8010F8h      unknown
  1F8010FCh      unknown
Timers (aka Root counters)
  1F801100h 2    Timer 0 Current Counter Value (R/W)  ;\
  1F801104h 2    Timer 0 Counter Mode          (R/W)  ; Dotclock
  1F801108h 2    Timer 0 Counter Target Value  (R/W)  ;/
  1F801110h 2    Timer 1 Current Counter Value (R/W)  ;\
  1F801114h 2    Timer 1 Counter Mode          (R/W)  ; Horizontal Retrace
  1F801118h 2    Timer 1 Counter Target Value  (R/W)  ;/
  1F801120h 2    Timer 2 Current Counter Value (R/W)  ;\
  1F801124h 2    Timer 2 Counter Mode          (R/W)  ; 1/8 system clock
  1F801128h 2    Timer 2 Counter Target Value  (R/W)  ;/
CDROM Registers (Address.Read/Write.Index)
  1F801800h.x.x   1   CD Index/Status Register (Bit0-1 R/W, Bit2-7 Read Only)
  1F801801h.R.x   1   CD Response Fifo (R) (usually with Index1)
  1F801802h.R.x   1/2 CD Data Fifo - 8bit/16bit (R) (usually with Index0..1)
  1F801803h.R.0   1   CD Interrupt Enable Register (R)
  1F801803h.R.1   1   CD Interrupt Flag Register (R/W)
  1F801803h.R.2   1   CD Interrupt Enable Register (R) (Mirror)
  1F801803h.R.3   1   CD Interrupt Flag Register (R/W) (Mirror)
  1F801801h.W.0   1   CD Command Register (W)
  1F801802h.W.0   1   CD Parameter Fifo (W)
  1F801803h.W.0   1   CD Request Register (W)
  1F801801h.W.1   1   Unknown/unused
  1F801802h.W.1   1   CD Interrupt Enable Register (W)
  1F801803h.W.1   1   CD Interrupt Flag Register (R/W)
  1F801801h.W.2   1   Unknown/unused
  1F801802h.W.2   1   CD Audio Volume for Left-CD-Out to Left-SPU-Input (W)
  1F801803h.W.2   1   CD Audio Volume for Left-CD-Out to Right-SPU-Input (W)
  1F801801h.W.3   1   CD Audio Volume for Right-CD-Out to Right-SPU-Input (W)
  1F801802h.W.3   1   CD Audio Volume for Right-CD-Out to Left-SPU-Input (W)
  1F801803h.W.3   1   CD Audio Volume Apply Changes (by writing bit5=1)
GPU Registers
  1F801810h.Write 4   GP0 Send GP0 Commands/Packets (Rendering and VRAM Access)
  1F801814h.Write 4   GP1 Send GP1 Commands (Display Control)
  1F801810h.Read  4   GPUREAD Read responses to GP0(C0h) and GP1(10h) commands
  1F801814h.Read  4   GPUSTAT Read GPU Status Register
MDEC Registers
  1F801820h.Write 4   MDEC Command/Parameter Register (W)
  1F801820h.Read  4   MDEC Data/Response Register (R)
  1F801824h.Write 4   MDEC Control/Reset Register (W)
  1F801824h.Read  4   MDEC Status Register (R)
SPU Voice 0..23 Registers
  1F801C00h+N*10h 2   Voice 0..23 Volume Left
  1F801C02h+N*10h 2   Voice 0..23 Volume Right
  1F801C04h+N*10h 2   Voice 0..23 ADPCM Sample Rate
  1F801C06h+N*10h 2   Voice 0..23 ADPCM Start Address
  1F801C08h+N*10h 2+2 Voice 0..23 ADSR Attack/Decay/Sustain/Release
  1F801C0Ch+N*10h 2   Voice 0..23 ADSR Current Volume
  1F801C0Eh+N*10h 2   Voice 0..23 ADPCM Repeat Address
SPU Control Registers
  1F801D80h 2   Main Volume Left
  1F801D82h 2   Main Volume Right
  1F801D84h 2+2 Reverb Output Volume Left/Right
  1F801D88h 2+2 Voice 0..23 Key ON (Start Attack/Decay/Sustain) (W)
  1F801D8Ch 2+2 Voice 0..23 Key OFF (Start Release) (W)
  1F801D90h 2+2 Voice 0..23 Channel FM (pitch lfo) mode (R/W)
  1F801D94h 2+2 Voice 0..23 Channel Noise mode (R/W)
  1F801D98h 2+2 Voice 0..23 Channel Reverb mode (R/W)
  1F801D9Ch 2+2 Voice 0..23 Channel ON/OFF (status) (R)
  1F801DA0h 2   Unknown? (R) or (W)
  1F801DA2h 2   Sound RAM Reverb Work Area Start Address
  1F801DA4h 2   Sound RAM IRQ Address
  1F801DA6h 2   Sound RAM Data Transfer Address
  1F801DA8h 2   Sound RAM Data Transfer Fifo
  1F801DAAh 2   SPU Control Register (SPUCNT)
  1F801DACh 2   Sound RAM Data Transfer Control
  1F801DAEh 2   SPU Status Register (SPUSTAT) (R)
  1F801DB0h 2+2 CD Volume Left/Right
  1F801DB4h 2+2 Extern Volume Left/Right
  1F801DB8h 2+2 Current Main Volume Left/Right
  1F801DBCh 2+2 Unknown? (R/W)
SPU Reverb Configuration Area
  1F801DC0h 2   dAPF1  Reverb APF Offset 1
  1F801DC2h 2   dAPF2  Reverb APF Offset 2
  1F801DC4h 2   vIIR   Reverb Reflection Volume 1
  1F801DC6h 2   vCOMB1 Reverb Comb Volume 1
  1F801DC8h 2   vCOMB2 Reverb Comb Volume 2
  1F801DCAh 2   vCOMB3 Reverb Comb Volume 3
  1F801DCCh 2   vCOMB4 Reverb Comb Volume 4
  1F801DCEh 2   vWALL  Reverb Reflection Volume 2
  1F801DD0h 2   vAPF1  Reverb APF Volume 1
  1F801DD2h 2   vAPF2  Reverb APF Volume 2
  1F801DD4h 4   mSAME  Reverb Same Side Reflection Address 1 Left/Right
  1F801DD8h 4   mCOMB1 Reverb Comb Address 1 Left/Right
  1F801DDCh 4   mCOMB2 Reverb Comb Address 2 Left/Right
  1F801DE0h 4   dSAME  Reverb Same Side Reflection Address 2 Left/Right
  1F801DE4h 4   mDIFF  Reverb Different Side Reflection Address 1 Left/Right
  1F801DE8h 4   mCOMB3 Reverb Comb Address 3 Left/Right
  1F801DECh 4   mCOMB4 Reverb Comb Address 4 Left/Right
  1F801DF0h 4   dDIFF  Reverb Different Side Reflection Address 2 Left/Right
  1F801DF4h 4   mAPF1  Reverb APF Address 1 Left/Right
  1F801DF8h 4   mAPF2  Reverb APF Address 2 Left/Right
  1F801DFCh 4   vIN    Reverb Input Volume Left/Right
SPU Internal Registers
  1F801E00h+N*04h  4 Voice 0..23 Current Volume Left/Right
  1F801E60h      20h Unknown? (R/W)
  1F801E80h     180h Unknown? (Read: FFh-filled) (Unused or Write only?)
Expansion Region 2 (default 128 bytes, max 8 KBytes)
  1F802000h      80h Expansion Region (8bit data bus, crashes on 16bit access?)
Expansion Region 2 - Dual Serial Port (for TTY Debug Terminal)
  1F802020h/1st    DUART Mode Register 1.A (R/W)
  1F802020h/2nd    DUART Mode Register 2.A (R/W)
  1F802021h/Read   DUART Status Register A (R)
  1F802021h/Write  DUART Clock Select Register A (W)
  1F802022h/Read   DUART Toggle Baud Rate Generator Test Mode (Read=Strobe)
  1F802022h/Write  DUART Command Register A (W)
  1F802023h/Read   DUART Rx Holding Register A (FIFO) (R)
  1F802023h/Write  DUART Tx Holding Register A (W)
  1F802024h/Read   DUART Input Port Change Register (R)
  1F802024h/Write  DUART Aux. Control Register (W)
  1F802025h/Read   DUART Interrupt Status Register (R)
  1F802025h/Write  DUART Interrupt Mask Register (W)
  1F802026h/Read   DUART Counter/Timer Current Value, Upper/Bit15-8 (R)
  1F802026h/Write  DUART Counter/Timer Reload Value,  Upper/Bit15-8 (W)
  1F802027h/Read   DUART Counter/Timer Current Value, Lower/Bit7-0 (R)
  1F802027h/Write  DUART Counter/Timer Reload Value,  Lower/Bit7-0 (W)
  1F802028h/1st    DUART Mode Register 1.B (R/W)
  1F802028h/2nd    DUART Mode Register 2.B (R/W)
  1F802029h/Read   DUART Status Register B (R)
  1F802029h/Write  DUART Clock Select Register B (W)
  1F80202Ah/Read   DUART Toggle 1X/16X Test Mode (Read=Strobe)
  1F80202Ah/Write  DUART Command Register B (W)
  1F80202Bh/Read   DUART Rx Holding Register B (FIFO) (R)
  1F80202Bh/Write  DUART Tx Holding Register B (W)
  1F80202Ch/None   DUART Reserved Register (neither R nor W)
  1F80202Dh/Read   DUART Input Port (R)
  1F80202Dh/Write  DUART Output Port Configuration Register (W)
  1F80202Eh/Read   DUART Start Counter Command (Read=Strobe)
  1F80202Eh/Write  DUART Set Output Port Bits Command (Set means Out=LOW)
  1F80202Fh/Read   DUART Stop Counter Command (Read=Strobe)
  1F80202Fh/Write  DUART Reset Output Port Bits Command (Reset means Out=HIGH)
Expansion Region 2 - Int/Dip/Post
  1F802000h 1 DTL-H2000: ATCONS STAT (R)
  1F802002h 1 DTL-H2000: ATCONS DATA (R and W)
  1F802004h 2 DTL-H2000: Whatever 16bit data ?
  1F802030h 1/4 DTL-H2000: Secondary IRQ10 Flags
  1F802032h 1 DTL-H2000: Whatever IRQ Control ?
  1F802040h 1 DTL-H2000: Bootmode "Dip switches" (R)
  1F802041h 1 PSX: POST (external 7 segment display, indicate BIOS boot status)
  1F802042h 1 DTL-H2000: POST/LED (similar to POST) (other addr, 2-digit wide)   1F802070h 1 PS2: POST2 (similar to POST, but PS2 BIOS uses this address)
Expansion Region 2 - Nocash Emulation Expansion
  1F802060h Emu-Expansion ID1 "E" (R)
  1F802061h Emu-Expansion ID2 "X" (R)
  1F802062h Emu-Expansion ID3 "P" (R)
  1F802063h Emu-Expansion Version (01h) (R)
  1F802064h Emu-Expansion Enable1 "O" (R/W)
  1F802065h Emu-Expansion Enable2 "N" (R/W)
  1F802066h Emu-Expansion Halt (R)
  1F802067h Emu-Expansion Turbo Mode Flags (R/W)
Expansion Region 3 (default 1 byte, max 2 MBytes)
  1FA00000h - Not used by BIOS or any PSX games
  1FA00000h - POST3 (similar to POST, but PS2 BIOS uses this address)
BIOS Region (default 512 Kbytes, max 4 MBytes)
  1FC00000h 80000h   BIOS ROM (512Kbytes) (Reset Entrypoint at BFC00000h)
Memory Control 3 (Cache Control)
  FFFE0130h 4        Cache Control

Coprocessor Registers
  COP0 System Control Coprocessor           - 32 registers (not all used)
  COP1 N/A
  COP2 Geometry Transformation Engine (GTE) - 64 registers (most are used)
  COP3 N/A


Graphics Processing Unit (GPU)

The GPU can render Polygons, Lines, or Rectangles to the Drawing Buffer, and sends the Display Buffer to the Television Set. Polygons are useful for 3D graphics (or rotated/scaled 2D graphics), Rectangles are useful for 2D graphics and Text output.

GPU I/O Ports, DMA Channels, Commands, VRAM
GPU Render Polygon Commands
GPU Render Line Commands
GPU Render Rectangle Commands
GPU Rendering Attributes
GPU Memory Transfer Commands
GPU Other Commands
GPU Display Control Commands (GP1)
GPU Status Register
GPU Versions
GPU Depth Ordering
GPU Video Memory (VRAM)
GPU (MISC)

Inner Workings
GPU FIFO
GPU Texture Caching
GPU Display Timings
GPU Rendering Timings


GPU I/O Ports, DMA Channels, Commands, VRAM

GPU I/O Ports (1F801810h and 1F801814h in Read/Write Directions)
  Port            Name    Expl.
  1F801810h-Write GP0     Send GP0 Commands/Packets (Rendering and VRAM Access)
  1F801814h-Write GP1     Send GP1 Commands (Display Control) (and DMA Control)
  1F801810h-Read  GPUREAD Receive responses to GP0(C0h) and GP1(10h) commands
  1F801814h-Read  GPUSTAT Receive GPU Status Register
It (=GP0 only?) has a 64-byte (16-word) command FIFO buffer.
Optionally, Port 1F801810h (Read/Write) can be also accessed via DMA2.

GPU Timers / Synchronization
Most of the Timers are bound to GPU timings, see
Timers
Interrupts

GPU-related DMA Channels (DMA2 and DMA6)
  Channel                  Recommended for
  DMA2 in Linked Mode    - Sending rendering commands  ;GP0(20h..7Fh,E1h..E6h)
  DMA2 in Continous Mode - VRAM transfers to/from GPU  ;GP0(A0h,C0h)
  DMA6                   - Initializing the Link List  ;Main RAM
Note: Before using DMA2, set up the DMA Direction in GP1(04h).
DMA2 is equivalent to accessing Port 1F801810h (GP0/GPUREAD) by software.
DMA6 just initializes data in Main RAM (not physically connected to the GPU).

GPU Command Summary
Commands/Packets consist of a 8bit command number (MSBs) and a 24bit parameter (LSBs), which are written as 32bit value to GP0 or GP1.
  GP0(00h)                 - Nop?
  GP0(01h,02h,80h,A0h,C0h) - Direct VRAM Access
  GP0(03h)                 - Timing Control
  GP0(1Fh)                 - Interrupt Request (IRQ1)
  GP0(20h..3Fh)            - Render Polygons
  GP0(40h..5Fh)            - Render Lines
  GP0(60h..7Fh)            - Render Rectangles
  GP0(E1h..E6h)            - Rendering Attributes
  GP1(00h..09h,10h,20h)    - Display Control (these via GP1 register)
Some GP0 commands require additional parameters, which are written (following to the command) as further 32bit values to GP0. The execution of the command starts when all parameters have been received (or, in case of Polygon/Line commands, when the first 3/2 vertices have been received).

VRAM Overview / VRAM Addressing
VRAM is 1MByte (not mapped to the CPU bus) (it can be read/written only via I/O or DMA). The memory is used for:
  Framebuffer(s)      ;Usually 2 buffers (Drawing Area, and Display Area)
  Texture Page(s)     ;Required when using Textures
  Texture Palette(s)  ;Required when using 4bit/8bit Textures
The 1MByte VRAM is organized as 512 lines of 2048 bytes. It is accessed via coordinates, ranging from (0,0)=Upper-Left to (N,511)=Lower-Right.
  Unit  = 4bit  8bit  16bit  24bit   Halfwords   | Unit   = Lines
  Width = 4096  2048  1024   682.66  1024        | Height = 512
The horizontal coordinates are addressing memory in 4bit/8bit/16bit/24bit/halfword units (depending on what data formats you are using) (or a mixup thereof, eg. a halfword-base address, plus a 4bit texture coordinate).


GPU Render Polygon Commands

GP0(20h) - Monochrome three-point polygon, opaque
GP0(22h) - Monochrome three-point polygon, semi-transparent
GP0(28h) - Monochrome four-point polygon, opaque
GP0(2Ah) - Monochrome four-point polygon, semi-transparent
  1st  Color+Command     (CcBbGgRrh)
  2nd  Vertex1           (YyyyXxxxh)
  3rd  Vertex2           (YyyyXxxxh)
  4th  Vertex3           (YyyyXxxxh)
 (5th) Vertex4           (YyyyXxxxh) (if any)

GP0(24h) - Textured three-point polygon, opaque, texture-blending
GP0(25h) - Textured three-point polygon, opaque, raw-texture
GP0(26h) - Textured three-point polygon, semi-transparent, texture-blending
GP0(27h) - Textured three-point polygon, semi-transparent, raw-texture
GP0(2Ch) - Textured four-point polygon, opaque, texture-blending
GP0(2Dh) - Textured four-point polygon, opaque, raw-texture
GP0(2Eh) - Textured four-point polygon, semi-transparent, texture-blending
GP0(2Fh) - Textured four-point polygon, semi-transparent, raw-texture
  1st  Color+Command     (CcBbGgRrh) (color is ignored for raw-textures)
  2nd  Vertex1           (YyyyXxxxh)
  3rd  Texcoord1+Palette (ClutYyXxh)
  4th  Vertex2           (YyyyXxxxh)
  5th  Texcoord2+Texpage (PageYyXxh)
  6th  Vertex3           (YyyyXxxxh)
  7th  Texcoord3         (0000YyXxh)
 (8th) Vertex4           (YyyyXxxxh) (if any)
 (9th) Texcoord4         (0000YyXxh) (if any)

GP0(30h) - Shaded three-point polygon, opaque
GP0(32h) - Shaded three-point polygon, semi-transparent
GP0(38h) - Shaded four-point polygon, opaque
GP0(3Ah) - Shaded four-point polygon, semi-transparent
  1st  Color1+Command    (CcBbGgRrh)
  2nd  Vertex1           (YyyyXxxxh)
  3rd  Color2            (00BbGgRrh)
  4th  Vertex2           (YyyyXxxxh)
  5th  Color3            (00BbGgRrh)
  6th  Vertex3           (YyyyXxxxh)
 (7th) Color4            (00BbGgRrh) (if any)
 (8th) Vertex4           (YyyyXxxxh) (if any)

GP0(34h) - Shaded Textured three-point polygon, opaque, texture-blending
GP0(36h) - Shaded Textured three-point polygon, semi-transparent, tex-blend
GP0(3Ch) - Shaded Textured four-point polygon, opaque, texture-blending
GP0(3Eh) - Shaded Textured four-point polygon, semi-transparent, tex-blend
  1st  Color1+Command    (CcBbGgRrh)
  2nd  Vertex1           (YyyyXxxxh)
  3rd  Texcoord1+Palette (ClutYyXxh)
  4th  Color2            (00BbGgRrh)
  5th  Vertex2           (YyyyXxxxh)
  6th  Texcoord2+Texpage (PageYyXxh)
  7th  Color3            (00BbGgRrh)
  8th  Vertex3           (YyyyXxxxh)
  9th  Texcoord3         (0000YyXxh)
 (10th) Color4           (00BbGgRrh) (if any)
 (11th) Vertex4          (YyyyXxxxh) (if any)
 (12th) Texcoord4        (0000YyXxh) (if any)

GP0(35h,37h,3Dh,3Fh) - Undocumented/Nonsense (Raw Texture + UNUSED shading)
These are undocumented inefficient nonsense commands: Parameters are same as for GP0(34h,36h,3Ch,3Eh), ie. with colors for all vertices, but without actually using that colors. Instead, the commands are rendering raw textures without blending.
In other words, the commands have same function as GP0(25h,27h,2Dh,2Fh), but with additional/unused parameters (and possible additional/unused internal gouraud shading calculations).
For whatever reason, Castlevania is actually using these nonsense commands, namely GP0(3Dh) and GP0(3Fh).

GP0(21h,23h,29h,2Bh,31h,33h,39h,3Bh) - Undocumented/Nonsense
These commands have texture-blending disabled, which is nonsense because they are using untextured polygons anyways, ie. they are probably same as GP0(20h,22h,28h,2Ah,30h,32h,38h,3Ah).
For whatever reason, Vampire Hunter D is actually using GP0(29h).

Notes
Polygons are displayed up to <excluding> their lower-right coordinates.
Four-point polygons are internally processed as two Three-point polygons, the first consisting of Vertices 1,2,3, and the second of Vertices 2,3,4.
Within the Three-point polygons, the ordering of the vertices is don't care at the GPU side (a front-back check, based on clockwise or anti-clockwise ordering, can be implemented at the GTE side).
Dither enable (in Texpage command) affects ONLY polygons that do use Gouraud Shading or Texture Blending.


GPU Render Line Commands

GP0(40h) - Monochrome line, opaque
GP0(42h) - Monochrome line, semi-transparent
GP0(48h) - Monochrome Poly-line, opaque
GP0(4Ah) - Monochrome Poly-line, semi-transparent
  1st   Color+Command     (CcBbGgRrh)
  2nd   Vertex1           (YyyyXxxxh)
  3rd   Vertex2           (YyyyXxxxh)
 (...)  VertexN           (YyyyXxxxh) (poly-line only)
 (Last) Termination Code  (55555555h) (poly-line only)

GP0(50h) - Shaded line, opaque
GP0(52h) - Shaded line, semi-transparent
GP0(58h) - Shaded Poly-line, opaque
GP0(5Ah) - Shaded Poly-line, semi-transparent
  1st   Color1+Command    (CcBbGgRrh)
  2nd   Vertex1           (YyyyXxxxh)
  3rd   Color2            (00BbGgRrh)
  4th   Vertex2           (YyyyXxxxh)
 (...)  ColorN            (00BbGgRrh) (poly-line only)
 (...)  VertexN           (YyyyXxxxh) (poly-line only)
 (Last) Termination Code  (55555555h) (poly-line only)

Note
Lines are displayed up to <including> their lower-right coordinates (ie. unlike as for polygons, the lower-right coordinate is not excluded).
If dithering is enabled (via Texpage command), then both monochrome and shaded lines are drawn with dithering (this differs from monochrome polygons and monochrome rectangles).

Termination Codes for Poly-Lines (aka Linestrips)
The termination code should be usually 55555555h, however, Wild Arms 2 uses 50005000h (unknown which exact bits/values are relevant there).

Wire-Frame
Poly-Lines can be used (among others) to create Wire-Frame polygons (by setting the last Vertex equal to Vertex 1).


GPU Render Rectangle Commands

Rectangles are drawn much faster than polygons. Unlike for polygons, gouroud shading is not possible, dithering isn't applied, the rectangle must forcefully have horizontal and vertical edges, textures cannot be rotated or scaled, and, of course, the GPU does render Rectangles at once (without splitting them into triangles).

GP0(60h) - Monochrome Rectangle (variable size) (opaque)
GP0(62h) - Monochrome Rectangle (variable size) (semi-transparent)
GP0(68h) - Monochrome Rectangle (1x1) (Dot) (opaque)
GP0(6Ah) - Monochrome Rectangle (1x1) (Dot) (semi-transparent)
GP0(70h) - Monochrome Rectangle (8x8) (opaque)
GP0(72h) - Monochrome Rectangle (8x8) (semi-transparent)
GP0(78h) - Monochrome Rectangle (16x16) (opaque)
GP0(7Ah) - Monochrome Rectangle (16x16) (semi-transparent)
  1st  Color+Command     (CcBbGgRrh)
  2nd  Vertex            (YyyyXxxxh)
 (3rd) Width+Height      (YsizXsizh) (variable size only) (max 1023x511)

GP0(64h) - Textured Rectangle, variable size, opaque, texture-blending
GP0(65h) - Textured Rectangle, variable size, opaque, raw-texture
GP0(66h) - Textured Rectangle, variable size, semi-transp, texture-blending
GP0(67h) - Textured Rectangle, variable size, semi-transp, raw-texture
GP0(6Ch) - Textured Rectangle, 1x1 (nonsense), opaque, texture-blending
GP0(6Dh) - Textured Rectangle, 1x1 (nonsense), opaque, raw-texture
GP0(6Eh) - Textured Rectangle, 1x1 (nonsense), semi-transp, texture-blending
GP0(6Fh) - Textured Rectangle, 1x1 (nonsense), semi-transp, raw-texture
GP0(74h) - Textured Rectangle, 8x8, opaque, texture-blending
GP0(75h) - Textured Rectangle, 8x8, opaque, raw-texture
GP0(76h) - Textured Rectangle, 8x8, semi-transparent, texture-blending
GP0(77h) - Textured Rectangle, 8x8, semi-transparent, raw-texture
GP0(7Ch) - Textured Rectangle, 16x16, opaque, texture-blending
GP0(7Dh) - Textured Rectangle, 16x16, opaque, raw-texture
GP0(7Eh) - Textured Rectangle, 16x16, semi-transparent, texture-blending
GP0(7Fh) - Textured Rectangle, 16x16, semi-transparent, raw-texture
  1st  Color+Command     (CcBbGgRrh) (color is ignored for raw-textures)
  2nd  Vertex            (YyyyXxxxh) (upper-left edge of the rectangle)
  3rd  Texcoord+Palette  (ClutYyXxh) (see bug on odd/even Texcoord.X values)
 (4th) Width+Height      (YsizXsizh) (variable size only) (max 1023x511)
Unlike for Textured-Polygons, the "Texpage" must be set up separately for Rectangles, via GP0(E1h). Width and Height can be up to 1023x511, however, the maximum size of the texture window is 256x256 (so the source data will be repeated when trying to use sizes larger than 256x256).

Odd/Even Texcoord.X bugs
For Rectangles, Texcoord.X must be even. Odd values will trigger a hardware glitch on each 4th or 8th pixel as shown below (the 1st error causes the same pixel to be drawn twice, the 2nd error can "undo" the 1st error, but it can also draw pixels that are outside of the texwindow area):
  if 15bpp then tex_error_mask=3, else tex_error_mask=7       ;4bpp/8bpp/15bpp
  if (tex.x AND tex_error_mask)=0 then
    tex.x=(tex.x-1)                                           ;1st error
    tex.x=(tex.x AND texwindow.mask) OR texwindow.offset      ;window
    if 4bpp AND (tex.x AND 8)=0 then tex.x=(tex.x+1) AND FFh  ;2nd error
  else    ;no error...
    tex.x=(tex.x AND texwindow.mask) OR texwindow.offset      ;window
That hardware glitch doesn't occur with X-Flip. However, X-Flip does completely ignore the LSB of Texcoord.X (and does forcefully start at odd Texcoord.X values).

Texture Origin and X/Y-Flip
Normally, Vertex & Texcoord specify the upper/left edge of the rectangle, and the screen coords and texture coords are both incremented during rendering the rectangle pixels.
Optionally, X/Y-Flip bits can be set in Texpage.Bit12/13, these bits cause the texture coordinates to be decremented (instead of incremented) (and accordingly, the Texcoord should be set to lower/right of the source bitmap, will appear on screen in upper/left after flipping). The X/Y-Flip bits do affect only Rectangles (not Polygons, nor VRAM Transfers).
Caution: The X/Y-Flip feature isn't supported on old 160pin GPUs:
GPU Versions

Note
There are also two VRAM Transfer commands which work similar to GP0(60h) and GP0(65h). Maybe that commands might be even faster (although... they don't use Texture Cache, so they might be slower when repeatly drawing the same source tile).
The difference is that VRAM Transfers do not clip to the Drawig Area boundary, do not support fully-transparent nor semi-transparent texture pixels, and do not convert color depths (eg. without 4bit texture to 16bit framebuffer conversion).


GPU Rendering Attributes

Vertex (Parameter for Polygon, Line, Rectangle commands)
  0-10   X-coordinate (signed, -1024..+1023)
  11-15  Not used (usually sign-extension, but ignored by hardware)
  16-26  Y-coordinate (signed, -1024..+1023)
  26-31  Not used (usually sign-extension, but ignored by hardware)
Size Restriction: The maximum distance between two vertices is 1023 horizontally, and 511 vertically. Polygons and lines that are exceeding that dimensions are NOT rendered. For example, a line from Y1=-300 to Y2=+300 is NOT rendered, a line from Y1=-100 to Y2=+400 is rendered (as far as it is within the drawing area).
If portions of the polygon/line/rectangle are located outside of the drawing area, then the hardware renders only the portion that is inside of the drawing area. Unknown if the hardware is skipping all clipped pixels at once (within a single clock cycle), or if it's (slowly) processing them pixel by pixel?

Color Attribute (Parameter for all Rendering commands, except Raw Texture)
  0-7    Red   (0..FFh)
  8-15   Green (0..FFh)
  16-23  Blue  (0..FFh)
  24-31  Command (in first parameter) (don't care in further parameters)
Caution: For untextured graphics, 8bit RGB values of FFh are brightest. However, for texture blending, 8bit values of 80h are brightest (values 81h..FFh are "brighter than bright" allowing to make textures about twice as bright as than they were originially stored in memory; of course the results can't exceed the maximum brightness, ie. the 5bit values written to the framebuffer are saturated to max 1Fh).

Texpage Attribute (Parameter for Textured-Polygons commands)
  0-8    Same as GP0(E1h).Bit0-8 (see there)
  9-10   Unused (does NOT change GP0(E1h).Bit9-10)
  11     Same as GP0(E1h).Bit11  (see there)
  12-13  Unused (does NOT change GP0(E1h).Bit12-13)
  14-15  Unused (should be 0)
This attribute is used in all Textured-Polygon commands.

Clut Attribute (Color Lookup Table, aka Palette)
This attribute is used in all Textured Polygon/Rectangle commands. Of course, it's relevant only for 4bit/8bit textures (don't care for 15bit textures).
  0-5      CLUT X coordinate bit4-9  (in 16-halfword steps)
  6-14     CLUT Y coordinate bit0-8  (in 1-line steps)
  15       CLUT Y coordinate bit9    (0=Normal, 1=Upper Mbyte, Open Bus)
Specifies the location of the CLUT data within VRAM.

GP0(E1h) - Draw Mode setting (aka "Texpage")
  0-3   Texture page X.bit6-9 (N*64) (ie. in 64-halfword steps)    ;GPUSTAT.0-3
  4     Texture page Y.bit8   (N*256) (ie. 0 or 256)               ;GPUSTAT.4
  5-6   Semi Transparency     (0=B/2+F/2, 1=B+F, 2=B-F, 3=B+F/4)   ;GPUSTAT.5-6
  7-8   Texture page colors   (0=4bit, 1=8bit, 2=15bit, 3=Reserved);GPUSTAT.7-8
  9     Dither 24bit to 15bit (0=Off/strip LSBs, 1=Dither Enabled) ;GPUSTAT.9
  10    Interlace Drawing     (0=All Lines, 1=Inactive Lines)      ;GPUSTAT.10
  11    Texture page Y.bit9   (0=Normal, 1=Upper Mbyte, Open Bus)  ;GPUSTAT.15
  12    Textured Rectangle X-Flip   (BIOS does set this bit on power-up...?)
  13    Textured Rectangle Y-Flip   (BIOS does set it equal to GPUSTAT.13...?)
  14-23 Not used (should be 0)
  24-31 Command  (E1h)
The GP0(E1h) command is required only for Lines, Rectangle, and Untextured-Polygons (for Textured-Polygons, the data is specified in form of the Texpage attribute; except that, Bit9-10 and Bit12-13 can be changed only via GP0(E1h), not via the Texpage attribute).
Texture page colors setting 3 (reserved) is same as setting 2 (15bit).
Note: GP0(00h) seems to be often inserted between Texpage and Rectangle commands, maybe it acts as a NOP, which may be required between that commands, for timing reasons...?

GP0(E2h) - Texture Window setting
  0-4    Texture window Mask X   (in 8 pixel steps)
  5-9    Texture window Mask Y   (in 8 pixel steps)
  10-14  Texture window Offset X (in 8 pixel steps)
  15-19  Texture window Offset Y (in 8 pixel steps)
  20-23  Not used (zero)
  24-31  Command  (E2h)
Mask specifies the bits that are to be manipulated, and Offset contains the new values for these bits, ie. texture X/Y coordinates are adjusted as so:
  Texcoord = (Texcoord AND (NOT (Mask*8))) OR ((Offset AND Mask)*8)
The area within a texture window is repeated throughout the texture page. The data is not actually stored all over the texture page but the GPU reads the repeated patterns as if they were there.

GP0(E3h) - Set Drawing Area top left (X1,Y1)
GP0(E4h) - Set Drawing Area bottom right (X2,Y2)
  0-9    X-coordinate (0..1023)
  10-18  Y-coordinate (0..511)   ;\on Old 160pin GPU (max 1MB VRAM)
  19-23  Not used (zero)         ;/
  10-19  Y-coordinate (0..1023)  ;\on New 208pin GPU (max 2MB VRAM)
  20-23  Not used (zero)         ;/(retail consoles have only 1MB though)
  24-31  Command  (Exh)
Sets the drawing area corners. The Render commands GP0(20h..7Fh) are automatically clipping any pixels that are outside of this region.

GP0(E5h) - Set Drawing Offset (X,Y)
  0-10   X-offset (-1024..+1023) (usually within X1,X2 of Drawing Area)
  11-21  Y-offset (-1024..+1023) (usually within Y1,Y2 of Drawing Area)
  22-23  Not used (zero)
  24-31  Command  (E5h)
If you have configured the GTE to produce vertices with coordinate "0,0" being located in the center of the drawing area, then the Drawing Offset must be "X1+(X2-X1)/2, Y1+(Y2-Y1)/2". Or, if coordinate "0,0" shall be the upper-left of the Drawing Area, then Drawing Offset should be "X1,Y1". Where X1,Y1,X2,Y2 are the values defined with GP0(E3h-E4h).
Note: The 11bit drawing offsets may be seen as signed or unsigned values (the 11bit offset is added to the signed 11bit vertex, and the result is truncated to signed 11bit range).

GP0(E6h) - Mask Bit Setting
  0     Set mask while drawing (0=TextureBit15, 1=ForceBit15=1)   ;GPUSTAT.11
  1     Check mask before draw (0=Draw Always, 1=Draw if Bit15=0) ;GPUSTAT.12
  2-23  Not used (zero)
  24-31 Command  (E6h)
When bit0 is off, the upper bit of the data written to the framebuffer is equal to bit15 of the texture color (ie. it is set for colors that are marked as "semi-transparent") (for untextured polygons, bit15 is set to zero).
When bit1 is on, any (old) pixels in the framebuffer with bit15=1 are write-protected, and cannot be overwritten by (new) rendering commands.
The mask setting affects all rendering commands, as well as CPU-to-VRAM and VRAM-to-VRAM transfer commands (where it acts on the separate halfwords, ie. as for 15bit textures). However, Mask does NOT affect the Fill-VRAM command.

Note
GP0(E3h..E5h) do not take up space in the FIFO, so they are probably executed immediately (even if there're still other commands in the FIFO). Best use them only if you are sure that the FIFO is empty (otherwise the new Drawing Area settings might accidently affect older Rendering Commands in the FIFO).


GPU Memory Transfer Commands

GP0(01h) - Clear Cache
  1st  Command           (Cc000000h)
This command does discard the content of CLUT Cache and Texture Cache, this is required if VRAM has been overwritten by new data whilst still having old data in the cache. In practice, this is mainly needed in two situations: When uploading new CLUTs to VRAM. And when using Polygon/Line/Rect/Fill commands to render into Texture memory.

GP0(02h) - Fill Rectangle in VRAM
  1st  Color+Command     (CcBbGgRrh)  ;24bit RGB value (see note)
  2nd  Top Left Corner   (YyyyXxxxh)  ;Xpos counted in halfwords, steps of 10h
  3rd  Width+Height      (YsizXsizh)  ;Xsiz counted in halfwords, steps of 10h
Fills the area in the frame buffer with the value in RGB. Horizontally the filling is done in 16-pixel (32-bytes) units (see below masking/rounding).
The "Color" parameter is a 24bit RGB value, however, the actual fill data is 16bit: The hardware automatically converts the 24bit RGB value to 15bit RGB (with bit15=0).
The VRAM chips have a special hardware feature that allows to write the same value to several addresses at once, that's making the Fill command VERY fast (about 0.075 CPU clocks/pixel, which is 8x faster than monochrome rects).

GP0(80h) - Copy Rectangle (VRAM to VRAM)
  1st  Command           (Cc000000h)
  2nd  Source Coord      (YyyyXxxxh)  ;Xpos counted in halfwords
  3rd  Destination Coord (YyyyXxxxh)  ;Xpos counted in halfwords
  4th  Width+Height      (YsizXsizh)  ;Xsiz counted in halfwords
Copys data within framebuffer. The transfer is affected by Mask setting.
Note: The command reads 128 halfwords from source to a temp buffer, then writes 128 halfwords from temp to dest; if the width isn't a multiple of 128 then the rightmost portion of each scanline will be less than 128 halfwords).

GP0(A0h) - Copy Rectangle (CPU to VRAM)
  1st  Command           (Cc000000h)
  2nd  Destination Coord (YyyyXxxxh)  ;Xpos counted in halfwords
  3rd  Width+Height      (YsizXsizh)  ;Xsiz counted in halfwords
  ...  Data              (...)      <--- usually transferred via DMA
Transfers data from CPU to frame buffer. If the number of halfwords to be sent is odd, an extra halfword should be sent (packets consist of 32bit units). The transfer is affected by Mask setting.

GP0(C0h) - Copy Rectangle (VRAM to CPU)
  1st  Command           (Cc000000h) ;\
  2nd  Source Coord      (YyyyXxxxh) ; write to GP0 port (as usually)
  3rd  Width+Height      (YsizXsizh) ;/
  ...  Data              (...)       ;<--- read from GPUREAD port (or via DMA)
Transfers data from frame buffer to CPU. Wait for bit27 of the status register to be set before reading the image data. When the number of halfwords is odd, an extra halfword is read at the end (packets consist of 32bit units).

Masking and Rounding for FILL Command parameters
  Xpos=(Xpos AND 3F0h)                       ;range 0..3F0h, in steps of 10h
  Ypos=(Ypos AND 1FFh)                       ;range 0..1FFh
  Xsiz=((Xsiz AND 3FFh)+0Fh) AND (NOT 0Fh)   ;range 0..400h, in steps of 10h
  Ysiz=((Ysiz AND 1FFh))                     ;range 0..1FFh
Fill does NOT occur when Xsiz=0 or Ysiz=0 (unlike as for Copy commands). Xsiz=400h works only indirectly: Param=400h is handled as Xsiz=0, however, Param=3F1h..3FFh is rounded-up and handled as Xsiz=400h.

Masking for COPY Commands parameters
  Xpos=(Xpos AND 3FFh)                       ;range 0..3FFh
  Ypos=(Ypos AND 1FFh)                       ;range 0..1FFh
  Xsiz=((Xsiz-1) AND 3FFh)+1                 ;range 1..400h
  Ysiz=((Ysiz-1) AND 1FFh)+1                 ;range 1..200h
Parameters are just clipped to 10bit/9bit range, the only special case is that Size=0 is handled as Size=max.

Notes
The three COPY commands do automatically clear the Texture Cache (but not CLUT cache). The FILL command doesn't clear any caches.
The coordinates for the above VRAM transfer commands are absolute framebuffer addresses (not relative to Draw Offset, and not clipped to Draw Area).
Non-DMA transfers seem to be working at any time, but GPU-DMA Transfers seem to be working ONLY during V-Blank (outside of V-Blank, portions of the data appear to be skipped, and the following words arrive at wrong addresses), unknown if it's possible to change that by whatever configuration settings...? That problem appears ONLY for continous DMA aka VRAM transfers (linked-list DMA aka Ordering Table works even outside V-Blank).

Wrapping
If the Source/Dest starting points plus the width/height value exceed the 1024x512 pixel VRAM size, then the Copy/Fill operations wrap to the opposite memory edge (without any carry-out from X to Y, nor from Y to X).


GPU Other Commands

GP0(1Fh) - Interrupt Request (IRQ1)
  1st  Command           (Cc000000h)                    ;GPUSTAT.24
Requests IRQ1. Can be acknowledged via GP1(02h). This feature is rarely used.
Note: The command is used by Blaze'n'Blade, but the game doesn't have IRQ1 enabled, and the written value (1F801810h) looks more like an I/O address, rather than like a command, so not sure if it's done intentionally, or if it is just a bug.

GP0(03h) - Timing Control - New 208pin GPU only
  1st  Command           (Cc00000xh)
The lower 4bit affect the GPU rendering speed (00h/01h for 100%, downto 0Fh=25%) (probably related to GPU clock or VRAM access or VRAM refresh timings). The other 20bit seem to have no effect on VRAM write timings (they might be unused, or have other purposes like VRAM read timings or buswidth/cache control or whatever).
The command isn't used by any known games, so the existing games are always using the default speed (which seems to be 00h/01h, or at least close to those values).
  Still unknown details...
  - measure clock cycles and try to determine any relation to pixels/texels
  - scope test memory access signals
  - verify if default is 00h/01h
Old 160pin GPUs do not add GP0(03h) to the FIFO (and the command doesn't affect the GPU speed at all) (old GPUs are somewhat constantly running at about 60% of the new GPU speed).

GP0(00h) - NOP (?)
This command doesn't take up space in the FIFO (eg. even if a VRAM-to-VRAM transfer is still busy, one can send dozens of GP0(00h) commands, without the command FIFO becoming full. So, either the command is ignored (or, if it has a function, it is executed immediately, even while the transfer is busy).
...
GP0(00h) unknown, used with parameter = 08A16Ch... or rather 08FDBCh ... the written value seems to be a bios/ram memory address, anded with 00FFFFFFh... maybe a bios bug?
GP0(00h) seems to be often inserted between Texpage and Rectangle commands, maybe it acts as a NOP, which may be required between that commands, for timing reasons...?

GP0(04h..1Eh,E0h,E7h..EFh) - Mirrors of GP0(00h) - NOP (?)
Like GP0(00h), these commands don't take up space in the FIFO. So, maybe, they are same as GP0(00h), however, the Drawing Area/Offset commands GP0(E3h..E5h) don't take up FIFO space either, so not taking up FIFO space doesn't neccessarily mean that the command has no function.

GP0(81h..9Fh) - Mirror of GP0(80h) - Copy Rectangle (VRAM to VRAM)
GP0(A1h..BFh) - Mirror of GP0(A0h) - Copy Rectangle (CPU to VRAM)
GP0(C1h..DFh) - Mirror of GP0(C0h) - Copy Rectangle (VRAM to CPU)
Mirrors.


GPU Display Control Commands (GP1)

GP1 Display Control Commands are sent by writing the 8bit Command number (MSBs), and 24bit parameter (LSBs) to Port 1F801814h. Unlike GP0 commands, GP1 commands are passed directly to the GPU (ie. they can be sent even when the FIFO is full).

GP1(00h) - Reset GPU
  0-23  Not used (zero)
Resets the GPU to the following values:
  GP1(01h)      ;clear fifo
  GP1(02h)      ;ack irq (0)
  GP1(03h)      ;display off (1)
  GP1(04h)      ;dma off (0)
  GP1(05h)      ;display address (0)
  GP1(06h)      ;display x1,x2 (x1=200h, x2=200h+256*10)
  GP1(07h)      ;display y1,y2 (y1=010h, y2=010h+240)
  GP1(08h)      ;display mode 320x200 NTSC (0)
  GP0(E1h..E6h) ;rendering attributes (0)
  ... XXX probably also GP0(01h) clear cache?
Accordingly, GPUSTAT becomes 14802000h. The x1,y1 values are too small, ie. the upper-left edge isn't visible. Note that GP0(03h) and GP1(09h) are NOT affected by the reset command.

GP1(01h) - Reset Command Buffer
  0-23  Not used (zero)
Clears the command FIFO, and aborts the current rendering command (eg. this may end up with an incompletely drawn triangle).

GP1(02h) - Acknowledge GPU Interrupt (IRQ1)
  0-23  Not used (zero)                                        ;GPUSTAT.24
Resets the IRQ flag in GPUSTAT.24. The flag can be set via GP0(1Fh).

GP1(03h) - Display Enable
  0     Display On/Off   (0=On, 1=Off, show black pixels)      ;GPUSTAT.23
  1-23  Not used (zero)
The "Off" settings displays a black picture (and still sends /SYNC signals to the television set). (Unknown if it still generates vblank IRQs though?)
Despite of displaying only black pixels, the GPU does still fetch pixels from VRAM (ie. the command won't speedup rendering and VRAM transfers; to do that, one can use GP1(07h) to increase the Vblank time).

GP1(04h) - DMA Direction / Data Request
  0-1  DMA Direction / Data Request mode (0..3)                ;GPUSTAT.29-30
  2-23 Not used (zero)
The selected mode affects DMA data requests, and also affects GPUSTAT.25. The four modes are:
  0 = Off (bit25 is always 0=No DRQ)
  1 = To GPU, drq when FIFO at least galf empty
  2 = To GPU, drq when FIFO empty                  ;Same as GPUSTAT.28
  3 = From GPU                                     ;Same as GPUSTAT.27
Mode=2 is most common for DMA. Mode=1 may be most useful when manually polling GPUSTAT.25 (because the other modes can be polled from GPUSTAT.27-28 anyways).
Manually sending/reading data (without DMA) is ALWAYS possible, regardless of the GP1(04h) setting. That is, without DMA, GP1(04h) does merely affect what can be read from GPUSTAT.25.

Display start/end
Specifies where the display area is positioned on the screen, and how much data gets sent to the screen. The screen sizes of the display area are valid only if the horizontal/vertical start/end values are default. By changing these you can get bigger/smaller display screens. On most TV's there is some black around the edge, which can be utilised by setting the start of the screen earlier and the end later. The size of the pixels is NOT changed with these settings, the GPU simply sends more data to the screen. Some monitors/TVs have a smaller display area and the extended size might not be visible on those sets. "(Mine is capable of about 330 pixels horizontal, and 272 vertical in 320*240 mode)"

GP1(05h) - Start of Display area (in VRAM)
  0-9   X (0-1023)    (halfword address in VRAM)  (relative to begin of VRAM)
  10-18 Y (0-511)     (scanline number in VRAM)   (relative to begin of VRAM)
  19-23 Not used (zero)
Upper/left Display source address in VRAM. The size and target position on screen is set via Display Range registers; target=X1,Y2; size=(X2-X1/cycles_per_pix), (Y2-Y1).
This register should be updated after rendering a new frame. That's needed when using two framebuffers, and, for a single frame buffers it's also recommended to to rewrite the same value each frame (the I/O map and VRAM viewer in no$psx debug version are using GP1(05h) writes to sense the begin of new frames).

GP1(06h) - Horizontal Display range (on Screen)
  0-11   X1 (260h+0)       ;12bit       ;\counted in 53.222400MHz units,
  12-23  X2 (260h+320*8)   ;12bit       ;/relative to HSYNC
Specifies the horizontal range within which the display area is displayed. For resolutions other than 320 pixels it may be necessary to fine adjust the value to obtain an exact match (eg. X2=X1+pixels*cycles_per_pix).
The number of displayed pixels per line is "(((X2-X1)/cycles_per_pix)+2) AND NOT 3" (ie. the hardware is rounding the width up/down to a multiple of 4 pixels).
Most games are using a width equal to the horizontal resolution (ie. 256, 320, 368, 512, 640 pixels). A few games are using slightly smaller widths (probably due to programming bugs). Pandemonium 2 is using a bigger "overscan" width (ensuring an intact picture without borders even on mis-calibrated TV sets).
The 260h value is the first visible pixel on normal TV Sets, this value is used by MOST NTSC games, and SOME PAL games (see below notes on Mis-Centered PAL games).

GP1(07h) - Vertical Display range (on Screen)
  0-9   Y1 (NTSC=88h-(224/2), (PAL=A3h-(264/2))  ;\scanline numbers on screen,
  10-19 Y2 (NTSC=88h+(224/2), (PAL=A3h+(264/2))  ;/relative to VSYNC
  20-23 Not used (zero)
Specifies the vertical range within which the display area is displayed. The number of lines is Y2-Y1 (unlike as for the width, there's no rounding applied to the height). If Y2 is bigger than 106h (NTSC) or 139h (PAL), then the hardware stops to generate vblank interrupts (IRQ0). And the height must be bigger than 0, ie. Y2>Y1.
The 88h/A3h values are the middle-scanlines on normal TV Sets, these values are used by MOST NTSC games, and SOME PAL games (see below notes on Mis-Centered PAL games).
The 224/264 values are for fullscreen pictures. Many NTSC games display 240 lines (overscan with hidden lines). Many PAL games display only 256 lines (underscan with black borders).

GP1(08h) - Display mode
  0-1   Horizontal Resolution 1     (0=256, 1=320, 2=512, 3=640) ;GPUSTAT.17-18
  2     Vertical Resolution         (0=240, 1=480, when Bit5=1)  ;GPUSTAT.19
  3     Video Mode                  (0=NTSC/60Hz, 1=PAL/50Hz)    ;GPUSTAT.20
  4     Display Area Color Depth    (0=15bit, 1=24bit)           ;GPUSTAT.21
  5     Vertical Interlace          (0=Off, 1=On)                ;GPUSTAT.22
  6     Horizontal Resolution 2     (0=256/320/512/640, 1=368)   ;GPUSTAT.16
  7     "Reverseflag"               (0=Normal, 1=Distorted)      ;GPUSTAT.14
  8-23  Not used (zero)
Note: Interlace must be enabled to see all lines in 480-lines mode (interlace is causing ugly flickering, so a non-interlaced low resolution image is typically having better quality than a high resolution interlaced image, a pretty bad example are the intro screens shown by the BIOS). The Display Area Color Depth does NOT affect the Drawing Area (the Drawing Area is <always> 15bit).
When the "Reverseflag" is set, the display scrolls down 2 lines or so, and colored regions are getting somehow hatched/distorted, but black and white regions are still looking okay. Don't know what that's good for? Probably relates to PAL/NTSC-Color Clock vs PSX-Dot Clock mismatches: Bit7=0 causes Flimmering errors (errors at different locations in each frame), and Bit7=1 causes Static errors (errors at same locations in all frames)?

GP1(10h) - Get GPU Info
GP1(11h..1Fh) - Mirrors of GP1(10h), Get GPU Info
After sending the command, the result can be immediately read from GPUREAD register (there's no NOP or other delay required) (namely GPUSTAT.Bit27 is used only for VRAM-Reads, but NOT for GPU-Info-Reads, so do not try to wait for that flag).
  0-23  Select Information which is to be retrieved (via following GPUREAD)
On Old 180pin GPUs, following values can be selected:
  00h-01h = Returns Nothing (old value in GPUREAD remains unchanged)
  02h     = Read Texture Window setting  ;GP0(E2h) ;20bit/MSBs=Nothing
  03h     = Read Draw area top left      ;GP0(E3h) ;19bit/MSBs=Nothing
  04h     = Read Draw area bottom right  ;GP0(E4h) ;19bit/MSBs=Nothing
  05h     = Read Draw offset             ;GP0(E5h) ;22bit
  06h-07h = Returns Nothing (old value in GPUREAD remains unchanged)
  08h-FFFFFFh = Mirrors of 00h..07h
On New 208pin GPUs, following values can be selected:
  00h-01h = Returns Nothing (old value in GPUREAD remains unchanged)
  02h     = Read Texture Window setting  ;GP0(E2h) ;20bit/MSBs=Nothing
  03h     = Read Draw area top left      ;GP0(E3h) ;20bit/MSBs=Nothing
  04h     = Read Draw area bottom right  ;GP0(E4h) ;20bit/MSBs=Nothing
  05h     = Read Draw offset             ;GP0(E5h) ;22bit
  06h     = Returns Nothing (old value in GPUREAD remains unchanged)
  07h     = Read GPU Type (usually 2)    ;see "GPU Versions" chapter
  08h     = Unknown (Returns 00000000h) (lightgun on some GPUs?)
  09h-0Fh = Returns Nothing (old value in GPUREAD remains unchanged)
  10h-FFFFFFh = Mirrors of 00h..0Fh
The selected data is latched in GPUREAD, the same/latched value can be read multiple times, but, the latch isn't automatically updated when changing GP0 registers.

GP1(09h) - New VRAM Size (new 208pin GPU only)
  0     VRAM Size (0=1MByte/normal, 1=2MByte/upper half is open bus)
  1-23  Unknown/unused
Allows to activate 2MByte VRAM mode (the PSX has only 1MByte VRAM, so the upper MByte will be open bus).


In 1Mbyte mode, VRAM Y=200h..3FFh are mirrored to Y=000h..1FFh. For Texture/CLUT, bit9 simply cannot be set in 1MByte mode (Texture Cache and CLUT Cache hits can occur when mixing normal with mirrored addresses). For Drawing Area Y1/Y2, bit9 can be set on New GPUs even when in 1MByte mode (that can mirror at Y=200h..3FFh to 0..1FFh, unlike as on Old GPUs which do never draw pixels at Y=200h..3FFh).
In 2Mbyte mode, writes to VRAM Y=200h..3FFh are cast to nowhere, and reads return open bus values (which tend to be 7FFFh or FFFFh).
Most released games do contain program code for changing GP1(09h), but do never execute it.
GP1(09h) seems to be supported only on New GPUs. Old GPUs don't support it all, and there seem to be some Special/Prototype GPUs that use GP1(20h) instead of GP1(09h).

GP1(20h) - Special/Prototype VRAM Size
  0-23  VRAM Size? (501h=Normal, 504h=2MByte Mode, or so?)
Seems to be a used only on whatever arcade/prototype GPUs. New GPUs are using GP1(09h) instead of GP1(20h).

GP1(0Bh) - Unknown/Internal?
  0-10  Unknown (GPU crashes after a while when set to 274h..7FFh)
  11-23 Unknown (seems to have no effect)
The register doesn't seem to be used by any games.

GP1(0Ah,0Ch..0Fh,21h..3Fh) - N/A
Not used?

GP1(40h..FFh) - N/A (Mirrors)
Mirrors of GP1(00h..3Fh).

Mis-Centered PAL Games (wrong GP1(06h)/GP1(07h) settings)
NTSC games are typically well centered (using X1=260h, and Y1/Y2=88h+/-N).
PAL games should be centered as X1=260h, and Y1/Y2=A3h+/-N) - these values would be looking well on a Philips Philetta TV Set, and do also match up with other common picture positions (eg. as used by Nintendo's SNES console).
However, most PAL games are using completely different "random" centering values (maybe caused by different developers trying to match the centering to the different TV Sets) (although it looks more as if the PAL developers just went amok: Many PAL games are even using different centerings for their Intro, Movie, and actual Game sequences).
In result, most PAL games are looking like crap when playing them on a real PSX. For PSX emulators it may be recommended to ignore the GP1(06h)/GP1(07h) centering, and instead, apply auto-centering to PAL games.
For PAL game developers, it may be recommended to add a screen centering option (as found in Tomb Raider 3, for example). Unknown if this is really required... or if X1=260h, and Y1/Y2=A3h+/-N would work fine on most or all PAL TV Sets?


GPU Status Register

1F801814h - GPUSTAT - GPU Status Register (R)
  0-3   Texture page X.bit6-9 (N*64)                              ;GP0(E1h).0-3
  4     Texture page Y.bit8   (N*256) (ie. 0 or 256)              ;GP0(E1h).4
  5-6   Semi Transparency     (0=B/2+F/2, 1=B+F, 2=B-F, 3=B+F/4)  ;GP0(E1h).5-6
  7-8   Texture page colors   (0=4bit, 1=8bit, 2=15bit, 3=Reserved)GP0(E1h).7-8
  9     Dither 24bit to 15bit (0=Off/strip LSBs, 1=Dither Enabled);GP0(E1h).9
  10    Interlace Drawing     (0=All Lines, 1=Inactive Lines)     ;GP0(E1h).10
  11    Set Mask-bit when drawing pixels (0=No, 1=Yes/Mask)       ;GP0(E6h).0
  12    Draw Pixels           (0=Always, 1=Not to Masked areas)   ;GP0(E6h).1
  13    Interlace Field       (or, always 1 when GP1(08h).5=0)
  14    "Reverseflag"         (0=Normal, 1=Distorted)             ;GP1(08h).7
  15    Texture page Y.bit9   (0=Normal, 1=Upper Mbyte, Open Bus) ;GP0(E1h).11
  16    Horizontal Resolution 2     (0=256/320/512/640, 1=368)    ;GP1(08h).6
  17-18 Horizontal Resolution 1     (0=256, 1=320, 2=512, 3=640)  ;GP1(08h).0-1
  19    Vertical Resolution         (0=240, 1=480, when Bit22=1)  ;GP1(08h).2
  20    Video Mode                  (0=NTSC/60Hz, 1=PAL/50Hz)     ;GP1(08h).3
  21    Display Area Color Depth    (0=15bit, 1=24bit)            ;GP1(08h).4
  22    Vertical Interlace          (0=Off, 1=On)                 ;GP1(08h).5
  23    Display Enable              (0=Enabled, 1=Disabled)       ;GP1(03h).0
  24    Interrupt Request (IRQ1)    (0=Off, 1=IRQ)       ;GP0(1Fh)/GP1(02h)
  25    DMA / Data Request          (0=No DRQ, 1=DRQ)
          Meaning of the DRQ bit depends on GP1(04h) DMA Direction:
          When GP1(04h)=0 ---> Off (bit25 is always 0=No DRQ)
          When GP1(04h)=1 ---> To GPU, drq when FIFO at least galf empty
          When GP1(04h)=2 ---> To GPU, drq when FIFO empty ;Same as GPUSTAT.28
          When GP1(04h)=3 ---> From GPU                    ;Same as GPUSTAT.27
  26    Ready to receive Cmd Word   (0=No, 1=Ready)  ;GP0(...) ;via GP0
  27    Read FIFO data available    (0=No, 1=Yes)    ;GP0(C0h) ;via GPUREAD
  28    Write FIFO empty            (0=No, 1=Empty)  ;GP0(...) ;via GP0
  29-30 DMA Direction (0=Off, 1=?, 2=CPUtoGP0, 3=GPUREADtoCPU)    ;GP1(04h).0-1
  31    Drawing even/odd lines in interlace mode (0=Even or Vblank, 1=Odd)
In 480-lines mode, bit31 changes per frame. And in 240-lines mode, the bit changes per scanline. The bit is always zero during Vblank (vertical retrace and upper/lower screen border).

Note
Further GPU status information can be retrieved via GP1(10h) and GP0(C0h).

Ready Bits
  Bit28: Write FIFO empty
  Bit27: Data available for reading
  Bit26: Ready to receive Cmd Word
  Bit25: DRQ (when GP1(04h)=1 --> Write FIFO not more than half full)

Bit28: Normally, this bit gets cleared when the command execution is busy (ie. once when the command and all of its parameters are received), however, for Polygon and Line Rendering commands, the bit gets cleared immediately after receiving the command word (ie. before receiving the vertex parameters). The bit is used as DMA request in DMA Mode 2, accordingly, the DMA would probably hang if the Polygon/Line parameters are transferred in a separate DMA block (ie. the DMA probably starts ONLY on command words).
  XXX basically: Bit28 seems to be just "FIFO Empty"
      (and the above corner cases rely on which commands are removing
      data from fifo "befure/during/after" command execution)
Bit27: Gets set after sending GP0(C0h) and its parameters, and stays set until all data words are received; used as DMA request in DMA Mode 3.
Bit26: Gets set when the GPU wants to receive a command. If the bit is cleared, then the GPU does either want to receive data, or it is busy with a command execution (and doesn't want to receive anything).
Bit25: This is the DMA Request bit, however, the bit is also useful for non-DMA transfers, especially in the FIFO State mode.


GPU Versions

Summary of GPU Differences
  Differences...                Old 160pin GPU          New 208pin GPU
  GPU Chip                      CXD8514Q                CXD8561Q/BQ/CQ/CXD9500Q
  Mainboard                     EARLY-PU-8 and below    LATE-PU-8 and up
  Memory Type                   Dual-ported VRAM        Normal DRAM
  Write Buffer                  None (1 halfword)       Yes (18 halfwords)
  Write Speed                   Slow (with pauses)      Fast (continous)
  GPUSTAT.13 when interlace=off Always 0                Always 1
  GPUSTAT.14                    Always 0                Reverseflag
  GPUSTAT.15                    Always 0                Texture page Y.bit9
  GP1(10h:index3..4)            19bit (1MB VRAM)        20bit (2MB VRAM)
  GP1(10h:index7)               N/A                     00000002h version
  GP1(10h:index8)               Mirror of index0        00000000h zero
  GP1(10h:index9..F)            Mirror of index1..7     N/A
  GP1(20h)                      Whatever? used for detecting old gpu
  GP0(E1h).bit12/13             without x/y-flip        with x/y-flip
  GP0(03h)                      N/A not stored in fifo  Timing control
  Shaded Textures               ((color/8)*texel)/2     (color*texel)/16
  GP0(02h) FillVram             xpos.bit0-3=0Fh=bugged  xpos.bit0-3=ignored
  dma-to-vram: doesn't work with blksiz>10h (new gpu works with blksiz=8C0h!)
  dma-to-vram: MAYBE also needs extra software-handshake to confirm DMA done?
   320*224 pix = 11800h pix = 8C00h words
  GP0(80h) VramToVram           works                   Freeze on large moves?

Shaded Textures
The Old GPU crops 8:8:8 bit gouraud shading color to 5:5:5 bit before multiplying it with the texture color, resulting in rather poor graphics. For example, the snow scence in the first level of Tomb Raider I looks a lot smoother on New GPUs.
The cropped colors are looking a bit as if dithering would be disabled (although, technically dithering works fine, but due to the crippled color input, it's always using the same dither pattern per 8 intensities, instead of using 8 different dither patterns).

Memory/Rendering Timings
The Old GPU uses two Dual-ported VRAM chips (each with two 16bit databusses, one for CPU/DMA/rendering access, and one for output to the video DAC). The New GPU uses s normal DRAM chip (with single 32bit databus).
The exact timing differences are unknown, but the different memory types should result in quite different timings:
The Old GPU might perform better on non-32bit aligned accesses, and on memory accesses performed simultaneously with DAC output.
On the other hand, the New GPU's DRAM seems to be faster in some cases (for example, during Vblank, it's fast enough to perform DMA's with blksiz>10h, which exceeds the GPU's FIFO size, and causes lost data on Old GPUs).

X/Y-Flip and 2MB Video RAM
The X/Y-flipping feature may be used by arcade games (provided that the arcade board is fitted with New GPUs). The flipping feature does also work on retail consoles with New GPUs, but PSX games should never use that feature (for maintaining compatiblity with older PSX consoles).
2Mbyte Video RAM is used on some arcade boards. Whilst PSX retail consoles are always containing only 1MByte RAM, so the feature cannot be used even if the console contains a New GPU. There's one special case: Some PSone consoles are actually fitted with 2MB chips (maybe because smaller chips haven't been in production anymore), but the chips are wired so that only half of the memory is accessible (the extra memory could be theoretically unlocked with some minimal hardware modification).

GPU Detection (and optional 2MByte VRAM Mode)
Below is slightly customized GPU Detection function taken from Perfect Assassin (the index7 latching works ONLY on New GPUs, whilst old GPUs would leave the latched value unchanged; as a workaround, the index4 latching is used to ensure that the latch won't contain 000002h on old GPUs, assuming that index4 is never set to 000002h).
  [1F801814h]=10000004h       ;GP1(10h).index4 (latch draw area bottom right)
  [1F801814h]=10000007h       ;GP1(10h).index7 (latch GPU version, if any)
  if ([1F801810h] AND 00FFFFFFh)=00000002h then goto @@gpu_v2
  [1F801810h]=([1F801814h] AND 3FFFh) OR E1001000h ;change GPUSTAT via GP0(E1h)
  dummy=[1F801810h]           ;dummy read (unknown purpose)
  if ([1F801814h] AND 00001000h) then goto @@gpu_v1 else goto @@gpu_v0
 ;---
 @@gpu_v0:  ;Old 160pin GPU (EARLY-PU-8)
  return 0
 ;---
 @@gpu_v1:  ;unknown GPU type, maybe some custom arcade/prototype version ?
  if want_2mbyte_vram then [1F801814h]=20000504h  ;GP1(20h)
  return 1
 ;---
 @@gpu_v2:  ;New 208pin GPU (LATE-PU-8 and up)
  if want_2mbyte_vram then [1F801814h]=09000001h  ;GP1(09h)
  return 2

GP0(02h) FillVram
The FillVram command does normally ignore the lower 4bit of the x-coordinate (and software should always set those bits to zero). However, if the 4bits are all set, then the Old GPU does write each 2nd pixel to wrong memory address. For example, a 32x4 pixel fill produces following results for x=0..1Fh:
  0h              10h             20h             30h             40h
  |               |               |               |               |
  ################################                                 ;\x=00h..0Eh
  ################################                                 ; and, x=0Fh
  ################################                                 ; on NEW GPU
  ################################                                 ;/
   # # # # # # # ################## # # # # # # #                  ;\
   # # # # # # # ################## # # # # # # #                  ; x=0Fh
   # # # # # # # ################## # # # # # # #                  ; on OLD GPU
   # # # # # # # ################## # # # # # # #                  ;/
                  ################################                 ;\x=10h..1Eh
                  ################################                 ; and, x=1Fh
                  ################################                 ; on NEW GPU
                  ################################                 ;/
                   # # # # # # # ################## # # # # # # #  ;\
                   # # # # # # # ################## # # # # # # #  ; x=1Fh
                   # # # # # # # ################## # # # # # # #  ; on OLD GPU
                   # # # # # # # ################## # # # # # # #  ;/

Arcade GPUs
Some arcade boards are using normal retail GPUs, however, there are also two special non-retail 208pin GPUs which seem to be solely used on arcade boards:
  IC21  - 208pin - "SONY CXD8538Q"   ;seen on GP-11 (namco System 11) boards
  IC103 - 208pin - "SONY CXD8654Q"   ;seen on GP-15 (namco System 12) boards
The exact differences to retail GPUs are unknown. One of the special GPUs is said to use entirely different command numbers for rendering commands (maybe some old prototype variant, or maybe some protection against cloning arcade boards with retail chips).


GPU Depth Ordering

Absent Depth Buffer
The PlayStation's GPU stores only RGB colors in the framebuffer (ie. unlike modern 3D processors, it's NOT buffering Depth values; leaving apart the Mask bit, which could be considered as a tiny 1bit "Depth" or "Priority" value). In fact, the GPU supports only X,Y coordinates, and it's totally unaware of Z coordinates. So, when rendering a polygon, the hardware CANNOT determine which of the new pixels are in front/behind of the old pixels in the buffer.

Simple Ordering
The rendering simply takes place in the ordering as the data is sent to the GPU (ie. the most distant objects should be sent first). For 2D graphics, it's fairly easy follow that order (eg. even multi-layer 2D graphics can be using DMA2-continous mode).

Depth Ordering Table (OT)
For 3D graphics, the ordering of the polygons may change more or less randomly (eg. when rotating/moving the camera). To solve that problem, the whole rendering data is usually first stored in a Depth Ordering Table (OT) in Main RAM, and, once when all polygons have been stored in the OT, the OT is sent to the GPU via "DMA2-linked-list" mode.

Initializing an empty OT (via DMA6)
DMA channel 6 can be used to set up an empty linked list, in which each entry points to the previous:
  DPCR    - enable bits                                 ;Example=x8xxxxxxh
  D6_MADR - pointer to the LAST table entry             ;Example=8012300Ch
  D6_BCR  - number of list entries                      ;Example=00000004h
  D6_CHCR - control bits (should be 11000002h)          ;Example=11000002h
Each entry has a size of 00h words (upper 8bit), and a pointer to the previous entry (lower 24bit). With the above Example values, the generated table would look like so:
  [80123000h]=00FFFFFFh  ;1st entry, points to end code (xxFFFFFFh)
  [80123004h]=00123000h  ;2nd entry, points to 1st entry
  [80123008h]=00123004h  ;3rd entry, points to 2nd entry
  [8012300Ch]=00123008h  ;last entry, points to 3rd entry (table entrypoint)

Inserting Entries (Passing GTE data to the OT) (by software)
The GTE commands AVSZ3 and AVSZ4 can be used to calculate the Average Z coordinates of a polygon (based on its three or four Z coordinates). The result is returned as a 16bit Z value in GTE register OTZ, the commands do also allow to divide the result, to make it less than 16bit (the full 16bit would require an OT of 256KBytes - for the EMPTY table, which would be a waste of memory, and which would slowdown the DMA2/DMA6 operations) (on the other hand, a smaller table means less depth resolution).
  [PacketAddr+0]      = [80123000h+OTZ*4] + (N SHL 24)   <--internal link chain
  [PacketAddr+4..N*4] = GP0 Command(s) and Parameters    <--data (send to GP0)
  [80123000h+OTZ*4]   = PacketAddr AND FFFFFFh           <--internal link chain
If there's been already an entry (at the same OTZ index), then the new polygon will be processed first (ie. it will appear "behind" of the old entry).
Not sure if the packet size must be limited to max N=16 words (ie. as for the DMA2-continous block size) (due to GP0 FIFO size limits)?

Sending the OT to the CPU (via DMA2-linked-list mode)
  1 - Wait until GPU is ready to receive commands ;GPUSTAT.28
  2 - Enable DMA channel 2                  ;DPCR
  3 - Set GPU to DMA cpu->gpu mode          ;[GP1]=04000002h aka GP1(04h)
  3 - Set D2_MADR to the start of the list  ;(LAST Entry) ;Example=80123010h
  4 - Set D2_BCR to zero                    ;(length unused, end at END-CODE)
  5 - Set D2_CHCR to link mode, mem->GPU and dma enable   ;=01000401h


GPU Video Memory (VRAM)

Framebuffer
The framebuffer contains the image that is to be output to the Television Set. The GPU supports 10 resolutions, with 16bit or 24bit per pixel.
  Resolution  16bit      24bit      |  Resolution  16bit      24bit
  256x240     120Kbytes  180Kbytes  |  256x480     240Kbytes  360Kbytes
  320x240     150Kbytes  225Kbytes  |  320x480     300Kbytes  450Kbytes
  368x240     xx0Kbytes  xx0Kbytes  |  368x480     xx0Kbytes  xx0Kbytes
  512x240     240Kbytes  360Kbytes  |  512x480     480Kbytes  720Kbytes
  640x240     300Kbytes  450Kbytes  |  640x480     600Kbytes  900Kbytes
Note: In most cases, you'll need TWO framebuffers (one being displayed, and used as rendering target) (unless you are able to draw the whole new image during vblank, or unless when using single-layer 2D graphics). So, resolutions that occupy more than 512K would exceed the available 1MB VRAM when using 2 buffers. Also, high resolutions mean higher rendering load, and less texture memory.
  15bit Direct Display (default) (works with polygons, lines, rectangles)
  0-4   Red       (0..31)
  5-9   Green     (0..31)
  10-14 Blue      (0..31)
  15    Mask flag (0=Normal, 1=Do not allow to overwrite this pixel)
  24bit Direct Display (works ONLY with direct vram transfers)
  0-7    Red      (0..255)
  8-15   Green    (0..255)
  16-23  Blue     (0..255)
Note: The 24bit pixels occupy 3 bytes (not 4 bytes with unused MSBs), so each 6 bytes contain two 24bit pixels. The 24bit display mode works only with VRAM transfer commands like GP0(A0h); the rendering commands GP0(20h..7Fh) cannot output 24bit data. Ie. 24bit mode is used mostly for MDEC videos (and some 2D games like Heart of Darkness).

Texture Bitmaps
A texture is an image put on a polygon or sprite. The data of a texture can be stored in 3 different modes:
  16bit Texture (Direct Color)             ;(One 256x256 page = 128Kbytes)
  0-4   Red       (0..31)         ;\Color 0000h        = Fully-Transparent
  5-9   Green     (0..31)         ; Color 0001h..7FFFh = Non-Transparent
  10-14 Blue      (0..31)         ; Color 8000h..FFFFh = Semi-Transparent (*)
  15    Semi Transparency Flag    ;/(*) or Non-Transparent for opaque commands
  8bit Texture (256 Color Palette)         ;(One 256x256 page = 64Kbytes)
  0-7   Palette index for 1st pixel (left)
  8-15  Palette index for 2nd pixel (right)
  4bit Texture (16 Color Palette)          ;(One 256x256 page = 32Kbytes)
  0-3   Palette index for 1st pixel (left)
  4-7   Palette index for 2nd pixel (middle/left)
  8-11  Palette index for 3rd pixel (middle/right)
  12-15 Palette index for 4th pixel (right)
A Texture Page is a 256x256 texel region in VRAM (the Polygon rendering commands are using Texcoords with 8bit X,Y coordinates, so polygons cannot use textures bigger than 256x256) (the Rectangle rendering commands with width/height parameters could theoretically use larger textures, but the hardware clips their texture coordinates to 8bit, too).
The GP0(E2h) Texture Window (aka Texture Repeat) command can be used to reduce the texture size to less than 256x256 texels.
The Texture Pages can be located in the frame buffer on X multiples of 64 halfwords and Y multiples of 256 lines.

Texture Palettes - CLUT (Color Lookup Table)
The clut is a the table where the colors are stored for the image data in the CLUT modes. The pixels of those images are used as indexes to this table. The clut is arranged in the frame buffer as a 256x1 image for the 8bit clut mode, and a 16x1 image for the 4bit clut mode.
  0-4   Red       (0..31)         ;\Color 0000h        = Fully-Transparent
  5-9   Green     (0..31)         ; Color 0001h..7FFFh = Non-Transparent
  10-14 Blue      (0..31)         ; Color 8000h..FFFFh = Semi-Transparent (*)
  15    Semi Transparency Flag    ;/(*) or Non-Transparent for opaque commands
The clut data can be arranged in the frame buffer at X multiples of 16 (X=0,16,32,48,etc) and anywhere in the Y range of 0-511.

Texture Color Black Limitations
On the PSX, texture color 0000h is fully-transparent, that means textures cannot contain Black pixels. However, in some cases, Color 8000h (Black with semi-transparent flag) can be used, depending on the rendering command:
  opaque command, eg. GP0(24h)      --> 8000h = Non-Transparent Black
  semi-transp command, eg. GP0(26h) --> 8000h = Semi-Transparent Black
So, with semi-transparent rendering commands, it isn't possible to use Non-Transparent Black pixels in textures, the only workaround is to use colors like 0001h (dark red) or 0400h (dark blue). However, due to the PSX's rather steeply increasing intensity ramp, these colors are clearly visible to be brighter than black.

RGB Intensity Notes
The Playstations RGB values aren't linear to normal RGB values (as used on PCs). The min/max values are of course the same, but the medium values differ:
  Intensity        PC      PSX
  Minimum          0       0
  Medium (circa)   16      8
  Maximum          31      31
Ie. on the PSX, the intensity increases steeply from 0 to 15, and less steeply from 16 to 31.


GPU (MISC)

GP0(20h..7Fh) - Render Command Bits
  0-23  Color for (first) Vertex                   (Not for Raw-Texture)
  24    Texture Mode      (0=Blended, 1=Raw)       (Textured-Polygon/Rect only)
  25    Semi Transparency (0=Off, 1=On)            (All Render Types)
  26    Texture Mapping   (0=Off, 1=On)            (Polygon/Rectangle only)
  27-28 Rect Size   (0=Var, 1=1x1, 2=8x8, 3=16x16) (Rectangle only)
  27    Num Vertices      (0=Triple, 1=Quad)       (Polygon only)
  27    Num Lines         (0=Single, 1=Poly)       (Line only)
  28    Shading           (0=Flat, 1=Gouroud)      (Polygon/Line only)
  29-31 Primitive Type    (1=Polygon, 2=Line, 3=Rectangle)

Perspective (in-)correct Rendering
The PSX doesn't support perspective correct rendering: Assume a polygon to be rotated so that it's right half becomes more distant to the camera, and it's left half becomes closer. Due to the GTE's perspective division, the right half should appear smaller than the left half.
The GPU supports only linear interpolations for rendering - that is correct concerning the X and Y screen coordinates (which are still linear to each other, even after perspective division, since both are divided by the same value).
However, texture coordinates (and Gouraud shaded colors) are NOT linear to the screen coordinates, and so, the linear interpolated PSX graphics are often looking rather distorted, that especially for textures that contain straight lines. For color shading the problem is less obvious (since shading is kinda blurry anyways).

Perspective correct Rendering
For perspective correct rendering, the polygon's Z-coordinates would be needed to be passed from the GTE to the GPU, and, the GPU would then need to use that Z-coordinates to "undo" the perspective division for each pixel (that'd require some additional memory, and especially a powerful division unit, which isn't implemented in the hardware).
As a workaround, you can try to reduce the size of your polygons (the interpolation errors increase in the center region of larger polygons). Reducing the size would be only required for polygons that occupy a larger screen region (which may vary depending on the distance to the camera).
Ie. you may check the size AFTER perspective division, if it's too large, then break it into smaller parts (using the original coordinates, NOT the screen coordinates), and then pass the fragments to the GTE another time.
Again, perspective correction would be relevant only for certain textures (not for randomly dithered textures like sand, water, fire, grass, and not for untextured polygons, and of course not for 2D graphics, so you may exclude those from size reduction).

Perspective correct rendering examples
  PSX (triangles)      Better (real quad)   Best (perspective)   Unrotated
             _.                   _.                   _.
         _.-' |               _.-' |               _.-' |
     _.-:     |           _.-:     |           _.-'     |
  .-'   |     |        .-'   |     |        .-' |       |         ____ ____
  |     |     |        |     |     |        |   |       |        |    |    |
  |  _.-:-._  |        |     |     |        |   |       |        |    |    |
  :-'   |   '-:        :-----+-----:        :---+-------:        :----+----:
  |     |     |        |     |     |        |   |       |        |    |    |
  |     |     |        |     |     |        |   |       |        |____|____|
  '-._  |     |        '-._  |     |        '-._|       |
      '-:_    |            '-:_    |            '-._    |
          '-._|                '-._|                '-._|

24bit RGB to 15bit RGB Dithering (enabled in Texpage attribute)
For dithering, VRAM is broken to 4x4 pixel blocks, depending on the location in that 4x4 pixel region, the corresponding dither offset is added to the 8bit R/G/B values, the result is saturated to +00h..+FFh, and then divided by 8, resulting in the final 5bit R/G/B values.
  -4  +0  -3  +1   ;\dither offsets for first two scanlines
  +2  -2  +3  -1   ;/
  -3  +1  -4  +0   ;\dither offsets for next two scanlines
  +3  -1  +2  -2   ;/(same as above, but shifted two pixels horizontally)
POLYGONs (triangles/quads) are dithered ONLY if they do use gouraud shading or texture blending.
LINEs are dithered (no matter if they are mono or do use gouraud shading).
RECTs are NOT dithered (no matter if they do use texture blending).

Shading information
"Texture RGB values control the brightness of the individual colors ($00-$7f). A value of $80 in a color will take the former value as data." (What...? probably means the "double brightness" effect... or does it want to tell that ALL colors of 80h..FFh have only single brightness.. rather than reaching double brightness at FFh...?)

Shading
The GPU has a shading function, which will scale the color of a primitive to a specified brightness. There are 2 shading modes: Flat shading, and gouraud shading. Flat shading is the mode in which one brightness value is specified for the entire primitive. In Gouraud shading mode, a different brightness value can be given for each vertex of a primitive, and the brightness between these points is automatically interpolated.

Semi Transparency
When semi transparency is set for a pixel, the GPU first reads the pixel it wants to write to, and then calculates the color it will write from the 2 pixels according to the semitransparency mode selected. Processing speed is lower in this mode because additional reading and calculating are necessary. There are 4 semitransparency modes in the GPU.
  B=Back  (the old pixel read from the image in the frame buffer)
  F=Front (the new halftransparent pixel)
    0.5 x B + 0.5 x F    ;aka B/2+F/2
    1.0 x B + 1.0 x F    ;aka B+F
    1.0 x B - 1.0 x F    ;aka B-F
    1.0 x B +0.25 x F    ;aka B+F/4


GPU FIFO

The GPU uses a 16-word (64-byte) write FIFO for sending commands and parameters (and VRAM data) from CPU to GPU.

FIFO Overrun
Internally, the FIFO is using 5bit counters for computing the FIFO size:
  fifo_rd_index = (rd_ptr) AND 0Fh                                ;\4bit range
  fifo_wr_index = (wr_ptr) AND 0Fh                                ;/
  fifo_size     = (wr_ptr-rd_ptr) AND 1Fh                         ;-5bit range
  fifo_not_more_than_half_full = cleared when fifo_size=09h..1Fh  ;\drq flags
  fifo_empty                   = cleared when fifo_size=01h..1Fh  ;/
The 5bit size should be in range 0..10h, however it can grow as tall as 1Fh in case overruns. Overruns do overwrite an old FIFO entry while appending the newly written value, and the newly written value will be then processed twice (once in place of the overwritten old value, and once in place of the newly appended value). If the size grows bigger than 1Fh then it will wrap to 00h, causing the FIFO to become empty.

FIFO Oddities
The above things are fairly common behaviour for FIFOs. The more confusing part is WHEN the GPU is removing the separate word(s) from the FIFO:
The different GPU commands behave differently in that aspect, some commands do remove the command word and some (or all) parameter words almost immediately after writing, other commands do not remove any words until after executing the command. Additionally, the GPU can prefetch the next command while the previous command is still busy, so some words may be removed before finishing the previous command.

FIFO Command Phases
Many commands consist of a precalculation phase and rendering phase; especially the POLY and LINE commands need some time for precalculating steps for screen coordinates (and for Texcoords and Gouraud RGB values).
Prefetching FIFO words seems to occur after the calculation phase(s), but can occur before/during the final rendering phase. In case of 4-point QUAD polygons, that would be after calculating & rendering the 1st triangle, and after calculating the 2nd triangle (but before/during rendering the 2nd triangle).

FIFO Prefetch
If a rendering command is busy, the following commands can prefetch the following amounts of words:
  NOP,INVALID,DRAWBASE,DRAWAREA,MASKBITS     1 word (and executed right away)
  TEXPAGE,TEXWINDOW,FLUSHCACHE,IRQ,REFRESH   1 word (but not yet executed)
  POLY, LINE                                 0 words (none)
  RECT (fixed size, without texture)         1 words (not all parameters)
  RECT (variable size, or with texture)      2 words (not all parameters)
  VRAM FILL                                  2 words (not all parameters)
  VRAM-to-VRAM, CPU-to-VRAM, VRAM-to-CPU     1 word (not all parameters)
Note: If there is no rendering command busy, then some commands (eg. RECT) seem to prefetch more word(s) than shown above (that is, more words are removed from fifo, even if the command cannot start yet because some parameters do still need to be written to fifo).
As shown above, NOPs (and some attributes) can be executed even when another command is still busy, that leads to cases where NOPs may or may not take up FIFO space, for example the following series of commands will act as so:
  RECT                ;-GPU gets busy
  NOP                 ;\
  NOP                 ; these are (almost) immediately REMOVED from FIFO
  NOP                 ; (even when RECT is still busy)
  NOP                 ;/
  TEXPAGE             ;-removed from FIFO, but not executed until RECT is done
  NOP                 ;\
  NOP                 ; these are KEPT in FIFO
  NOP                 ; (until RECT is done, and TEXPAGE is executed)
  NOP                 ;/
When rendering a series of POLYs, the precalculation of the next triangle can occur while rendering the previous triangle (that is, there will be a delay before starting to draw pixels of the first triangle, but pixels of the following triangles can be drawn seamlessly after each other).


GPU Texture Caching

The GPU has 2 Kbyte Texture Cache, plus 512 byte CLUT Cache.

CLUT Cache (512 byte)
The CLUT Cache is 100h halfwords (512 bytes) tall, and consists of two cache lines:
  One line with 16 halfwords (shared for 4bpp/8bpp color 00h..0Fh)
  One line with 240 halfwords (solely used for 8bpp color 10h..FFh)
The CLUT Cache is updated upon any textured Rect/Polygon commands with changed CLUT address. The cache updates are always loading the whole 16 or 256 colors into the cache:
  Updates whole 16 or 256 colors even when drawing tiny 1x1 pix RECTs
  Updates even if the RECT isn't drawn because outside of the Drawing Area
Both 4bpp and 8bpp mode will update color 00h..0Fh when color 00h..0Fh had used different CLUT. 8bpp mode will update color 00h..FFh when color 10h..0Fh had used different CLUT (that case is always updating ALL colors, even if color 00h..0Fh were already loaded from the desired CLUT).

Texture Cache (2Kbyte)
The Texture Cache is 400h halfwords (2Kbytes) tall, and consists of 256 cache lines (which can each hold horizontal lines of 4 halfwords).
  15bpp   32x32 pixels   ;\arranged as 32x32 halfwords (shared cache mode)
  8bpp    64x32 pixels   ;/
  4bpp    64x64 pixels   ;-arranged as 16x64 halfwords (other cache mode)
The cache can hold the above amount of pixels (eg. one 32x32x15bpp texture), or fractions thereof (eg. two 16x32x15bpp textures). However, the cache lines have fixed mapping to the VRAM halfword addresses:
  8bpp/15bpp:  Line = X AND 1Ch, Y AND 1Fh
  4bpp:        Line = X AND 0Ch, Y AND 3Fh
  Accordingly, coordinates 0,0 and 20h,0 are using the same cache line
  (and thus cannot be cached simultaneously).
There are several cases that do automatically flush the Texture Cache (the CLUT cache isn't affected):
  Executing any VRAM COPY command: GP0(80h,A0h,C0h) (but not VRAM FILL command)
  Changing TexPage Base X,Y
  Changing TexPage between 4bpp and Non-4bpp mode
Note: The TexPage changes can be triggered via GP0(24h..3Fh, 64h..7Fh) and GP0(E1h), that includes cache flushes when merely changing TexPage without actually drawing anything.
Cache loading occurs only when actually drawing pixels (and one special case: also when trying to draw pixels to VRAM addresses that have Mask bit15 set).

Write Buffer (36 bytes) (18 halfwords) (New GPU only)
Textured Rects and Polygons can overwrite their own Texture and CLUT (of course that should never happen in practice, unless when accidently or intentionally triggering rendering glitches).
One general issue is that the texture/clut caches may still contain OLD data when overwiting texture/clut with new data. The other issue (on new 208pin GPUs) is that VRAM isn't overwritten immediately:
Pixels are drawn to a write buffer, so NEW texture cache updates may still read OLD data from VRAM (because the NEW data is still in the write buffer). The effect can be reproduced by buffering the following amounts of data (and then draining the buffer after each step).
 For lines with EVEN screen.vertex.x:
  At begin of scanline store 16+1 halfwords in write buffer, drain 16 halfwords
  In middle of scanline store 16 new halfwords, drain 16 halfwords
  At end of scanline store remaining N halfwords, drain N+1 halfwords
 For lines with ODD screen.vertex.x:
  At begin of scanline store 16+1 halfwords in write buffer, drain 15 halfwords
  In middle of scanline store 16 new halfwords, drain 16 halfwords
  At end of scanline store remaining N halfwords, drain N+1(+1) halfwords
That effect is 100% stable during Vblank. However, the results are only 99% stable outside of Vblank, rendering the exact same scene can produce slightly different outputs: There appears to be a timing issue that can cause write buffer updates to occur slightly earlier or later than cache updates.
Note: Technically, the buffer might be implemented as a Read Buffer (for incoming texels) or Write Buffer (for outgoing pixels), the result should be about same either way.

Note
When changing CLUT or TexPage base X coordinates, the new region may overlap with the previously cached region, but the GPU is unable to identify such overlapping regions as cache hits.


GPU Display Timings

Video Clock
The PSone/PAL video clock is the cpu clock multiplied by 11/7.
  CPU Clock   =  33.868800MHz (44100Hz*300h)
  Video Clock =  53.222400MHz (44100Hz*300h*11/7)
For other PSX/PSone PAL/NTSC variants, see:
Pinouts - CLK Pinouts

Vertical Timings
  PAL:  314 scanlines per frame (13Ah)
  NTSC: 263 scanlines per frame (107h)
Timer1 can use the hblank signal as input, allowing to count scanlines (unless the display is configured to 0 pixels width, which would cause an endless hblank). The hblank signal is generated even during vertical blanking/retrace.

Horizontal Timings
  PAL:  3406 video cycles per scanline (or 3406.1 or so?)
  NTSC: 3413 video cycles per scanline (or 3413.6 or so?)
Dotclocks:
  PSX.256-pix Dotclock =  5.322240MHz (44100Hz*300h*11/7/10)
  PSX.320-pix Dotclock =  6.652800MHz (44100Hz*300h*11/7/8)
  PSX.368-pix Dotclock =  7.603200MHz (44100Hz*300h*11/7/7)
  PSX.512-pix Dotclock = 10.644480MHz (44100Hz*300h*11/7/5)
  PSX.640-pix Dotclock = 13.305600MHz (44100Hz*300h*11/7/4)
  Namco GunCon 385-pix =  8.000000MHz (from 8.00MHz on lightgun PCB)
Dots per scanline are, depending on horizontal resolution, and on PAL/NTSC:
  320pix/PAL: 3406/8  = 425.75 dots     320pix/NTSC: 3413/8  = 426.625 dots
  640pix/PAL: 3406/4  = 851.5 dots      640pix/NTSC: 3413/4  = 853.25 dots
  256pix/PAL: 3406/10 = 340.6 dots      256pix/NTSC: 3413/10 = 341.3 dots
  512pix/PAL: 3406/5  = 681.2 dots      512pix/NTSC: 3413/5  = 682.6 dots
  368pix/PAL: 3406/7  = 486.5714 dots   368pix/NTSC: 3413/7  = 487.5714 dots
Timer0 can use the dotclock as input, however, the Timer0 input "ignores" the fractional portions (in most cases, the values are rounded down, ie. with 340.6 dots/line, the timer increments only 340 times/line; the only value that is rounded up is 425.75 dots/line) (for example, due to the rounding, the timer isn't running exactly twice as fast in 512pix/PAL mode than in 256pix/PAL mode). The dotclock signal is generated even during horizontal/vertical blanking/retrace.

Frame Rates
  PAL:  53.222400MHz/314/3406 = ca. 49.76 Hz (ie. almost 50Hz)
  NTSC: 53.222400MHz/263/3413 = ca. 59.29 Hz (ie. almost 60Hz)

Note
Above values include "hidden" dots and scanlines (during horizontal and vertical blanking/retrace).


GPU Rendering Timings

Here are the GPU rendering timings. All values are measured in 33MHz CPU clock cycles. The GPU can render up to 66 million pixels per second, that figure applies for monochrome Rects, textured Rects, and even for Rects with texture blending.
Monochrome Polygons can also reach 66Mpix/s, however, the speed will drop to 33Mpix/s for Polygons with Texture or Gouraud shading (that's an apparant design mistake that can make the GPU twice as slow as needed, although it isn't as bad as it sounds because other overload may outweight that mistake).
Overload can include cache misses, semi-transparency, per-scanline overload (most noticeable in short scanlines), and precalculation (most noticeable in small polygons), and collisions with memory refresh and display fetching. The exact overload depends on the scenery, the average rendering speed might be around 6-11Mpix/s.
To avoid overload, it may be recommended to omit small polygons (or to use a reduced polygon count for more distant objects).

 _________________________________ Rectangles _________________________________

GP0(60h..7Fh) Rectangles
  1.00 clks     per any-scanline (even if outside of draw area y1,y2)
  5.00 clks     per scanline                                    ;\
  0.50 clks     per pixel, when non-fully-transp ;\without      ;
  0.25 clks     per pixel, when fully-transp     ;/semi-transp  ; Old GPU
  1.00 clks     per pixel-read, when non-fully-transp  ;\with   ;
  0.00 clks     per pixel-read, when fully-transp      ; semi   ;
  0.50 clks     per pixel-write                        ;/       ;/
  3.50 clks     per scanline, when width=1      ;\              ;\
  2.50 clks     per scanline, when width=2..3   ; without       ;
  2.00 clks     per scanline, when width=4..5   ; semi-transp   ; New GPU
  1.50 clks     per scanline, when width=6..7   ;               ;
  1.00 clks     per scanline, when width>=8     ;/              ;
  6.00 clks     per scanline                    ;\with          ;
  3.75 clks     per 16pix chunk                 ;/semi-transp   ;
  0.50 clks     per pixel, when non-fully-transp                ;
  0.25 clks     per pixel, when fully-transp (color 0000h)      ;/
  and...        extra time per cache-misses (when textured)
The timing for number of pixels per scanline is rounded to pixel-pairs, generally that is "width AND NOT 1" (except: on Old GPU for pixel-reads it is "num+1 AND NOT 1").

 __________________________________ Polygons __________________________________

GP0(20h..3Fh) Polygons
Polygon timings consist of precalculation and rendering phases:
  3-point Poly (one triangle)  --> precalc + render
  4-point Poly (two triangles) --> precalc + render + precalc + render
The precalc computes the fixed point steps for screen coords (and texcoords and gouraud RGB values, if any). The precalc can be quite slow, however, it can be done during the rendering phase of the previous command/triangle (so the precalc won't take up any extra time, provided that the previous rendering phase takes long enough to finish the precalc in parallel).
  10.00 clks    per triangle, base cycles                       ;\
  90.00 clks    per triangle, extra cycles when textured        ; precalc
  150.00 clks   per triangle, extra cycles when gouraud shaded  ;/
  1.00 clks     per any-scanline (even if outside of draw area y1,y2)
  4.75 clks     per scanline, without semi                      ;\
  5.50 clks     per scanline, with semi                         ;
  3.00 clks     per pixel, with semi, with gouraud/texture      ; Old GPU
  1.50 clks     per pixel, with semi, without gouraud/texture   ;
  1.00 clks     per pixel, without semi, with gouraud/texture   ;
  0.50 clks     per pixel, without semi, without gouraud/texture;/
  1.00 clks     per scanline, without semi                      ;\
  2.00 clks     per scanline, with semi, with gouraud/texture   ;
  5.25 clks     per scanline, with semi, without gouraud/texture; New GPU
  2.00 clks     per scanline, when width=1      ;\              ;
  1.50 clks     per scanline, when width=2      ; without       ;
  1.25 clks     per scanline, when width=3      ; semi-transp,  ;
  0.75 clks     per scanline, when width=4..5   ; and without   ;
  0.50 clks     per scanline, when width=6..7   ; gouraud/tex   ;
  0.00 clks     per scanline, when width>=8     ;/              ;
  3.75 clks     per 16pix chunk, with semi, without gouraud/tex ;
  1.00 clks     per pixel, with gouraud/texture                 ;
  0.50 clks     per pixel, without gouraud/texture              ;/
  and...        extra time per cache-misses (when textured)
XXX probably has faster cases for fully-transp pixels, alike Rectangles?
There's one odditity: 0-pixel polygons can be slower than a 1-pixel polygons (maybe the precalculation timings get messed up when dividing by size=0).

 ___________________________________ Lines ____________________________________

GP0(40h..5Fh) Lines
Line timings consist of precalculation and rendering phases (similar as Polygons). Lines aren't pariticulary fast, the per-pixel timing isn't optimal, and non-horizontal lines do additionally have a high per-scanline overload (versus few pixels per scanline). Nonetheless, Lines may be faster than large filled shapes (that require more pixels).
  40.00 clks    per line segment, base cycles                       ;\precalc
  60.00 clks    per line segment, extra cycles when gouraud shaded  ;/
  1.00 clks     per pixel, base time for horizontal lines           ;\
  2.00 clks     per pixel, base time for non-horizontal lines       ; pixels
  2.00 clks     per pixel, extra when Old GPU with semi-transp      ;/
  0.00 clks     per offscreen-scanline (outside of draw area y1,y2)
  0.00 clks     per scanline, when 0..5' (flat)                     ;\
  ??   clks     per scanline, when 5..44'                           ; Old GPU
  5.00 clks     per scanline, when 45..90' (steep)                  ;/
  2.00 clks     per scanline, when 0..30' (flat)                    ;\
  2.00 clks     per scanline, when 40' without semi-transp          ;
  ??   clks     per scanline, when 40' with semi-transp             ; New GPU
  2.50 clks     per scanline, when 45..90' (steep) without semi     ;
  5.50 clks     per scanline, when 45..90' (steep) with semi-transp ;/


 ______________________________ Memory Transfers ______________________________

GP0(02h) VRAM Fill
The VRAM chips have a special hardware feature for writing the fill value to several pixels at once, that's making the fill command very fast (about 0.0625 clks per 16bit pixel). The overall timings consist of the pixel time plus some scanline overload:
  1.00 clks     per 16 pixels
  7.00 clks     per scanline, when xsiz>0, on Old GPU
  5.00 clks     per scanline, when xsiz>0, on New GPU
  1.00 clks     per scanline, when xsiz=0, should never happen in practice

GP0(80h) VRAM-to-VRAM Copy
  1.50 clks     per pixel, without Mask Check                    ;\
  2.50 clks     per pixel, with Mask Check                       ; Old GPU
  2.50 clks     per scanline                                     ;/
  1.25 clks     per pixel, without Mask Check                    ;\
  1.50 clks     per pixel, with Mask Check, when width<16        ;
  1.00 clks     per pixel, with Mask Check, when width>=16       ; New GPU
  19.50 clks    per scanline, without Mask Check                 ;
  22.25 clks    per scanline, with Mask Check, when width<16     ;
  25.50 clks    per 16pix chunk, with Mask Check, when width>=16 ;/
Like many other commands, data is transferred in Pixel-Pairs (albeit oddly, this command seems to use pairs that begin on odd X texcoords).

GP0(A0h) CPU-to-VRAM Copy
The timings do mainly rely on the transfer rate on CPU side, the transfer should be usually done via DMA (manually polling the I/O ports would be about 10x slower). The DMA timings depend on the DRQ mode and DMA blocksize (plus additional slowdown if other DMA channels are simultaneously active). The following timings per 16bit pixel are possible with DMA:
  1.00 clks     per pixel, without Mask Check                    ;\Old GPU
  1.50 clks     per pixel, with Mask Check                       ;/
  1.00 clks     per pixel, with/without Mask Check               ;-New GPU
  plus some overload per scanline/chunk

GP0(C0h) VRAM-to-CPU Copy
Again, the timings do mainly rely on the transfer rate on CPU side. The following timings per 16bit pixel are possible with DMA:
  1.50 clks     per pixel                                        ;-Old GPU
  1.00 clks     per pixel                                        ;-New GPU
  plus some overload per scanline/chunk (especially on New GPU)


 ____________________________ Additional Overload _____________________________

Cache Misses (for textured Rects/Polys)
CLUT Cache misses take 1.00 clks per halfword. That is,
  16.00 clks    when loading 16-color CLUT (color 00h..0Fh)
  256.00 clks   when loading 256-color CLUT (color 00h..FFh)
Texture cache misses do theoretically take 8.00 clks (2.00 clks per halfword). However, there appears to be some overload resulting in timings like this:
  8.25 clks     for 16bpp, with/without semi-transparency   ;-without CLUT
  10.00 clks    for 4bpp/8bpp, without semi-transparency    ;\with CLUT
  11.00 clks    for 4bpp/8bpp, with semi-transparency       ;/
There are cases where cache misses are triggering yet more overload (maybe because cache loading can increase memory refresh collisions).

Semi-Transparency and Mask Check
These features require reading old pixels from framebuffer. Both Semi-Transparency and Mask Check have the same overload (in the above tables, the timings for "semi-transp" do also apply when using mask check). These timings do always apply when using semi-transparent commands (no matter if the actual texture pixels have the semi-transparent flag in color.bit15 set or cleared).

Memory Refresh
The Old GPU appears to require a lot of refresh cycles, resulting in an average overload of 2% to be added to the overall rendering time (albeit with rather unstable results, the rendering time for the exact same polygon can vary greatly depending on whether it's colliding with refresh cycles or not).
The New GPU requires very few refresh cycles, resulting in little overload and much more stable timings. However, setting GP0(03h) to nonstandard values may (or may not) slow down rendering:
  Rect 3x128    rendering with GP0(03h)=0Fh is about 4x slower than GP0(03h)=0
  Rect 512x128  rendering time is constant, no matter of GP0(03h)
  (in the latter case, refresh probably occurs inbetween write buffer draining)

Vblank vs Display Area
The full rendering speed can be reached only during Vblank. There will be additional overload outside of Vblank, the exact overload depends on the size of the Display Area and on the horizontal resolution (dotclock).
  XXX Todo: add some examples for Rects/Polys at different resolutions
Note: Trying to use GP1(03h) to disable display does NOT disable the overload (the pixel VRAM fetches do still occur despite of not actually displaying those pixels). However, setting Display Area Y2=Y1+1 will will cause the GPU to be (almost) always in Vblank, and thus disable most of the overload.
Note: The Old GPU is using Dual-ported VRAM chips (with two data busses) which do theoretically allow to fetch pixels during rendering (unknown if that's actually working free of overload).

 ___________________________________ Notes ____________________________________

Pixel-Pairs
Most rendering commands are capable of doing two 16bit pixels as a single 32bit pixel-pair (except, the Line command doesn't seem to do that). For example, Rects with 3x200 or 4x200 pixels are both having the same rendering time (at least so with even screen X coords, the timing is probably different on odd screen X coords).

16-pixel Buffer
The New GPU is rendering most scanlines in 16-pix chunks, that new feature is usually making it faster than Old GPU (although, it can also be slower for short scanlines).
The feature is probably related to the Write Buffer (see GPU Texture Cache chapter), and accordingly the timings do probably differ for odd/even screen X coords, and with the first chunk being 15-17 pixels wide instead of 16.

Oscillators
All rendering timings seem to be bound to the 33MHz CPU clock (aka derived from the 67MHz oscillator). The 53MHz GPU clock doesn't seem to affect GPU rendering timings at all (it appears to be solely used to generate the PAL/NTSC color clock & horizontal resolution dotclock; the latter might indirectly affect rendering timings when rendering is colliding with display fetches).

Notes
The above timings are hopefully more or less correct. But they might include some measurement inaccuracies and some other mistakes; it can be difficult to tell apart which factors (or combination of factors) are causing which delays.
Timings like 0.50 or 0.25 clks may rely on the GPU being clocked at twice 33MHz, and on rendering pixel-pairs; some odd timings may also rely on things like average refresh collisions.


Geometry Transformation Engine (GTE)

GTE Overview
GTE Registers
GTE Saturation
GTE Opcode Summary
GTE Coordinate Calculation Commands
GTE General Purpose Calculation Commands
GTE Color Calculation Commands
GTE Division Inaccuracy


GTE Overview

GTE Operation
The GTE doesn't have any memory or I/O ports mapped to the CPU memory bus, instead, it's solely accessed via coprocessor opcodes:
  mov  cop0r12,rt          ;-enable/disable COP2 (GTE) via COP0 status register
  mov  cop2r0-63,rt        ;\write parameters to GTE registers
  mov  cop2r0-31,[rs+imm]  ;/
  mov  cop2cmd,imm25       ;-issue GTE command
  mov  rt,cop2r0-63        ;\read results from GTE registers
  mov  [rs+imm],cop2r0-31  ;/
  jt   cop2flg,dest        ;-jump never  ;\implemented (no exception), but,
  jf   cop2flg,dest        ;-jump always ;/flag seems to be always "false"
GTE (memory-?) load and store instructions have a delay of 2 instructions, for any GTE commands or operations accessing that register. Any? That's wrong!
GTE instructions and functions should not be used in
  - Delay slots of jumps and branches
  - Event handlers or interrupts (sounds like nonsense?) (need push/pop though)
If an instruction that reads a GTE register or a GTE command is executed before the current GTE command is finished, the CPU will hold until the instruction has finished. The number of cycles each GTE instruction takes is shown in the command list.

GTE Command Encoding (COP2 imm25 opcodes)
  31-25  Must be 0100101b for "COP2 imm25" instructions
  20-24  Fake GTE Command Number (00h..1Fh) (ignored by hardware)
  19     sf - Shift Fraction in IR registers (0=No fraction, 1=12bit fraction)
  17-18  MVMVA Multiply Matrix    (0=Rotation. 1=Light, 2=Color, 3=Reserved)
  15-16  MVMVA Multiply Vector    (0=V0, 1=V1, 2=V2, 3=IR/long)
  13-14  MVMVA Translation Vector (0=TR, 1=BK, 2=FC/Bugged, 3=None)
  11-12  Always zero                        (ignored by hardware)
  10     lm - Saturate IR1,IR2,IR3 result (0=To -8000h..+7FFFh, 1=To 0..+7FFFh)
  6-9    Always zero                        (ignored by hardware)
  0-5    Real GTE Command Number (00h..3Fh) (used by hardware)
The MVMVA bits are used only by the MVMVA opcode (the bits are zero for all other opcodes).
The "sf" and "lm" bits are usually fixed (either set, or cleared, depending on the command) (for MVMVA, the bits are variable) (also, "sf" can be changed for some commands like SQR) (although they are usually fixed for most other opcodes, changing them might have some effect on some/all opcodes)?

GTE Data Register Summary (cop2r0-31)
  cop2r0-1   3xS16 VXY0,VZ0              Vector 0 (X,Y,Z)
  cop2r2-3   3xS16 VXY1,VZ1              Vector 1 (X,Y,Z)
  cop2r4-5   3xS16 VXY2,VZ2              Vector 2 (X,Y,Z)
  cop2r6     4xU8  RGBC                  Color/code value
  cop2r7     1xU16 OTZ                   Average Z value (for Ordering Table)
  cop2r8     1xS16 IR0                   16bit Accumulator (Interpolate)
  cop2r9-11  3xS16 IR1,IR2,IR3           16bit Accumulator (Vector)
  cop2r12-15 6xS16 SXY0,SXY1,SXY2,SXYP   Screen XY-coordinate FIFO  (3 stages)
  cop2r16-19 4xU16 SZ0,SZ1,SZ2,SZ3       Screen Z-coordinate FIFO   (4 stages)
  cop2r20-22 12xU8 RGB0,RGB1,RGB2        Color CRGB-code/color FIFO (3 stages)
  cop2r23    4xU8  (RES1)                Prohibited
  cop2r24    1xS32 MAC0                  32bit Maths Accumulators (Value)
  cop2r25-27 3xS32 MAC1,MAC2,MAC3        32bit Maths Accumulators (Vector)
  cop2r28-29 1xU15 IRGB,ORGB             Convert RGB Color (48bit vs 15bit)
  cop2r30-31 2xS32 LZCS,LZCR             Count Leading-Zeroes/Ones (sign bits)

GTE Control Register Summary (cop2r32-63)
  cop2r32-36 9xS16 RT11RT12,..,RT33 Rotation matrix     (3x3)        ;cnt0-4
  cop2r37-39 3x 32 TRX,TRY,TRZ      Translation vector  (X,Y,Z)      ;cnt5-7
  cop2r40-44 9xS16 L11L12,..,L33    Light source matrix (3x3)        ;cnt8-12
  cop2r45-47 3x 32 RBK,GBK,BBK      Background color    (R,G,B)      ;cnt13-15
  cop2r48-52 9xS16 LR1LR2,..,LB3    Light color matrix source (3x3)  ;cnt16-20
  cop2r53-55 3x 32 RFC,GFC,BFC      Far color           (R,G,B)      ;cnt21-23
  cop2r56-57 2x 32 OFX,OFY          Screen offset       (X,Y)        ;cnt24-25
  cop2r58 BuggyU16 H                Projection plane distance.       ;cnt26
  cop2r59      S16 DQA              Depth queing parameter A (coeff) ;cnt27
  cop2r60       32 DQB              Depth queing parameter B (offset);cnt28
  cop2r61-62 2xS16 ZSF3,ZSF4        Average Z scale factors          ;cnt29-30
  cop2r63      U20 FLAG             Returns any calculation errors   ;cnt31


GTE Registers

Note in some functions format is different from the one that's given here.

Matrix Registers
  Rotation matrix (RT)   Light matrix (LLM)     Light Color matrix (LCM)
  cop2r32.lsbs=RT11      cop2r40.lsbs=L11       cop2r48.lsbs=LR1
  cop2r32.msbs=RT12      cop2r40.msbs=L12       cop2r48.msbs=LR2
  cop2r33.lsbs=RT13      cop2r41.lsbs=L13       cop2r49.lsbs=LR3
  cop2r33.msbs=RT21      cop2r41.msbs=L21       cop2r49.msbs=LG1
  cop2r34.lsbs=RT22      cop2r42.lsbs=L22       cop2r50.lsbs=LG2
  cop2r34.msbs=RT23      cop2r42.msbs=L23       cop2r50.msbs=LG3
  cop2r35.lsbs=RT31      cop2r43.lsbs=L31       cop2r51.lsbs=LB1
  cop2r35.msbs=RT32      cop2r43.msbs=L32       cop2r51.msbs=LB2
  cop2r36     =RT33      cop2r44     =L33       cop2r52     =LB3
Each element is 16bit (1bit sign, 3bit integer, 12bit fraction). Reading the last elements (RT33,L33,LB3) returns the 16bit value sign-expanded to 32bit.

Translation Vector (TR) (Input, R/W?)
  cop2r37 (cnt5) - TRX - Translation vector X (R/W?)
  cop2r38 (cnt6) - TRY - Translation vector Y (R/W?)
  cop2r39 (cnt7) - TRZ - Translation vector Z (R/W?)
Each element is 32bit (1bit sign, 31bit integer).
Used only for MVMVA, RTPS, RTPT commands.

Background Color (BK) (Input?, R/W?)
  cop2r45 (cnt13) - RBK - Background color red component
  cop2r46 (cnt14) - GBK - Background color green component
  cop2r47 (cnt15) - BBK - Background color blue component
Each element is 32bit (1bit sign, 19bit integer, 12bit fraction).

Far Color (FC) (Input?) (R/W?)
  cop2r53 (cnt21) - RFC - Far color red component
  cop2r54 (cnt22) - GFC - Far color green component
  cop2r55 (cnt23) - BFC - Far color blue component
Each element is 32bit (1bit sign, 27bit integer, 4bit fraction).

Screen Offset and Distance (Input, R/W?)
  cop2r56 (cnt24) - OFX - Screen offset X
  cop2r57 (cnt25) - OFY - Screen offset Y
  cop2r58 (cnt26) - H   - Projection plane distance
  cop2r59 (cnt27) - DQA - Depth queing parameter A.(coeff.)
  cop2r60 (cnt28) - DQB - Depth queing parameter B.(offset.)
The X and Y values are each 32bit (1bit sign, 15bit integer, 16bit fraction).
The H value is 16bit unsigned (0bit sign, 16bit integer, 0bit fraction). BUG: When reading the H register, the hardware does accidently <sign-expand> the <unsigned> 16bit value (ie. values +8000h..+FFFFh are returned as FFFF8000h..FFFFFFFFh) (this bug applies only to "mov rd,cop2r58" opcodes; the actual calculations via RTPS/RTPT opcodes are working okay).
The DQA value is only 16bit (1bit sign, 7bit integer, 8bit fraction).
The DQB value is 32bit (1bit sign, 7bit integer, 24bit? fraction).
Used only for RTPS/RTPT commands.

Average Z Registers (ZSF3/ZSF4=Input, R/W?) (OTZ=Result, R)
  cop2r61 (cnt29) ZSF3 |  0|ZSF3 1,3,12| Z3 average scale factor (normally 1/3)
  cop2r62 (cnt30) ZSF4 |  0|ZSF4 1,3,12| Z4 average scale factor (normally 1/4)
  cop2r7       OTZ (R) |   |OTZ 0,15, 0| Average Z value (for Ordering Table)
Used only for AVSZ3/AVSZ4 commands.

Screen XYZ Coordinate FIFOs
  cop2r12 - SXY0  rw|SY0 1,15, 0|SX0 1,15, 0| Screen XY fifo (older)
  cop2r13 - SXY1  rw|SY1 1,15, 0|SX1 1,15, 0| Screen XY fifo (old)
  cop2r14 - SXY2  rw|SY2 1,15, 0|SX2 1,15, 0| Screen XY fifo (new)
  cop2r15 - SXYP  rw|SYP 1,15, 0|SXP 1,15, 0| SXY2-mirror with move-on-write
  cop2r16 - SZ0   rw|          0|SZ0 0,16, 0| Screen Z fifo (oldest)
  cop2r17 - SZ1   rw|          0|SZ1 0,16, 0| Screen Z fifo (older)
  cop2r18 - SZ2   rw|          0|SZ2 0,16, 0| Screen Z fifo (old)
  cop2r19 - SZ3   rw|          0|SZ3 0,16, 0| Screen Z fifo (new)
SX,SY,SZ are used as Output for RTPS/RTPT. Additionally, SX,SY are used as Input for NCLIP, and SZ is used as Input for AVSZ3/AVSZ4.
The SZn Fifo has 4 stages (required for AVSZ4 command), the SXYn Fifo has only 3 stages, and a special mirrored register: SXYP is a mirror of SXY2, the difference is that writing to SXYP moves SXY2/SXY1 to SXY1/SXY0, whilst writing to SXY2 (or any other SXYn or SZn registers) changes only the written register, but doesn't move any other Fifo entries.

16bit Vectors (R/W)
  Vector 0 (V0)         Vector 1 (V1)       Vector 2 (V2)       Vector 3 (IR)
  cop2r0.lsbs - VX0     cop2r2.lsbs - VX1   cop2r4.lsbs - VX2   cop2r9  - IR1
  cop2r0.msbs - VY0     cop2r2.msbs - VY1   cop2r4.msbs - VY2   cop2r10 - IR2
  cop2r1      - VZ0     cop2r3      - VZ1   cop2r5      - VZ2   cop2r11 - IR3
All elements are signed 16bit. The IRn and VZn elements occupy a whole 32bit register, reading these registers returns the 16bit value sign-expanded to 32bit. Note: IRn can be also indirectly accessed via IRGB/ORGB registers.

Color Register and Color FIFO
  cop2r6  - RGBC  rw|CODE |B    |G    |R    | Color/code
  cop2r20 - RGB0  rw|CD0  |B0   |G0   |R0   | Characteristic color fifo.
  cop2r21 - RGB1  rw|CD1  |B1   |G1   |R1   |
  cop2r22 - RGB2  rw|CD2  |B2   |G2   |R2   |
  cop2r23 - (RES1)  |                       | Prohibited
RES1 seems to be unused... looks like an unused Fifo stage... RES1 is read/write-able... unlike SXYP (for SXYn Fifo) it does not mirror to RGB2, nor does it have a move-on-write function...

Interpolation Factor
  cop2r8   IR0   rw|Sign       |IR0 1, 3,12| Intermediate value 0.
Used as Output for RTPS/RTPT, and as Input for various commands.

XX...
  cop2r24  MAC0  rw|MAC0 1,31,0            | Sum of products value 0

XX...
  cop2r25  MAC1  rw|MAC1 1,31,0            | Sum of products value 1
  cop2r26  MAC2  rw|MAC2 1,31,0            | Sum of products value 2
  cop2r27  MAC3  rw|MAC3 1,31,0            | Sum of products value 3

cop2r28 - IRGB - Color conversion Input (R/W)
Expands 5:5:5 bit RGB (range 0..1Fh) to 16:16:16 bit RGB (range 0000h..0F80h).
  0-4    Red   (0..1Fh) (R/W)  ;multiplied by 80h, and written to IR1
  5-9    Green (0..1Fh) (R/W)  ;multiplied by 80h, and written to IR2
  10-14  Blue  (0..1Fh) (R/W)  ;multiplied by 80h, and written to IR3
  15-31  Not used (always zero) (Read only)
After writing to IRGB, the result can be read from IR3 after TWO nop's, and from IR1,IR2 after THREE nop's (for uncached code, ONE nop would work). When using IR1,IR2,IR3 as parameters for GTE commands, similar timing restrictions might apply... depending on when the specific commands use the parameters?

cop2r29 - ORGB - Color conversion Output (R)
Collapses 16:16:16 bit RGB (range 0000h..0F80h) to 5:5:5 bit RGB (range 0..1Fh). Negative values (8000h..FFFFh/80h) are saturated to 00h, large positive values (1000h..7FFFh/80h) are saturated to 1Fh, there are no overflow or saturation flags set in cop2r63 though.
  0-4    Red   (0..1Fh) (R)  ;IR1 divided by 80h, saturated to +00h..+1Fh
  5-9    Green (0..1Fh) (R)  ;IR2 divided by 80h, saturated to +00h..+1Fh
  10-14  Blue  (0..1Fh) (R)  ;IR3 divided by 80h, saturated to +00h..+1Fh
  15-31  Not used (always zero) (Read only)
Any changes to IR1,IR2,IR3 are reflected to this register (and, actually also to IRGB) (ie. ORGB is simply a read-only mirror of IRGB).

cop2r30 - LZCS - Count Leading Bits Source data (R/W)
cop2r31 - LZCR - Count Leading Bits Result (R)
Reading LZCR returns the leading 0 count of LZCS if LZCS is positive and the leading 1 count of LZCS if LZCS is negative. The results are in range 1..32.

cop2r63 (cnt31) - FLAG - Returns any calculation errors.
See GTE Saturation chapter.


GTE Saturation

Maths overflows are indicated in FLAG register. In most cases, the result is saturated to MIN/MAX values (except MAC0,MAC1,MAC2,MAC3 which aren't saturated). For IR1,IR2,IR3 many commands allow to select the MIN value via "lm" bit of the GTE opcode (though not all commands, RTPS/RTPT always act as if lm=0).

cop2r63 (cnt31) - FLAG - Returns any calculation errors.
  31   Error Flag (Bit30..23, and 18..13 ORed together) (Read only)
  30   MAC1 Result positive 44bit overflow (max +7FFFFFFFFFFh) ;\triggered
  29   MAC2 Result positive 44bit overflow (max +7FFFFFFFFFFh) ; during
  28   MAC3 Result positive 44bit overflow (max +7FFFFFFFFFFh) ; calculations
  27   MAC1 Result negative 44bit overflow (min -80000000000h) ;
  26   MAC2 Result negative 44bit overflow (min -80000000000h) ;
  25   MAC3 Result negative 44bit overflow (min -80000000000h) ;/
  24   IR1 saturated to +0000h..+7FFFh (lm=1) or to -8000h..+7FFFh (lm=0)
  23   IR2 saturated to +0000h..+7FFFh (lm=1) or to -8000h..+7FFFh (lm=0)
  22   IR3 saturated to +0000h..+7FFFh (lm=1) or to -8000h..+7FFFh (lm=0)
  21   Color-FIFO-R saturated to +00h..+FFh
  20   Color-FIFO-G saturated to +00h..+FFh
  19   Color-FIFO-B saturated to +00h..+FFh
  18   SZ3 or OTZ saturated to +0000h..+FFFFh
  17   Divide overflow. RTPS/RTPT division result saturated to max=1FFFFh
  16   MAC0 Result positive 32bit overflow (max +7FFFFFFFh)    ;\triggered on
  15   MAC0 Result negative 32bit overflow (min -80000000h)    ;/final result
  14   SX2 saturated to -0400h..+03FFh
  13   SY2 saturated to -0400h..+03FFh
  12   IR0 saturated to +0000h..+1000h
  0-11 Not used (always zero) (Read only)
Bit30-12 are read/write-able, ie. they can be set/reset by software, however, that's normally not required - all bits are automatically reset at the begin of a new GTE command.
44bit MAC1-3 overflows can occur during calculations (positive+positive+negative can trigger positive overflow on 1st addition, and negative overflow on 2nd addition, in that case the final result is okay, but both overflow flags are set).
32bit MAC0 overflows occur if the final result exceeds 32bit (internally, the register seems to be bigger than 32bit).
IR1-3 overflows occur when lower 32bit of MAC1-3 exceeds the desired range (MAC1-3 are 44bit wide, but the upper 12bit are ignored for IR1-3).
Bit31 is apparently intended for RTPS/RTPT commands, since it triggers only on flags that are affected by these two commands, but even for that commands it's totally useless since one could as well check if FLAG is nonzero.
Note: Writing 32bit values to 16bit GTE registers by software does not trigger any overflow/saturation flags (and does not do any saturation), eg. writing 12008900h (positive 32bit) to a signed 16bit register sets that register to FFFF8900h (negative 16bit).


GTE Opcode Summary

GTE Command Summary (sorted by Real Opcode bits) (bit0-5)
  Opc  Name      Clk Expl.
  00h  -             N/A (modifies similar registers than RTPS...)
  01h  RTPS      15  Perspective Transformation single
  0xh  -             N/A
  06h  NCLIP     8   Normal clipping
  0xh  -             N/A
  0Ch  OP(sf)    6   Outer product of 2 vectors
  0xh  -             N/A
  10h  DPCS      8   Depth Cueing single
  11h  INTPL     8   Interpolation of a vector and far color vector
  12h  MVMVA(..) 8   Multiply vector by matrix and add vector (see below)
  13h  NCDS      19  Normal color depth cue single vector
  14h  CDP       13  Color Depth Que
  15h  -             N/A
  16h  NCDT      44  Normal color depth cue triple vectors
  1xh  -             N/A
  1Bh  NCCS      17  Normal Color Color single vector
  1Ch  CC        11  Color Color
  1Dh  -             N/A
  1Eh  NCS       14  Normal color single
  1Fh  -             N/A
  20h  NCT       30  Normal color triple
  2xh  -             N/A
  28h  SQR(sf)   5   Square of vector IR
  29h  DCPL      8   Depth Cue Color light
  2Ah  DPCT      17  Depth Cueing triple (should be fake=08h, but isn't)
  2xh  -             N/A
  2Dh  AVSZ3     5   Average of three Z values
  2Eh  AVSZ4     6   Average of four Z values
  2Fh  -             N/A
  30h  RTPT      23  Perspective Transformation triple
  3xh  -             N/A
  3Dh  GPF(sf)   5   General purpose interpolation
  3Eh  GPL(sf)   5   General purpose interpolation with base
  3Fh  NCCT      39  Normal Color Color triple vector
Unknown if/what happens when using the "N/A" opcodes?

GTE Command Summary (sorted by Fake Opcode bits) (bit20-24)
The fake opcode number in bit20-24 has absolutely no effect on the hardware, it seems to be solely used to (or not to) confuse developers. Having the opcodes sorted by their fake numbers gives a more or less well arranged list:
  Fake Name      Clk Expl.
  00h  -             N/A
  01h  RTPS      15  Perspective Transformation single
  02h  RTPT      23  Perspective Transformation triple
  03h  -             N/A
  04h  MVMVA(..) 8   Multiply vector by matrix and add vector (see below)
  05h  -             N/A
  06h  DCPL      8   Depth Cue Color light
  07h  DPCS      8   Depth Cueing single
  08h  DPCT      17  Depth Cueing triple (should be fake=08h, but isn't)
  09h  INTPL     8   Interpolation of a vector and far color vector
  0Ah  SQR(sf)   5   Square of vector IR
  0Bh  -             N/A
  0Ch  NCS       14  Normal color single
  0Dh  NCT       30  Normal color triple
  0Eh  NCDS      19  Normal color depth cue single vector
  0Fh  NCDT      44  Normal color depth cue triple vectors
  10h  NCCS      17  Normal Color Color single vector
  11h  NCCT      39  Normal Color Color triple vector
  12h  CDP       13  Color Depth Que
  13h  CC        11  Color Color
  14h  NCLIP     8   Normal clipping
  15h  AVSZ3     5   Average of three Z values
  16h  AVSZ4     6   Average of four Z values
  17h  OP(sf)    6   Outer product of 2 vectors
  18h  -             N/A
  19h  GPF(sf)   5   General purpose interpolation
  1Ah  GPL(sf)   5   General purpose interpolation with base
  1Bh  -             N/A
  1Ch  -             N/A
  1Dh  -             N/A
  1Eh  -             N/A
  1Fh  -             N/A
For the sort-effect, DCPT should use fake=08h, but Sony seems to have accidently numbered it fake=0Fh in their devkit (giving it the same fake number as for NCDT). Also, "Wipeout 2097" accidently uses 0140006h (fake=01h and distorted bit18) instead of 1400006h (fake=14h) for NCLIP.

GTE nonsense SDK command numbers (as from SDK file INLINE_A.H)
  RTPS   macro               dw   $0000007f              (01x40)
  RTPT   macro               dw   $000000bf              (02x40)
  DCPL   macro               dw   $00000dff              (37x40)
  DPCS   macro               dw   $00000e3f              (38x40)
  DPCT   macro               dw   $00000e7f              (39x40)
  INTPL  macro               dw   $00000ebf              (3Ax40)
  NCS    macro               dw   $00000f7f              (3Dx40)
  NCT    macro               dw   $00000fbf              (3Ex40)
  NCDS   macro               dw   $00000fff              (3Fx40)
  NCDT   macro               dw   $0000103f              (40x40)
  NCCS   macro               dw   $0000107f              (41x40)
  NCCT   macro               dw   $000010bf              (42x40)
  CDP    macro               dw   $000010ff              (43x40)
  CC     macro               dw   $0000113f              (44x40)
  NCLIP  macro               dw   $0000117f              (45x40)
  AVSZ3  macro               dw   $000011bf              (46x40)
  AVSZ4  macro               dw   $000011ff              (47x40)
  MVMVA  macro sf,mx,v,cv,lm dw   $000013bf|sf<<25|mx<<23|v<<21|cv<<19|lm<<18
  SQR    macro sf            dw   $000013ff|sf<<25       (4Fx40)
  OP     macro sf            dw   $0000143f|sf<<25       (50x40)
  GPF    macro sf            dw   $0000147f|sf<<25       (51x40)
  GPL    macro sf            dw   $000014bf|sf<<25       (52x40)
"Be warned that the DWORD codes are actually not GTE cop2 instructions. The way you deal with them in the official SDK is that you'd run the compiled object file of your assembly source that uses said macros through DMPSX which translates those DWORD codes into the correct GTE cop2 instructions. I don't know why Sony made it this way."

GTE Clock Cycles
The overall command execution time is shown in the above tables. The MIPS CPU will be automatically halted when trying to read a cop2 register (or executiong another cop2 command) when the GTE command is still busy.
The CPU isn't halted when writing cop2 registers or when trying to use the conditional cop2 jump opcodes.
For whatever reason, trying to read the IRGB/ORGB registers (cop2r28/cop2r29) will add an extra clock cycle (if a GTE command is busy).

Additional Functions
The LZCS/LZCR registers offer a Count-Leading-Zeroes/Leading-Ones function.
The IRGB/ORGB registers allow to convert between 48bit and 15bit RGB colors.
These registers work without needing to send any COP2 commands. However, unlike for commands (which do automatically halt the CPU when needed), one must insert dummy opcodes between writing and reading the registers.


GTE Coordinate Calculation Commands

COP2 0180001h - 15 Cycles - RTPS - Perspective Transformation (single)
COP2 0280030h - 23 Cycles - RTPT - Perspective Transformation (triple)
RTPS performs final Rotate, translate and perspective transformation on vertex V0. Before writing to the FIFOs, the older entries are moved one stage down. RTPT is same as RTPS, but repeats for V1 and V2. The "sf" bit should be usually set.
  IR1 = MAC1 = (TRX*1000h + RT11*VX0 + RT12*VY0 + RT13*VZ0) SAR (sf*12)
  IR2 = MAC2 = (TRY*1000h + RT21*VX0 + RT22*VY0 + RT23*VZ0) SAR (sf*12)
  IR3 = MAC3 = (TRZ*1000h + RT31*VX0 + RT32*VY0 + RT33*VZ0) SAR (sf*12)
  SZ3 = MAC3 SAR ((1-sf)*12)                           ;ScreenZ FIFO 0..+FFFFh
  MAC0=(((H*20000h/SZ3)+1)/2)*IR1+OFX, SX2=MAC0/10000h ;ScrX FIFO -400h..+3FFh
  MAC0=(((H*20000h/SZ3)+1)/2)*IR2+OFY, SY2=MAC0/10000h ;ScrY FIFO -400h..+3FFh
  MAC0=(((H*20000h/SZ3)+1)/2)*DQA+DQB, IR0=MAC0/1000h  ;Depth cueing 0..+1000h
If the result of the "(((H*20000h/SZ3)+1)/2)" division is greater than 1FFFFh, then the division result is saturated to +1FFFFh, and the divide overflow bit in the FLAG register gets set; that happens if the vertex is exceeding the "near clip plane", ie. if it is very close to the camera (SZ3<=H/2), exactly at the camara position (SZ3=0), or behind the camera (negative Z coordinates are saturated to SZ3=0). For details on the division, see:
GTE Division Inaccuracy
For "far plane clipping", one can use the SZ3 saturation flag (MaxZ=FFFFh), or the IR3 saturation flag (MaxZ=7FFFh) (eg. used by Wipeout 2097), or one can compare the SZ3 value with any desired MaxZ value by software.
Note: The command does saturate IR1,IR2,IR3 to -8000h..+7FFFh (regardless of lm bit). When using RTP with sf=0, then the IR3 saturation flag (FLAG.22) gets set <only> if "MAC3 SAR 12" exceeds -8000h..+7FFFh (although IR3 is saturated when "MAC3" exceeds -8000h..+7FFFh).
  IR1,IR2,IR3 are saturated according to lm, but without setting FLAG.22 on IR3
  FLAG.22 is set when SZ3 exceeds -8000h..+7FFFh
  FLAG.18 is set when SZ3 exceeds 0000h..+FFFFh (and SZ3 is staturate as so).
  For RTPT, the DQA,DQB,IR0 calculation is done ONLY for 3rd vertex (V2)
  FLAG.12 is thus set only on last vertex (ie for RTPT: on V2)

COP2 1400006h - 8 Cycles - NCLIP - Normal clipping
  MAC0 = SX0*SY1 + SX1*SY2 + SX2*SY0 - SX0*SY2 - SX1*SY0 - SX2*SY1     ;slow
Or, more efficient, with same result:
  MAC0 = SX0*(SY1-SY2) + SX1*(SY2-SY0) + SX2*(SY0-SY1)                 ;fast
Error FLAG bit31,16,15 can get set if the final result exceeds 32bit range.
The sign of the result indicates whether the polygon coordinates are arranged clockwise or anticlockwise (ie. whether the front side or backside is visible). If the result is zero, then it's neither one (ie. the vertices are all arranged in a straight line; the GPU renders such straight lines as invisble 0 pixel width lines).

COP2 158002Dh - 5 Cycles - AVSZ3 - Average of three Z values (for Triangles)
COP2 168002Eh - 6 Cycles - AVSZ4 - Average of four Z values (for Quads)
  MAC0 = ZSF3*(SZ1+SZ2+SZ3)       ;for AVSZ3
  MAC0 = ZSF4*(SZ0+SZ1+SZ2+SZ3)   ;for AVSZ4
  OTZ  = MAC0/1000h               ;for both (saturated to 0..FFFFh)
Adds three or four Z values together and multiplies them by a fixed point value. The result can be used as index in the GPU's Ordering Table (OT).
GPU Depth Ordering
Commonly used scaling factors are ZSF3=N/30h and ZSF4=N/40h, where "N" is the number of entries in the OT (max 10000h). SZn and OTZ are unsigned 16bit values, for whatever reason ZSFn registers are signed 16bit values (negative values would allow a negative result in MAC0, but would saturate OTZ to zero).


GTE General Purpose Calculation Commands

COP2 0400012h - 8 Cycles - MVMVA(sf,mx,v,cv,lm)
Multiply vector by matrix and vector addition.
  Mx = matrix specified by mx  ;RT/LLM/LCM - Rotation, light or color matrix
  Vx = vector specified by v   ;V0, V1, V2, or [IR1,IR2,IR3]
  Tx = translation vector specified by cv  ;TR or BK or Bugged/FC, or None
Calculation:
  MAC1 = (Tx1*1000h + Mx11*Vx1 + Mx12*Vx2 + Mx13*Vx3) SAR (sf*12)
  MAC2 = (Tx2*1000h + Mx21*Vx1 + Mx22*Vx2 + Mx23*Vx3) SAR (sf*12)
  MAC3 = (Tx3*1000h + Mx31*Vx1 + Mx32*Vx2 + Mx33*Vx3) SAR (sf*12)
  [IR1,IR2,IR3] = [MAC1,MAC2,MAC3]
Multiplies a vector with either the rotation matrix, the light matrix or the color matrix and then adds the translation vector or background color vector.
Vx=2 selects the far color vector (FC), but this vector is not added correctly by the hardware: The MAC calculation is split into two parts, part1 does merely affect the IR saturation flags and resets sum to 0. For example, for MAC1 (and equivalent for MAC2,MAC3):
  IR1 = MAC1 = (Tx1*1000h + Mx11*Vx1) SAR (sf*12)  ;part1, saturate as if lm=0
  IR1 = MAC1 = (Mx12*Vx2 + Mx13*Vx3) SAR (sf*12)   ;part2, saturate by lm
Mx=3 selects a garbage matrix (with elements -R*10h, +R*10h, IR0, RT13, RT13, RT13, RT22, RT22, RT22; whereas, R is LSB of RGBC register).

COP2 0A00428h+sf*80000h - 5 Cycles - SQR(sf) - Square vector
  [MAC1,MAC2,MAC3] = [IR1*IR1,IR2*IR2,IR3*IR3] SHR (sf*12)
  [IR1,IR2,IR3]    = [MAC1,MAC2,MAC3]    ;IR1,IR2,IR3 saturated to max 7FFFh
Calculates the square of a vector. The result is, of course, always positive, so the "lm" flag for negative saturation has no effect.

COP2 170000Ch+sf*80000h - 6 Cycles - OP(sf,lm) - Outer product of 2 vectors
  [MAC1,MAC2,MAC3] = [IR3*D2-IR2*D3, IR1*D3-IR3*D1, IR2*D1-IR1*D2] SAR (sf*12)
  [IR1,IR2,IR3]    = [MAC1,MAC2,MAC3]                        ;copy result
Calculates the outer product of two signed 16bit vectors. Note: D1,D2,D3 are meant to be the RT11,RT22,RT33 elements of the RT matrix "misused" as vector. lm should be usually zero.

LZCS/LZCR registers - ? Cycles - Count-Leading-Zeroes/Leading-Ones
The LZCS/LZCR registers offer a Count-Leading-Zeroes/Leading-Ones function.


GTE Color Calculation Commands

COP2 0C8041Eh - 14 Cycles - NCS - Normal color (single)
COP2 0D80420h - 30 Cycles - NCT - Normal color (triple)
COP2 108041Bh - 17 Cycles - NCCS - Normal Color Color (single vector)
COP2 118043Fh - 39 Cycles - NCCT - Normal Color Color (triple vector)
COP2 0E80413h - 19 Cycles - NCDS - Normal color depth cue (single vector)
COP2 0F80416h - 44 Cycles - NCDT - Normal color depth cue (triple vectors)
In: V0=Normal vector (for triple variants repeated with V1 and V2), BK=Background color, RGBC=Primary color/code, LLM=Light matrix, LCM=Color matrix, IR0=Interpolation value.
  [IR1,IR2,IR3] = [MAC1,MAC2,MAC3] = (LLM*V0) SAR (sf*12)
  [IR1,IR2,IR3] = [MAC1,MAC2,MAC3] = (BK*1000h + LCM*IR) SAR (sf*12)
  [MAC1,MAC2,MAC3] = [R*IR1,G*IR2,B*IR3] SHL 4          ;<--- for NCDx/NCCx
  [MAC1,MAC2,MAC3] = MAC+(FC-MAC)*IR0                   ;<--- for NCDx only
  [MAC1,MAC2,MAC3] = [MAC1,MAC2,MAC3] SAR (sf*12)       ;<--- for NCDx/NCCx
  Color FIFO = [MAC1/16,MAC2/16,MAC3/16,CODE], [IR1,IR2,IR3] = [MAC1,MAC2,MAC3]

COP2 138041Ch - 11 Cycles - CC(lm=1) - Color Color
COP2 1280414h - 13 Cycles - CDP(...) - Color Depth Que
In: [IR1,IR2,IR3]=Vector, RGBC=Primary color/code, LCM=Color matrix, BK=Background color, and, for CDP, IR0=Interpolation value, FC=Far color.
  [IR1,IR2,IR3] = [MAC1,MAC2,MAC3] = (BK*1000h + LCM*IR) SAR (sf*12)
  [MAC1,MAC2,MAC3] = [R*IR1,G*IR2,B*IR3] SHL 4
  [MAC1,MAC2,MAC3] = MAC+(FC-MAC)*IR0                   ;<--- for CDP only
  [MAC1,MAC2,MAC3] = [MAC1,MAC2,MAC3] SAR (sf*12)
  Color FIFO = [MAC1/16,MAC2/16,MAC3/16,CODE], [IR1,IR2,IR3] = [MAC1,MAC2,MAC3]

COP2 0680029h - 8 Cycles - DCPL - Depth Cue Color light
COP2 0780010h - 8 Cycles - DPCS - Depth Cueing (single)
COP2 0x8002Ah - 17 Cycles - DPCT - Depth Cueing (triple)
COP2 0980011h - 8 Cycles - INTPL - Interpolation of a vector and far color
In: [IR1,IR2,IR3]=Vector, FC=Far Color, IR0=Interpolation value, CODE=MSB of RGBC, and, for DCPL, R,G,B=LSBs of RGBC.
  [MAC1,MAC2,MAC3] = [R*IR1,G*IR2,B*IR3] SHL 4          ;<--- for DCPL only
  [MAC1,MAC2,MAC3] = [IR1,IR2,IR3] SHL 12               ;<--- for INTPL only
  [MAC1,MAC2,MAC3] = [R,G,B] SHL 16                     ;<--- for DPCS/DPCT
  [MAC1,MAC2,MAC3] = MAC+(FC-MAC)*IR0
  [MAC1,MAC2,MAC3] = [MAC1,MAC2,MAC3] SAR (sf*12)
  Color FIFO = [MAC1/16,MAC2/16,MAC3/16,CODE], [IR1,IR2,IR3] = [MAC1,MAC2,MAC3]
DPCT executes thrice, and reads the R,G,B values from RGB0 (ie. reads from the Bottom of the Color FIFO, instead of from the RGBC register) (the CODE value is kept read from RGBC as usually), so, after DPCT execution, the RGB0,RGB1,RGB2 Fifo entries are modified.

COP2 190003Dh - 5 Cycles - GPF(sf,lm) - General purpose Interpolation
COP2 1A0003Eh - 5 Cycles - GPL(sf,?) - General Interpolation with base
  [MAC1,MAC2,MAC3] = [0,0,0]                            ;<--- for GPF only
  [MAC1,MAC2,MAC3] = [MAC1,MAC2,MAC3] SHL (sf*12)       ;<--- for GPL only
  [MAC1,MAC2,MAC3] = (([IR1,IR2,IR3] * IR0) + [MAC1,MAC2,MAC3]) SAR (sf*12)
  Color FIFO = [MAC1/16,MAC2/16,MAC3/16,CODE], [IR1,IR2,IR3] = [MAC1,MAC2,MAC3]
Note: Although the SHL in GPL is theoretically undone by the SAR, 44bit overflows can occur internally when sf=1.

Details on "MAC+(FC-MAC)*IR0"
  [IR1,IR2,IR3] = (([RFC,GFC,BFC] SHL 12) - [MAC1,MAC2,MAC3]) SAR (sf*12)
  [MAC1,MAC2,MAC3] = (([IR1,IR2,IR3] * IR0) + [MAC1,MAC2,MAC3])
Note: Above "[IR1,IR2,IR3]=(FC-MAC)" is saturated to -8000h..+7FFFh (ie. as if lm=0), anyways, further writes to [IR1,IR2,IR3] (within the same command) are saturated as usually (ie. depending on lm setting).

Details on "(LLM*V0) SAR (sf*12)" and "(BK*1000h + LCM*IR) SAR (sf*12)"
Works like MVMVA command (see there), but with fixed Tx/Vx/Mx parameters, the sf/lm bits can be changed and do affect the results (although normally both bits should be set for use with color matrices).

Notes
The 8bit RGB values written to the top of Color Fifo are the 32bit MACn values divided by 16, and saturated to +00h..+FFh, and of course, the older Fifo entries are moved downwards. Note that, at the GPU side, the meaning of the RGB values depends on whether or not texture blending is used (for untextured polygons FFh is max brightness) (for texture blending FFh is double brightness and 80h is normal brightness).
The 8bit CODE value is intended to contain a GP0(20h..7Fh) Rendering command, allowing to automatically merge the 8bit command number, with the 24bit color value.
The IRGB/ORGB registers allow to convert between 48bit and 15bit RGB colors.
Although the result of the commands in this chapter is written to the Color FIFO, some commands like GPF/GPL may be also used for other purposes (eg. to scale or scale/translate single vertices).


GTE Division Inaccuracy

GTE Division Inaccuracy (for RTPS/RTPT commands)
Basically, the GTE division does (attempt to) work as so (using 33bit maths):
  n = (((H*20000h/SZ3)+1)/2)
alternatly, below would give (almost) the same result (using 32bit maths):
  n = ((H*10000h+SZ3/2)/SZ3)
in both cases, the result is saturated about as so:
  if n>1FFFFh or division_by_zero then n=1FFFFh, FLAG.Bit17=1, FLAG.Bit31=1
However, the real GTE hardware is using a fast, but less accurate division mechanism (based on Unsigned Newton-Raphson (UNR) algorithm):
  if (H < SZ3*2) then                            ;check if overflow
    z = count_leading_zeroes(SZ3)                ;z=0..0Fh (for 16bit SZ3)
    n = (H SHL z)                                ;n=0..7FFF8000h
    d = (SZ3 SHL z)                              ;d=8000h..FFFFh
    u = unr_table[(d-7FC0h) SHR 7] + 101h        ;u=200h..101h
    d = ((2000080h - (d * u)) SHR 8)             ;d=10000h..0FF01h
    d = ((0000080h + (d * u)) SHR 8)             ;d=20000h..10000h
    n = min(1FFFFh, (((n*d) + 8000h) SHR 16))    ;n=0..1FFFFh
  else n = 1FFFFh, FLAG.Bit17=1, FLAG.Bit31=1    ;n=1FFFFh plus overflow flag
the GTE's unr_table[000h..100h] consists of following values:
  FFh,FDh,FBh,F9h,F7h,F5h,F3h,F1h,EFh,EEh,ECh,EAh,E8h,E6h,E4h,E3h ;\
  E1h,DFh,DDh,DCh,DAh,D8h,D6h,D5h,D3h,D1h,D0h,CEh,CDh,CBh,C9h,C8h ; 00h..3Fh
  C6h,C5h,C3h,C1h,C0h,BEh,BDh,BBh,BAh,B8h,B7h,B5h,B4h,B2h,B1h,B0h ;
  AEh,ADh,ABh,AAh,A9h,A7h,A6h,A4h,A3h,A2h,A0h,9Fh,9Eh,9Ch,9Bh,9Ah ;/
  99h,97h,96h,95h,94h,92h,91h,90h,8Fh,8Dh,8Ch,8Bh,8Ah,89h,87h,86h ;\
  85h,84h,83h,82h,81h,7Fh,7Eh,7Dh,7Ch,7Bh,7Ah,79h,78h,77h,75h,74h ; 40h..7Fh
  73h,72h,71h,70h,6Fh,6Eh,6Dh,6Ch,6Bh,6Ah,69h,68h,67h,66h,65h,64h ;
  63h,62h,61h,60h,5Fh,5Eh,5Dh,5Dh,5Ch,5Bh,5Ah,59h,58h,57h,56h,55h ;/
  54h,53h,53h,52h,51h,50h,4Fh,4Eh,4Dh,4Dh,4Ch,4Bh,4Ah,49h,48h,48h ;\
  47h,46h,45h,44h,43h,43h,42h,41h,40h,3Fh,3Fh,3Eh,3Dh,3Ch,3Ch,3Bh ; 80h..BFh
  3Ah,39h,39h,38h,37h,36h,36h,35h,34h,33h,33h,32h,31h,31h,30h,2Fh ;
  2Eh,2Eh,2Dh,2Ch,2Ch,2Bh,2Ah,2Ah,29h,28h,28h,27h,26h,26h,25h,24h ;/
  24h,23h,22h,22h,21h,20h,20h,1Fh,1Eh,1Eh,1Dh,1Dh,1Ch,1Bh,1Bh,1Ah ;\
  19h,19h,18h,18h,17h,16h,16h,15h,15h,14h,14h,13h,12h,12h,11h,11h ; C0h..FFh
  10h,0Fh,0Fh,0Eh,0Eh,0Dh,0Dh,0Ch,0Ch,0Bh,0Ah,0Ah,09h,09h,08h,08h ;
  07h,07h,06h,06h,05h,05h,04h,04h,03h,03h,02h,02h,01h,01h,00h,00h ;/
  00h    ;<-- one extra table entry (for "(d-7FC0h)/80h"=100h)    ;-100h
Above can be generated as "unr_table[i]=min(0,(40000h/(i+100h)+1)/2-101h)".
Some special cases: NNNNh/0001h uses a big multiplier (d=20000h), in practice, this can occur only for 0000h/0001h and 0001h/0001h (due to the H<SZ3*2 overflow check).
The min(1FFFFh) limit is needed for cases like FE3Fh/7F20h, F015h/780Bh, etc. (these do produce UNR result 20000h, and are saturated to 1FFFFh, but without setting overflow FLAG bits).


Macroblock Decoder (MDEC)

The MDEC is a JPEG-style Macroblock Decoder, that can decompress pictures (or a series of pictures, for being displayed as a movie).

MDEC I/O Ports
MDEC Commands
MDEC Decompression
MDEC Data Format


MDEC I/O Ports

1F801820h - MDEC0 - MDEC Command/Parameter Register (W)
  31-0  Command or Parameters
Used to send command word, followed by parameter words to the MDEC (usually, only the command word is written to this register, and the parameter words are transferred via DMA0).

1F801820h.Read - MDEC Data/Response Register (R)
  31-0  Macroblock Data (or Garbage if there's no data available)
The data is always output as a 8x8 pixel bitmap, so, when manually reading from this register and using colored 16x16 pixel macroblocks, the data from four 8x8 blocks must be re-ordered accordingly (usually, the data is received via DMA1, which is doing the re-ordering automatically). For monochrome 8x8 macroblocks, no re-ordering is needed (that works with DMA1, too).

1F801824h - MDEC1 - MDEC Status Register (R)
  31    Data-Out Fifo Empty (0=No, 1=Empty)
  30    Data-In Fifo Full   (0=No, 1=Full, or Last word received)
  29    Command Busy  (0=Ready, 1=Busy receiving or processing parameters)
  28    Data-In Request  (set when DMA0 enabled and ready to receive data)
  27    Data-Out Request (set when DMA1 enabled and ready to send data)
  26-25 Data Output Depth  (0=4bit, 1=8bit, 2=24bit, 3=15bit)      ;CMD.28-27
  24    Data Output Signed (0=Unsigned, 1=Signed)                  ;CMD.26
  23    Data Output Bit15  (0=Clear, 1=Set) (for 15bit depth only) ;CMD.25
  22-19 Not used (seems to be always zero)
  18-16 Current Block (0..3=Y1..Y4, 4=Cr, 5=Cb) (or for mono: always 4=Y)
  15-0  Number of Parameter Words remaining minus 1  (FFFFh=None)  ;CMD.Bit0-15
If there's data in the output fifo, then the Current Block bits are always set to the current output block number (ie. Y1..Y4; or Y for mono) (this information is apparently passed to the DMA1 controller, so that it knows if and how it must re-order the data in RAM). If the output fifo is empty, then the bits indicate the currently processsed incoming block (ie. Cr,Cb,Y1..Y4; or Y for mono).

1F801824h - MDEC1 - MDEC Control/Reset Register (W)
  31    Reset MDEC (0=No change, 1=Abort any command, and set status=80040000h)
  30    Enable Data-In Request  (0=Disable, 1=Enable DMA0 and Status.bit28)
  29    Enable Data-Out Request (0=Disable, 1=Enable DMA1 and Status.bit27)
  28-0  Unknown/Not used - usually zero
The data requests are required to be enabled for using DMA (and for reading the request status flags by software). The Data-Out request acts a bit strange: It gets set when a block is available, but, it gets cleared after reading the first some words of that block (nethertheless, one can keep reading the whole block, until the fifo-empty flag gets set).

DMA
MDEC decompression uses a lot of DMA channels (and CPU processing):
  1) DMA3 (CDROM)    to send Huffman compressed data from CDROM to RAM
  2) CPU  (MIPS)     to convert Huffman bitstream to 16bit MDEC RLE values
  3) DMA0 (MDEC.In)  to send MDEC compressed data from RAM to MDEC
  4) DMA1 (MDEC.Out) to send uncompressed macroblocks from MDEC to RAM
  5) DMA2 (GPU)      to send uncompressed macroblocks from RAM to GPU
DMA0 and DMA1 should be usually used with a blocksize of 20h words. If necessary, the parameters for the MDEC(1) command should be padded with FE00h halfwords to match the 20h words (40h halfwords) DMA blocksize.


MDEC Commands

MDEC(1) - Decode Macroblock(s)
  31-29 Command (1=decode_macroblock)
  28-27 Data Output Depth  (0=4bit, 1=8bit, 2=24bit, 3=15bit)      ;STAT.26-25
  26    Data Output Signed (0=Unsigned, 1=Signed)                  ;STAT.24
  25    Data Output Bit15  (0=Clear, 1=Set) (for 15bit depth only) ;STAT.23
  24-16 Not used (should be zero)
  15-0  Number of Parameter Words (size of compressed data)
This command is followed by one or more Macroblock parameters (usually, all macroblocks for the whole image are sent at once).

MDEC(2) - Set Quant Table(s)
  31-29 Command (2=set_iqtab)
  28-1  Not used (should be zero)  ;Bit25-28 are copied to STAT.23-26 though
  0     Color   (0=Luminance only, 1=Luminance and Color)
The command word is followed by 64 unsigned parameter bytes for the Luminance Quant Table (used for Y1..Y4), and if Command.Bit0 was set, by another 64 unsigned parameter bytes for the Color Quant Table (used for Cr and Cb).

MDEC(3) - Set Scale Table
  31-29 Command (3=set_scale)
  28-0  Not used (should be zero)  ;Bit25-28 are copied to STAT.23-26 though
The command is followed by 64 signed halfwords with 14bit fractional part, the values should be usually/always the same values (based on the standard JPEG constants, although, MDEC(3) allows to use other values than that constants).

MDEC(0) - No function
This command has no function. Command bits 25-28 are reflected to Status bits 23-26 as usually. Command bits 0-15 are reflected to Status bits 0-15 (similar as the "number of parameter words" for MDEC(1), but without the "minus 1" effect, and without actually expecting any parameters).

MDEC(4..7) - Invalid
These commands act identical as MDEC(0).


MDEC Decompression

decode_colored_macroblock ;MDEC(1) command (at 15bpp or 24bpp depth)
  rl_decode_block(Crblk,src,iq_uv)                 ;Cr (low resolution)
  rl_decode_block(Cbblk,src,iq_uv)                 ;Cb (low resolution)
  rl_decode_block(Yblk,src,iq_y), yuv_to_rgb(0,0)  ;Y1 (and upper-left Cr,Cb)
  rl_decode_block(Yblk,src,iq_y), yuv_to_rgb(0,8)  ;Y2 (and upper-right Cr,Cb)
  rl_decode_block(Yblk,src,iq_y), yuv_to_rgb(8,0)  ;Y3 (and lower-left Cr,Cb)
  rl_decode_block(Yblk,src,iq_y), yuv_to_rgb(8,8)  ;Y4 (and lower-right Cr,Cb)

decode_monochrome_macroblock ;MDEC(1) command (at 4bpp or 8bpp depth)
  rl_decode_block(Yblk,src,iq_y), y_to_mono        ;Y

rl_decode_block(blk,src,qt)
  for i=0 to 63, blk[i]=0, next i   ;initially zerofill all entries (for skip)
 @@skip:
  n=[src], src=src+2, k=0           ;get first entry, init dest addr k=0
  if n=FE00h then @@skip            ;ignore padding (FE00h as first halfword)
  q_scale=(n SHR 10) AND 3Fh        ;contains scale value (not "skip" value)
  val=signed10bit(n AND 3FFh)*qt[k] ;calc first value (without q_scale/8) (?)
 @@lop:
  if q_scale=0 then val=signed10bit(n AND 3FFh)*2   ;special mode without qt[k]
  val=minmax(val,-400h,+3FFh)            ;saturate to signed 11bit range
  val=val*scalezag[i]                    ;<-- for "fast_idct_core" only
  if q_scale>0 then blk[zagzig[k]]=val   ;store entry (normal case)
  if q_scale=0 then blk[k]=val           ;store entry (special, no zigzag)
  n=[src], src=src+2                     ;get next entry (or FE00h end code)
  k=k+((n SHR 10) AND 3Fh)+1             ;skip zerofilled entries
  val=(signed10bit(n AND 3FFh)*qt[k]*q_scale+4)/8  ;calc value for next entry
  if k<=63 then jump @@lop          ;should end with n=FE00h (that sets k>63)
  idct_core(blk)
  return (with "src" address advanced)

fast_idct_core(blk) ;fast "idct_core" version
Fast code with only 80 multiplications, works only if the scaletable from MDEC(3) command contains standard values (which is the case for all known PSX games).
  src=blk, dst=temp_buffer
  for pass=0 to 1
    for i=0 to 7
      if src[(1..7)*8+i]=0 then      ;when src[(1..7)*8+i] are all zero:
        dst[i*8+(0..7)]=src[0*8+i]   ;quick fill by src[0*8+i]
      else
        z10=src[0*8+i]+src[4*8+i], z11=src[0*8+i]-src[4*8+i]
        z13=src[2*8+i]+src[6*8+i], z12=src[2*8+i]-src[6*8+i]
        z12=(1.414213562*z12)-z13          ;=sqrt(2)
        tmp0=z10+z13, tmp3=z10-z13, tmp1=z11+z12, tmp2=z11-z12
        z13=src[3*8+i]+src[5*8+i], z10=src[3*8+i]-src[5*8+i]
        z11=src[1*8+i]+src[7*8+i], z12=src[1*8+i]-src[7*8+i]
        z5  =(1.847759065*(z12-z10))       ;=sqrt(2)*scalefactor[2]
        tmp7=z11+z13
        tmp6=(2.613125930*(z10))+z5-tmp7   ;=scalefactor[2]*2
        tmp5=(1.414213562*(z11-z13))-tmp6  ;=sqrt(2)
        tmp4=(1.082392200*(z12))-z5+tmp5   ;=sqrt(2)/scalefactor[2]
        dst[i*8+0]=tmp0+tmp7, dst[i*8+7]=tmp0-tmp7
        dst[i*8+1]=tmp1+tmp6, dst[i*8+6]=tmp1-tmp6
        dst[i*8+2]=tmp2+tmp5, dst[i*8+5]=tmp2-tmp5
        dst[i*8+4]=tmp3+tmp4, dst[i*8+3]=tmp3-tmp4
      endif
    next i
    swap(src,dst)
  next pass

real_idct_core(blk) ;low level "idct_core" version
Low level code with 1024 multiplications, using the scaletable from the MDEC(3) command. Computes dst=src*scaletable (using normal matrix maths, but with "src" being diagonally mirrored, ie. the matrices are processed column by column, instead of row by column), repeated with src/dst exchanged.
  src=blk, dst=temp_buffer
  for pass=0 to 1
    for x=0 to 7
      for y=0 to 7
        sum=0
        for z=0 to 7
          sum=sum+src[y+z*8]*(scaletable[x+z*8]/8)
        next z
        dst[x+y*8]=(sum+0fffh)/2000h               ;<-- or so?
      next y
    next x
    swap(src,dst)
  next pass
The "(sum+0fffh)/2000h" part is meant to strip fractional bits, and to round-up the result if the fraction was BIGGER than 0.5. The hardware appears to be working roughly like that, still the results aren't perfect.
Maybe the real hardware is doing further roundings in other places, possibly stripping some fractional bits before summing up "sum", possibly stripping different amounts of bits in the two "pass" cycles, and possibly keeping a final fraction passed on to the y_to_mono stage.

yuv_to_rgb(xx,yy)
  for y=0 to 7
    for x=0 to 7
      R=[Crblk+((x+xx)/2)+((y+yy)/2)*8], B=[Cbblk+((x+xx)/2)+((y+yy)/2)*8]
      G=(-0.3437*B)+(-0.7143*R), R=(1.402*R), B=(1.772*B)
      Y=[Yblk+(x)+(y)*8]
      R=MinMax(-128,127,(Y+R))
      G=MinMax(-128,127,(Y+G))
      B=MinMax(-128,127,(Y+B))
      if unsigned then BGR=BGR xor 808080h  ;aka add 128 to the R,G,B values
      dst[(x+xx)+(y+yy)*16]=BGR
    next x
  next y
Note: The exact fixed point resolution for "yuv_to_rgb" is unknown. And, there's probably also some 9bit limit (similar as in "y_to_mono").

y_to_mono
  for i=0 to 63
    Y=[Yblk+i]
    Y=Y AND 1FFh                  ;clip to signed 9bit range
    Y=MinMax(-128,127,Y)          ;saturate from 9bit to signed 8bit range
    if unsigned then Y=Y xor 80h  ;aka add 128 to the Y value
    dst[i]=Y
  next i

set_iqtab ;MDEC(2) command
  iqtab_core(iq_y,src), src=src+64       ;luminance quant table
  if command_word.bit0=1
    iqtab_core(iq_uv,src), src=src+64    ;color quant table (optional)
  endif

iqtab_core(iq,src) ;src = 64 unsigned parameter bytes
  for i=0 to 63, iq[i]=src[i], next i
Note: For "fast_idct_core" one could precalc "iq[i]=src[i]*scalezag[i]", but that would conflict with the RLE saturation/rounding steps (though those steps aren't actually required, so a very-fast decoder could omit them).

scalefactor[0..7] = cos((0..7)*90'/8) ;for [1..7]: multiplied by sqrt(2)
  1.000000000, 1.387039845, 1.306562965, 1.175875602,
  1.000000000, 0.785694958, 0.541196100, 0.275899379

zigzag[0..63] =
  0 ,1 ,5 ,6 ,14,15,27,28,
  2 ,4 ,7 ,13,16,26,29,42,
  3 ,8 ,12,17,25,30,41,43,
  9 ,11,18,24,31,40,44,53,
  10,19,23,32,39,45,52,54,
  20,22,33,38,46,51,55,60,
  21,34,37,47,50,56,59,61,
  35,36,48,49,57,58,62,63

scalezag[0..63] (precalulated factors, for "fast_idct_core")
  for y=0 to 7
   for x=0 to 7
    scalezag[zigzag[x+y*8]] = scalefactor[x] * scalefactor[y] / 8
   next x
  next y

zagzig[0..63] (reversed zigzag table)
  for i=0 to 63, zagzig[zigzag[i]]=i, next i

set_quant_table: ;MDEC(2) command
This command defines the quant tables, there are two tables (one for luminance and one for chroma). For STR movies and BS pictures both 64-byte tables should be almost always set to following 64 bytes:
  02h,10h,10h,13h,10h,13h,16h,16h
  16h,16h,16h,16h,1Ah,18h,1Ah,1Bh
  1Bh,1Bh,1Ah,1Ah,1Ah,1Ah,1Bh,1Bh
  1Bh,1Dh,1Dh,1Dh,22h,22h,22h,1Dh
  1Dh,1Dh,1Bh,1Bh,1Dh,1Dh,20h,20h
  22h,22h,25h,26h,25h,23h,23h,22h
  23h,26h,26h,28h,28h,28h,30h,30h
  2Eh,2Eh,38h,38h,3Ah,45h,45h,53h
Note: The exception are BS fraquant movies in X-Files and Eagle One (these do also use the above values, but do have them multiplied with a fixed point number).

set_scale_table: ;MDEC(3) command
This command defines the IDCT scale matrix, which should be usually/always:
  5A82 5A82 5A82 5A82 5A82 5A82 5A82 5A82
  7D8A 6A6D 471C 18F8 E707 B8E3 9592 8275
  7641 30FB CF04 89BE 89BE CF04 30FB 7641
  6A6D E707 8275 B8E3 471C 7D8A 18F8 9592
  5A82 A57D A57D 5A82 5A82 A57D A57D 5A82
  471C 8275 18F8 6A6D 9592 E707 7D8A B8E3
  30FB 89BE 7641 CF04 CF04 7641 89BE 30FB
  18F8 B8E3 6A6D 8275 7D8A 9592 471C E707
Note that the hardware does actually use only the upper 13bit of those 16bit values. The values are choosen like so,
  +s0  +s0  +s0  +s0  +s0  +s0  +s0  +s0
  +s1  +s3  +s5  +s7  -s7  -s5  -s3  -s1
  +s2  +s6  -s6  -s2  -s2  -s6  +s6  +s2
  +s3  -s7  -s1  -s5  +s5  +s1  +s7  -s3
  +s4  -s4  -s4  +s4  +s4  -s4  -s4  +s4
  +s5  -s1  +s7  +s3  -s3  -s7  +s1  -s5
  +s6  -s2  +s2  -s6  -s6  +s2  -s2  +s6
  +s7  -s5  +s3  -s1  +s1  -s3  +s5  -s7
whereas, s0..s7 = scalefactor[0..7], multiplied by sqrt(2) (ie. by 1.414), and multiplied by 4000h (ie. with 14bit fractional part).


MDEC Data Format

Colored Macroblocks (16x16 pixels) (in 15bpp or 24bpp depth mode)
Each macroblock consists of six blocks: Two low-resolution blocks with color information (Cr,Cb) and four full-resolution blocks with luminance (grayscale) information (Y1,Y2,Y3,Y4). The color blocks are zoomed from 8x8 to 16x16 pixel size, merged with the luminance blocks, and then converted from YUV to RGB format.
   .-----.       .-----.       .-----.         .-----.
   |     |       |     |       |Y1|Y2|         |     |
   | Cr  |   +   | Cb  |   +   |--+--|  ---->  | RGB |
   |     |       |     |       |Y3|Y4|         |     |
   '-----'       '-----'       '-----'         '-----'
Native PSX files are usually containing vertically arranged Macroblocks (eg. allowing to send them to the GPU as 16x240 portion) (JPEG-style horizontally arranged Macroblocks would require to send the data in 16x16 pixel portions to the GPU) (something like 320x16 won't work, since that'd require to wrap from the bottom of the first macroblock to the top of the next macroblock).

Monochrome Macroblocks (8x8 pixel) (in 4bpp or 8bpp depth mode)
Each macroblock consist of only one block: with luminance (grayscale) information (Y), the data comes out as such (it isn't converted to RGB).
   .--.         .--.
   |Y |  ---->  |Y |
   '--'         '--'
The output is an 8x8 bitmap (not 16x16), so it'd be send to the GPU as 8x8 pixel rectangle, or multiple blocks at once as 8x240 pixel rectangle. Since the data isn't RGB, it should be written to Texture memory (and then it can be forwarded to the frame buffer in form of a texture with monochrome 15bit palette with 32 grayscales). Alternately, one could convert the 8bpp image to 24bpp by software (this would allow to use 256 grayscales).

Blocks (8x8 pixels)
An (uncompressed) block consists of 64 values, representing 8x8 pixels. The first (upper-left) value is an absolute value (called "DC" value), the remaining 63 values are relative to the DC value (called "AC" values). After decompression and zig-zag reordering, the data in unfiltered horizontally and vertically (IDCT conversion, ie. the relative "AC" values are converted to absolute "DC" values).

.STR Files
PSX Video files are usually having file extension .STR (for "Streaming").
CDROM File Video STR Streaming and BS Picture Compression (Sony)

MDEC vs JPEG
The MDEC data format is very similar to the JPEG file format, the main difference is that JPEG uses Huffman compressed blocks, whilst MDEC uses Run-Length (RL) compressed blocks.
The (uncompressed) blocks are same as in JPEGs, using the same zigzag ordering, AC to DC conversion, and YUV to RGB conversion (ie. the MDEC hardware can be also used to decompress JPEGs, when handling the file header and huffman decompression by software).
Some other differences are that MDEC has only 2 fixed-purpose quant tables, whilst JPEGs <can> use up to 4 general-purpose quant tables. Also, JPEGs <can> use other color resolutions than the 8x8 color info for 16x16 pixels. Whereas, JPEGs <can> do that stuff, but most standard JPEG files aren't actually using 4 quant tables, nor higher color resolution.

Run-Length compressed Blocks
Within each block the DCT information and RLE compressed data is stored:
  DCT               ;1 halfword
  RLE,RLE,RLE,etc.  ;0..63 halfwords
  EOB               ;1 halfword

DCT (1st value)
DCT data has the quantization factor and the Direct Current (DC) reference.
  15-10 Q    Quantization factor (6 bits, unsigned)
  9-0   DC   Direct Current reference (10 bits, signed)
Contains the absolute DC value (the upper-left value of the 8x8 block).

RLE (Run length data, for 2nd through 64th value)
  15-10 LEN  Number of zero AC values to be inserted (6 bits, unsigned)
  9-0   AC   Relative AC value (10 bits, signed)
Example: AC values "000h,000h,123h" would be compressed as "(2 shl 10)+123h".

EOB (End Of Block)
Indicates the end of a 8x8 pixel block, causing the rest of the block to be padded with zero AC values.
  15-0  End-code (Fixed, FE00h)
EOB isn't required if the block was already fully defined (up to including blk[63]), however, most games seem to append EOB to all blocks (although it's just acting as dummy/padding value in case of fully defined blocks).

Dummy halfwords
Data is sent in units of words (or, when using DMA, even in units of 32-words), which is making it neccessary to send some dummy halfwords (unless the compressed data size should match up the transfer unit). The value FE00h can be used as dummy value: When FE00h appears at the begin of a new block, or after the end of block, then it is simply ignored by the hardware (if it occurs elsewhere, then it acts as EOB end code, as described above).


Sound Processing Unit (SPU)

SPU Overview
SPU ADPCM Samples
SPU ADPCM Pitch
SPU Volume and ADSR Generator
SPU Voice Flags
SPU Noise Generator
SPU Control and Status Register
SPU Memory Access
SPU Interrupt
SPU Reverb Registers
SPU Reverb Formula
SPU Reverb Examples
SPU Unknown Registers


SPU Overview

SPU I/O Port Summary
  1F801C00h..1F801D7Fh - Voice 0..23 Registers (eight 16bit regs per voice)
  1F801D80h..1F801D87h - SPU Control (volume)
  1F801D88h..1F801D9Fh - Voice 0..23 Flags (six 1bit flags per voice)
  1F801DA2h..1F801DBFh - SPU Control (memory, control, etc.)
  1F801DC0h..1F801DFFh - Reverb configuration area
  1F801E00h..1F801E5Fh - Voice 0..23 Internal Registers
  1F801E60h..1F801E7Fh - Unknown?
  1F801E80h..1F801FFFh - Unused?

SPU Memory layout (512Kbyte RAM)
  00000h-003FFh  CD Audio left  (1Kbyte) ;\CD Audio before Volume processing
  00400h-007FFh  CD Audio right (1Kbyte) ;/signed 16bit samples at 44.1kHz
  00800h-00BFFh  Voice 1 mono   (1Kbyte) ;\Voice 1 and 3 after ADSR processing
  00C00h-00FFFh  Voice 3 mono   (1Kbyte) ;/signed 16bit samples at 44.1kHz
  01000h-xxxxxh  ADPCM Samples  (first 16bytes usually contain a Sine wave)
  xxxxxh-7FFFFh  Reverb work area
As shown above, the first 4Kbytes are used as special capture buffers, and, if desired, one can also use the Reverb hardware to capture output from other voice(s).
The SPU memory is not mapped to the CPU bus, it can be accessed only via I/O, or via DMA transfers (DMA4).

Voices
The SPU has 24 hardware voices. These voices can be used to reproduce sample data, noise or can be used as frequency modulator on the next voice. Each voice has it's own programmable ADSR envelope filter. The main volume can be programmed independently for left and right output.

Voice Capabilities
All 24 voices are having exactly the same capabilities(?), with the exception that Voice 1 and 3 are having a special Capture feature (see SPU Memory map).
There seems to be no way to produce square waves (without storing a square wavefrom in memory... although, since SPU RAM isn't connected to the CPU bus, the "useless" DMA for square wave data wouldn't slowdown the CPU bus)?

Additional Sound Inputs
External Audio can be input (from the Expansion Port?), and the CDROM drive can be commanded to playback normal Audio CDs (via Play command), or XA-ADPCM sectors (via Read command), and to pass that data to the SPU.

Delayed I/O
The SPU seems to process written values at 44100Hz rate (so it may take 1/44100 seconds (300h clock cycles) until it has actually realized the new value).

Unstable 32bit Writes
All SPU registers must be written in 16bit halfword units. Trying to write 32bit words is unstable (it can result in the lower 16bit to be left unchanged; that effect appears to be timing depending, occurring on each 8th clock cycle) (one bad workaround is to issue all 32bit writes twice: Two consecutive writes do somewhat ensure that at least one of the two writes will occur on a good clock cycle, but it could be still unstable if an IRQ occurs between the 'consecutive' writes, and two 32bit writes are slower then two 16bit writes, which is more recommended).

Mono/Stereo Audio Output
The standard PSX Audio cables have separate Left/Right signals, that is good for stereo TVs, but, when using a normal mono TV, only one of the two audio signals (Left or Right) can be connected. PSX programs should thus offer an option to disable stereo effects, and to output an equal volume to both cables.

SPU Bus-Width
The SPU is connected to a 16bit databus. 8bit/16bit/32bit reads and 16bit/32bit writes are implemented. However, 8bit writes are NOT implemented: 8bit writes to ODD addresses are simply ignored (without causing any exceptions), 8bit writes to EVEN addresses are executed as 16bit writes (eg. "movp r1,12345678h, movb [spu_port],r1" will write 5678h instead of 78h).


SPU ADPCM Samples

The SPU supports only ADPCM compressed samples (uncompressed samples seem to be totally unsupported; leaving apart that one can write uncompressed 16bit PCM samples to the Reverb Buffer, which can be then output at 22050Hz, as long as they aren't overwritten by the hardware).

1F801C06h+N*10h - Voice 0..23 ADPCM Start Address (R/W)
This register holds the sample start address (not the current address, ie. the register doesn't increment during playback).
  15-0   Startaddress of sound in Sound buffer (in 8-byte units)
Writing to this register has no effect on the currently playing voice.
The start address is copied to the current address upon Key On.

1F801C0Eh+N*10h - Voice 0..23 ADPCM Repeat Address (R/W)
If the hardware finds an ADPCM header with Loop-Start-Bit, then it copies the current address to the repeat addresss register.
If the hardware finds an ADPCM header with Loop-Stop-Bit, then it copies the repeat addresss register setting to the current address; that, <after> playing the current ADPCM block.
  15-0  Address sample loops to at end (in 8-byte units)
Normally, repeat works automatically via the above start/stop bits, and software doesn't need to deal with the Repeat Address Register. However, reading from it may be useful to sense if the hardware has reached a start bit, and writing may be also useful in some cases, eg. to redirect a one-shot sample (with stop-bit, but without any start-bits) to a silent-loop located elsewhere in memory.

Sample Data (SPU-ADPCM)
Samples consist of one or more 16-byte blocks:
  00h       Shift/Filter (reportedly same as for CDROM XA-ADPCM) (see there)
  01h       Flag Bits (see below)
  02h       Compressed Data (LSBs=1st Sample, MSBs=2nd Sample)
  03h       Compressed Data (LSBs=3rd Sample, MSBs=4th Sample)
  04h       Compressed Data (LSBs=5th Sample, MSBs=6th Sample)
  ...       ...
  0Fh       Compressed Data (LSBs=27th Sample, MSBs=28th Sample)

Flag Bits (in 2nd byte of ADPCM Header)
  0   Loop End    (0=No change, 1=Set ENDX flag and Jump to [1F801C0Eh+N*10h])
  1   Loop Repeat (0=Force Release and set ADSR Level to Zero; only if Bit0=1)
  2   Loop Start  (0=No change, 1=Copy current address to [1F801C0Eh+N*10h])
  3-7 Unknown    (usually 0)
Possible combinations for Bit0-1 are:
  Code 0 = Normal     (continue at next 16-byte block)
  Code 1 = End+Mute   (jump to Loop-address, set ENDX flag, Release, Env=0000h)
  Code 2 = Ignored    (same as Code 0)
  Code 3 = End+Repeat (jump to Loop-address, set ENDX flag)

Looped and One-shot Samples
The Loop Start/End flags in the ADPCM Header allow to play one or more sample block(s) in a loop, that can be either all block(s) endless repeated, or only the last some block(s) of the sample.
There's no way to stop the output, so a one-shot sample must be followed by dummy block (with Loop Start/End flags both set, and all data nibbles set to zero; so that the block gets endless repeated, but doesn't produce any sound).

SPU-ADPCM vs XA-ADPCM
The PSX supports two ADPCM formats: SPU-ADPCM (as described above), and XA-ADPCM. XA-ADPCM is decompressed by the CDROM Controller, and sent directly to the sound mixer, without needing to store the data in SPU RAM, nor needing to use a Voice channel.
The actual decompression algorithm is the same for both formats. However, the XA nibbles are arranged in different order, and XA uses 2x28 nibbles per block (instead of 2x14), XA blocks can contain mono or stereo data, XA supports only two sample rates, and, XA doesn't support looping.


SPU ADPCM Pitch

1F801C04h+N*10h - Voice 0..23 ADPCM Sample Rate (R/W) (VxPitch)
  0-15  Sample rate (0=stop, 4000h=fastest, 4001h..FFFFh=usually same as 4000h)
Defines the ADPCM sample rate (1000h = 44100Hz). This register (and PMON) does only affect the ADPCM sample frequency (but not the Noise frequency, which is defined - and shared for all voices - in the SPUCNT register).

1F801D90h - Voice 0..23 Pitch Modulation Enable Flags (PMON), bit0-15
1F801D92h - Voice 0..23 Pitch Modulation Enable Flags (PMON), bit16-31
Pitch modulation allows to generate "Frequency Sweep" effects by mis-using the amplitude from channel (x-1) as pitch factor for channel (x).
  0     Unknown... Unused?
  1-23  Flags for Voice 1..23 (0=Normal, 1=Modulate by Voice 0..22)
  24-31 Not used
For example, output a very loud 1Hz sine-wave on channel 4 (with ADSR volume 4000h, and with Left/Right volume=0; unless you actually want to output it to the speaker). Then additionally output a 2kHz sine wave on channel 5 with PMON.Bit5 set. The "2kHz" sound should then repeatedly sweep within 1kHz..3kHz range (or, for a more decent sweep in 1.8kHz..2.2kHz range, drop the ADSR volume of channel 4).

Pitch Counter
The pitch counter is adjusted at 44100Hz rate as follows:
  Step = VxPitch                  ;range +0000h..+FFFFh (0...705.6 kHz)
  IF PMON.Bit(x)=1 AND (x>0)      ;pitch modulation enable
    Factor = VxOUTX(x-1)          ;range -8000h..+7FFFh (prev voice amplitude)
    Factor = Factor+8000h         ;range +0000h..+FFFFh (factor = 0.00 .. 1.99)
    Step=SignExpand16to32(Step)   ;hardware glitch on VxPitch>7FFFh, make sign
    Step = (Step * Factor) SAR 15 ;range 0..1FFFFh (glitchy if VxPitch>7FFFh)
    Step=Step AND 0000FFFFh       ;hardware glitch on VxPitch>7FFFh, kill sign
  IF Step>3FFFh then Step=4000h   ;range +0000h..+3FFFh (0.. 176.4kHz)
  Counter = Counter + Step
Counter.Bit12 and up indicates the current sample (within a ADPCM block).
Counter.Bit3..11 are used as 8bit gaussian interpolation index.

Maximum Sound Frequency
The Mixer and DAC supports a 44.1kHz output rate (allowing to produce max 22.1kHz tones). The Reverb unit supports only half the frequency.
The pitch counter supports sample rates up to 176.4kHz. However, exceeding the 44.1kHz limit causes the hardware to skip samples (or actually: to apply incomplete interpolation on the 'skipped' samples).
VxPitch can be theoretically 0..FFFFh (max 705.6kHz), normally 4000h..FFFFh are simply clipped to max=4000h (176.4kHz). Except, 4000h..FFFFh could be used with pitch modulation (as they are multiplied by 0.00..1.99 before clipping; in practice this works only for 4000h..7FFFh; as values 8000h..FFFFh are mistaken as signed values).

4-Point Gaussian Interpolation
Interpolation is applied on the 4 most recent 16bit ADPCM samples (new,old,older,oldest), using bit4-11 of the pitch counter as 8bit interpolation index (i=00h..FFh):
  out =       ((gauss[0FFh-i] * oldest) SAR 15)
  out = out + ((gauss[1FFh-i] * older)  SAR 15)
  out = out + ((gauss[100h+i] * old)    SAR 15)
  out = out + ((gauss[000h+i] * new)    SAR 15)
The Gauss table contains the following values (in hex):
  -001h,-001h,-001h,-001h,-001h,-001h,-001h,-001h ;\
  -001h,-001h,-001h,-001h,-001h,-001h,-001h,-001h ;
  0000h,0000h,0000h,0000h,0000h,0000h,0000h,0001h ;
  0001h,0001h,0001h,0002h,0002h,0002h,0003h,0003h ;
  0003h,0004h,0004h,0005h,0005h,0006h,0007h,0007h ;
  0008h,0009h,0009h,000Ah,000Bh,000Ch,000Dh,000Eh ;
  000Fh,0010h,0011h,0012h,0013h,0015h,0016h,0018h ; entry
  0019h,001Bh,001Ch,001Eh,0020h,0021h,0023h,0025h ; 000h..07Fh
  0027h,0029h,002Ch,002Eh,0030h,0033h,0035h,0038h ;
  003Ah,003Dh,0040h,0043h,0046h,0049h,004Dh,0050h ;
  0054h,0057h,005Bh,005Fh,0063h,0067h,006Bh,006Fh ;
  0074h,0078h,007Dh,0082h,0087h,008Ch,0091h,0096h ;
  009Ch,00A1h,00A7h,00ADh,00B3h,00BAh,00C0h,00C7h ;
  00CDh,00D4h,00DBh,00E3h,00EAh,00F2h,00FAh,0101h ;
  010Ah,0112h,011Bh,0123h,012Ch,0135h,013Fh,0148h ;
  0152h,015Ch,0166h,0171h,017Bh,0186h,0191h,019Ch ;/
  01A8h,01B4h,01C0h,01CCh,01D9h,01E5h,01F2h,0200h ;\
  020Dh,021Bh,0229h,0237h,0246h,0255h,0264h,0273h ;
  0283h,0293h,02A3h,02B4h,02C4h,02D6h,02E7h,02F9h ;
  030Bh,031Dh,0330h,0343h,0356h,036Ah,037Eh,0392h ;
  03A7h,03BCh,03D1h,03E7h,03FCh,0413h,042Ah,0441h ;
  0458h,0470h,0488h,04A0h,04B9h,04D2h,04ECh,0506h ;
  0520h,053Bh,0556h,0572h,058Eh,05AAh,05C7h,05E4h ; entry
  0601h,061Fh,063Eh,065Ch,067Ch,069Bh,06BBh,06DCh ; 080h..0FFh
  06FDh,071Eh,0740h,0762h,0784h,07A7h,07CBh,07EFh ;
  0813h,0838h,085Dh,0883h,08A9h,08D0h,08F7h,091Eh ;
  0946h,096Fh,0998h,09C1h,09EBh,0A16h,0A40h,0A6Ch ;
  0A98h,0AC4h,0AF1h,0B1Eh,0B4Ch,0B7Ah,0BA9h,0BD8h ;
  0C07h,0C38h,0C68h,0C99h,0CCBh,0CFDh,0D30h,0D63h ;
  0D97h,0DCBh,0E00h,0E35h,0E6Bh,0EA1h,0ED7h,0F0Fh ;
  0F46h,0F7Fh,0FB7h,0FF1h,102Ah,1065h,109Fh,10DBh ;
  1116h,1153h,118Fh,11CDh,120Bh,1249h,1288h,12C7h ;/
  1307h,1347h,1388h,13C9h,140Bh,144Dh,1490h,14D4h ;\
  1517h,155Ch,15A0h,15E6h,162Ch,1672h,16B9h,1700h ;
  1747h,1790h,17D8h,1821h,186Bh,18B5h,1900h,194Bh ;
  1996h,19E2h,1A2Eh,1A7Bh,1AC8h,1B16h,1B64h,1BB3h ;
  1C02h,1C51h,1CA1h,1CF1h,1D42h,1D93h,1DE5h,1E37h ;
  1E89h,1EDCh,1F2Fh,1F82h,1FD6h,202Ah,207Fh,20D4h ;
  2129h,217Fh,21D5h,222Ch,2282h,22DAh,2331h,2389h ; entry
  23E1h,2439h,2492h,24EBh,2545h,259Eh,25F8h,2653h ; 100h..17Fh
  26ADh,2708h,2763h,27BEh,281Ah,2876h,28D2h,292Eh ;
  298Bh,29E7h,2A44h,2AA1h,2AFFh,2B5Ch,2BBAh,2C18h ;
  2C76h,2CD4h,2D33h,2D91h,2DF0h,2E4Fh,2EAEh,2F0Dh ;
  2F6Ch,2FCCh,302Bh,308Bh,30EAh,314Ah,31AAh,3209h ;
  3269h,32C9h,3329h,3389h,33E9h,3449h,34A9h,3509h ;
  3569h,35C9h,3629h,3689h,36E8h,3748h,37A8h,3807h ;
  3867h,38C6h,3926h,3985h,39E4h,3A43h,3AA2h,3B00h ;
  3B5Fh,3BBDh,3C1Bh,3C79h,3CD7h,3D35h,3D92h,3DEFh ;/
  3E4Ch,3EA9h,3F05h,3F62h,3FBDh,4019h,4074h,40D0h ;\
  412Ah,4185h,41DFh,4239h,4292h,42EBh,4344h,439Ch ;
  43F4h,444Ch,44A3h,44FAh,4550h,45A6h,45FCh,4651h ;
  46A6h,46FAh,474Eh,47A1h,47F4h,4846h,4898h,48E9h ;
  493Ah,498Ah,49D9h,4A29h,4A77h,4AC5h,4B13h,4B5Fh ;
  4BACh,4BF7h,4C42h,4C8Dh,4CD7h,4D20h,4D68h,4DB0h ;
  4DF7h,4E3Eh,4E84h,4EC9h,4F0Eh,4F52h,4F95h,4FD7h ; entry
  5019h,505Ah,509Ah,50DAh,5118h,5156h,5194h,51D0h ; 180h..1FFh
  520Ch,5247h,5281h,52BAh,52F3h,532Ah,5361h,5397h ;
  53CCh,5401h,5434h,5467h,5499h,54CAh,54FAh,5529h ;
  5558h,5585h,55B2h,55DEh,5609h,5632h,565Bh,5684h ;
  56ABh,56D1h,56F6h,571Bh,573Eh,5761h,5782h,57A3h ;
  57C3h,57E2h,57FFh,581Ch,5838h,5853h,586Dh,5886h ;
  589Eh,58B5h,58CBh,58E0h,58F4h,5907h,5919h,592Ah ;
  593Ah,5949h,5958h,5965h,5971h,597Ch,5986h,598Fh ;
  5997h,599Eh,59A4h,59A9h,59ADh,59B0h,59B2h,59B3h ;/
The PSX table is a bit different as the SNES table: Values up to 3569h are smaller as on SNES, the remaining values are bigger as on SNES, and the width of the PSX table entries is 4bit higher as on SNES.
The PSX table is slightly bugged: Theoretically, each four values (gauss[000h+i], gauss[0FFh-i], gauss[100h+i], gauss[1FFh-i]) should sum up to 8000h, but in practice they do sum up to 7F7Fh..7F81h (fortunately the PSX sum doesn't exceed the 8000h limit; meaning that the PSX interpolations won't overflow, which has been a hardware glitch on the SNES).

Waveform Examples
  Incoming ADPCM Data ---> Interpolated Data
   _   _   _   _
  | | | | | | | |           .   .   .   .    Nibbles=79797979, Filter=0
  | | | | | | | |     ---> / \ / \ / \ / \   HALF-volume ZIGZAG-wave
  | |_| |_| |_| |_            '   '   '   '
   ___     ___
  |   |   |   |              .'.     .'.     Nibbles=77997799, Filter=0
  |   |   |   |       --->  /   \   /   \    FULL-volume SINE-wave
  |   |___|   |___         '     '.'     '.
   _______                     ___
  |       |                  .'   '.         Nibbles=77779999, Filter=0
  |       |           --->  /       \        SQUARE wave (with rounded edges)
  |       |_______         '         '.____
   _____         _             __
  |     |_     _|            .'  ''.    .'   Nibbles=7777CC44, Filter=0
  |       |___|       --->  /       '..'     CUSTOM wave-form
  |                        '
   ___     __
  |   |___|  |    _         \ ! /  .  \ ! /  Nibbles=77DE9HZK, Filter=V
  |_     ____|  _|    --->  - + -  +  - + -  SOLAR STORM wave-form
  __|   |______|___         / ! \  '  / ! \


SPU Volume and ADSR Generator

1F801C08h+N*10h - Voice 0..23 Attack/Decay/Sustain/Release (ADSR), bit0-15
1F801C0Ah+N*10h - Voice 0..23 Attack/Decay/Sustain/Release (ADSR), bit16-31
  ____lower 16bit (at 1F801C08h+N*10h)___________________________________
  15    Attack Mode       (0=Linear, 1=Exponential)
  -     Attack Direction  (Fixed, always Increase) (until Level 7FFFh)
  14-10 Attack Shift      (0..1Fh = Fast..Slow)
  9-8   Attack Step       (0..3 = "+7,+6,+5,+4")
  -     Decay Mode        (Fixed, always Exponential)
  -     Decay Direction   (Fixed, always Decrease) (until Sustain Level)
  7-4   Decay Shift       (0..0Fh = Fast..Slow)
  -     Decay Step        (Fixed, always "-8")
  3-0   Sustain Level     (0..0Fh)  ;Level=(N+1)*800h
  ____upper 16bit (at 1F801C0Ah+N*10h)___________________________________
  31    Sustain Mode      (0=Linear, 1=Exponential)
  30    Sustain Direction (0=Increase, 1=Decrease) (until Key OFF flag)
  29    Not used?         (should be zero)
  28-24 Sustain Shift     (0..1Fh = Fast..Slow)
  23-22 Sustain Step      (0..3 = "+7,+6,+5,+4" or "-8,-7,-6,-5") (inc/dec)
  21    Release Mode      (0=Linear, 1=Exponential)
  -     Release Direction (Fixed, always Decrease) (until Level 0000h)
  20-16 Release Shift     (0..1Fh = Fast..Slow)
  -     Release Step      (Fixed, always "-8")
The Attack phase gets started when the software sets the voice ON flag (see below), the hardware does then automatically go through Attack/Decay/Sustain, and switches from Sustain to Release when the software sets the Key OFF flag.

  Typical ADSR Shape
    A  D  S  R              Volume
      /\____                Loud (7FFFh)
     /      \_              Med  (4000h)
  __/         ""--....____  Mute (0000h)

1F801D80h - Mainvolume Left
1F801D82h - Mainvolume Right
1F801C00h+N*10h - Voice 0..23 Volume Left
1F801C02h+N*10h - Voice 0..23 Volume Right
Fixed Volume Mode (when Bit15=0):
  15    Must be zero      (0=Volume Mode)
  0-14  Voice volume/2    (-4000h..+3FFFh = Volume -8000h..+7FFEh)
Sweep Volume Mode (when Bit15=1):
  15    Must be set       (1=Sweep Mode)
  14    Sweep Mode        (0=Linear, 1=Exponential)
  13    Sweep Direction   (0=Increase, 1=Decrease)
  12    Sweep Phase       (0=Positive, 1=Negative)
  7-11  Not used?         (should be zero)
  6-2   Sweep Shift       (0..1Fh = Fast..Slow)
  1-0   Sweep Step        (0..3 = "+7,+6,+5,+4" or "-8,-7,-6,-5") (inc/dec)
Sweep is another Volume envelope, additionally to the ADSR volume envelope (unlike ADSR, sweep can be used for stereo effects, such like blending from left to right).
Sweep starts at the current volume (which can be set via Bit15=0, however, caution - the Bit15=0 setting isn't applied until the next 44.1kHz cycle; so setting the initial level with Bit15=0, followed by the sweep parameter with Bit15=1 works only if there's a suitable delay between the two operations). Once when sweep is started, the current volume level increases to +7FFFh, or decreases to 0000h.
Sweep Phase should be equal to the sign of the current volume (not yet tested, in the negative mode it does probably "increase" to -7FFFh?). The Phase bit seems to have no effect in Exponential Decrease mode.

1F801DB0h - CD Audio Input Volume, Left
1F801DB2h - CD Audio Input Volume, Right
1F801DB4h - External Audio Input Volume, Left
1F801DB6h - External Audio Input Volume, Right
CD Audio Input can be uncompressed CD-DA, or compressed XA-ADPCM). External Audio Input can be from expansion (which is generally never used).
  0-15  Volume        (-8000h..+7FFFh)
Note: The CDROM controller supports additional CD volume control (including ability to convert stereo CD output to mono, or to swap left/right channels).

Envelope Operation depending on Shift/Step/Mode/Direction
  AdsrCycles = 1 SHL Max(0,ShiftValue-11)
  AdsrStep = StepValue SHL Max(0,11-ShiftValue)
  IF exponential AND increase AND AdsrLevel>6000h THEN AdsrCycles=AdsrCycles*4
  IF exponential AND decrease THEN AdsrStep=AdsrStep*AdsrLevel/8000h
  Wait(AdsrCycles)              ;cycles counted at 44.1kHz clock
  AdsrLevel=AdsrLevel+AdsrStep  ;saturated to 0..+7FFFh
Exponential Increase is a fake (simply changes to a slower linear increase rate at higher volume levels).

1F801C0Ch+N*10h - Voice 0..23 Current ADSR volume (R/W)
  15-0  Current ADSR Volume  (0..+7FFFh) (or -8000h..+7FFFh on manual write)
Reportedly Release can go down to -1 (FFFFh), but that isn't true; and release ends at 0... or does THAT depend on an END flag found in the sample-data?
The register is read/writeable, writing allows to let the ADSR generator to "jump" to a specific volume level. But, ACTUALLY, the ADSR generator does overwrite the setting (from another internal register) whenever applying a new Step?!

1F801DB8h - Current Main Volume Left
1F801DBAh - Current Main Volume Right
1F801E00h+voice*04h - Voice 0..23 Current Volume Left
1F801E02h+voice*04h - Voice 0..23 Current Volume Right
  0-15  Current Volume       (-8000h..+7FFFh)
These are internal registers, normally not used by software (the Volume settings are usually set via Ports 1F801D80h and 1F801C00h+N*10h).

Note
Negative volumes are phase inverted, otherwise same as positive.


SPU Voice Flags

1F801D88h - Voice 0..23 Key ON (Start Attack/Decay/Sustain, KON) (W) bit0-15
1F801D8Ah - Voice 0..23 Key ON (Start Attack/Decay/Sustain, KON) (W) bit16-31
  0-23  Voice 0..23 On  (0=No change, 1=Start Attack/Decay/Sustain)
  24-31 Not used
Starts the ADSR Envelope, and automatically initializes ADSR Volume to zero, and copies Voice Start Address to Voice Repeat Address.

1F801D8Ch - Voice 0..23 Key OFF (Start Release) (KOFF) (W) bit0-15
1F801D8Eh - Voice 0..23 Key OFF (Start Release) (KOFF) (W) bit16-31
  0-23  Voice 0..23 Off (0=No change, 1=Start Release)
  24-31 Not used
For a full ADSR pattern, OFF would be usually issued in the Sustain period, however, it can be issued at any time (eg. to abort Attack, skip the Decay and Sustain periods, and switch immediately to Release).

1F801D9Ch - Voice 0..23 ON/OFF (status) (ENDX) (R) bit0-15
1F801D9Eh - Voice 0..23 ON/OFF (status) (ENDX) (R) bit16-31
  0-23  Voice 0..23 Status (0=Newly Keyed On, 1=Reached LOOP-END)
  24-31 Not used
The bits get CLEARED when setting the corresponding KEY ON bits.
The bits get SET when reaching an LOOP-END flag in ADPCM header.bit0.

R/W
Key On and Key Off should be treated as write-only (reading returns the most recently written value, but that doesn't provide any meaningful status information about whether sound is on or off).
The on/off (status) (ENDX) register should be treated read-only (writing is possible in so far that the written value can be read-back for a short moment, however, thereafter the hardware is overwriting that value).


SPU Noise Generator

1F801D94h - Voice 0..23 Noise mode enable (NON), bit0-15
1F801D96h - Voice 0..23 Noise mode enable (NON), bit16-31
  0-23  Voice 0..23 Noise (0=ADPCM, 1=Noise)
  24-31 Not used

SPU Noise Generator
The signed 16bit output Level is calculated as so (repeated at 44.1kHz clock):
  Wait(1 cycle)          ;at 44.1kHz clock
  Timer=Timer-NoiseStep  ;subtract Step (4..7)
  ParityBit = NoiseLevel.Bit15 xor Bit12 xor Bit11 xor Bit10 xor 1
  IF Timer<0 then NoiseLevel = NoiseLevel*2 + ParityBit
  IF Timer<0 then Timer=Timer+(20000h SHR NoiseShift)  ;reload timer once
  IF Timer<0 then Timer=Timer+(20000h SHR NoiseShift)  ;reload again if needed
Note that the Noise frequency is solely controlled by the Shift/Step values in SPUCNT register (the ADPCM Sample Rate has absolutely no effect on noise), so when using noise for multiple voices, all of them are forcefully having the same frequency; the only workaround is to store a random ADPCM pattern in SPU RAM, which can be then used with any desired sample rate(s).


SPU Control and Status Register

1F801DAAh - SPU Control Register (SPUCNT)
  15    SPU Soft Reset          (0=Reset/KeyOff, 1=Normal)  ;\Don't care
  14    Mute SPU                (0=Mute, 1=Unmute)          ;/for CD Audio)
  13-10 Noise Frequency Shift   (0..0Fh = Low .. High Frequency)
  9-8   Noise Frequency Step    (0..03h = Step "4,5,6,7")
  7     Reverb Master Enable    (0=Disabled, 1=Enabled)
  6     IRQ9 Enable (0=Disabled/Acknowledge, 1=Enabled; only when Bit15=1)
  5-4   Sound RAM Transfer Mode (0=Stop, 1=ManualWrite, 2=DMAwrite, 3=DMAread)
  3     External Audio Reverb   (0=Off, 1=On)
  2     CD Audio Reverb         (0=Off, 1=On) (for CD-DA and XA-ADPCM)
  1     External Audio Enable   (0=Off, 1=On)
  0     CD Audio Enable         (0=Off, 1=On) (for CD-DA and XA-ADPCM)
Changes to bit0-5 aren't applied immediately; after writing to SPUCNT, it'd be usually recommended to wait until the LSBs of SPUSTAT are updated accordingly. Before setting a new Transfer Mode, it'd be recommended first to set the "Stop" mode (and, again, wait until Stop is applied in SPUSTAT).
If and as long as SPUCNT.bit15=0: All voices are Keyed Off, writes to Key On are ignored, and all voices are forced to ADSR volume=0000h.

1F801DAEh - SPU Status Register (SPUSTAT) (R)
  15-12 Unknown/Unused (seems to be usually zero)
  11    Writing to First/Second half of Capture Buffers (0=First, 1=Second)
  10    Data Transfer Busy Flag          (0=Ready, 1=Busy)
  9     Data Transfer DMA Read Request   (0=No, 1=Yes)
  8     Data Transfer DMA Write Request  (0=No, 1=Yes)
  7     Data Transfer DMA Read/Write Request ;seems to be same as SPUCNT.Bit5
  6     IRQ9 Flag                        (0=No, 1=Interrupt Request)
  5-0   Current SPU Mode   (same as SPUCNT.Bit5-0, but, applied a bit delayed)
When switching SPUCNT to DMA-read mode, status bit9 and bit7 aren't set immediately (apparently the SPU is first internally collecting the data in the Fifo, before transferring it).
Bit11 indicates if data is currently written to the first or second half of the four 1K-byte capture buffers (for CD Audio left/right, and voice 1/3). Note: Bit11 works only if Bit2 and/or Bit3 of Port 1F801DACh are set.
The SPUSTAT register should be treated read-only (writing is possible in so far that the written value can be read-back for a short moment, however, thereafter the hardware is overwriting that value).


SPU Memory Access

1F801DA6h - Sound RAM Data Transfer Address
  15-0  Address in sound buffer divided by eight
Used for manual write and DMA read/write SPU memory. Writing to this registers stores the written value in 1F801DA6h, and does additional store the value (multiplied by 8) in another internal "current address" register (that internal register does increment during transfers, whilst the 1F801DA6h value DOESN'T increment).

1F801DA8h - Sound RAM Data Transfer Fifo
  15-0  Data (max 32 halfwords)
Used for manual-write. Not sure if it can be also used for manual read?

1F801DACh - Sound RAM Data Transfer Control (should be 0004h)
  15-4   Unknown/no effect?                       (should be zero)
  3-1    Sound RAM Data Transfer Type (see below) (should be 2)
  0      Unknown/no effect?                       (should be zero)
The Transfer Type selects how data is forwarded from Fifo to SPU RAM:
  __Transfer Type___Halfwords in Fifo________Halfwords written to SPU RAM__
  0,1,6,7  Fill     A,B,C,D,E,F,G,H,...,X    X,X,X,X,X,X,X,X,...
  2        Normal   A,B,C,D,E,F,G,H,...,X    A,B,C,D,E,F,G,H,...
  3        Rep2     A,B,C,D,E,F,G,H,...,X    A,A,C,C,E,E,G,G,...
  4        Rep4     A,B,C,D,E,F,G,H,...,X    A,A,A,A,E,E,E,E,...
  5        Rep8     A,B,C,D,E,F,G,H,...,X    H,H,H,H,H,H,H,H,...
Rep2 skips the 2nd halfword, Rep4 skips 2nd..4th, Rep8 skips 1st..7th.
Fill uses only the LAST halfword in Fifo, that might be useful for memfill purposes, although, the length is probably determined by the number of writes to the Fifo (?) so one must still issue writes for ALL halfwords...?
Note:
The above rather bizarre results apply to WRITE mode. In READ mode, the register causes the same halfword to be read 2/4/8 times (for rep2/4/8).

SPU RAM Manual Write
- Be sure that [1F801DACh] is set to 0004h
- Set SPUCNT to "Stop" (and wait until it is applied in SPUSTAT)
- Set the transfer address
- Write 1..32 halfword(s) to the Fifo
- Set SPUCNT to "Manual Write" (and wait until it is applied in SPUSTAT)
- Wait until Transfer Busy in SPUSTAT goes off (that, AFTER above apply-wait)
For multi-block transfers: Repeat the above last three steps (that is rarely done by any games, but it is done by the BIOS intro; observe that waiting for SPUCNT writes being applied in SPUSTAT won't work in that case (since SPUCNT was already in manual write mode from previous block), so one must instead use some hardcoded delay of at least 300h cycles; the BIOS is using a much longer bizarre delay though).

SPU RAM DMA-Write
- Be sure that [1F801DACh] is set to 0004h
- Set SPUCNT to "Stop" (and wait until it is applied in SPUSTAT)
- Set the transfer address
- Set SPUCNT to "DMA Write" (and wait until it is applied in SPUSTAT)
- Start DMA4 at CPU Side (blocksize=10h, control=01000201h)
- Wait until DMA4 finishes (at CPU side)

SPU RAM Manual-Read
As by now, there's no known method for reading SPU RAM without using DMA.

SPU RAM DMA-Read (stable reading, with [1F801014h].bit24-27 = nonzero)
- Be sure that [1F801014h] is set to 220931E1h (bit24-27 MUST be nonzero)
- Be sure that [1F801DACh] is set to 0004h
- Set SPUCNT to "Stop" (and wait until it is applied in SPUSTAT)
- Set the transfer address
- Set SPUCNT to "DMA Read" (and wait until it is applied in SPUSTAT)
- Start DMA4 at CPU Side (blocksize=10h, control=01000200h)
- Wait until DMA4 finishes (at CPU side)

SPU RAM DMA-Read (unstable reading, with [1F801014h].bit24-27 = zero)
Below describes some dirt effects and some trickery to get around those dirt effects.
  Below problems (and workarounds) apply ONLY if [1F801014h].bit24-27 = zero.
  Ie. below info describes what happens when [1F801014h] is mis-initialized.
  Normally one should set [1F801014h]=220931E1h (and can ignore below info).
With [1F801014h].bit24-27=zero, reading SPU RAM via DMA works glitchy:
The first received halfword within each block is FFFFh. So with a DMA blocksize of 10h words (=20h halfwords), the following is received:
  1st block:   FFFFh, halfwords[00h..1Eh]
  2nd block:   FFFFh, halfwords[20h..3Eh]
  etc.
that'd theoretically match the SPU Fifo Size, but, because of the inserted FFFFh value, the last Fifo entry isn't received, ie. halfword[1Fh,3Fh] are lost. As a workaround, one can increase the DMA blocksize to 11h words, and then the following is received:
  1st block:   FFFFh, halfwords[00h..1Eh], twice halfword[1Fh]
  2nd block:   FFFFh, halfwords[20h..3Eh], twice halfword[3Fh]
  etc.
this time, all data is received, but after the transfer one must still remove the FFFFh values, and the duplicated halfwords by software. Aside from the <inserted> FFFFh values there are occassionaly some unstable halfwords ORed by FFFFh (or ORed by other garbage values), this can be fixed by using "rep2" mode, which does then receive:
  1st block:   FFFFh, halfwords[00h,00h,..0Eh,0Eh], triple halfword[0Fh]
  2nd block:   FFFFh, halfwords[10h,10h,..1Eh,1Eh], triple halfword[1Fh]
  etc.
again, remove the first halfword (FFFFh) and the last halfword, and, take the duplicated halfwords ANDed together. Unstable values occur only every 32 halfwords or so (probably when the SPU is simultaneously reading ADPCM data), but do never occur on two continous halfwords, so, even if one halfword was ORed by garbage, the other halfword is always correct, and the result of the ANDed halfwords is 100% stable.
Note: The unstable reading does NOT occur always, when resetting the PSX a couple of times it does occassionally boot-up with totally stable reading, since there is no known way to activate the stable "mode" via I/O ports, the stable/unstable behaviour does eventually depend on internal clock dividers/multipliers, and whether they are starting in sync with the CPU or not.
Caution: The "rep2" trick cannot be used in combination with reverb (reverb seems to be using the Port 1F801DACh Sound RAM Data Transfer Control, too).


SPU Interrupt

1F801DA4h - Sound RAM IRQ Address (IRQ9)
  15-0  Address in sound buffer divided by eight
See also: SPUCNT (IRQ enable/disable/acknowledge) and SPUSTAT (IRQ flag).

Voice Interrupt
Triggers an IRQ when a voice reads ADPCM data from the IRQ address.
Mind that ADPCM cannot be stopped (uh, except, probably they CAN be stopped, by setting the sample rate to zero?), all voices are permanently reading data from SPU RAM - even in Noise mode, even if the Voice Volume is zero, and even if the ADSR pattern has finished the Release period - so even inaudible voices can trigger IRQs. To prevent unwanted IRQs, best set all unused voices to an endless looped dummy ADPCM block.
For stable IRQs, the IRQ address should be aligned to the 16-byte ADPCM blocks. If if the IRQ address is in the middle of a 16-byte ADPCM block, then the IRQ doesn't seem to trigger always (unknown why, but it seems to occassionally miss IRQs, even if the block gets repeated several times).

Capture Interrupt
Setting the IRQ address to 0000h..01FFh (aka byte address 00000h..00FFFh) will trigger IRQs on writes to the four capture buffers. Each of the four buffers contains 400h bytes (=200h samples), so the IRQ rate will be around 86.13Hz (44100Hz/200h).
CD-Audio capture is always active (even if CD-Audio output is disabld in SPUCNT, and even if the drive door is open). Voice capture is (probably) also always active (even if the corresponding voice is off).
Capture IRQs do NOT occur if 1F801DACh.bit3-2 are both zero.

Reverb Interrupt
Reverb is also triggering interrupts if the IRQ address is located in the reverb buffer area. Unknown <which> of the various reverb read(s) and/or reverb write(s) are triggering interrupts.

Data Transfers
Data Transfers (usually via DMA4) to/from SPU-RAM do also trap SPU interrupts.

Note
IRQ Address is used by Metal Gear Solid, Legend of Mana, Tokimeki Memorial 2, Crash Team Racing, The Misadventures of Tron Bonne, and (somewhat?) by Need For Speed 3.


SPU Reverb Registers

Reverb Volume and Address Registers (R/W)
  Port      Reg   Name    Type    Expl.
  1F801D84h spu   vLOUT   volume  Reverb Output Volume Left
  1F801D86h spu   vROUT   volume  Reverb Output Volume Right
  1F801DA2h spu   mBASE   base    Reverb Work Area Start Address in Sound RAM
  1F801DC0h rev00 dAPF1   disp    Reverb APF Offset 1
  1F801DC2h rev01 dAPF2   disp    Reverb APF Offset 2
  1F801DC4h rev02 vIIR    volume  Reverb Reflection Volume 1
  1F801DC6h rev03 vCOMB1  volume  Reverb Comb Volume 1
  1F801DC8h rev04 vCOMB2  volume  Reverb Comb Volume 2
  1F801DCAh rev05 vCOMB3  volume  Reverb Comb Volume 3
  1F801DCCh rev06 vCOMB4  volume  Reverb Comb Volume 4
  1F801DCEh rev07 vWALL   volume  Reverb Reflection Volume 2
  1F801DD0h rev08 vAPF1   volume  Reverb APF Volume 1
  1F801DD2h rev09 vAPF2   volume  Reverb APF Volume 2
  1F801DD4h rev0A mLSAME  src/dst Reverb Same Side Reflection Address 1 Left
  1F801DD6h rev0B mRSAME  src/dst Reverb Same Side Reflection Address 1 Right
  1F801DD8h rev0C mLCOMB1 src     Reverb Comb Address 1 Left
  1F801DDAh rev0D mRCOMB1 src     Reverb Comb Address 1 Right
  1F801DDCh rev0E mLCOMB2 src     Reverb Comb Address 2 Left
  1F801DDEh rev0F mRCOMB2 src     Reverb Comb Address 2 Right
  1F801DE0h rev10 dLSAME  src     Reverb Same Side Reflection Address 2 Left
  1F801DE2h rev11 dRSAME  src     Reverb Same Side Reflection Address 2 Right
  1F801DE4h rev12 mLDIFF  src/dst Reverb Different Side Reflect Address 1 Left
  1F801DE6h rev13 mRDIFF  src/dst Reverb Different Side Reflect Address 1 Right
  1F801DE8h rev14 mLCOMB3 src     Reverb Comb Address 3 Left
  1F801DEAh rev15 mRCOMB3 src     Reverb Comb Address 3 Right
  1F801DECh rev16 mLCOMB4 src     Reverb Comb Address 4 Left
  1F801DEEh rev17 mRCOMB4 src     Reverb Comb Address 4 Right
  1F801DF0h rev18 dLDIFF  src     Reverb Different Side Reflect Address 2 Left
  1F801DF2h rev19 dRDIFF  src     Reverb Different Side Reflect Address 2 Right
  1F801DF4h rev1A mLAPF1  src/dst Reverb APF Address 1 Left
  1F801DF6h rev1B mRAPF1  src/dst Reverb APF Address 1 Right
  1F801DF8h rev1C mLAPF2  src/dst Reverb APF Address 2 Left
  1F801DFAh rev1D mRAPF2  src/dst Reverb APF Address 2 Right
  1F801DFCh rev1E vLIN    volume  Reverb Input Volume Left
  1F801DFEh rev1F vRIN    volume  Reverb Input Volume Right
All volume registers are signed 16bit (range -8000h..+7FFFh).
All src/dst/disp/base registers are addresses in SPU memory (divided by 8), src/dst are relative to the current buffer address, the disp registers are relative to src registers, the base register defines the start address of the reverb buffer (the end address is fixed, at 7FFFEh). Writing a value to mBASE does additionally set the current buffer address to that value.

1F801D98h - Voice 0..23 Reverb mode aka Echo On (EON) (R/W), bit0-15
1F801D9Ah - Voice 0..23 Reverb mode aka Echo On (EON) (R/W), bit16-31
  0-23  Voice 0..23 Destination (0=To Mixer, 1=To Mixer and to Reverb)
  24-31 Not used
Sets reverb for the channel. As soon as the sample ends, the reverb for that channel is turned off... that's fine, but WHEN does it end?
In Reverb mode, the voice seems to output BOTH normal (immediately) AND via Reverb (delayed).

Reverb Bits in SPUCNT Register (R/W)
The SPUCNT register contains a Reverb Master Enable flag, and Reverb Enable flags for External Audio input and CD Audio input.
When the Reverb Master Enable flag is cleared, the SPU stops to write any data to the Reverb buffer (that is useful when zero-filling the reverb buffer; ensuring that already-zero values aren't overwritten by still-nonzero values).
However, the Reverb Master Enable flag does not disable output from Reverb buffer to the speakers (that might be useful to output uncompressed 22050Hz samples) (otherwise, to disable the buffer output, set the Reverb Output volume to zero and/or zerofill the reverb buffer).


SPU Reverb Formula

Reverb Formula
  ___Input from Mixer (Input volume multiplied with incoming data)_____________
  Lin = vLIN * LeftInput    ;from any channels that have Reverb enabled
  Rin = vRIN * RightInput   ;from any channels that have Reverb enabled
  ____Same Side Reflection (left-to-left and right-to-right)___________________
  [mLSAME] = (Lin + [dLSAME]*vWALL - [mLSAME-2])*vIIR + [mLSAME-2]  ;L-to-L
  [mRSAME] = (Rin + [dRSAME]*vWALL - [mRSAME-2])*vIIR + [mRSAME-2]  ;R-to-R
  ___Different Side Reflection (left-to-right and right-to-left)_______________
  [mLDIFF] = (Lin + [dRDIFF]*vWALL - [mLDIFF-2])*vIIR + [mLDIFF-2]  ;R-to-L
  [mRDIFF] = (Rin + [dLDIFF]*vWALL - [mRDIFF-2])*vIIR + [mRDIFF-2]  ;L-to-R
  ___Early Echo (Comb Filter, with input from buffer)__________________________
  Lout=vCOMB1*[mLCOMB1]+vCOMB2*[mLCOMB2]+vCOMB3*[mLCOMB3]+vCOMB4*[mLCOMB4]
  Rout=vCOMB1*[mRCOMB1]+vCOMB2*[mRCOMB2]+vCOMB3*[mRCOMB3]+vCOMB4*[mRCOMB4]
  ___Late Reverb APF1 (All Pass Filter 1, with input from COMB)________________
  Lout=Lout-vAPF1*[mLAPF1-dAPF1], [mLAPF1]=Lout, Lout=Lout*vAPF1+[mLAPF1-dAPF1]
  Rout=Rout-vAPF1*[mRAPF1-dAPF1], [mRAPF1]=Rout, Rout=Rout*vAPF1+[mRAPF1-dAPF1]
  ___Late Reverb APF2 (All Pass Filter 2, with input from APF1)________________
  Lout=Lout-vAPF2*[mLAPF2-dAPF2], [mLAPF2]=Lout, Lout=Lout*vAPF2+[mLAPF2-dAPF2]
  Rout=Rout-vAPF2*[mRAPF2-dAPF2], [mRAPF2]=Rout, Rout=Rout*vAPF2+[mRAPF2-dAPF2]
  ___Output to Mixer (Output volume multiplied with input from APF2)___________
  LeftOutput  = Lout*vLOUT
  RightOutput = Rout*vROUT
  ___Finally, before repeating the above steps_________________________________
  BufferAddress = MAX(mBASE, (BufferAddress+2) AND 7FFFEh)
  Wait one 22050Hz cycle, then repeat the above stuff

Notes
The values written to memory are saturated to -8000h..+7FFFh.
The multiplication results are divided by +8000h, to fit them to 16bit range.
All memory addresses are relative to the current BufferAddress, and wrapped within mBASE..7FFFEh when exceeding that region.
  Caution
  That wrapping mechanism seems to work only in the upper portion of SPU RAM,
  but does somehow go wrong if mBASE is too small (it does then accidentally
  wrap to addresses outside of the mBASE..7FFFEh region, where it could
  trigger unintended voice IRQs or the like). Some examples:
    mBASE>=60000h should be safe to use
    mBASE>=48000h might work (SEEMS to be stable, at least with current tests)
    mBASE=45000h bad (does mis-trigger IRQs, sometimes, at SOME IRQ locations)
    mBASE=44000h bad (does mis-trigger IRQs, every some seconds)
    mBASE=40000h bad (does mis-trigger IRQs, MANY times per second)
    mBASE=10000h bad (does mis-trigger IRQs, every some seconds)
All data in the Reverb buffer consists of signed 16bit samples. The Left and Right Reverb Buffer addresses should be choosen so that one half of the buffer contains Left samples, and the other half Right samples (ie. the data is L,L,L,L,... R,R,R,R,...; it is NOT interlaced like L,R,L,R,...), during operation, when the buffer address increases, the Left half will overwrite the older samples of the Right half, and vice-versa.
The reverb hardware spends one 44100Hz cycle on left calculations, and the next 44100Hz cycle on right calculations (unlike as shown in the above formula, where left/right are shown simultaneously at 22050Hz).

Reverb Disable
SPUCNT.bit7 disables writes to reverb buffer, but reads from reverb buffer do still occur. If vAPF2 is zero then it does simply read "Lout=[mLAPF2-dAPF2]" and "Rout=[mRAPF2-dAPF2]". If vAPF2 is nonzero then it does additionally use data from APF1, if vAPF1 and vAPF2 are both nonzero then it's also using data from COMB. However, the SAME/DIFF stages aren't used when reverb is disabled.

Bug
vIIR works only in range -7FFFh..+7FFFh. When set to -8000h, the multiplication by -8000h is still done correctly, but, the final result (the value written to memory) gets negated (this is a pretty strange feature, it is NOT a simple overflow bug, it does affect the "+[mLSAME-2]" addition; although that part normally shouldn't be affected by the "*vIIR" multiplication). Similar effects might (?) occur on some other volume registers when they are set to -8000h.

Speed of Sound
The speed of sound is circa 340 meters per second (in dry air, at room temperature). For example, a voice that travels to a wall at 17 meters distance, and back to its origin, should have a delay of 0.1 seconds.


SPU Reverb Examples

Reverb Examples
Below are some Reverb examples, showing the required memory size (ie. set Port 1F801DA2h to "(80000h-size)/8"), and the Reverb register settings for Port 1F801DC0h..1F801DFFh, ie. arranged like so:
  dAPF1  dAPF2  vIIR   vCOMB1 vCOMB2  vCOMB3  vCOMB4  vWALL   ;1F801DC0h..CEh
  vAPF1  vAPF2  mLSAME mRSAME mLCOMB1 mRCOMB1 mLCOMB2 mRCOMB2 ;1F801DD0h..DEh
  dLSAME dRSAME mLDIFF mRDIFF mLCOMB3 mRCOMB3 mLCOMB4 mRCOMB4 ;1F801DE0h..EEh
  dLDIFF dRDIFF mLAPF1 mRAPF1 mLAPF2  mRAPF2  vLIN    vRIN    ;1F801DF0h..FEh
Also, don't forget to initialize Port 1F801D84h, 1F801D86h, 1F801D98h, and SPUCNT, and to zerofill the Reverb Buffer (so that no garbage values are output when activating reverb). For whatever reason, one MUST also initialize Port 1F801DACh (otherwise reverb stays off).

Room (size=26C0h bytes)
  007Dh,005Bh,6D80h,54B8h,BED0h,0000h,0000h,BA80h
  5800h,5300h,04D6h,0333h,03F0h,0227h,0374h,01EFh
  0334h,01B5h,0000h,0000h,0000h,0000h,0000h,0000h
  0000h,0000h,01B4h,0136h,00B8h,005Ch,8000h,8000h

Studio Small (size=1F40h bytes)
  0033h,0025h,70F0h,4FA8h,BCE0h,4410h,C0F0h,9C00h
  5280h,4EC0h,03E4h,031Bh,03A4h,02AFh,0372h,0266h
  031Ch,025Dh,025Ch,018Eh,022Fh,0135h,01D2h,00B7h
  018Fh,00B5h,00B4h,0080h,004Ch,0026h,8000h,8000h

Studio Medium (size=4840h bytes)
  00B1h,007Fh,70F0h,4FA8h,BCE0h,4510h,BEF0h,B4C0h
  5280h,4EC0h,0904h,076Bh,0824h,065Fh,07A2h,0616h
  076Ch,05EDh,05ECh,042Eh,050Fh,0305h,0462h,02B7h
  042Fh,0265h,0264h,01B2h,0100h,0080h,8000h,8000h

Studio Large (size=6FE0h bytes)
  00E3h,00A9h,6F60h,4FA8h,BCE0h,4510h,BEF0h,A680h
  5680h,52C0h,0DFBh,0B58h,0D09h,0A3Ch,0BD9h,0973h
  0B59h,08DAh,08D9h,05E9h,07ECh,04B0h,06EFh,03D2h
  05EAh,031Dh,031Ch,0238h,0154h,00AAh,8000h,8000h

Hall (size=ADE0h bytes)
  01A5h,0139h,6000h,5000h,4C00h,B800h,BC00h,C000h
  6000h,5C00h,15BAh,11BBh,14C2h,10BDh,11BCh,0DC1h
  11C0h,0DC3h,0DC0h,09C1h,0BC4h,07C1h,0A00h,06CDh
  09C2h,05C1h,05C0h,041Ah,0274h,013Ah,8000h,8000h

Half Echo (size=3C00h bytes)
  0017h,0013h,70F0h,4FA8h,BCE0h,4510h,BEF0h,8500h
  5F80h,54C0h,0371h,02AFh,02E5h,01DFh,02B0h,01D7h
  0358h,026Ah,01D6h,011Eh,012Dh,00B1h,011Fh,0059h
  01A0h,00E3h,0058h,0040h,0028h,0014h,8000h,8000h

Space Echo (size=F6C0h bytes)
  033Dh,0231h,7E00h,5000h,B400h,B000h,4C00h,B000h
  6000h,5400h,1ED6h,1A31h,1D14h,183Bh,1BC2h,16B2h
  1A32h,15EFh,15EEh,1055h,1334h,0F2Dh,11F6h,0C5Dh
  1056h,0AE1h,0AE0h,07A2h,0464h,0232h,8000h,8000h

Chaos Echo (almost infinite) (size=18040h bytes)
  0001h,0001h,7FFFh,7FFFh,0000h,0000h,0000h,8100h
  0000h,0000h,1FFFh,0FFFh,1005h,0005h,0000h,0000h
  1005h,0005h,0000h,0000h,0000h,0000h,0000h,0000h
  0000h,0000h,1004h,1002h,0004h,0002h,8000h,8000h

Delay (one-shot echo) (size=18040h bytes)
  0001h,0001h,7FFFh,7FFFh,0000h,0000h,0000h,0000h
  0000h,0000h,1FFFh,0FFFh,1005h,0005h,0000h,0000h
  1005h,0005h,0000h,0000h,0000h,0000h,0000h,0000h
  0000h,0000h,1004h,1002h,0004h,0002h,8000h,8000h

Reverb off (size=10h dummy bytes)
  0000h,0000h,0000h,0000h,0000h,0000h,0000h,0000h
  0000h,0000h,0001h,0001h,0001h,0001h,0001h,0001h
  0000h,0000h,0001h,0001h,0001h,0001h,0001h,0001h
  0000h,0000h,0001h,0001h,0001h,0001h,0000h,0000h
Note that the memory offsets should be 0001h here (not 0000h), otherwise zerofilling the reverb buffer seems to fail (maybe because zero memory offsets somehow cause the fill-value to mixed with the old value or so; that appears even when reverb master enable is zero). Also, when not using reverb, Port 1F801D84h, 1F801D86h, 1F801D98h, and the SPUCNT reverb bits should be set to zero.


SPU Unknown Registers

1F801DA0h - Some kind of a read-only status register.. or just garbage..?
  0-15 Unknown?
Usually 9D78h, occassionaly changes to 17DAh or 108Eh for a short moment.
Other day: Usually 9CF8h, or occassionally 9CFAh.
Another day: Usually 0000h, or occassionally 4000h.

1F801DBCh - 4 bytes - Unknown? (R/W)
  80 21 4B DF
Other day (dots = same as above):
  .. 31 .. ..

1F801E60h - 32 bytes - Unknown? (R/W)
  7E 61 A9 96 47 39 F9 1E E1 E1 80 DD E8 17 7F FB
  FB BF 1D 6C 8F EC F3 04 06 23 89 45 C1 6D 31 82
Other day (dots = same as above):
  .. .. .. .. .. .. .. .. .. .. .. .. .. .. 7B ..
  .. .. .. .. .. .. .. .. 04 .. .. .. .. .. .. 86

The bytes at 1F801DBCh and 1F801E60h usually have the above values on cold-boot. The registers are read/write-able, although writing any values to them doesn't seem to have any effect on sound output. Also, the SPU doesn't seem to modify the registers at any time during sound output, nor reverb calculations, nor activated external audio input... the registers seem to be just some kind of general-purpose RAM.

1F801E80h - 180h bytes - Unused? (N/A)
Read: FFh-filled (Unused or Write only?)


Interrupts

1F801070h I_STAT - Interrupt status register (R=Status, W=Acknowledge)
1F801074h I_MASK - Interrupt mask register (R/W)
Status: Read I_STAT (0=No IRQ, 1=IRQ)
Acknowledge: Write I_STAT (0=Clear Bit, 1=No change)
Mask: Read/Write I_MASK (0=Disabled, 1=Enabled)
  0     IRQ0 VBLANK (PAL=50Hz, NTSC=60Hz)
  1     IRQ1 GPU   Can be requested via GP0(1Fh) command (rarely used)
  2     IRQ2 CDROM
  3     IRQ3 DMA
  4     IRQ4 TMR0  Timer 0 aka Root Counter 0 (Sysclk or Dotclk)
  5     IRQ5 TMR1  Timer 1 aka Root Counter 1 (Sysclk or H-blank)
  6     IRQ6 TMR2  Timer 2 aka Root Counter 2 (Sysclk or Sysclk/8)
  7     IRQ7 Controller and Memory Card - Byte Received Interrupt
  8     IRQ8 SIO
  9     IRQ9 SPU
  10    IRQ10 Controller - Lightpen Interrupt (reportedly also PIO...?)
  11-15 Not used (always zero)
  16-31 Garbage

Secondary IRQ10 Controller (Port 1F802030h)
EXP2 DTL-H2000 I/O Ports

Interrupt Request / Execution
The interrupt request bits in I_STAT are edge-triggered, ie. the get set ONLY if the corresponding interrupt source changes from "false to true".
If one or more interrupts are requested and enabled, ie. if "(I_STAT AND I_MASK)=nonzero", then cop0r13.bit10 gets set, and when cop0r12.bit10 and cop0r12.bit0 are set, too, then the interrupt gets executed.

Interrupt Acknowledge
To acknowledge an interrupt, write a "0" to the corresponding bit in I_STAT. Most interrupts (except IRQ0,4,5,6) must be additionally acknowledged at the I/O port that has caused them (eg. JOY_CTRL.bit4).
Observe that the I_STAT bits are edge-triggered (they get set only on High-to-Low, or False-to-True edges). The correct acknowledge order is:
  First, acknowledge I_STAT                (eg. I_STAT.bit7=0)
  Then, acknowledge corresponding I/O port (eg. JOY_CTRL.bit4=1)
When doing it vice-versa, the hardware may miss further IRQs (eg. when first setting JOY_CTRL.4=1, then a new IRQ may occur in JOY_STAT.4 within a single clock cycle, thereafter, setting I_STAT.7=0 would successfully reset I_STAT.7, but, since JOY_STAT.4 is already set, there'll be no further edge, so I_STAT.7 won't be ever set in future).

COP0 Interrupt Handling
Relevant COP0 registers are cop0r13 (CAUSE, reason flags), and cop0r12 (SR, control flags), and cop0r14 (EPC, return address), and, cop0cmd=10h (aka RFE opcode) is used to prepare the return from interrupts. For more info, see
COP0 - Exception Handling

PSX specific COP0 Notes
COP0 has six hardware interrupt bits, of which, the PSX uses only cop0r13.bit10 (the other ones, cop0r13.bit11-15 are always zero). cop0r13.bit10 is NOT a latch, ie. it gets automatically cleared as soon as "(I_STAT AND I_MASK)=zero", so there's no need to do an acknowledge at the cop0 side. COP0 additionally has two software interrupt bits, cop0r13.bit8-9, which do exist in the PSX, too, these bits are read/write-able latches which can be set/cleared manually to request/acknowledge exceptions by software.

Halt Function (Wait for Interrupt)
The PSX doesn't have a HALT opcode, so, even if the program is merely waiting for an interrupt to occur, the CPU is always running at full speed, which is resulting in high power consumption, and, in case of emulators, high CPU emulation load. To save energy, and to make emulation smoother on slower computers, I've added a Halt function for use in emulators:
EXP2 Nocash Emulation Expansion


DMA Channels

DMA Register Summary
  1F80108xh DMA0 channel 0  MDECin  (RAM to MDEC)
  1F80109xh DMA1 channel 1  MDECout (MDEC to RAM)
  1F8010Axh DMA2 channel 2  GPU (lists + image data)
  1F8010Bxh DMA3 channel 3  CDROM   (CDROM to RAM)
  1F8010Cxh DMA4 channel 4  SPU
  1F8010Dxh DMA5 channel 5  PIO (Expansion Port)
  1F8010Exh DMA6 channel 6  OTC (reverse clear OT) (GPU related)
  1F8010F0h DPCR - DMA Control register
  1F8010F4h DICR - DMA Interrupt register
These ports control DMA at the CPU-side. In most cases, you'll additionally need to initialize an address (and transfer direction, transfer enabled, etc.) at the remote-side (eg. at the GPU-side for DMA2).

1F801080h+N*10h - D#_MADR - DMA base address (Channel 0..6) (R/W)
  0-23  Memory Address where the DMA will start reading from/writing to
  24-31 Not used (always zero)
In SyncMode=0, the hardware doesn't update the MADR registers (it will contain the start address even during and after the transfer) (unless Chopping is enabled, in that case it does update MADR, same does probably also happen when getting interrupted by a higher priority DMA channel).
In SyncMode=1 and SyncMode=2, the hardware does update MADR (it will contain the start address of the currently transferred block; at transfer end, it'll hold the end-address in SyncMode=1, or the 00FFFFFFh end-code in SyncMode=2)
Note: Address bit0-1 are writeable, but any updated current/end addresses are word-aligned with bit0-1 forced to zero.

1F801084h+N*10h - D#_BCR - DMA Block Control (Channel 0..6) (R/W)
For SyncMode=0 (ie. for OTC and CDROM):
  0-15  BC    Number of words (0001h..FFFFh) (or 0=10000h words)
  16-31 0     Not used (usually 0 for OTC, or 1 ("one block") for CDROM)
For SyncMode=1 (ie. for MDEC, SPU, and GPU-vram-data):
  0-15  BS    Blocksize (words) ;for GPU/SPU max 10h, for MDEC max 20h
  16-31 BA    Amount of blocks  ;ie. total length = BS*BA words
For SyncMode=2 (ie. for GPU-command-lists):
  0-31  0     Not used (should be zero) (transfer ends at END-CODE in list)
BC/BS/BA can be in range 0001h..FFFFh (or 0=10000h). For BS, take care not to set the blocksize larger than the buffer of the corresponding unit can hold. (GPU and SPU both have a 16-word buffer). A larger blocksize means faster transfer.
SyncMode=1 decrements BA to zero, SyncMode=0 with chopping enabled decrements BC to zero (aside from that two cases, D#_BCR isn't changed during/after transfer).

1F801088h+N*10h - D#_CHCR - DMA Channel Control (Channel 0..6) (R/W)
  0       Transfer Direction    (0=To Main RAM, 1=From Main RAM)
  1       Memory Address Step   (0=Forward;+4, 1=Backward;-4)
  2-7     Not used              (always zero)
  8       Chopping Enable       (0=Normal, 1=Chopping; run CPU during DMA gaps)
  9-10    SyncMode, Transfer Synchronisation/Mode (0-3):
            0  Start immediately and transfer all at once (used for CDROM, OTC)
            1  Sync blocks to DMA requests   (used for MDEC, SPU, and GPU-data)
            2  Linked-List mode              (used for GPU-command-lists)
            3  Reserved                      (not used)
  11-15   Not used              (always zero)
  16-18   Chopping DMA Window Size (1 SHL N words)
  19      Not used              (always zero)
  20-22   Chopping CPU Window Size (1 SHL N clks)
  23      Not used              (always zero)
  24      Start/Busy            (0=Stopped/Completed, 1=Start/Enable/Busy)
  25-27   Not used              (always zero)
  28      Start/Trigger         (0=Normal, 1=Manual Start; use for SyncMode=0)
  29      Unknown (R/W) Pause?  (0=No, 1=Pause?)     (For SyncMode=0 only?)
  30      Unknown (R/W)
  31      Not used              (always zero)
The Start/Trigger bit is automatically cleared upon BEGIN of the transfer, this bit needs to be set only in SyncMode=0 (setting it in other SyncModes would force the first block to be transferred instantly without DRQ, which isn't desired).
The Start/Busy bit is automatically cleared upon COMPLETION of the transfer, this bit must be always set for all SyncModes when starting a transfer.
For DMA6/OTC there are some restrictions, D6_CHCR has only three read/write-able bits: Bit24,28,30. All other bits are read-only: Bit1 is always 1 (step=backward), and the other bits are always 0.

1F8010F0h - DPCR - DMA Control Register (R/W)
  0-2   DMA0, MDECin  Priority      (0..7; 0=Highest, 7=Lowest)
  3     DMA0, MDECin  Master Enable (0=Disable, 1=Enable)
  4-6   DMA1, MDECout Priority      (0..7; 0=Highest, 7=Lowest)
  7     DMA1, MDECout Master Enable (0=Disable, 1=Enable)
  8-10  DMA2, GPU     Priority      (0..7; 0=Highest, 7=Lowest)
  11    DMA2, GPU     Master Enable (0=Disable, 1=Enable)
  12-14 DMA3, CDROM   Priority      (0..7; 0=Highest, 7=Lowest)
  15    DMA3, CDROM   Master Enable (0=Disable, 1=Enable)
  16-18 DMA4, SPU     Priority      (0..7; 0=Highest, 7=Lowest)
  19    DMA4, SPU     Master Enable (0=Disable, 1=Enable)
  20-22 DMA5, PIO     Priority      (0..7; 0=Highest, 7=Lowest)
  23    DMA5, PIO     Master Enable (0=Disable, 1=Enable)
  24-26 DMA6, OTC     Priority      (0..7; 0=Highest, 7=Lowest)
  27    DMA6, OTC     Master Enable (0=Disable, 1=Enable)
  28-30 Unknown, Priority Offset or so? (R/W)
  31    Unknown, no effect? (R/W)
Initial value on reset is 07654321h. If two or more channels have the same priority setting, then the priority is determined by the channel number (DMA0=Lowest, DMA6=Highest).

1F8010F4h - DICR - DMA Interrupt Register (R/W)
  0-5   Unknown  (read/write-able)
  6-14  Not used (always zero)
  15    Force IRQ (sets bit31)                        (0=None, 1=Force Bit31=1)
  16-22 IRQ Enable setting bit24-30 upon DMA0..DMA6    (0=None, 1=Enable)
  23    IRQ Enable setting bit31 when bit24-30=nonzero (0=None, 1=Enable)
  24-30 IRQ Flags for DMA0..DMA6    (Write 1 to reset) (0=None, 1=IRQ)
  31    IRQ Signal (0-to-1 triggers 1F801070h.bit3)    (0=None, 1=IRQ) (R)
IRQ flags in Bit(24+n) are set upon DMAn completion - but caution - they are set ONLY if enabled in Bit(16+n).
Bit31 is a simple readonly flag that follows the following rules:
  IF bit15=1 OR (bit23=1 AND bit(24-30)>0) THEN bit31=1 ELSE bit31=0
Upon 0-to-1 transition of Bit31, the IRQ3 flag (in Port 1F801070h) gets set.
Bit24-30 are acknowledged (reset to zero) when writing a "1" to that bits (and, additionally, IRQ3 (DMA) must be acknowledged via Port 1F801070h).

1F8010F8h (usually 7FFAC68Bh? or 0BFAC688h)
    (changes to 7FE358D1h after DMA transfer)
1F8010FCh (usually 00FFFFF7h) (...maybe OTC fill-value)
    (stays so even after DMA transfer)
Contains strange read-only values (but not the usual "Garbage").
Not yet tested during transfer, might be remaining length and address?

Commonly used DMA Control Register values for starting DMA transfers
  DMA0 MDEC.IN  01000201h (always)
  DMA1 MDEC.OUT 01000200h (always)
  DMA2 GPU      01000200h (VramRead), 01000201h (VramWrite), 01000401h (List)
  DMA3 CDROM    11000000h (normal), 11400100h (chopped, rarely used)
  DMA4 SPU      01000201h (write), 01000200h (read, rarely used)
  DMA5 PIO      N/A       (not used by any known games)
  DMA6 OTC      11000002h (always)
XXX: DMA2 values 01000201h (VramWrite), 01000401h (List) aren't 100% confirmed to be used by ALL existing games. All other values are always used as listed above.

DMA Transfer Rates
  DMA0 MDEC.IN     1 clk/word   ;0110h clks per 100h words ;\plus whatever
  DMA1 MDEC.OUT    1 clk/word   ;0110h clks per 100h words ;/decompression time
  DMA2 GPU         1 clk/word   ;0110h clks per 100h words ;-plus ...
  DMA3 CDROM/BIOS  24 clks/word ;1800h clks per 100h words ;\plus single/double
  DMA3 CDROM/GAMES 40 clks/word ;2800h clks per 100h words ;/speed sector rate
  DMA4 SPU         4 clks/word  ;0420h clks per 100h words ;-plus ...
  DMA5 PIO         20 clks/word ;1400h clks per 100h words ;-not actually used
  DMA6 OTC         1 clk/word   ;0110h clks per 100h words ;-plus nothing
MDEC decompression time is still unknown (may vary on RLE and color/mono).
GPU polygon rendering time is unknown (may be quite slow for large polys).
GPU vram read/write time is unknown (may vary on horizontal screen resolution).
CDROM BIOS default is 24 clks, for some reason most games change it to 40 clks.
SPU transfer is unknown (may have some extra delays).
XXX is SPU really only 4 clks (theoretically SPU access should be slower)?
PIO isn't used by any games (and if used: could be configured to other rates)
OTC is just writing to RAM without extra overload.
CDROM/SPU/PIO timings can be configured via Memory Control registers.

DRAM Hyper Page mode
DMA is using DRAM Hyper Page mode, allowing it to access DRAM rows at 1 clock cycle per word (effectively around 17 clks per 16 words, due to required row address loading, probably plus some further minimal overload due to refresh cycles). This is making DMA much faster than CPU memory accesses (CPU DRAM access takes 1 opcode cycle plus 6 waitstates, ie. 7 cycles in total)

CPU Operation during DMA
Basically, the CPU is stopped during DMA (theoretically, the CPU could be kept running when accessing only cache, scratchpad and on-chip I/O ports like DMA registers, and during the CDROM/SPU/PIO waitstates it could even access Main RAM, but these situations aren't supported).
However, the CPU operation resumes during periods when DMA gets interrupted (ie. after SyncMode 1 blocks, after SyncMode 2 list entries) (or in SyncMode 0 with Chopping enabled).


Timers

1F801100h+N*10h - Timer 0..2 Current Counter Value (R/W)
  0-15  Current Counter value (incrementing)
  16-31 Garbage
This register is automatically incrementing. It is write-able (allowing to set it to any value). It gets forcefully reset to 0000h on any write to the Counter Mode register, and on counter overflow (either when exceeding FFFFh, or when exceeding the selected target value).

1F801104h+N*10h - Timer 0..2 Counter Mode (R/W)
  0     Synchronization Enable (0=Free Run, 1=Synchronize via Bit1-2)
  1-2   Synchronization Mode   (0-3, see lists below)
         Synchronization Modes for Counter 0:
           0 = Pause counter during Hblank(s)
           1 = Reset counter to 0000h at Hblank(s)
           2 = Reset counter to 0000h at Hblank(s) and pause outside of Hblank
           3 = Pause until Hblank occurs once, then switch to Free Run
         Synchronization Modes for Counter 1:
           Same as above, but using Vblank instead of Hblank
         Synchronization Modes for Counter 2:
           0 or 3 = Stop counter at current value (forever, no h/v-blank start)
           1 or 2 = Free Run (same as when Synchronization Disabled)
  3     Reset counter to 0000h  (0=After Counter=FFFFh, 1=After Counter=Target)
  4     IRQ when Counter=Target (0=Disable, 1=Enable)
  5     IRQ when Counter=FFFFh  (0=Disable, 1=Enable)
  6     IRQ Once/Repeat Mode    (0=One-shot, 1=Repeatedly)
  7     IRQ Pulse/Toggle Mode   (0=Short Bit10=0 Pulse, 1=Toggle Bit10 on/off)
  8-9   Clock Source (0-3, see list below)
         Counter 0:  0 or 2 = System Clock,  1 or 3 = Dotclock
         Counter 1:  0 or 2 = System Clock,  1 or 3 = Hblank
         Counter 2:  0 or 1 = System Clock,  2 or 3 = System Clock/8
  10    Interrupt Request       (0=Yes, 1=No) (Set after Writing)    (W=1) (R)
  11    Reached Target Value    (0=No, 1=Yes) (Reset after Reading)        (R)
  12    Reached FFFFh Value     (0=No, 1=Yes) (Reset after Reading)        (R)
  13-15 Unknown (seems to be always zero)
  16-31 Garbage (next opcode)
In one-shot mode, the IRQ is pulsed/toggled only once (one-shot mode doesn't stop the counter, it just suppresses any further IRQs until a new write to the Mode register occurs; if both IRQ conditions are enabled in Bit4-5, then one-shot mode triggers only one of those conditions; whichever occurs first).
Normally, Pulse mode should be used (Bit10 is permanently set, except for a few clock cycles when an IRQ occurs). In Toggle mode, Bit10 is set after writing to the Mode register, and becomes inverted on each IRQ (in one-shot mode, it remains zero after the IRQ) (in repeat mode it inverts Bit10 on each IRQ, so IRQ4/5/6 are triggered only each 2nd time, ie. when Bit10 changes from 1 to 0).

1F801108h+N*10h - Timer 0..2 Counter Target Value (R/W)
  0-15  Counter Target value
  16-31 Garbage
When the Target flag is set (Bit3 of the Control register), the counter increments up to (including) the selected target value, and does then restart at 0000h.

Dotclock/Hblank
For more info on dotclock and hblank timings, see:
GPU Display Timings
Caution: Reading the Current Counter Value can be a little unstable (when using dotclk or hblank as clock source); the GPU clock isn't in sync with the CPU clock, so the timer may get changed during the CPU read cycle. As a workaround: repeat reading the timer until the received value is the same (or slightly bigger) than the previous value.


CDROM Drive

Playstation CDROM I/O Ports
CDROM Controller I/O Ports

Playstation CDROM Commands
CDROM Controller Command Summary
CDROM - Control Commands
CDROM - Seek Commands
CDROM - Read Commands
CDROM - Status Commands
CDROM - CD Audio Commands
CDROM - Test Commands
CDROM - Secret Unlock Commands
CDROM - Video CD Commands
CDROM - Mainloop/Responses
CDROM - Response Timings
CDROM - Response/Data Queueing

General CDROM Disk Format
CDROM Disk Format
CDROM Subchannels
CDROM Sector Encoding
CDROM Scrambling
CDROM XA Subheader, File, Channel, Interleave
CDROM XA Audio ADPCM Compression
CDROM ISO Volume Descriptors
CDROM ISO File and Directory Descriptors
CDROM ISO Misc
CDROM Problems and Repair
CDROM File Formats
CDROM Video CDs (VCD)

Playstation CDROM Protection
CDROM Protection - SCEx Strings
CDROM Protection - Bypassing it
CDROM Protection - Modchips
CDROM Protection - Chipless Modchips
CDROM Protection - LibCrypt

General CDROM Disk Images
CDROM Disk Images CCD/IMG/SUB (CloneCD)
CDROM Disk Images CDI (DiscJuggler)
CDROM Disk Images CUE/BIN/CDT (Cdrwin)
CDROM Disk Images MDS/MDF (Alcohol 120%)
CDROM Disk Images NRG (Nero)
CDROM Disk Images PBP (Sony)
CDROM Disk Images CHD (MAME)
CDROM Disk Image/Containers CDZ
CDROM Disk Image/Containers ECM
CDROM Subchannel Images
CDROM Disk Images Other Formats
CDROM Patch Files

Playstation CDROM Coprocessor
CDROM Internal Info on PSX CDROM Controller


CDROM Controller I/O Ports

1F801800h - Index/Status Register (Bit0-1 R/W) (Bit2-7 Read Only)
  0-1 Index   Port 1F801801h-1F801803h index (0..3 = Index0..Index3)   (R/W)
  2   ADPBUSY XA-ADPCM fifo empty  (0=Empty) ;set when playing XA-ADPCM sound
  3   PRMEMPT Parameter fifo empty (1=Empty) ;triggered before writing 1st byte
  4   PRMWRDY Parameter fifo full  (0=Full)  ;triggered after writing 16 bytes
  5   RSLRRDY Response fifo empty  (0=Empty) ;triggered after reading LAST byte
  6   DRQSTS  Data fifo empty      (0=Empty) ;triggered after reading LAST byte
  7   BUSYSTS Command/parameter transmission busy  (1=Busy)
Bit3,4,5 are bound to 5bit counters; ie. the bits become true at specified amount of reads/writes, and thereafter once on every further 32 reads/writes.

1F801801h.Index0 - Command Register (W)
  0-7  Command Byte
Writing to this address sends the command byte to the CDROM controller, which will then read-out any Parameter byte(s) which have been previously stored in the Parameter Fifo. It takes a while until the command/parameters are transferred to the controller, and until the response bytes are received; once when completed, interrupt INT3 is generated (or INT5 in case of invalid command/parameter values), and the response (or error code) can be then read from the Response Fifo. Some commands additionally have a second response, which is sent with another interrupt.

1F801802h.Index0 - Parameter Fifo (W)
  0-7  Parameter Byte(s) to be used for next Command
Before sending a command, write any parameter byte(s) to this address.

1F801803h.Index0 - Request Register (W)
  0-4 0    Not used (should be zero)
  5   SMEN Want Command Start Interrupt on Next Command (0=No change, 1=Yes)
  6   BFWR ...
  7   BFRD Want Data         (0=No/Reset Data Fifo, 1=Yes/Load Data Fifo)

1F801802h.Index0..3 - Data Fifo - 8bit/16bit (R)
After ReadS/ReadN commands have generated INT1, software must set the Want Data bit (1F801803h.Index0.Bit7), then wait until Data Fifo becomes not empty (1F801800h.Bit6), the datablock (disk sector) can be then read from this register.
  0-7  Data 8bit  (one byte), or alternately,
  0-15 Data 16bit (LSB=First byte, MSB=Second byte)
The PSX hardware allows to read 800h-byte or 924h-byte sectors, indexed as [000h..7FFh] or [000h..923h], when trying to read further bytes, then the PSX will repeat the byte at index [800h-8] or [924h-4] as padding value.
Port 1F801802h can be accessed with 8bit or 16bit reads (ie. to read a 2048-byte sector, one can use 2048 load-byte opcodes, or 1024 load halfword opcodes, or, more conventionally, a 512 word DMA transfer; the actual CDROM databus is only 8bits wide, so CPU/DMA are apparently breaking 16bit/32bit reads into multiple 8bit reads from 1F801802h).

1F801801h.Index1 - Response Fifo (R)
1F801801h.Index0,2,3 - Response Fifo (R) (Mirrors)
  0-7  Response Byte(s) received after sending a Command
The response Fifo is a 16-byte buffer, most or all responses are less than 16 bytes, after reading the last used byte (or before reading anything when the response is 0-byte long), Bit5 of the Index/Status register becomes zero to indicate that the last byte was received.
When reading further bytes: The buffer is padded with 00h's to the end of the 16-bytes, and does then restart at the first response byte (that, without receiving a new response, so it'll always return the same 16 bytes, until a new command/response has been sent/received).

1F801802h.Index1 - Interrupt Enable Register (W)
1F801803h.Index0 - Interrupt Enable Register (R)
1F801803h.Index2 - Interrupt Enable Register (R) (Mirror)
  0-4  Interrupt Enable Bits (usually all set, ie. 1Fh=Enable All IRQs)
  5-7  Unknown/unused (write: should be zero) (read: usually all bits set)
XXX WRITE: bit5-7 unused should be 0 // READ: bit5-7 unused

1F801803h.Index1 - Interrupt Flag Register (R/W)
1F801803h.Index3 - Interrupt Flag Register (R) (Mirror)
  0-2   Read: Response Received   Write: 7=Acknowledge   ;INT1..INT7
  3     Read: Unknown (usually 0) Write: 1=Acknowledge   ;INT8  ;XXX CLRBFEMPT
  4     Read: Command Start       Write: 1=Acknowledge   ;INT10h;XXX CLRBFWRDY
  5     Read: Always 1 ;XXX "_"   Write: 1=Unknown              ;XXX SMADPCLR
  6     Read: Always 1 ;XXX "_"   Write: 1=Reset Parameter Fifo ;XXX CLRPRM
  7     Read: Always 1 ;XXX "_"   Write: 1=Unknown              ;XXX CHPRST
Writing "1" bits to bit0-4 resets the corresponding IRQ flags; normally one should write 07h to reset the response bits, or 1Fh to reset all IRQ bits. Writing values like 01h is possible (eg. that would change INT3 to INT2, but doing that would be total nonsense). After acknowledge, the Response Fifo is made empty, and if there's been a pending command, then that command gets send to the controller.
The lower 3bit indicate the type of response received,
  INT0   No response received (no interrupt request)
  INT1   Received SECOND (or further) response to ReadS/ReadN (and Play+Report)
  INT2   Received SECOND response (to various commands)
  INT3   Received FIRST response (to any command)
  INT4   DataEnd (when Play/Forward reaches end of disk) (maybe also for Read?)
  INT5   Received error-code (in FIRST or SECOND response)
         INT5 also occurs on SECOND GetID response, on unlicensed disks
         INT5 also occurs when opening the drive door (even if no command
            was sent, ie. even if no read-command or other command is active)
  INT6   N/A
  INT7   N/A
The other 2bit indicate something else,
  INT8   Unknown (never seen that bit set yet)
  INT10h Command Start (when INT10h requested via 1F801803h.Index0.Bit5)
The response interrupts are queued, for example, if the 1st response is INT3, and the second INT5, then INT3 is delivered first, and INT5 is not delivered until INT3 is acknowledged (ie. the response interrupts are NOT ORed together to produce INT7 or so). The upper bits however can be ORed with the lower bits (ie. Command Start INT10h and 1st Response INT3 would give INT13h).
Caution - Unstable IRQ Flag polling
IRQ flag changes aren't synced with the MIPS CPU clock. If more than one bit gets set (and the CPU is reading at the same time) then the CPU does occassionally see only one of the newly bits:
  0 ----------> 3   ;99.9%  normal case INT3's
  0 ----------> 5   ;99%    normal case INT5's
  0 ---> 1 ---> 3   ;0.1%   glitch: occurs about once per thousands of INT3's
  0 ---> 4 ---> 5   ;1%     glitch: occurs about once per hundreds of INT5's
As workaround, do something like:
 @@polling_lop:
  irq_flags = [1F801803h] AND 07h       ;<-- 1st read (may be still unstable)
  if irq_flags = 00h then goto @@polling_lop
  irq_flags = [1F801803h] AND 07h       ;<-- 2nd read (should be stable now)
  handle irq_flags and acknowledge them
The problem applies only when manually polling the IRQ flags (an actual IRQ handler will get triggered when the flags get nonzero, and the flags will have stabilized once when the IRQ handler is reading them) (except, a combination of INT10h followed by INT3 can also have unstable LSBs within the IRQ handler).
The problem occurs only on older consoles (like LATE-PU-8), not on newer consoles (like PSone).

1F801802h.Index2 - Audio Volume for Left-CD-Out to Left-SPU-Input (W)
1F801803h.Index2 - Audio Volume for Left-CD-Out to Right-SPU-Input (W)
1F801801h.Index3 - Audio Volume for Right-CD-Out to Right-SPU-Input (W)
1F801802h.Index3 - Audio Volume for Right-CD-Out to Left-SPU-Input (W)
Allows to configure the CD for mono/stereo output (eg. values "80h,0,80h,0" produce normal stereo volume, values "40h,40h,40h,40h" produce mono output of equivalent volume).
When using bigger values, the hardware does have some incomplete saturation support; the saturation works up to double volume (eg. overflows that occur on "FFh,0,FFh,0" or "80h,80h,80h,80h" are clipped to min/max levels), however, the saturation does NOT work properly when exceeding double volume (eg. mono with quad-volume "FFh,FFh,FFh,FFh").
  0-7  Volume Level (00h..FFh) (00h=Off, FFh=Max/Double, 80h=Default/Normal)
After changing these registers, write 20h to 1F801803h.Index3.
Unknown if any existing games are actually supporting mono output. Resident Evil 2 uses these ports to produce fade-in/fade-out effects (although, for that purpose, it should be much easier to use Port 1F801DB0h).

1F801803h.Index3 - Audio Volume Apply Changes (by writing bit5=1)
  0    ADPMUTE Mute ADPCM                 (0=Normal, 1=Mute)
  1-4  -       Unused (should be zero)
  5    CHNGATV Apply Audio Volume changes (0=No change, 1=Apply)
  6-7  -       Unused (should be zero)

1F801801h.Index1 - Sound Map Data Out (W)
  0-7  Data
This register seems to be restricted to 8bit bus, unknown if/how the PSX DMA controller can write to it (it might support only 16bit data for CDROM).

1F801801h.Index2 - Sound Map Coding Info (W)
  0    Mono/Stereo     (0=Mono, 1=Stereo)
  1    Reserved        (0)
  2    Sample Rate     (0=37800Hz, 1=18900Hz)
  3    Reserved        (0)
  4    Bits per Sample (0=4bit, 1=8bit)
  5    Reserved        (0)
  6    Emphasis        (0=Off, 1=Emphasis)
  7    Reserved        (0)


 =============================================================================

Command Execution
Command/Parameter transmission is indicated by bit7 of 1F801800h.
When that bit gets zero, the response can be read immediately (immediately for MOST commands, but not ALL commands; so better wait for the IRQ).
Alternately, you can wait for an IRQ (which seems to take place MUCH later), and then read the response.
If there are any pending cdrom interrupts, these MUST be acknowledged before sending the command (otherwise bit7 of 1F801800h will stay set forever).

Command Busy Flag - 1F801800h.Bit7
Indicates ready-to-send-new-command,
  0=Ready to send a new command
  1=Busy sending a command/parameters
Trying to send a new command in the Busy-phase causes malfunction (the older command seems to get lost, the newer command executes and returns its results and triggers an interrupt, but, thereafter, the controller seems to hang). So, always wait until the Busy-bit goes off before sending a command.
When the Busy-flag goes off, a new command can be send immediately (even if the response from the previous command wasn't received yet), however, the new command stays in the Busy-phase until the IRQ from the previous command is acknowledged, at that point the actual transmission of the new command starts, and the Busy-flag goes off (once when the transmission completes).

Misc
Trying to do a 32bit read from 1F801800h returns the 8bit value at 1F801800h multiplied by 01010101h.

To init the CD
  -Flush all IRQs
  -1F801803h.Index0=0
  -Com_Delay=4901 (=1325h) (Port 1F801020h) (means 16bit or 32bit write?)
     (the write seems to be 32bit, clearing the upper16bit of the register)
  -Send two Getstat commands
  -Send Command 0Ah (Init)
  -Demute

Seek-Busy Phase
Warning: most or all of the info in the sentence below appear to incorrect (either that, or I didn't understand that rather confusing sentence).
REPORTEDLY:
"You should not send some commands while the CD is seeking (ie. Getstat returns with bit6 set). Thing is that stat only gets updated after a new command. I haven't tested this for other command, but for the play command (03h) you can just keep repeating the [which?] command and checking stat returned by that, for bit6 to go low (and bit7 to go high in this case). If you don't and try to do a getloc [GetlocP and/or GetlocL?] directly after the play command reports it's done [what done? meaning sending start-to-play was "done"? or meaning play reached end-of-disc?], the CD will stop. (I guess the CD can't get it's current location while it's seeking, so the logic stops the seek to get an exact fix, but never restarts..)"

Sound Map Flowchart
Sound Map mode allows to output XA-ADPCM from Main RAM (rather than from CDROM).
  SPU: Init Master Volume Left/Right (Port 1F801D80h/1F801D82h)
  SPU: Init CD Audio Volume Left/Right (Port 1F801DB0h/1F801DB2h)
  SPU: Enable CD Audio (Port 1F801DAAh.Bit0=1)
  CDROM/CMD: send Stop command (probably better to avoid conflicts)
  CDROM/CMD: send Demute command (if muted) (but works only if disc inserted)
  CDROM/HOST: init Codinginfo (Port 1F801801h.Index2)
  CDROM/HOST: enable ADPCM (Port 1F801803h.Index3.Bit0=0)  ;probably needed?
  ... set dummy addr/len with DISHXFRC=1 ?  <-- NOT required !
  ... set SMEN ... and dummy BFWR?    <-- BOTH bits required ?
  ... maybe SMADPCLR (1F801803h.Index1.bit5) does clear SoundMap ADPCM buf?
  transfer 900h bytes (same format as ADPCM sectors) (Port 1F801801h.Index1)
  Note: Before sending a byte, one should wait for DRQs (1F801801h.Bit6=1)
  Note: ADPCM output doesn't start until the last (900h'th) byte is transferred
Sound Map mode may be very useful for testing XA-ADPCM directly from within an exe file (without needing a cdrom with ADPCM sectors). And, Sound Map supports both 4bit and 8bit compression (the SPU supports only 4bit).
Caution: If ADPCM wasn't playing, and one sends one 900h-byte block, then it will get stored in one of three 900h-byte slots in SRAM, and one would expect that slot to be played when the ADPCM output starts - however, actually, the hardware will more or less randomly play one of the three slots; not necessarily the slot that was updated most recently.


CDROM Controller Command Summary

Command Summary
  Command          Parameters      Response(s)
  00h -            -               INT5(11h,40h)  ;reportedly "Sync" uh?
  01h Getstat      -               INT3(stat)
  02h Setloc     E amm,ass,asect   INT3(stat)
  03h Play       E (track)         INT3(stat), optional INT1(report bytes)
  04h Forward    E -               INT3(stat), optional INT1(report bytes)
  05h Backward   E -               INT3(stat), optional INT1(report bytes)
  06h ReadN      E -               INT3(stat), INT1(stat), datablock
  07h MotorOn    E -               INT3(stat), INT2(stat)
  08h Stop       E -               INT3(stat), INT2(stat)
  09h Pause      E -               INT3(stat), INT2(stat)
  0Ah Init         -               INT3(late-stat), INT2(stat)
  0Bh Mute       E -               INT3(stat)
  0Ch Demute     E -               INT3(stat)
  0Dh Setfilter  E file,channel    INT3(stat)
  0Eh Setmode      mode            INT3(stat)
  0Fh Getparam     -               INT3(stat,mode,null,file,channel)
  10h GetlocL    E -               INT3(amm,ass,asect,mode,file,channel,sm,ci)
  11h GetlocP    E -               INT3(track,index,mm,ss,sect,amm,ass,asect)
  12h SetSession E session         INT3(stat), INT2(stat)
  13h GetTN      E -               INT3(stat,first,last)  ;BCD
  14h GetTD      E track (BCD)     INT3(stat,mm,ss)       ;BCD
  15h SeekL      E -               INT3(stat), INT2(stat)  ;\use prior Setloc
  16h SeekP      E -               INT3(stat), INT2(stat)  ;/to set target
  17h -            -               INT5(11h,40h)  ;reportedly "SetClock" uh?
  18h -            -               INT5(11h,40h)  ;reportedly "GetClock" uh?
  19h Test         sub_function    depends on sub_function (see below)
  1Ah GetID      E -               INT3(stat), INT2/5(stat,flg,typ,atip,"SCEx")
  1Bh ReadS      E?-               INT3(stat), INT1(stat), datablock
  1Ch Reset        -               INT3(stat), Delay            ;-not DTL-H2000
  1Dh GetQ       E adr,point       INT3(stat), INT2(10bytesSubQ,peak_lo) ;\not
  1Eh ReadTOC      -               INT3(late-stat), INT2(stat)           ;/vC0
  1Fh VideoCD      sub,a,b,c,d,e   INT3(stat,a,b,c,d,e)   ;<-- SCPH-5903 only
  1Fh..4Fh -       -               INT5(11h,40h)  ;-Unused/invalid
  50h Secret 1     -               INT5(11h,40h)  ;\
  51h Secret 2     "Licensed by"   INT5(11h,40h)  ;
  52h Secret 3     "Sony"          INT5(11h,40h)  ; Secret Unlock Commands
  53h Secret 4     "Computer"      INT5(11h,40h)  ; (not in version vC0, and,
  54h Secret 5     "Entertainment" INT5(11h,40h)  ; nonfunctional in japan)
  55h Secret 6     "<region>"      INT5(11h,40h)  ;
  56h Secret 7     -               INT5(11h,40h)  ;/
  57h SecretLock   -               INT5(11h,40h)  ;-Secret Lock Command
  58h..5Fh Crash   -               Crashes the HC05 (jumps into a data area)
  6Fh..FFh -       -               INT5(11h,40h)  ;-Unused/invalid
E = Error 80h appears on some commands (02h..09h, 0Bh..0Dh, 10h..16h, 1Ah, 1Bh?, and 1Dh) when the disk is missing, or when the drive unit is disconnected from the mainboard.
Some commands (04h,05h,10h,11h,1Dh) do also trigger Error 80h when the disk is stopped.

sub_function numbers (for command 19h)
Test commands are invoked with command number 19h, followed by a sub_function number as first parameter byte. The Kernel seems to be using only sub_function 20h (to detect the CDROM Controller version).
  sub  params  response           ;Effect
  00h      -   INT3(stat)         ;Force motor on, clockwise, even if door open
  01h      -   INT3(stat)         ;Force motor on, anti-clockwise, super-fast
  02h      -   INT3(stat)         ;Force motor on, anti-clockwise, super-fast
  03h      -   INT3(stat)         ;Force motor off (ignored during spin-up)
  04h      -   INT3(stat)         ;Start SCEx reading and reset counters
  05h      -   INT3(total,success);Stop SCEx reading and get counters
  06h *    n   INT3(old)  ;\early ;Adjust balance in RAM, send CX(30+n XOR 7)
  07h *    n   INT3(old)  ; PSX   ;Adjust gain in RAM, send CX(38+n XOR 7)
  08h *    n   INT3(old)  ;/only  ;Adjust balance in RAM only
  06h..0Fh -   INT5(11h,10h)      ;N/A (11h,20h when NONZERO number of params)
  10h      -   INT3(stat) ;CX(..) ;Force motor on, anti-clockwise, super-fast
  11h      -   INT3(stat) ;CX(03) ;Move Lens Up (leave parking position)
  12h      -   INT3(stat) ;CX(02) ;Move Lens Down (enter parking position)
  13h      -   INT3(stat) ;CX(28) ;Move Lens Outwards
  14h      -   INT3(stat) ;CX(2C) ;Move Lens Inwards
  15h      -   INT3(stat) ;CX(22) ;If motor on: Move outwards,inwards,motor off
  16h      -   INT3(stat) ;CX(23) ;No effect?
  17h      -   INT3(stat) ;CX(E8) ;Force motor on, clockwise, super-fast
  18h      -   INT3(stat) ;CX(EA) ;Force motor on, anti-clockwise, super-fast
  19h      -   INT3(stat) ;CX(25) ;No effect?
  1Ah      -   INT3(stat) ;CX(21) ;No effect?
  1Bh..1Fh -   INT5(11h,10h)      ;N/A (11h,20h when NONZERO number of params)
  20h      -   INT3(yy,mm,dd,ver) ;Get cdrom BIOS date/version (yy,mm,dd,ver)
  21h      -   INT3(n)            ;Get Drive Switches (bit0=POS0, bit1=DOOR)
  22h ***  -   INT3("for ...")    ;Get Region ID String
  23h ***  -   INT3("CXD...")     ;Get Chip ID String for Servo Amplifier
  24h ***  -   INT3("CXD...")     ;Get Chip ID String for Signal Processor
  25h ***  -   INT3("CXD...")     ;Get Chip ID String for Decoder/FIFO
  26h..2Fh -   INT5(11h,10h)      ;N/A (11h,20h when NONZERO number of params)
  30h *    i,x,y     INT3(stat)       ;Prototype/Debug stuff   ;\supported on
  31h *    x,y       INT3(stat)       ;Prototype/Debug stuff   ; early PSX only
  4xh *    i         INT3(x,y)        ;Prototype/Debug stuff   ;/
  30h..4Fh ..        INT5(11h,10h)    ;N/A always 11h,10h (no matter of params)
  50h      a[,b[,c]] INT3(stat)       ;Servo/Signal send CX(a:b:c)
  51h **   39h,xx    INT3(stat,hi,lo) ;Servo/Signal send CX(39xx) with response
  51h..5Fh -         INT5(11h,10h)    ;N/A
  60h      lo,hi     INT3(databyte)   ;HC05 SUB-CPU read RAM and I/O ports
  61h..70h -         INT5(11h,10h)    ;N/A
  71h ***  adr       INT3(databyte)   ;Decoder Read one register
  72h ***  adr,dat   INT3(stat)       ;Decoder Write one register
  73h ***  adr,len   INT3(databytes..);Decoder Read multiple registers, bugged
  74h ***  adr,len,..INT3(stat)       ;Decoder Write multiple registers, bugged
  75h ***  -         INT3(lo,hi,lo,hi);Decoder Get Host Xfer Info Remain/Addr
  76h ***  a,b,c,d   INT3(stat)       ;Decoder Prepare Transfer to/from SRAM
  77h..FFh -         INT5(11h,10h)    ;N/A
  80h..8Fh a,b       ?                ;seem to do something on PS2
* sub_functions 06h..08h, 30h..31h, and 4xh are supported only in vC0 and vC1.
** sub_function 51h is supported only in BIOS version vC2 and up.
*** sub_functions 22h..25h, 71h..76h supported only in BIOS version vC1 and up.

Unsupported GetQ,VCD,SecretUnlock (command 1Dh,1Fh,5xh)
INT5 will be returned if the command is unsupported. That, WITHOUT removing the Parameters from the FIFO, so the parameters will be accidently passed to the NEXT command. To avoid that: clear the parameter FIFO via [1F801803h.Index1]=40h after receiving the INT5 error.


CDROM - Control Commands

Sync - Command 00h --> INTx(stat+1,40h) (?)
Reportedly "command does not succeed until all other commands complete. This can be used for synchronization - hence the name."
Uh, actually, returns error code 40h = Invalid Command...?

Setfilter - Command 0Dh,file,channel --> INT3(stat)
Automatic ADPCM (CD-ROM XA) filter ignores sectors except those which have the same channel and file numbers in their subheader. This is the mechanism used to select which of multiple songs in a single .XA file to play.
Setfilter does not affect actual reading (sector reads still occur for all sectors).
XXX err... that is... does not affect reading of non-ADPCM sectors (normal "data" sectors are kept received regardless of Setfilter).

Setmode - Command 0Eh,mode --> INT3(stat)
  7   Speed       (0=Normal speed, 1=Double speed)
  6   XA-ADPCM    (0=Off, 1=Send XA-ADPCM sectors to SPU Audio Input)
  5   Sector Size (0=800h=DataOnly, 1=924h=WholeSectorExceptSyncBytes)
  4   Ignore Bit  (0=Normal, 1=Ignore Sector Size and Setloc position)
  3   XA-Filter   (0=Off, 1=Process only XA-ADPCM sectors that match Setfilter)
  2   Report      (0=Off, 1=Enable Report-Interrupts for Audio Play)
  1   AutoPause   (0=Off, 1=Auto Pause upon End of Track) ;for Audio Play
  0   CDDA        (0=Off, 1=Allow to Read CD-DA Sectors; ignore missing EDC)
The "Ignore Bit" does reportedly force a sector size of 2328 bytes (918h), however, that doesn't seem to be true. Instead, Bit4 seems to cause the controller to ignore the sector size in Bit5 (instead, the size is kept from the most recent Setmode command which didn't have Bit4 set). Also, Bit4 seems to cause the controller to ignore the <exact> Setloc position (instead, data is randomly returned from the "Setloc position minus 0..3 sectors"). And, Bit4 causes INT1 to return status.Bit3=set (IdError). Purpose of Bit4 is unknown?

Init - Command 0Ah --> INT3(stat) --> INT2(stat)
Multiple effects at once. Sets mode=20h, activates drive motor, Standby, abort all commands.

Reset - Command 1Ch,(...) --> INT3(stat) --> Delay(1/8 seconds)
  Caution: Not supported on DTL-H2000 (v01)
Resets the drive controller, reportedly, same as opening and closing the drive door. The command executes no matter if/how many parameters are used (tested with 0..7 params). INT3 indicates that the command was started, but there's no INT that would indicate when the command is finished, so, before sending any further commands, a delay of 1/8 seconds (or 400000h clock cycles) must be issued by software.

MotorOn - Command 07h --> INT3(stat) --> INT2(stat)
Activates the drive motor, works ONLY if the motor was off (otherwise fails with INT5(stat,20h); that error code would normally indicate "wrong number of parameters", but means "motor already on" in this case).
Commands like Read, Seek, and Play are automatically starting the Motor when needed (which makes the MotorOn command rather useless, and it's rarely used by any games).
Myth: Older homebrew docs are referring to MotorOn as "Standby", claiming that it would work similar as "Pause", that is wrong: the command does NOT pause anything (if the motor is on, then it does simply trigger INT5, but without pausing reading or playing).
Note: The game "Nightmare Creatures 2" does actually attempt to use MotorOn to "pause" after reading files, but the hardware does simply ignore that attempt (aside from doing the INT5 thing).

Stop - Command 08h --> INT3(stat) --> INT2(stat)
Stops motor with magnetic brakes (stops within a second or so) (unlike power-off where it'd keep spinning for about 10 seconds), and moves the drive head to the begin of the first track. Official way to restart is command 0Ah, but almost any command will restart it.
The first response returns the current status (this already with bit5 cleared), the second response returns the new status (with bit1 cleared).

Pause - Command 09h --> INT3(stat) --> INT2(stat)
Aborts Reading and Playing, the motor is kept spinning, and the drive head maintains the current location within reasonable error.
The first response returns the current status (still with bit5 set if a Read command was active), the second response returns the new status (with bit5 cleared).

Data/ADPCM Sector Filtering/Delivery
The PSX CDROM BIOS is first trying to send sectors to the ADPCM decoder, and, if that didn't work out, then it's trying to send them to the main CPU (and if that didn't work out either, then it's silently ignoring the sector).
 try_deliver_as_adpcm_sector:
  reject if CD-DA AUDIO format
  reject if sector isn't MODE2 format
  reject if adpcm_disabled(setmode.6)
  reject if filter_enabled(setmode.3) AND selected file/channel doesn't match
  reject if submode isn't audio+realtime (bit2 and bit6 must be both set)
  deliver: send sector to xa-adpcm decoder when passing above cases
 try_deliver_as_data_sector:
  reject data-delivery if "try_deliver_as_adpcm_sector" did do adpcm-delivery
  reject if filter_enabled(setmode.3) AND submode is audio+realtime (bit2+bit6)
  1st delivery attempt: send INT1+data, unless there's another INT pending
  delay, and retry at later time... but this time with file/channel checking!
  reject if filter_enabled(setmode.3) AND selected file/channel doesn't match
  2nd delivery attempt: send INT1+data, unless there's another INT pending
BUG: Note that the data delivery is done in two different attempts: The first one regardless of file/channel, and the second one only on matching file/channel (if filtering is enabled).


CDROM - Seek Commands

Setloc - Command 02h,amm,ass,asect --> INT3(stat)
Sets the seek target - but without yet starting the seek operation. The actual seek is invoked by certain commands: SeekL (Data) and SeekP (Audio) are doing plain seeks (and do Pause after completion). ReadN/ReadS are similar to SeekL (and do start reading data after the seek operation). Play is similar to SeekP (and does start playing audio after the seek operation).
The amm,ass,asect parameters refer to the entire disk (not to the current track). To seek to a specific location within a specific track, use GetTD to get the start address of the track, and add the desired time offset to it.

SeekL - Command 15h --> INT3(stat) --> INT2(stat)
Seek to Setloc's location in data mode (using data sector header position data, which works/exists only on Data tracks, not on CD-DA Audio tracks).
After the seek, the disk stays on the seeked location forever (namely: when seeking sector N, it does stay at around N-8..N-0 in single speed mode, or at around N-5..N+2 in double speed mode).
Trying to use SeekL on Audio CDs passes okay on the first response, but (after two seconds or so) the second response will return an error (stat+4,04h), and stop the drive motor... that error doesn't appear ALWAYS though... works in some situations... such like when previously reading data sectors or so...?

SeekP - Command 16h --> INT3(stat) --> INT2(stat)
Seek to Setloc's location in audio mode (using the Subchannel Q position data, which works on both Audio on Data disks).
After the seek, the disk stays on the seeked location forever (namely: when seeking sector N, it does stay at around N-9..N-1 in single speed mode, or at around N-2..N in double speed mode).
Note: Some older docs claim that SeekP would recurse only "MM:SS" of the "MM:SS:FF" position from Setloc - that is wrong, it does seek to MM:SS:FF (verified on a PSone).
After the seek, status is stat.bit7=0 (ie. audio playback off), until sending a new Play command (without parameters) to start playback at the seeked location.

SetSession - Command 12h,session --> INT3(stat) --> INT2(stat)
Seeks to session (ie. moves the drive head to the session, with stat bit6 set during the seek phase).
When issued during active-play, the command returns error code 80h.
When issued during play-spin-up, play is aborted.
  ___Errors___
  session = 00h causes error code 10h.     ;INT5(03h,10h), no 2nd/3rd response
  ___On a non-multisession-disk___
  session = 01h passes okay.               ;INT3(stat), and once INT2(stat)
  session = 02h or higher cause seek error ;INT3(stat), and twice INT5(06h,40h)
  ___On a multisession-disk with N sessions___
  session = 01h..N+1 passes okay   ;where N+1 moves to the END of LAST session
  session = N+2 or higher cause seek error  ;2nd response = INT5(06h,20h)
after seek error --> disk stops spinning at 2nd response, then restarts spinning for 1 second or so, then stops spinning forever... and following gettn/gettd/getid/getlocl/getlocp fail with error 80h...
The command does automatically read the TOC of the new session. BUG: Older CD Firmwares (16 May 1995 and older) don't clear the old TOC when loading Session 1, in that case SetSession(1) may update some (not all) TOC entries; ending up with a mixup of old and new TOC entries.
There seems to be no way to determine the current sessions number (via Getparam or so), and more important, no way to determine if the disk is a multi-session disk or not... except by trial... which would stop the drive motor on seek errors on single-session disks...?
  XXX a nonzero ATIP byte in GetID may indicate a multisession disc
For setloc, one must probably specifiy minutes within the 1st track of the new session (the 1st track of 1st session usually/always starts at 00:02:00, but for other sessions one would need to use GetTD)...?
  XXX but GetTD is only MM:SS (not MM:SS:FF)
      so must either assume sessions to start at FF=00
      or, scan MM:SS upwards (and search for ISO descriptors)


CDROM - Read Commands

ReadN - Command 06h --> INT3(stat) --> INT1(stat) --> datablock
Read with retry. The command responds once with "stat,INT3", and then it's repeatedly sending "stat,INT1 --> datablock", that is continued even after a successful read has occured; use the Pause command to terminate the repeated INT1 responses.
Unknown which responses are sent in case of read errors?
====
ReadN and ReadS cause errors if you're trying to read an unlicensed CD or CD-R without a mod chip. Sectors on Audio CDs can be read only when CDDA is enabled via Setmode (otherwise error code 40h is returned).
====
Actually, Read seems to work on unlicensed CD-R's, but the returned data is the whole sector or so (the 2048 data bytes preceeded by a 12byte header, and probably/maybe followed by error-correction info; in fact the total received data in the Data Fifo is 4096 bytes; the last some bytes probably being garbage) (however error correction is NOT performed by hardware, so the 2048 data bytes may be trashy) (however, if the error correction info IS received, then error correction could be performed by software) (also Setloc doesn't seem to work accurately on unlicensed CD-R's).
====
     ;Read occasionally returns 11h,40h ..? when TOC isn't loaded?
After receiving INT1, the Kernel does,
  [1F801800h]=00h
  00h=[1F801800h]
  [1F801803h]=00h
  00h=[1F801803h]
  [1F801800h]=00h
  [1F801803h]=80h
and then,
  [1F801018h]=00020943h  ;cdrom_delay
  [1F801020h]=0000132Ch  ;com_delay
then,
  x=[1F8010F4h] AND 00FFFFFFh   ;result is 00840000h
  [1F8010F4h] = x OR 00880000h
  [1F8010F0h] = [1F8010F0h] OR 00008000h
  [1F8010B0h] = A0010000h ;addr
  [1F8010B4h] = 00010200h ;LSBs=num words, MSBs=ignored/bullshit
  [1F8010B4h] = 11000000h ;DMA control
thereafter,
  [1F801800h]=01h
  [1F801803h]=40h    ;reset parameter fifo
  [0]=00000000h
  [0]=00000001h
  [0]=00000002h
  [0]=00000003h
  [1F801800h]=00h
  [1F801801h]=09h    ;command9 (pause)

ReadS - Command 1Bh --> INT3(stat) --> INT1(stat) --> datablock
Read without automatic retry. Not sure what that means... does WHAT on errors? Maybe intended for continous streaming video output (to skip bad frames, rather than to interrupt the stream by performing read-retrys).

ReadN/ReadS
Both ReadN/ReadS are reading data sequentially, starting at the sector specified with Setloc, and then automatically reading the following sectors.

CDROM Incoming Data / Buffer Overrun Timings
The Read commands are continously receiving 75 sectors per second (or 150 sectors at double speed), and, basically, the software must be fast enough to process that amount of incoming data. However, the PSX hardware includes a buffer that can hold up to a handful (exact number is unknown?) of sectors, so, occasional delays of more than 1/75 seconds between processing two sectors aren't causing lost sectors, unless the delay(s) are summing up too much. The relevant steps for receiving data are:
  Wait for Interrupt Request (INT1)          ;indicates that data is available
  Send Data Request (1F801803h.Index0.Bit7=1);accept data
  Acknowledge INT1                           ;
  Copy Data to Main RAM (via I/O or DMA)     ;read data
The Data Request accepts the data for the currently pending interrupt, it should be usually issued between receiving/acknowledging INT1 (however, it can be also issued shortly after the acknowledge; even if there are further sectors in the buffer, there seems to be a small delay between the acknowledge and the next interrupt, and Data Requests during that period are still treated to belong to the old interrupt).
If a buffer overrun has occured <before> issuing the Data Request, then wrong data will be received, ie. some sectors will be skipped (the hardware doesn't seem to support a buffer-overrun error flag? Anyways, see GetlocL description for a possible way to detect buffer-overruns).
If a buffer overrun occurs <after> issuing the Data Request, then the requested data can be still read via I/O or DMA intactly, ie. the requested data is "locked", and the overrun will affect only the following sectors.

ReadTOC - Command 1Eh --> INT3(stat) --> INT2(stat)
  Caution: Supported only in BIOS version vC1 and up. Not supported in vC0.
Reread the Table of Contents of current session without reset. The command is rather slow, the second response appears after about 1 second delay. The command itself returns only status information (to get the actual TOC info, use GetTD and GetTN commands).
Note: The TOC contains information about the tracks on the disk (not file names or so, that kind of information is obtained via Read commands). The TOC is read automatically on power-up, when opening/closing the drive door, and when changing sessions (so, normally, it isn't required to use this command).

Setloc, Read, Pause
A normal CDROM access (such like reading a file) consists of three commands:
  Setloc, Read, Pause
Normally one shouldn't mess up the ordering of those commands, but if one does, following rules do apply:
Setloc is memorizing the wanted target, and marks it as unprocessed, and has no other effect (it doesn't start reading or seeking, and doesn't interrupt or redirect any active reads).
If Read is issued with an unprocessed Setloc, then the drive is automatically seeking the Setloc location (and marks Setloc as processed).
If Read is issued without an unprocessed Setloc, the following happens: If reading is already in progress then it just continues reading. If Reading was Paused, then reading resumes at the most recently received sector (ie. returning that sector once another time).


CDROM - Status Commands

Status code (stat)
The 8bit status code is returned by Getstat command (and many other commands), the meaning of the separate stat bits is:
  7  Play          Playing CD-DA         ;\only ONE of these bits can be set
  6  Seek          Seeking               ; at a time (ie. Read/Play won't get
  5  Read          Reading data sectors  ;/set until after Seek completion)
  4  ShellOpen     Once shell open (0=Closed, 1=Is/was Open)
  3  IdError       (0=Okay, 1=GetID denied) (also set when Setmode.Bit4=1)
  2  SeekError     (0=Okay, 1=Seek error)     (followed by Error Byte)
  1  Spindle Motor (0=Motor off, or in spin-up phase, 1=Motor on)
  0  Error         Invalid Command/parameters (followed by Error Byte)
If the shell is closed, then bit4 is automatically reset to zero after reading stat with the Getstat command (most or all other commands do not reset that bit after reading). If stat bit0 or bit2 is set, then the normal respons(es) and interrupt(s) are not send, and, instead, INT5 occurs, and an error-byte is send as second response byte, with the following values:
  ___These values appear in the FIRST response; with stat.bit0 set___
  10h - Invalid Sub_function (for command 19h), or invalid parameter value
  20h - Wrong number of parameters
  40h - Invalid command
  80h - Cannot respond yet (eg. required info was not yet read from disk yet)
           (namely, TOC not-yet-read or so)
           (also appears if no disk inserted at all)
  ___These values appear in the SECOND response; with stat.bit2 set___
  04h - Seek failed (when trying to use SeekL on Audio CDs)
  ___These values appear even if no command was sent; with stat.bit2 set___
  08h - Drive door became opened
80h appears on some commands (02h..09h, 0Bh..0Dh, 10h..16h, 1Ah, 1Bh?, and 1Dh) when the disk is missing, or when the drive unit is disconnected from the mainboard.

Stat Seek/Play/Read bits
There's is only max ONE of the three Seek/Play/Read bits set at a time, ie. during Seek, ONLY the seek bit is set (and Read or Play doesn't get until seek completion), that is important for Gran Turismo 1, which checks for seek completion by waiting for READ getting set (rather than waiting for SEEK getting cleared).

Getstat - Command 01h --> INT3(stat)
Returns stat (like many other commands), and additionally does reset the shell open flag (for the following commands; unless the shell is still opened). This is different as for most or all other commands (which may return stat, but which do not reset the shell open flag).
In other docs, the command is eventually referred to as "Nop", believing that it does nothing than returning stat (ignoring the fact that it's having the special shell open reset feature).

Getparam - Command 0Fh --> INT3(stat,mode,null,file,channel)
Returns stat (see Getstat above), mode (see Setmode), a null byte (always 00h), and file/channel filter values (see Setfilter).

GetlocL - Command 10h --> INT3(amm,ass,asect,mode,file,channel,sm,ci)
Retrieves 4-byte sector header, plus 4-byte subheader of the current sector. GetlocL can be send during active Read commands (but, mind that the GetlocL-INT3-response can't be received until any pending Read-INT1's are acknowledged).
The PSX hardware can buffer a handful of sectors, the INT1 handler receives the <oldest> buffered sector, the GetlocL command returns the header and subheader of the <newest> buffered sector. Note: If the returned <newest> sector number is much bigger than the expected <oldest> sector number, then it's likely that a buffer overrun has occured.
GetlocL fails (with error code 80h) when playing Audio CDs (or Audio Tracks on Data CDs). These errors occur because Audio sectors don't have any header/subheader (instead, equivalent data is stored in Subchannel Q, which can be read with GetlocP).
GetlocL also fails (with error code 80h) when the drive is in Seek phase (such like shortly after a new ReadN/ReadS command). In that case one can retry issuing GetlocL (until it passes okay, ie. until the seek has completed). During Seek, the drive seems to decode only Subchannel position data (but no header/subheader data), accordingly GetlocL won't work during seek (however, GetlocP does work during Seek).

GetlocP - Command 11h - INT3(track,index,mm,ss,sect,amm,ass,asect)
Retrieves 8 bytes of position information from Subchannel Q with ADR=1. Mainly intended for displaying the current audio position during Play. All results are in BCD.
  track:  track number (AAh=Lead-out area) (FFh=unknown, toc, none?)
  index:  index number (Usually 01h)
  mm:     minute number within track (00h and up)
  ss:     second number within track (00h to 59h)
  sect:   sector number within track (00h to 74h)
  amm:    minute number on entire disk (00h and up)
  ass:    second number on entire disk (00h to 59h)
  asect:  sector number on entire disk (00h to 74h)
Note: GetlocP is also used for reading the LibCrypt protection data:
CDROM Protection - LibCrypt

GetTN - Command 13h --> INT3(stat,first,last) ;BCD
Get first track number, and last track number in the TOC of the current Session. The number of tracks in the current session can be calculated as (last-first+1). The first track number is usually 01h in the first (or only) session, and "last track of previous session plus 1" in further sessions.

GetTD - Command 14h,track --> INT3(stat,mm,ss) ;BCD
For a disk with NN tracks, parameter values 01h..NNh return the start of the specified track, parameter value 00h returns the end of the last track, and parameter values bigger than NNh return error code 10h.
The GetTD values are relative to Index=1 and are rounded down to second boundaries (eg. if track=N Index=0 starts at 12:34:56, and Track=N Index=1 starts at 12:36:56, then GetTD(N) will return 12:36, ie. the sector number is truncated, and the Index=0 region is skipped).

GetQ - Command 1Dh,adr,point --> INT3(stat) --> INT2(10bytesSubQ,peak_lo)
  Caution: Supported only in BIOS version vC1 and up. Not supported in vC0.
  Caution: When unsupported, Parameter Fifo isn't cleared after the command.
Allows to read 10 bytes from Subchannel Q in Lead-In (see CDROM Subchannels chapter for details). Unlike GetTD, this command allows to receive the exact MM:SS:FF address of the point'ed Track (GetTD reads a memorized MM:SS value from RAM, whilst GetQ reads the full MM:SS:FF from the disk, which is slower than GetTD, due to the disk-access).
With ADR=1, point can be a any point number for ADR=1 in Lead-in (eg. 01h..99h=Track N, A2h=Lead-Out). The returned 10 bytes are raw SubQ data (starting with the ADR/Control value; of which the lower 4bits are always ADR=1).
The 11th returned byte is the Peak LSB (similar as in Play+Report, but in this case only the LSB is transferred, which is apparently a bug in CDROM BIOS, the programmer probably wanted to send 10 bytes without peak, or 12 bytes with full peak; although peak wouldn't be too useful, as it should always zero during Lead-In... but some discs do seem return non-zero values for whatever reason).
Aside from ADR=1, a value of ADR=5 can be used on multisession disks (eg. with point B0h, C0h). Not sure if any other ADR values can be used (ADR=3, ISRC is usually not in the Lead-In, ADR=2, EAN may be in the lead-in, but one may need to specify point equal to the first EAN byte).
If the ADR/Point combination isn't found, then a timeout occurs after circa 6 seconds (to avoid this, use GetTN to see which tracks/points exist). After the timeout, the command starts playing track 1. If the controller wasn't already in audio mode before sending the command, then it does switch off the drive motor for a moment (that, after the timeout, and before starting playback).
In case of timeout, the normal INT3/INT2 responses are replaced by INT3/INT5/INT5 (INT3 at command start, 1st INT5 at timeout/stop, and 2nd INT5 at restart/play).
Note: GetQ sends scratch noise to the SPU while seeking to the Lead-In area.

GetID - Command 1Ah --> INT3(stat) --> INT2/5 (stat,flags,type,atip,"SCEx")
  Drive Status           1st Response   2nd Response
  Door Open              INT5(11h,80h)  N/A
  Spin-up                INT5(01h,80h)  N/A
  Detect busy            INT5(03h,80h)  N/A
  No Disk                INT3(stat)     INT5(08h,40h, 00h,00h, 00h,00h,00h,00h)
  Audio Disk             INT3(stat)     INT5(0Ah,90h, 00h,00h, 00h,00h,00h,00h)
  Unlicensed:Mode1       INT3(stat)     INT5(0Ah,80h, 00h,00h, 00h,00h,00h,00h)
  Unlicensed:Mode2       INT3(stat)     INT5(0Ah,80h, 20h,00h, 00h,00h,00h,00h)
  Unlicensed:Mode2+Audio INT3(stat)     INT5(0Ah,90h, 20h,00h, 00h,00h,00h,00h)
  Debug/Yaroze:Mode2     INT3(stat)     INT2(02h,00h, 20h,00h, 20h,20h,20h,20h)
  Licensed:Mode2         INT3(stat)     INT2(02h,00h, 20h,00h, 53h,43h,45h,4xh)
  Modchip:Audio/Mode1    INT3(stat)     INT2(02h,00h, 00h,00h, 53h,43h,45h,4xh)
The status byte (ie. the first byte in the responses), may differ in some cases; values shown above are typically received when issuing GetID shortly after power-up; however, shortly after the detect-busy phase, seek-busy flag (bit6) bit may be set, and, after issuing commands like Play/Read/Stop, bit7,6,5,1 may differ. The meaning of the separate 2nd response bytes is:
  1st byte: stat  (as usually, but with bit3 same as bit7 in 2nd byte)
  2nd byte: flags (bit7=denied, bit4=audio... or reportedly import, uh?)
    bit7: Licensed (0=Licensed Data CD, 1=Denied Data CD or Audio CD)
    bit6: Missing  (0=Disk Present, 1=Disk Missing)
    bit4: Audio CD (0=Data CD, 1=Audio CD) (always 0 when Modchip installed)
  3rd byte: Disk type (from TOC Point=A0h) (eg. 00h=Audio or Mode1, 20h=Mode2)
  4th byte: Usually 00h (or 8bit ATIP from Point=C0h, if session info exists)
    that 8bit ATIP value is taken form the middle 8bit of the 24bit ATIP value
  5th-8th byte: SCEx region (eg. ASCII "SCEE" = Europe) (0,0,0,0 = Unlicensed)
The fourth letter of the "SCEx" string contains region information: "SCEI" (Japan/NTSC), "SCEA" (America/NTSC), "SCEE" (Europe/PAL). The "SCEx" string is displayed in the intro, and the PSX refuses to boot if it doesn't match up for the local region.
With a modchip installed, the same response is sent for Mode1 and Audio disks (except for Audio disks with very short TOCs (eg. singles) because SCEX reading is aborted immediately after reading all TOC entries on Audio disks); whether it is Audio or Mode1 can be checked by examining Subchannel Q ADR/Control.Bit6 (eg. via command 19h,60h,50h,00h).
Yaroze does return "SCEA" for SCEA discs, but, for SCEI,SCEE,SCEW discs it does return four ASCII spaces (20h).


CDROM - CD Audio Commands

To play CD-DA Audio CDs, init the following SPU Registers: CD Audio Volume, Main Volume, and SPU Control Bit0. Then send Demute command, and Play command.

Mute - Command 0Bh --> INT3(stat)
Turn off audio streaming to SPU (affects both CD-DA and XA-ADPCM).
Even when muted, the CDROM controller is internally processing audio sectors (as seen in 1F801800h.Bit2, which works as usually for XA-ADPCM), muting is just forcing the CD output volume to zero.
Mute is used by Dino Crisis 1 to mute noise during modchip detection.

Demute - Command 0Ch --> INT3(stat)
Turn on audio streaming to SPU (affects both CD-DA and XA-ADPCM). The Demute command is needed only if one has formerly used the Mute command (by default, the PSX is demuted after power-up (...and/or after Init command?), and is demuted after cdrom-booting).

Play - Command 03h (,track) --> INT3(stat) --> optional INT1(report bytes)
Starts CD Audio Playback. The parameter is optional, if there's no parameter given (or if it is 00h), then play either starts at Setloc position (if there was a pending unprocessed Setloc), or otherwise starts at the current location (eg. the last point seeked, or the current location of the current song; if it was already playing). For a disk with N songs, Parameters 1..N are starting the selected track. Parameters N+1..99h are restarting the begin of current track. The motor is switched off automatically when Play reaches the end of the disk, and INT4(stat) is generated (with stat.bit7 cleared).
The track parameter seems to be ignored when sending Play shortly after power-up (ie. when the drive hasn't yet read the TOC).
===
"Play is almost identical to CdlReadS, believe it or not. The main difference is that this does not trigger a completed read IRQ. CdlPlay may be used on data sectors. However, all sectors from data tracks are treated as 00, so no sound is played. As CdlPlay is reading, the audio data appears in the sector buffer, but is not reliable. Game Shark "enhancement CDs" for the 2.x and 3.x versions used this to get around the PSX copy protection."
Hmmm, what/where is the sector buffer... in the SPU?
And, what/who are the 2.x and 3.x versions?

Forward - Command 04h --> INT3(stat) --> optional INT1(report bytes)
Backward - Command 05h --> INT3(stat) --> optional INT1(report bytes)
After sending the command, the drive is in fast forward/backward mode, skipping every some sectors. The skipping rate is fixed (it doesn't increase after some seconds) (however, it increases when (as long as) sending the command again and again). The sound becomes (obviously) non-continous, and also rather very silent, muffled, and almost inaudible (that's making it rather useless; unless it's combined with a track/minute/second display). To terminate forward/backward, send a new Play command (with no parameters, so play starts at the "searched" location). Backward automatically switches to Play when reaching the begin of Track 1. Forward automatically Stops the drive motor with INT4(stat) when reaching the end of the last track.
Forward/Backwards work only if the drive was in Play state, and only if Play had already started (ie. not shortly/immediately after a Play command); if the drive was not in Play state, then INT5(stat+1,80h) occurs.

Setmode bits used for Play command
During Play, only bit 7,2,1 of Setmode are used, all other Setmode bits are ignored (that, including bit0, ie. during Play the drive is always in CD-DA mode, regardless of that bit).
Bit7 (double speed) should be usually off, although it can be used for a fast forward effect (with audible output). Bit2 (report) activates an optional interrupt for Play, Forward, and Backward commands (see below). Bit1 (autopause) pauses play at the end of the track.

Report --> INT1(stat,track,index,mm/amm,ss+80h/ass,sect/asect,peaklo,peakhi)
With report enabled via Setmode, the Play, Forward, and Backward commands do repeatedly generate INT1 interrupts, with eight bytes response length. The interrupt isn't generated on ALL sectors, and the response changes between absolute time, and time within current track (the latter one indicated by bit7 of ss):
  amm/ass/asect are returned on asect=00h,20h,40h,60h   ;-absolute time
  mm/ss+80h/sect are returned on asect=10h,30h,50h,70h  ;-within current track
  (or, in case of read errors, report may be returned on other asect's)
The last two response bytes (peaklo,peakhi) contain the Peak value, as received from the CXD2510Q Signal Processor. That is: An unsigned absolute peak level in lower 15bit, and an L/R flag in upper bit. The L/R bit is toggled after each SUBQ read, however the PSX Report mode does usually forward SUBQ only every 10 frames (but does read SUBQ in <every> frame), so L/R will stay stuck in one setting (but may toggle after one second; ie. after 75 frames). And, peak is reset after each read, so 9 of the 10 frames are lost.
Note: Report mode affects only CD Audio (not Data, nor XA-ADPCM sectors).

AutoPause --> INT4(stat)
Autopause can be enabled/disabled via Setmode.bit1:
  Setmode.bit1=1: AutoPause=On  --> Issue INT4(stat) and PAUSE at end of TRACK
  Setmode.bit1=0: AutoPause=Off --> Issue INT4(stat) and STOP at end of DISC
End of Track is determined by sensing a track number transition in SubQ position info. After autopause, the disc stays at the <end> of the old track, NOT at the <begin> of the next track (so trying to resume playing by sending a new Play command without new Seek/Setloc command will instantly pause again).
Caution: SubQ track transitions may pause instantly when accidently starting to play at the end of the previous track rather than at begin of desired track (this <might> happen due to seek inaccuracies, for example, GetTD does round down TOC entries from MM:SS:FF to MM:SS:00, which may be off by 0.99 seconds, although this error should be usually compensated by the leading 2-second pregap/index0 region at the begin of each track, unfortunately there are a few .CUE sheet files that do lack both PREGAP and INDEX 00 entries on audio tracks, which might cause problems with autopause).
AutoPause is used by Rayman and Tactics Ogre.

Playing XA-ADPCM Sectors (compressed audio data)
Aside from normal uncompressed CD Audio disks, the PSX can also play XA-ADPCM compressed sectors. XA-ADPCM sectors are organized in Files (not in tracks), and are "played" with Read command (not Play command).
To play XA-ADPCM, initialize the SPU for CD Audio input (as described above), enable ADPCM via Setmode, then select the sector via Setloc, and issue a Read command (typically ReadS).
XA-ADPCM sectors are interleaved, ie. only each Nth sector should be played (where "N" depends on the Motor Speed, mono/stereo format, and sample rate). If the "other" sectors do contain XA-ADPCM data too, then the Setfilter command (and XA-Filter enable flag in Setmode) must be used to select the desired sectors. If the "other" sectors do contain code or data (eg. MDEC video data) which is wanted to be send to the CPU, then SetFilter isn't required to be enabled (although it shouldn't disturb reading even if it is enabled).
If XA-ADPCM (and/or XA-Filter) is enabled via Setmode, then INT1 is generated only for non-ADPCM sectors.
The Setmode sector-size selection is don't care for forwarding XA-ADPCM sectors to the SPU (the hardware does always decompress all 900h bytes).


CDROM - Test Commands

CDROM - Test Commands - Version, Switches, Region, Chipset, SCEx
CDROM - Test Commands - Test Drive Mechanics
CDROM - Test Commands - Prototype Debug Transmission
CDROM - Test Commands - Read/Write Decoder RAM and I/O Ports
CDROM - Test Commands - Read HC05 SUB-CPU RAM and I/O Ports


CDROM - Test Commands - Version, Switches, Region, Chipset, SCEx

19h,20h --> INT3(yy,mm,dd,ver)
Indicates the date (Year-month-day, in BCD format) and version of the HC05 CDROM controller BIOS. Known/existing values are:
  (unknown)        ;DTL-H2000 (with SPC700 instead HC05)
  94h,09h,19h,C0h  ;PSX (PU-7)               19 Sep 1994, version vC0 (a)
  94h,11h,18h,C0h  ;PSX (PU-7)               18 Nov 1994, version vC0 (b)
  94h,11h,28h,01h  ;PSX (DTL-H2000)          28 Nov 1994, version v01 (debug)
  95h,05h,16h,C1h  ;PSX (LATE-PU-8)          16 May 1995, version vC1 (a)
  95h,07h,24h,C1h  ;PSX (LATE-PU-8)          24 Jul 1995, version vC1 (b)
  95h,07h,24h,D1h  ;PSX (LATE-PU-8,debug ver)24 Jul 1995, version vD1 (debug)
  96h,08h,15h,C2h  ;PSX (PU-16, Video CD)    15 Aug 1996, version vC2 (VCD)
  96h,08h,18h,C1h  ;PSX (LATE-PU-8,yaroze)   18 Aug 1996, version vC1 (yaroze)
  96h,09h,12h,C2h  ;PSX (PU-18) (japan)      12 Sep 1996, version vC2 (a.jap)
  97h,01h,10h,C2h  ;PSX (PU-18) (us/eur)     10 Jan 1997, version vC2 (a)
  97h,08h,14h,C2h  ;PSX (PU-20)              14 Aug 1997, version vC2 (b)
  98h,06h,10h,C3h  ;PSX (PU-22)              10 Jun 1998, version vC3 (a)
  99h,02h,01h,C3h  ;PSX/PSone (PU-23, PM-41) 01 Feb 1999, version vC3 (b)
  A1h,03h,06h,C3h  ;PSone/late (PM-41(2))    06 Jun 2001, version vC3 (c)
  (unknown)        ;PS2,   xx xxx xxxx, late PS2 models...?

19h,21h --> INT3(flags)
Returns the current status of the POS0 and DOOR switches.
  Bit0   = HeadIsAtPos0 (0=No, 1=Pos0)
  Bit1   = DoorIsOpen   (0=No, 1=Open)
  Bit2   = EjectButtonOrOutSwOrSo? (DTL-H2000 only) (always 0 on retail)
  Bit3-7 = AlwaysZero

19h,22h --> INT3("for Europe")
  Caution: Supported only in BIOS version vC1 and up. Not supported in vC0.
Indicates the region that console is to be used in:
  INT5(11h,10h)      --> NTSC, Japan (vC0)         --> requires "SCEI" discs
  INT3("for Europe") --> PAL, Europe               --> requires "SCEE" discs
  INT3("for U/C")    --> NTSC, North America       --> requires "SCEA" discs
  INT3("for Japan")  --> NTSC, Japan / NTSC, Asia  --> requires "SCEI" discs
  INT3("for NETNA")  --> Region-free yaroze version--> requires "SCEx" discs
  INT3("for US/AEP") --> Region-free debug version --> accepts unlicensed CDRs
The CDROMs must contain a matching SCEx string accordingly.
The string "for Europe" does also suggest 50Hz PAL/SECAM video hardware.
The Yaroze accepts any normal SCEE,SCEA,SCEI discs, plus special SCEW discs.

19h,23h --> INT3("CXD2940Q/CXD1817Q/CXD2545Q/CXD1782BR") ;Servo Amplifier
19h,24h --> INT3("CXD2940Q/CXD1817Q/CXD2545Q/CXD2510Q") ;Signal Processor
19h,25h --> INT3("CXD2940Q/CXD1817Q/CXD1815Q/CXD1199BQ") ;Decoder/FIFO
  Caution: Supported only in BIOS version vC1 and up. Not supported in vC0.
Indicates the chipset that the CDROM controller is intended to be used with. The strings aren't always precisely correct (CXD1782BR is actually CXA1782BR, ie. CXA, not CXD) (and CXD1199BQ chips exist on PU-7 boards, but later PU-8 boards do actually use CXD1815Q) (and CXD1817Q is actually CXD1817R) (and newer PSones are using CXD2938Q or possibly CXD2941R chips, but nothing called CXD2940Q).
Note: Yaroze responds by CXD1815BQ instead of CXD1199BQ (but not by CXD1815Q).

19h,04h --> INT3(stat) ;Read SCEx string (and force motor on)
Resets the total/success counters to zero, and does then try to read the SCEx string from the current location (the SCEx is stored only in the Lead-In area, so, if the drive head is elsewhere, it will usually not find any strings, unless a modchip is permanently simulating SCEx strings).
This is a raw test command (the successful or unsuccessful results do not lock/unlock the disk). The results can be read with command 19h,05h (which will terminate the SCEx reading), or they can be read from RAM with command 19h,60h,lo,hi (which doesn't stop reading). Wait 1-2 seconds before expecting any results.
Note: Like 19h,00h, this command forces the drive motor to spin at standard speed (synchronized with the data on the disk), works even if the shell is open (but stops spinning after a while if the drive is empty).

19h,05h --> INT3(total,success) ;Get SCEx Counters
Returns the total number of "Sxxx" strings received (where at least the first byte did match), and the number of full "SCEx" strings (where all bytes did match). Typically, the values are "01h,01h" for Licensed PSX Data CDs, or "00h,00h" for disk missing, unlicensed data CDs, Audio CDs.
The counters are reset to zero, and SCEx receive mode is active for a few seconds after booting a new disk (on power up, on closing the drive door, on sending a Reset command, and on sub_function 04h). The disk is unlocked if the "success" counter is nonzero, the only exception is sub_function 04h which does update the counters, but does not lock/unlock the disk.


CDROM - Test Commands - Test Drive Mechanics

Signal Processor and Servo Amplifier

19h,50h,msb[,mid,[lsb[,xlo]]] --> INT3(stat)
Sends an 8bit/16bit/24bit command to the hardware, depending on number of parameters:
  1 byte  --> send CX(Xx)       ;short 8bit command
  2 bytes --> send CX(Xxxx)     ;longer 16bit command
  3 bytes --> send CX(Xxxxxx)   ;full 24bit command
  4 bytes --> send CX(Xxxxxxxx) ;extended 32bit command (BIOS vC3 only)
  4..15 bytes: acts same as max (3 or 4 bytes) (extra bytes are ignored)
  0 bytes or more than 15 bytes: generates an error

19h,51h,msb[,mid,[lsb]] --> INT3(stat,hi,lo) ;BIOS vC2/vC3 only
Supported by newer CDROM BIOSes only (such that use CXD2545Q or newer chips).
Works same as 19h,50h, but does additionally receive a response.
The command is always sending a 24bit CX(Xxxxxx) command, but it doesn't verify the number of parameter bytes (when using more than 3 bytes: extra bytes are ignored, when using less than 3 bytes: garbage is appended, which is somewhat valid because 8bit/16bit commands can be padded to 24bit size by appending "don't care" bits).
The command can be used to send any CX(..) command, but actually it does make sense only for the get-status commands, see below "19h,51h,39h,xxh" description.

19h,51h,39h,xxh --> INT3(stat,hi,lo) ;BIOS vC2/vC3 only
Supported by newer CDROM BIOSes only (such that use CXD2545Q or newer chips).
Sends CX(39xx) to the hardware, and receives a response (the response.hi byte is usually 00h for 8bit responses, or 00h..01h for 9bit responses). For example, this can be used to dump the Coefficient RAM.

19h,03h --> INT3(stat) ;force motor off
Forces the motor to stop spinning (ignored during spin-up phase).

19h,17h --> INT3(stat) ;force motor on, clockwise, super-fast
19h,01h --> INT3(stat) ;force motor on, anti-clockwise, super-fast
19h,02h --> INT3(stat) ;force motor on, anti-clockwise, super-fast
19h,10h --> INT3(stat) ;force motor on, anti-clockwise, super-fast
19h,18h --> INT3(stat) ;force motor on, anti-clockwise, super-fast
Forces the drive motor to spin at maximum speed (which is much faster than normal or double speed), in normal (clockwise), or reversed (anti-clockwise) direction. The commands work even if the shell is open. The commands do not try to synchronize the motor with the data on the disk (and do thus work even if no disk is inserted).

19h,00h --> INT3(stat) ;force motor on, clockwise (even if shell open)
This command seems to have effect only if the drive motor was off. If it was off, it does FFh-fills the TOC entries in RAM, and seek to the begin of the TOC at 98:30:00 or so (where minute=98 means minus two). From that location, it follows the spiral on the disk, although it does occassionally jump back some seconds. After clearing the TOC, the command does not write new data to the TOC buffer in RAM.
Note: Like 19h,04h, this command forces the drive motor to spin at standard speed (synchronized with the data on the disk), works even if the shell is open (but stops spinning after a while if the drive is empty).

19h,11h --> INT3(stat) ;Move Lens Up (leave parking position)
19h,12h --> INT3(stat) ;Move Lens Down (enter parking position)
19h,13h --> INT3(stat) ;Move Lens Outwards (away from center of disk)
19h,14h --> INT3(stat) ;Move Lens Inwards (towards center of disk)
Moves the laser lens. The inwards/outwards commands do move ONLY the lens (ie. unlike as for Seek commands, the overall-laser-unit remains in place, only the lens is moved).

19h,15h - if motor on: move head outwards + inwards + motor off
Moves the drive head to outer-most and inner-most position. Note that the drive doesn't have a switch that'd tell the controller when it has reached the outer-most position (so it'll forcefully hit against the outer edge) (ie. using this command too often may destroy the drive mechanics).
Note: The same destructive hit-outer-edge effect happens when using Setloc/Seek with too large values (like minute=99h).

19h,16h --> INT3(stat) ;Unknown / makes some noise if motor is on
19h,19h --> INT3(stat) ;Unknown / no effect
19h,1Ah --> INT3(stat) ;Unknown / makes some noise if motor is on
Seem to have no effect?
19h,16h seems to Move Lens Inwards, too.

19h,06h,new --> INT3(old) ;Adjust balance in RAM, and apply it via CX(30+n)
19h,07h,new --> INT3(old) ;Adjust gain in RAM, and apply it via CX(38+n)
19h,08h,new --> INT3(old) ;Adjust balance in RAM only
These commands are supported only by older CDROM BIOS versions (those with CXA1782BR Servo Amplifier).
Later BIOSes will respond with INT5(11h,20h) when trying to use these commands (because CXD2545Q and later Servo Amplifiers don't support the CX(30/38+n) commands).


CDROM - Test Commands - Prototype Debug Transmission

Serial Debug Messages
Older CDROM BIOSes are supporting debug message transmission via serial bus, using lower 3bit of the HC05 "databus" combined with the so-called "ROMSEL" pin (which apparently doesn't refer to Read-Only-Memory, but rather something like Runtime-Output-Message, or whatever).
Data is transferred in 24bit units (8bit command/index from HC05, followed by 16bit data to/from HC05), bigger messages are divided into multiple such 24bit snippets.
There are no connectors for external debug hardware on any PSX mainboards, so the whole stuff seems to be dating back to prototypes. And it seems to be removed from later BIOSes (which appear to use "ROMSEL" as "SCLK"; for receiving status info from the new CXD2545Q chips).

19h,30h,index,dat1,dat2 --> INT3(stat) ;Prototype/Debug stuff
19h,31h,dat1,dat2 --> INT3(stat) ;Prototype/Debug stuff
19h,4xh,index --> INT3(dat1,dat2) ;Prototype/Debug stuff
These functions are supported on older CDROM BIOS only; later BIOSes respond by INT5(11h,10h).
The functions do not affect the CDROM operation (they do simple allow to transfer data between Main CPU and external debug hardware).
Sub functions 30h and 31h may fail with INT5(11h,80h) when receiving wrong signals on the serial input line.
Sub function "4xh" value can be 40h..4Fh (don't care).

INT5 Debug Messages
Alongsides to INT5 errors, the BIOS is usually also sending information via the above serial bus (the error info is divided into multiple 8bit+16bit snippets, and contains stat, error code, mode, current SubQ position, and most recently issued command).


CDROM - Test Commands - Read/Write Decoder RAM and I/O Ports

Caution: Below commands 19h,71h..76h are supported only in BIOS version vC1 and up. Not supported in vC0.

19h,71h,index --> INT3(databyte) ;Read single register
index can be 00h..1Fh, bigger values seem to be mirrored to "index AND 1Fh", with one exception: index 13h in NOT mirrored, instead, index 33h, 53h, 93h, B3h, D3h, F3h return INT5(stat+1,10h), and index 73h returns INT5(stat+1,20h).
Aside from returning a value, the commands seem to DO something (like moving the drive head when a disk is inserted). Return values are usually:
  index     value
  00h       04h      ;04h=empty, 8Eh=licensed, 24h=audio
  01h       [0B1h]   ;DCh=empty/licensed, DDh=audio
  02h       00h
  03h       00h          ;or variable when disk inserted
  04h       00h
  05h       80h          ;or 86h or 89h when disk inserted
  06h       C0h
  07h       02h
  08h       8Ah
  09h       C0h
  0Ah       00h
  0Bh       C0h
  0Ch       [1F2h]
  0Dh       [1F3h]
  0Eh       00h          ;or 8Eh or E6h when disk inserted    ;D4h/audio
  0Fh       00h          ;or sometimes 01h when disk inserted ;50h/audio
  10h       C0h
  11h       E0h
  12h       71h
  13h       stat
  14h       FFh
  15h..1Fh  C0h-filled        ;or 17h --> DEh

19h,72h,index,databyte --> INT3(stat) ;Write single register
  ;other response on param xx16h,xx18h with xx>00h

19h,73h,index,len --> INT3(databytes...) ;Read multiple registers (bugged)
19h,74h,index,len,databytes --> INT3(stat) ;Write multiple registers (bugged)
Same as read/write single register, but trying to transfer multiple registers at once. BUG: The transfer should range from 00h to len-1, but the loop counter is left uninitialized (set to X=48h aka "command number 19h-minus-1-mul-2" instead of X=00h). Causing to the function to read/write garbage at index 48h..FFh, it does then wrap to 00h and do the correct intended transfer, but the preceeding bugged part may have smashed RAM or I/O ports.

19h,75h --> INT3(remain.lo,remain.hi,addr.lo,addr.hi) ;Get Host Xfer Info
Returns a 4-byte value. In my early tests, on the first day it returned B1h,CEh,4Ch,01h, on the next day 2Ch,E4h,95h,D5h, and on all following days 00h,C0h,00h,00h (no idea why/where the earlier values came from).
The first byte seems to be always 00h; no matter of [1F0h].
The second byte seems to be always C0h; no matter of [1F1h].
The third,fourth bytes are [1F2h,1F3h].
That two bytes are 0Ch,08h after Read commands.
  The first bytes are NOT affected by:
  destroying [1F0h] via too-many-parameters in command-buffer,
  changes to [1F1h] which may occur after read command (eg. may be 20h)

19h,76h,len_lo,len_hi,addr_lo,addr_hi --> INT3(stat) ;Prepare SRAM Transfer
Prepare Transfer to/from 32K SRAM.
After INT3, data can be read (same way as sector data after INT1).


CDROM - Test Commands - Read HC05 SUB-CPU RAM and I/O Ports

19h,60h,addr_lo,addr_hi --> INT3(data) ;Read one byte from Drive RAM or I/O
Reads one byte from the controller's RAM or I/O area, see the memory map below for more info. Among others, the command allows to read Subchannel Q data, eg. at [200h..209h], including ADR=2/UPC/EAN and ADR=3/ISRC values (which are suppressed by GetlocP). Eg. wait for ADR<>2, then for ADR=2, then read the remaining 9 bytes (because of the delayed IRQs, this works only at single speed) (at double speed one can read only 5 bytes before the values get overwritten by new data). Unknown if older boards (with 4.00MHz oscillators) are fast enough to read all 10 SubQ bytes.

CDROM Controller I/O Area and RAM Memory Map
First 40h bytes are I/O ports (as in MC68HC05 datasheet):
  000h 4        FF 7B 00 FF  (other when disk inserted)
  004h 5        11 00 20 20 0C
  009h 1        00 (when disk inserted: changes between 00 or 80)
  00Ah 2        71 00
  00Ch 1        00 (when disk inserted: changes between 00 or 80)
  00Dh 3        20 20 20
  010h 8        02 80 00 60 00 00 99(orBB) 98
  018h 4     changes randomly (even when no disk inserted)
  01Ch 3        40 00 41
  01Fh 1     changes randomly (even when no disk inserted)
  020h 30    20h-filled
  03Eh 2        82h 20h
Next 200h bytes are RAM:
  040h 4        08 00 00 00  ;or 98 07 xx 0B when disk inserted ;[40].Bit1=MUTE
  044h 4     00h-filled
  048h 3        40 20 00     ;or 58 71 0F when disk inserted
  04Bh 1     changes randomly (nodisk: 00 or 80 / disk: BFh)
  04Ch 1     Zero (or C0h)
  04Dh 3     MM:SS:FF (begin of current track MM:SS:00h) (or increasing addr)
  050h 10    Subchannel Q (adjusted position values)
  05Ah 2        ...
  05Ch 1     00h (or 64h)
  05Dh 3     MM:SS:FF (current read address) (sticky address during pause)
  060h 1     increments at circa 16Hz or so (or other rate when spinning)
  061h 12    00h-filled ;or else when disk inserted
  06Dh 1        01      ;or 0C when disk inserted
  06Eh 2     SetFilter setting (file,channel)
  070h 16    00h-filled ;or else when disk inserted
  080h 8     00h-filled
  088h 3        03:SS:FF (three, second, fraction)
  08Bh 3        03:SS:FF (three, second, fraction)
  08Eh 2        01 FF (or other values)
  090h 1        00h (or 91h when disk inserted + spinning)
  091h 13    Zero
  09Eh 1        00h (or 01h when disk inserted + spinning)
  09Fh 1     Zero
  0A0h 1     Always 23h
  0A1h 1        09h (5Dh when disk inserted)
  0A2h 7     00h-filled
  0A9h 1        40
  0AAh 4     00h-filled
  0AEh 1        00 (no disk) or 01 (disk) or so
  0AFh 1        00            ;or 06 when disk inserted
  0B0h 7        00 DC 00 02 00 E0 08             ;\or else when disk inserted
  0B7h 1        20         ;Bit6+7=MUTE          ;
  0B8h 3        DE 00 00                         ;/
  0BBh 1     SetMode setting (mode)
  0BCh 1     GetStat setting (stat)
  0BDh 3     00h-filled
  0C0h 6     FFh-filled            ;stack...                    ;\
  0C6h 1     Usually DFh           ;sometimes [0EBh and up] are non-FFh, too
  0C7h 15    FFh-filled            ;(depending on disk or commands or so)
  0D6h 1     Usually FDh (or FFh)  ;                            ;
  0D7h 24    FFh-filled                                         ; stack
  0EFh 4     on power-up FFh-filled, other once when disk read  ;
  0F3h 7     changes randomly (even when no disk inserted)      ;
  0FAh 6       2E 3C 2A D6 10 95                                ;/
  100h 2x99  TOC Entries for Start of Track 1..99 (MM:SS)
  1C6h 1     TOC First Track number (usually 01h)
  1C7h 1     TOC Last Track number (usually 01h or higher)
  1C8h 3     TOC Entry for Start of Lead-Out (MM:SS:FF)
  1CBh 2     Zero
  1CDh 1     Depends on disk (01 or 02 or 06) (or 00 when no disk)
  1CEh 1     Zero
  1CFh 1     Depends on disk (NULL minus N*6) (or 00 when no disk)
               (maybe reflection level / laser intensity or so)
                [1CDh..1CFh]
                01 00 E8 --> licensed/metalgear/kain
                01 00 EE --> licensed/alone2
                06 00 E2 or 00 00 02 00 E8 --> licensed/wipeout
                02 00 DC --> unlicensed/elo
                02 00 D6 --> unlicensed/driver
                00 00 EE --> audio/lola
                00 00 FA --> audio/marilyn
                00 00 F4 --> audio/westen
                00 00 00 --> disk missing
               last byte is always in steps of 6
  1D0h 4     SCEx String
  1D4h 4     Zero
  1D8h 2     SCEx Counters (total,success)  ;for command 19h,05h
  1DAh 6       00h-filled     (or ... SS:FF)
  1E0h 6     Command Buffer (usually 19h,60h,E2h,01h = Read RAM Command)
  1E6h 7       00h-filled (unless destroyed by more-than-6-byte-commands)
  1EDh 3     Setloc setting (MM:SS:FF)
  1F0h 1       00h          (unless destroyed by more-than-6-byte-commands)
  1F1h 3       C0h 00h 00h ;or 20h,0Ch,50h or C0h,0Ch,08h ;for command(19h,75h)
                           ;or 00h,00h,00h for audio
                           ;or 80h,00h,00h for disk missing
  1F4h 4       00h-filled ... or SCEx string
  1F8h 1       00h
  1F9h 1     Selected Target (parameter from Play and SetSession commands)
  1FAh 5       00h-filled       ;01 01 00 8B 00 00   ;or 01 02 8B 00 00
                       01 00 8B 00 00 -- audio/unlicensed
                       01 01 00 00 00 -- licensed
  1FFh 1       00h-on power up, changes when disk inserted  ;or 01 = Playing
    1FDh 3       MM:SS:FF (only during command 19h,00h) (MM=98..99=TOC)
  200h 10    Subchannel Q (real values)
  20Ah 2       whatever
  20Ch 1     Zero
  20Dh 1     Desired Session (from SetSession command)
  20Eh 1     Current Session (actual location of drive head)
  20Fh 1     Zero
  210h 10    Subchannel Q (adjusted position values)
  21Ah 6     00h-filled
  220h 4     Data Sector Header (MM:SS:FF:Mode)
  224h 4     Data Sector CD-XA Subheader (file,channel,sm,ci)
  228h 1         00h
  229h 1     Usually 00h (shortly other value on power-up, and maybe on seek)
  22Ah 1         10h (or 00h when no disk)
  22Bh 3     00h-filled
  22Eh 2         01,03 or 0A,00 or 03,01 (or else for other disk)
  230h 3     00h-filled (or other during spin-up / read-toc or so)
  233h 0Dh   00h-filled (unused RAM)
Other/invalid addresses are:
  240h..2FFh  - Invalid (00h-filled) (no ROM, RAM, or I/O mapped here)
  300h..3FFh  - Mirror of 200h..2FFh    ;\the BIOS is doing that
  400h..FFFFh - Mirrors of 000h..3FFh   ;/mirroring by software

DTL-H2000 Memory Map
This version allows to read the whole 64Kbyte memory space (withou mirroring everything to first 300h bytes). I/O Ports and Variables are at different locations:
  000h..0DFh   RAM Part 1 (C0h bytes)
  0E0h..0FFh   I/O Area
  100h..1DFh   RAM Part 2 (C0h bytes)
  1E0h..1FFh   I/O Area
  200h..2DFh   RAM Part 3 (100h bytes)
  2E0h..7FFFh  Unknown
  8000h-BFFFh  Unknown  (lower 16K of 32K EPROM) (or unused?)
  C000h-FFFFh  Firmware (upper 16K of 32K EPROM)

Writing to RAM
There is no command for writing to RAM. Except that, one can write to the command/parameter buffer at 1E0h and up. Normally, the longest known command should have 6 bytes (19h,76h,a,b,c,d), and longer commands results in "bad number of parameters" response - however, despite of that error message, the controller does still store ALL parameter bytes in RAM (at address 1E1h..2E0h, then wrapping back to 1E1h). Whereas, writing more than 16 bytes (FIFO storage size) will mirror the FIFO content twice, and more than 32 bytes (FIFO counter size) will work only when feeding extra data into the FIFO during transmission. Anyways, writing to 1E1h and up doesn't allow to do interesting things (such like manipulating the stack and executing custom code on the CPU).

Subchannel Q Notes
The "adjusted position values" at 050h, 210h, 310h contain only position information (with ADR=1) (the PSX seems to check only the lower 2bit of the 4bit ADR value, so it also treats ADR=5 as ADR=1, too). Additionally, during Lead-In, bytes 7..9 are overwritten by the position value from bytes 3..5. The "real values" contain unadjusted data, including ADR=2 and ADR=3 etc.


CDROM - Secret Unlock Commands

SecretUnlockPart1 - Command 50h --> INT5(11h,40h)
SecretUnlockPart2 - Command 51h,"Licensed by" --> INT5(11h,40h)
SecretUnlockPart3 - Command 52h,"Sony" --> INT5(11h,40h)
SecretUnlockPart4 - Command 53h,"Computer" --> INT5(11h,40h)
SecretUnlockPart5 - Command 54h,"Entertainment" --> INT5(11h,40h)
SecretUnlockPart6 - Command 55h,<region> --> INT5(11h,40h)
SecretUnlockPart7 - Command 56h --> INT5(11h,40h)
  Caution: Supported only in BIOS version vC1 and up. Not supported in vC0.
  Caution: Supported only in Europe/USA. Nonfunctional in Japan/Asia.
  Caution: When unsupported, Parameter Fifo isn't cleared after the command.
Sending these commands with the correct strings (in order 50h through 56h) does disable the "SCEx" protection. The region can be detected via test command 19h,22h, and must be translated to the following <region> string:
  "of America"    ;for NTSC/US          ;\
  "(Europe)"      ;for PAL/Europe       ; handled, and actually working
  "World wide"    ;for Yaroze           ;/
  "Inc."          ;for NTSC/JP          ;-non-functional
In the unlocked state, ReadN/ReadS are working for unlicensed CD-Rs, and for imported CDROMs from other regions (both without needing modchips). However there are some cases which may still cause problems: The GetID command (1Ah) does still identify the disc as being unlicensed, same for the Get SCEx Counters test command (19h,05h). And, if a game should happen to send the Reset command (1Ch) for some weird reason, then the BIOS would forget the unlocking, same for games that set the "HCRISD" I/O port bit. On the contrary, opening/closing the drive door does not affect the unlocking state.
The commands have been discovered in September 2013, and appear to be supported by all CDROM BIOS versions (from old PSXes up to later PSones).
Note that the commands do always respond with INT5 errors (even on successful unlocking).
Japanese consoles are internally containing code for processing the Secret Unlock commands, but they are not actually executing that code, and even if they would do so: they are ignoring the resulting unlocking flag, making the commands nonfunctional in Japan/Asia regions.

SecretLock - Command 57h --> INT5(11h,40h)
Undoes the unlocking and restores the normal locked state (same happens when sending the Unlocking commands in wrong order or with wrong parameters).

SecretCrash - Command 58h..5Fh --> Crash
Jumps to a data area and executes random code. Results are more or less unpredictable (as they involve executing undefined opcodes). Eventually the CPU might hit a RET opcode and recover from the crash.


CDROM - Video CD Commands 

  Caution: Supported only on SCPH-5903, not supported on any other consoles.
  Caution: When unsupported, Parameter Fifo isn't cleared after the command.


  1Fh VideoCD      sub,a,b,c,d,e   INT3(stat,a,b,c,d,e)   ;<-- SCPH-5903 only
  1Fh..4Fh -       -               INT5(11h,40h)  ;-Unused/invalid

VideoCdSio - Cmd 1Fh,01h,JoyL,JoyH,State,Task,0 --> INT3(stat,req,mm,ss,ff,x)
The JoyL/JoyH bytes contain 16bit button (and drive door) bits:
  0  Drive Door  (0=Open)    (from CDROM stat bit4) ;Open
  1  Button /\   (0=Pressed) (from PSX pad bit12) ;N/A       ;PBC: Back/LevelUp
  2  Button []   (0=Pressed) (from PSX pad bit15) ;Enter Menu
  3  Button ()   (0=Pressed) (from PSX pad bit13) ;Leave Menu     ;PBC: Confirm
  4  Button ><   (0=Pressed) (from PSX pad bit14) ;N/A
  5  Start       (0=Pressed) (from PSX pad bit3)  ;Play/Pause
  6  Select      (0=Pressed) (from PSX pad bit0)  ;Stop (prompt restart/resume)
  7  Always 0    (0)         (fixed)              ;N/A
  8  DPAD Up     (0=Pressed) (from PSX pad bit4)  ;Menu Up           ;PBC: +1
  9  DPAD Right  (0=Pressed) (from PSX pad bit5)  ;Menu Right/change ;PBC: +10
  10 DPAD Down   (0=Pressed) (from PSX pad bit6)  ;Menu Down         ;PBC: -1
  11 DPAD Left   (0=Pressed) (from PSX pad bit7)  ;Menu Left/change  ;PBC: -10
  12 Button R1   (0=Pressed) (from PSX pad bit11) ;Prev Track/Restart Track
  13 Button R2   (0=Pressed) (from PSX pad bit9)  ;Fast Forward (slowly)
  14 Button L1   (0=Pressed) (from PSX pad bit10) ;Next Track (if any)
  15 Button L2   (0=Pressed) (from PSX pad bit8)  ;Fast Backward (slowly)
The State byte can be:
  00h  Motor Off (or spin-up)   (when stat.bit1=0)
  01h  Playing                  (when stat.bit7=1)
  02h  Paused (and not seeking) (when stat.bit6=0)
  (note: State remains unchanged when seeking)
The Task byte can be:
  00h = Confirms that "Tocread" (aka setsession 1) request was processed
  01h = Detect VCD Disc (used on power-up, and after door open) (after spin-up)
  02h = Handshake (request ack response)
  0Ah = Door opened during play (int5/door error)
  80h = No disc
  FFh = No change (nop)
The req byte in the INT3 response can be:
  00h  Normal (no special event occured and no action requested)
  01h  Request CD to Seek_and_play (using mm:ss:ff response parameter bytes)
  02h  Request CD to Pause                ;cmd(09h)    -->int3(stat),int2(stat)
  03h  Request CD to Stop                 ;cmd(08h)    -->int3(stat),int2(stat)
  04h  Request CD to Tocread (setsession1);cmd(12h,01h)-->int3(stat),int2(stat)
  05h  Handshake Command was processed, and this is the "ack" response
  06h  Request CD to Fast Forward         ;cmd(04h)    -->int3(stat)
  07h  Request CD to Fast Backward        ;cmd(05h)    -->int3(stat)
  80h  Detect Command was processed, and disc was detected as VCD
  81h  Detect Command was processed, and disc was detected as Non-VCD

VideoCdSwitch - Cmd 1Fh,02h,flag,x,x,x,x --> INT3(stat,0,0,x,x,x)
  00h      = Normal PSX Mode  (PortF.3=LOW)  (Audio/Video from GPU/SPU chips)
  01h..FFh = Special VCD Mode (PortF.3=HIGH) (Audio/Video from MDEC/OSD chips)

Some findings on the SC430924 firmware...
The version/date is "15 Aug 1996, version C2h", although the "C2h" is misleading: The firmware is nearly identical to version "C1h" from PU-8 boards (the stuff added in normal "C2h" versions would be for PU-18 boards with different cdrom chipset).

Compared to the original C1h version, there are only a few changes: A initialization function for initializing port F on power-up. And new command (command 1Fh, inserted in the various command tables), with two subfunctions (01h and 02h):
- Command 1Fh,01h,a,b,c,d,e --> INT3(stat,a,b,c,d,e) Serial 5-byte read-write
- Command 1Fh,02h,v,x,x,x,x --> INT3(stat,0,0,x,x,x) Toggle 1bit (port F.bit3)
Whereas,
  x = don't care/garbage
  v = toggle state (00h=normal=PortF.3=LOW, 01h..FFh=special=PortF.3=HIGH)
      (toggle gpu vs mpeg maybe?)
  a,b,c,d,e = five bytes sent serially, and five bytes response received
      serially (send/receive done simultaneously)

The Port F bits are:
  Port F.Bit0 = Serial Data In
  Port F.Bit1 = Serial Data Out
  Port F.Bit2 = Serial Clock Out
  Port F.Bit3 = Toggle (0=Normal, 1=Special)

And that's about all. Ie. essentially, the only change is that the new command controls Port F. There is no interaction with the remaining firmware (ie. reading, seeking, and everything is working as usually, without any video-cd related changes).
The SCEx stuff is also not affected (ie. Video CDs would be seen as unlicensed discs, so the PSX couldn't read anything from those discs, aside from Sub-Q position data, of course). The SCEx region is SCEI aka "Japan" (or actually for Asia in this case).

Note
The SPU MUTE Flag (SPUCNT.14) does also affect VCD Audio (mute is applied to the final analog audio amplifier). All other SPUCNT bits can be zero for VCD.


CDROM - Mainloop/Responses

SUB-CPU Mainloop
The SUB-CPU is running a mainloop that is handling hardware events (by simple polling, not by IRQs):
  check for incoming sectors (from CDROM decoder)
  check for incoming commands (from Main CPU)
  do maintenance stuff on the drive mechanics
There is no fixed priority: if both incoming sector and incoming command are present, then the SUB-CPU may handle either one, depending on which portion of the mainloop it is currently executing.
There is no fixed timing: if the mainloop is just checking for a specific event, then a new event may be processed immediately, otherwise it may take whole mainloop cycle until the SUB-CPU sees the event.
Whereas, the mainloop cycle execution time isn't constant: It may vary depending on various details. Especially, some maintenance stuff is only handled approximately around 15 times per second (so there are 15 slow mainloop cycles per second).

Responses
The PSX can deliver one INT after another. Instead of using a real queue, it's merely using some flags that do indicate which INT(s) need to be delivered. Basically, there seem to be two flags: One for Second Response (INT2), and one for Data/Report Response (INT1). There is no flag for First Response (INT3); because that INT is generated immediately after executing a command.
The flag mechanism means that the SUB-CPU cannot hold more than one undelivered INT1. That, although the CDROM Decoder does notify the SUB-CPU about all newly received sectors, and it can hold up to eight sectors in the 32K SRAM. However, the SUB-CPU BIOS merely sets a sector-delivery-needed flag (instead of memorizing which/how many sectors need to be delivered, and, accordingly, the PSX can use only three of the available eight SRAM slots: One for currently pending INT1, one for undelivered INT1, and one for currently/incompletely received sector).

First Response (INT3) (or INT5 if failed)
The first response is sent immediately after processing a command. In detail:
The mainloop checks for incoming commands once every some clock cycles, and executes commands under following condition:
  Main CPU has sent a command, AND, there is no INT pending
  (if an INT is pending, then the command won't be executed yet, but will be
  executed in following mainloop cycles; once when INT got acknowledged)
  (even if no INT is pending, the mainloop may generate INT1/INT2 before
  executing the command, if so, as said above, the command won't execute yet)
Once when the command gets executed it will sent the first response immediately after the command execution (which may only take a few clock cycles, or some more cycles, for example Init/ReadTOC do include some time consuming initializations). Anyways, there will be no other INTs generated during command execution, so once when the command execution has started, it's guaranteed that the next INT will contain the first response.

Second Responses (INT2) (or INT5 if failed)
Some commands do send a second response after actual command execution:
  07h MotorOn    E -               INT3(stat), INT2(stat)
  08h Stop       E -               INT3(stat), INT2(stat)
  09h Pause      E -               INT3(stat), INT2(stat)
  0Ah Init         -               INT3(late-stat), INT2(stat)
  12h SetSession E session         INT3(stat), INT2(stat)
  15h SeekL      E -               INT3(stat), INT2(stat)  ;\use prior Setloc
  16h SeekP      E -               INT3(stat), INT2(stat)  ;/to set target
  1Ah GetID      E -               INT3(stat), INT2/5(stat,flg,typ,atip,"SCEx")
  1Dh GetQ       E adr,point       INT3(stat), INT2(10bytesSubQ,peak_lo)
  1Eh ReadTOC      -               INT3(late-stat), INT2(stat)
In some cases (like seek or spin-up), it may take more than a second until the 2nd response is sent.
It should be highly recommended to WAIT until the second response is generated BEFORE sending a new command (it wouldn't make too much sense to send a new command between first and second response, and results would be unknown, and probably totally unpredictable).
Error Notes: If the command has been rejected (INT5 sent as 1st response) then the 2nd response isn't sent (eg. on wrong number of parameters, or if disc missing). If the command fails at a later stage (INT5 as 2nd response), then there are cases where another INT5 occurs as 3rd response (eg. on SetSession=02h on non-multisession-disk).

Data/Report Responses (INT1)
  03h Play       E (track)         INT3(stat), optional INT1(report bytes)
  04h Forward    E -               INT3(stat), optional INT1(report bytes)
  05h Backward   E -               INT3(stat), optional INT1(report bytes)
  06h ReadN      E -               INT3(stat), INT1(stat), datablock
  1Bh ReadS      E?-               INT3(stat), INT1(stat), datablock


CDROM - Response Timings

Here are some response timings, measured in 33MHz units on a PAL PSone. The CDROM BIOSes mainloop is doing some maintenance stuff once and when, meaning that the response time will be higher in such mainloop cycles (max values), and less in normal cycles (min values). The maintenance timings do also depend on whether the motor is on or off (and probably on various other factors like seeking).

First Response
The First Response interrupt is sent almost immediately after processing the command (that is, when the mainloop sees a new command without any old interrupt pending). For GetStat, timings are as so:
  Command                Average   Min       Max
  GetStat (normal)       000c4e1h  0004a73h..003115bh
  GetStat (when stopped) 0005cf4h  000483bh..00093f2h
Timings for most other commands should be similar as above. One exception is the Init command, which is doing some initialization before sending the 1st response:
  Init                   0013cceh  000f820h..00xxxxxh
The ReadTOC command is doing similar initialization, and should have similar timing as Init command. Some (rarely used) Test commands include things like serial data transfers, which may be also quite slow.

Second Response
  Command                Average   Min       Max
  GetID                  0004a00h  0004922h..0004c2bh
  Pause (single speed)   021181ch  020eaefh..0216e3ch ;\time equal to
  Pause (double speed)   010bd93h  010477Ah..011B302h ;/about 5 sectors
  Pause (when paused)    0001df2h  0001d25h..0001f22h
  Stop (single speed)    0d38acah  0c3bc41h..0da554dh
  Stop (double speed)    18a6076h  184476bh..192b306h
  Stop (when stopped)    0001d7bh  0001ce8h..0001eefh
Moreover, Seek/Play/Read/SetSession/MotorOn/Init/ReadTOC are sending second responses which depend on seek time (and spin-up time if the motor was off). The seek timings are still unknown, and they are probably quite complicated:
The CDROM BIOS seems to split seek distance somehow into coarse steps (eg. minutes) and fine steps (eg. seconds/sectors), so 1-minute seek distance may have completely different timings than 59-seconds distance.
The amount of data per spiral winding increases towards ends of the disc (so the drive head will need to be moved by shorter distance when moving from minute 59 to 60 as than moving from 00 to 01).
The CDROM BIOS contains some seek distance table, which is optimized for official 71-minute PSX discs. More common 74-minute or 80-minute CDRs may have tighter spiral windings (the above seek table is probably causing the drive head to be moved too far on such discs, which will raise the seek time as the head needs to be moved backwards to compensate that error).

INT1 Rate
  Command                Average   Min       Max
  Read (single speed)    006e1cdh  00686dah..0072732h
  Read (double speed)    0036cd2h  00322dfh..003ab2bh
The INT1 rate needs to be precise for CD-DA and CD-XA Audio streaming, exact clock cycle values should be: SystemClock*930h/4/44100Hz for Single Speed (and half as much for Double Speed) (the "Average" values are AVERAGE values, not exact values).


CDROM - Response/Data Queueing

[Below are some older/outdated test cases]

Sector Buffer
The CDROM sector buffer is 32Kx8 SRAM (IC303). The buffer is apparently divided into 8 slots, theoretically allowing to buffer up to 8 sectors.
BUG: The drive controller seems to allow only 2 of those 8 sectors (the oldest sector, and the current/newest sector).
Ie. after processing the INT1 for the oldest sector, one would expect the controller to generate another INT1 for next newer sector - but instead it appears to jump directly to INT1 for the newest sector (skipping all other unprocessed sectors). There is no known way to get around that effect.
So far, the big 32Kbyte buffer is entirely useless (the two accessible sectors could have been as well stored in a 8Kbyte chip) (unless, maybe the 32Kbytes have been intended for some error-correction "read-ahead" purposes, rather than as "look-back" buffer for old sectors; one of the unused slots might be also used for XA-ADPCM sectors).
The bottom line is that one should process INT1's as soon as possible (ie. before the cdrom controller receives and skips further sectors). Otherwise sectors would be lost without notice (there appear to be absolutely no overrun status flags, nor overrun error interrupts).

Sector Buffer Test Cases
  Setloc(0:2:0)+Read
  Process INT1 --> receives sector header for 0:2:0
  Process INT1 --> receives sector header for 0:2:1
  Process INT1 --> receives sector header for 0:2:2
  Process INT1 --> receives sector header for 0:2:3
Above shows the normal flow when processing INT1's as they arise. Now, inserting delays (and not processing INT1's during that delays):
  Setloc(0:2:0)+Read
  Process INT1 --> receives sector header for 0:2:0
  delay(1)
  Process INT1 --> receives sector header for 0:2:1 (oldest sector)
  Process INT1 --> receives sector header for 0:2:6 (newest sector)
  Process INT1 --> receives sector header for 0:2:7 (next sector)
Above suggests that the CDROM buffer can hold max 2 sectors (the oldest and current one). However, using a longer delay:
  Setloc(0:2:0)+Read
  Process INT1 --> receives sector header for 0:2:0
  delay(2)
  Process INT1 --> receives sector header for 0:2:9  (oldest/overwritten)
  Process INT1 --> receives sector header for 0:2:11 (newest sector)
  Process INT1 --> receives sector header for 0:2:12 (next sector)
Above indicates that sector buffer can hold 8 sectors (as the sector 1 slot is overwritten by sector 9). And, another test with even longer delay:
  Setloc(0:2:0)+Read
  Process INT1 --> receives sector header for 0:2:0
  delay(3)
  Process INT1 --> receives sector header for 0:2:17 (currently received)
  Process INT1 --> receives sector header for 0:2:16 (newest full sector)
  Process INT1 --> receives sector header for 0:2:17 (next sector)
  Process INT1 --> receives sector header for 0:2:18 (next sector)
Above is a special case where sector 17 appears twice; the first one is the sector 1 slot (which was overwritten by sector 9, and apparently then half overwritten by sector 17).

Sector Buffer VS GetlocL Response Tests
  Setloc(0:2:0)+Read
  Process INT1 --> receives sector header for 0:2:0
  GetlocL
  Process INT3 --> receives getloc info for 0:2:0
  Process INT1 --> receives sector header for 0:2:1
  Process INT1 --> receives sector header for 0:2:2
  Process INT1 --> receives sector header for 0:2:3
Another test, with Delay BEFORE Getloc:
  Setloc(0:2:0)+Read
  Process INT1 --> receives sector header for 0:2:0
  Delay(1)
  GetlocL
  Process INT1 --> receives sector header for 0:2:1
  Process INT3 --> receives getloc info for 0:2:6
  Process INT1 --> receives sector header for 0:2:6
  Process INT1 --> receives sector header for 0:2:7
Another test, with Delay AFTER Getloc:
  Setloc(0:2:0)+Read
  Process INT1 --> receives sector header for 0:2:0
  GetlocL
  Delay(1)
  Process INT3 --> receives getloc info for 0:2:0
  Process INT1 --> receives sector header for 0:2:5
  Process INT1 --> receives sector header for 0:2:6
  Process INT1 --> receives sector header for 0:2:7
Another test, with Delay BEFORE and AFTER Getloc:
  Setloc(0:2:0)+Read
  Process INT1 --> receives sector header for 0:2:0
  Delay(1)
  GetlocL
  Delay(1)
  Process INT1 --> receives sector header for 0:2:9
  Process INT1 --> receives sector header for 0:2:11
  Process INT3 --> receives getloc info for 0:2:12
  Process INT1 --> receives sector header for 0:2:12
  Process INT1 --> receives sector header for 0:2:13

Sector Buffer VS Pause Response Tests
  Setloc(0:2:0)+Read
  Process INT1 --> receives sector header for 0:2:0
  Pause
  Process INT3 --> receives stat=22h (first pause response)
  Process INT2 --> receives stat=02h (second pause response)
Another test, with Delay BEFORE Pause:
  Setloc(0:2:0)+Read
  Process INT1 --> receives sector header for 0:2:0
  Delay(1)
  Pause
  Process INT1 --> receives sector header for 0:2:1 (oldest)
  Process INT3 --> receives stat=22h (first pause response)
  Process INT2 --> receives stat=02h (second pause response)
Another test, with Delay AFTER Pause:
  Setloc(0:2:0)+Read
  Process INT1 --> receives sector header for 0:2:0
  Pause
  Delay(1)
  Process INT3 --> receives stat=22h (first pause response)
  Process INT2 --> receives stat=02h (second pause response)
Another test, with Delay BEFORE and AFTER Pause:
  Setloc(0:2:0)+Read
  Process INT1 --> receives sector header for 0:2:0
  Delay(1)
  Pause
  Delay(1)
  Process INT1 --> receives sector header for 0:2:9 (oldest/overwritten)
  Process INT3 --> receives stat=22h (first pause response)
  Process INT2 --> receives stat=02h (second pause response)
For above: Note that, despite of Pause, the CDROM is still writing to the internal buffer (and overwrites slot 1 by sector 9) (this might be because the Pause command isn't processed at all until INT1 is processed).

Double Commands (Getloc then Pause)
  Setloc(0:2:0)+Read
  Process INT1 --> receives sector header for 0:2:0
  GetlocL
  Pause
  Process INT3 --> receives stat=22h (first pause response)
  Process INT2 --> receives stat=02h (second pause response)
Another test,
  Setloc(0:2:0)+Read
  Process INT1 --> receives sector header for 0:2:0
  Delay(1)
  GetlocL
  Pause
  Process INT1 --> receives sector header for 0:2:1
  Process INT1 --> receives sector header for 0:2:6
  Process INT3 --> receives stat=22h (first pause response)
  Process INT2 --> receives stat=02h (second pause response)
Another test,
  Setloc(0:2:0)+Read
  Process INT1 --> receives sector header for 0:2:0
  GetlocL
  Delay(1)
  Pause
  Process INT3 --> receives getloc info for 0:2:0 (first getloc response)
  Process INT3 --> receives stat=22h (first pause response)
  Process INT2 --> receives stat=02h (second pause response)
Another test,
  Setloc(0:2:0)+Read
  Process INT1 --> receives sector header for 0:2:0
  Delay(1)
  GetlocL
  Delay(1)
  Pause
  Process INT1 --> receives sector header for 0:2:9 (oldest/overwritten)
  Process INT3 --> receives stat=22h (first pause response)
  Process INT2 --> receives stat=02h (second pause response)

Double Commands (Pause then Getloc)
  Setloc(0:2:0)+Read
  Process INT1 --> receives sector header for 0:2:0
  Pause
  GetlocL
  Process INT3 --> receives getloc info for 0:2:0 (first getloc response)
  Process INT1 --> receives sector header for 0:2:1
  Process INT1 --> receives sector header for 0:2:2
  Process INT1 --> receives sector header for 0:2:3
Another test,
  Setloc(0:2:0)+Read
  Process INT1 --> receives sector header for 0:2:0
  Delay(1)
  Pause
  GetlocL
  Process INT1 --> receives sector header for 0:2:1
  Process INT3 --> receives getloc info for 0:2:6 (first getloc response)
  Process INT1 --> receives sector header for 0:2:6
  Process INT1 --> receives sector header for 0:2:7
Another test,
  Setloc(0:2:0)+Read
  Process INT1 --> receives sector header for 0:2:0
  Pause
  Delay(1)
  GetlocL
  Process INT3 --> receives stat=22h (first pause response)
  Process INT3 --> receives getloc info for 0:2:6 (first getloc response)
  (No further INT's, ie. read is paused, but second-pause-response is lost).
Another test,
  Setloc(0:2:0)+Read
  Process INT1 --> receives sector header for 0:2:0
  Pause
  Delay(1)
  GetlocL
  Delay(1)
  Process INT3 --> receives stat=22h (first pause response)
  Process INT3 --> receives getloc info for 0:2:6 (first getloc response)
  Process INT2 --> receives stat=02h (second pause response)
Another test,
  Setloc(0:2:0)+Read
  Process INT1 --> receives sector header for 0:2:0
  Delay(1)
  Pause
  Delay(1)
  GetlocL
  Process INT1 --> receives sector header for 0:2:9
  Process INT1 --> receives sector header for 0:2:11
  Process INT3 --> receives getloc info for 0:2:12 (first getloc response)
  Process INT1 --> receives sector header for 0:2:12
  Process INT1 --> receives sector header for 0:2:13


CDROM Disk Format

Overview
The PSX uses a ISO 9660 filesystem, with data stored on CD-XA (Mode2) Sectors. ISO 9660 is standard for CDROM disks, although newer CDROMs may use extended filesystems, allowing to use long filenames and lowercase filenames, the PSX Kernel doesn't support such stuff, and, in fact, it's putting some restrictions on the ISO standard: it's limiting file names to MSDOS-style 8.3 format, and it's allowing only a limited number of files and directories per disk.

CDROM Filesystem (ISO 9660 aka ECMA-119)
  Originally intended for Mode1 Sectors (but is also used for CD-XA Mode2)
  Supports "FILENAME.EXT;VERSION" filenames (version is usually "1")
  Supports all-uppercase filenames and directory names (0-9, A-Z, underscore)
  For PSX: Max 8-character filenames with max 3-character extensions
  For PSX: Max 8-character directory names, without extension
  For PSX: Max one sector per directory (?) (but Resident Evil 2 has bigger??)
  For PSX: Max one sector (or less?) per path table (?)

CDROM Extended Architecture (CD-ROM XA aka CD-XA)
  Uses Mode2 Sectors (see Sector Encoding chapter)
  Allows 800h or 914h byte data per sector (with/without error correction)
  Allows to break interleaved data into separate files/channels
  Supports XA-ADPCM compressed audio data
  Stores "CD-XA001" at 400h Primary Volume Descriptor (?)
  Stores 14 extra bytes in System Use area (LEN_SU) of Directory Entries

Physical Audio/CDROM Disk Format (ISO/IEC 10149 aka ECMA-130)
  Defines physical metrics of the CDROM and Audio disks
  Defines Sub-channels and Track.Index and Minute.Second.Fraction numbering
  Defines 14bit-per-byte encoding, and splits sectors into frames
  Defines ECC and EDC (error correction and error detection codes)

Available Documentation
ISO documents are commercial standards (not available for download), however, they are based on ECMA standards (which are free for download, however, the ECMA stuff is in PDF format, so one may treat it as commercial bullshit, too). CD-ROM XA is commercial only (not available for download), and, CD-XA doesn't seem to have become very popular outside of the PSX-world, so there's very little information available, portions of CD-XA are also used in the CD-i standard (which may be a little better or worse documented).

Stuff
  sessions  one or more sessions per disk
  tracks    99 tracks per disk     (01h..99h) (usually only 01h on Data Disks)
  index     99 indices per track   (01h..99h) (rarely used, usually always 01h)
  minutes   74 minutes per disk    (00h..73h) (or more, with some restrictions)
  seconds   60 seconds per minute  (00h..59h)
  sectors   75 sectors per second  (00h..74h)
  frames    98 frames per sector
  bytes     33 bytes per frame (24+1+8 = data + subchannel + error correction)
  bits      14 bits per byte   (256 valid combinations, and many invalid ones)

Track.Index (stored in subchannel, in BCD format)
Multiple Tracks are usually used only on Audio Disks (one track for each song, numbered 01h and up), a few Audio Disks may also split Tracks into separate fragments with different Index values (numbered 01h and up, but most tracks have only Index 01h). A simple Data Disk would usually contain only one Track (all sectors marked Track=01h and Index=01h), although some more complex Data Disks may have multiple Data tracks and/or Audio tracks.

Minute.Second.Sector (stored in subchannel, and in Data sectors, BCD format)
The sectors on CDROMs and CD Audio disks are numbered in Minutes, Seconds, and 1/75 fragments of a second (where a "second" is referring to single-speed drives, ie. the normal CD Audio playback speed).
Minute.Second.Sector is stored twice in the subchannel (once the "absolute" time, and once the "local" time).
The "absolute" sector number (counted from the begin of the disk) is mainly relevant for Seek purposes (telling the controller if the drive head is on the desired location, or if it needs to move the head backwards or forwards).
The "local" sector number (counted from the begin of the track) is mainly relevant for Audio Players, allowing to pass the data directly to the Minute:Second display, without needing to subtract the start address of the track.
Data disks are additionally storing the "absolute" values in their Data Areas, basically that's just the subchannel data duplicated, but more precisely assigned - the problem with the subchannel data is that the CD Audio standard seems to lack a clear definition that would assign the begin of the sub-channel block to the exact begin of a sector; so, when using only the subchannel data, some Drive Controllers may assign the begin of a new sector to another location as than other Controllers do, for Audio Disks that isn't too much of a problem, but for Data Disks it'd be fatal.

Subchannels
Each frame contains 8 subchannel bits (named P,Q,R,S,T,U,V,W). So, a sector (with 98 frames) contains 98 bits (12.25 bytes) for each subchannel.
CDROM Subchannels

Error Correction
Each Frame contains 8 bytes Error Correction information, which is mainly used for Audio Disks, but it isn't 100% fail-proof, for that reason, Data Disks are containing additional Error Correction in the 930h-byte data area (the audio correction is probably focusing on repairing the MSBs of the 16bit samples, and gives less priority on the LSBs). Error Correction is some kind of a huge complex checksum, which allows to detect the location of faulty bytes, and to fix them.

930h-Byte Sectors
The "user" area for each sector is 930h bytes (2352 bytes). That region is combined of the 24-byte data per frame (and excludes the 8-byte audio error correction info, and the 1-byte subchannel data).
Most CDROM Controllers are only giving access to this 930h-byte region (ie. there's no way to read the audio error correction info by software, and only limited access to the subchannel data, such like allowing to read only the Q-channel for showing track/minute/second in audio playback mode).
On Audio disks, the 930h bytes are plain data, on Data disks that bytes are containing headers, error correction, and usually only 800h bytes user data (for more info see Sector Encoding chapter).

Sessions
Multi-Sessions are mainly used on CDR's, allowing to append newer data at the end of the disk at a later time. First of, the old session must contain a flag indicating that there may be a newer session, telling the CDROM Controller to search if one such exists (and if that is equally flagged, to search for an even newer session, and so on until reaching the last and newest session).
Each session contains a complete new ISO Volume Descriptor, and may additionally contain new Path Tables, new Directories, and new Files. The Driver Controller is usually recursing only the Volume Descriptor of the newest session. However, the various Directory Records of the new session may refer to old files or old directories from previous sessions, allowing to "import" the older files, or to "rename" or "delete" them by assigning new names to that files, or by removing them from the directory.
The PSX is reportedly not supporting multi-session disks, but that doesn't seem to be correct, namely, the Setsession command is apparently intended for that purpose... though not sure if the PSX Kernel is automatically searching the newest session... otherwise the boot executable in the first session would need to do that manually by software, and redirect control to the boot executable in the last session.


CDROM Subchannels

Subchannel P
Subchannel P contains some kind of a Pause flag (to indicate muted areas between Audio Tracks). This subchannel doesn't have any checksum, so the data cannot be trusted to be intact (unless when sensing a longer stream of all-one's, or all zero's). Theoretically, the 98 pause bits are somehow associated to the 98 audio frames (with 24 audio bytes each) of the sector. However, reportedly, Subchannel P does contain two sync bits, if that is true, then there'd be only 96 pause flags for 98 audio frames. Strange.
Note: Another way to indicate "paused" regions is to set Subchannel Q to ADR=1 and Index=00h.

Subchannel Q
contains the following information:
  Bits Expl.
  2    Sub-channel synchronization field
  8    ADR/Control (see below)
  72   Data (content depends on ADR)
  16   CRC-16-CCITT error detection code (big-endian: bytes ordered MSB, LSB)
Possible values for the ADR/Control field are:
  Bit0-3 ADR (0=No data, 1..3=see below, 4..0Fh=Reserved)
  Bit4   Audio Preemphasis  (0=No, 1=Yes)      (Audio only, must be 0 for Data)
  Bit5   Digital Copy       (0=Prohibited, 1=Allowed)
  Bit6   Data               (0=Audio, 1=Data)
  Bit7   Four-Channel Audio (0=Stereo, 1=Quad) (Audio only, must be 0 for Data)
The 72bit data regions are, depending on the ADR value...

Subchannel Q with ADR=1 during Lead-In -- Table of Contents (TOC)
  8    Track number (fixed, must be 00h=Lead-in)
  8    Point (01h..99h or A0h..A2h, see last three bytes for more info)
  24   MSF address (incrementing address within the Lead-in area)
         Note: On some disks, these values are choosen so that the lead-in
         <starts> at 00:00:00, on other disks so that it <ends> at 99:59:74.
  8    Reserved (00h)
When Point=01h..99h (Track 1..99) or Point=A2h (Lead-Out):
  24   MSF address (absolute address, start address of the "Point" track)
When Point=A0h (First Track Number):
  8    First Track number (BCD)
  8    Disk Type Byte (00h=CD-DA or CD-ROM, 10h=CD-I, 20h=CD-ROM-XA)
  8    Reserved (00h)
When Point=A1h (Last Track Number):
  8    Last Track number (BCD)
  16   Reserved (0000h)
ADR=1 should exist in 3 consecutive lead-in sectors.

Subchannel Q with ADR=1 in Data region -- Position
  8    Track number (01h..99h=Track 1..99)
  8    Index number (00h=Pause, 01h..99h=Index within Track)
  24   Track relative MSF address (decreasing during Pause)
  8    Reserved (00h)
  24   Absolute MSF address
ADR=1 is required to exist in at least 9 out of 10 consecutive data sectors.

Subchannel Q with ADR=1 during Lead-Out -- Position
  8    Track number (fixed, must be AAh=Lead-Out)
  8    Index number (fixed, must be 01h) (there's no Index=00h in Lead-Out)
  24   Track relative MSF address (increasing, 00:00:00 and up)
  8    Reserved (00h)
  24   Absolute MSF address
ADR=1 should exist in 3 consecutive lead-out sectors (and may then be followed by ADR=5 on multisession disks).

Subchannel Q with ADR=2 -- Catalogue number of the disc (UPC/EAN barcode)
  52   EAN-13 barcode number (13-digit BCD)
  12   Reserved (000h)
  8    Absolute Sector number (BCD, 00h..74h) (always 00h during Lead-in)
If the first digit of the EAN-13 number is "0", then the remaining digits are a UPC-A barcode number. Either the 13-digit EAN-13 number, or the 12-digit UPC-A number should be printed as barcode on the rear-side of the CD package.
The first some digits contain a country code (EAN only, not UPC), followed by a manufacturer code, followed by a serial number. The last digit contains a checksum, which can be calculated as 250 minus the sum of the first 12 digits, minus twice the sum of each second digit, modulated by 10.
ADR=2 isn't included on all CDs, and, many CDs do have ADR=2, but the 13 digits are all zero. Most CDROM drives do not allow to read EAN/UPC numbers.
If present, ADR=2 should exist in at least 1 out of 100 consecutive sectors. ADR=2 may occur also in Lead-in.

Subchannel Q with ADR=3 -- ISRC number of the current track
(ISO 3901 and DIN-31-621):
  12   Country Code      (two 6bit characters)   (ASCII minus 30h) ;eg. "US"
  18   Owner Code        (three 6bit characters) (ASCII minus 30h)
  2    Reserved          (zero)
  8    Year of recording (2-digit BCD) ;eg. 82h for 1982
  20   Serial number     (5-digit BCD) ;usually increments by 1 or 10 per track
  4    Reserved          (zero)
  8    Absolute Sector number (BCD, 00h..74h) (always 00h during Lead-in)
Most CDROM drives for PC's do not allow to read ISRC numbers (or even worse, they may accidently return the same ISRC number on every two tracks).
If present, ADR=3 should exist in at least 1 out of 100 consecutive sectors. However, reportedly, ADR=3 should not occur in Lead-in.

Subchannel Q with ADR=5 in Lead-in -- Multisession Lead-In Info
When Point=B0h:
  8    Track number (fixed, must be 00h=Lead-in)
  8    POINT = B0h (multi-session disc)
  24   MM:SS:FF = the start time for the next possible session's program area,
       a final session is indicated by FFh:FFh:FFh,
       or when the ADR=5 / Point=B0h is absent.
  8    Number of different Mode-5 pointers present.
  24   MM:SS:FF = the maximum possible start time of the outermost Lead-out
When Point=C0h:
  8    Track number (fixed, must be 00h=Lead-in)
  8    POINT = C0h (Identifies a Multisession disc, together with POINT=B0h)
  24   ATIP values from Special Information 1, ID=101
  8    Reserved (must be 00h)
  24   MM:SS:FF = Start time of the first Lead-in area of the disc
And, optionally, when Point=C1h:
  8    Track number (fixed, must be 00h=Lead-in)
  8    POINT=C1h
  8x7  Copy of information from A1 point in ATIP

Subchannel Q with ADR=5 in Lead-Out -- Multisession Lead-Out Info
  8    Track number (fixed, must be AAh=Lead-out)
  8    POINT = D1h (Identifies a Multisession lead-out)
  24   Usually zero (or maybe ATIP as in Lead-In with Point=C0h...?)
  8    Seems to be the session number?
  24   MM:SS:FF = Absolute address of the First data sector of the session
Present in 3 consequtive sectors (3x ADR=1, 3x ADR=5, 3x ADR=1, 3x ADR=5, etc).

Subchannel Q with ADR=5 in Lead-in -- CDR/CDRW Skip Info (Audio Only)
When Point=01h..40h:
  8    Track number (fixed, must be 00h=Lead-in)
  8    POINT=01h..40h (This identifies a specific playback skip interval)
  24   MM:SS:FF Skip interval stop time in 6 BCD digits
  8    Reserved (must be 00h)
  24   MM:SS:FF Skip interval start time in 6 BCD digits
When Point=B1h:
  8    Track number (fixed, must be 00h=Lead-in)
  8    POINT=B1h (Audio only: This identifies the presence of skip intervals)
  8x4  Reserved (must be 00h,00h,00h,00h)
  8    the number of skip interval pointers in POINT=01h..40h
  8    the number of skip track assignments in POINT=B2h..B4h
  8    Reserved (must be 00h)
When Point=B2h,B3h,B4h:
  8    Track number (fixed, must be 00h=Lead-in)
  8    POINT=B2h,B3h,B4h (This identifies tracks that should be skipped)
  8    1st Track number to skip upon playback (01h..99h, must be nonzero)
  8    2nd Track number to skip upon playback (01h..99h, or 00h=None)
  8    3rd Track number to skip upon playback (01h..99h, or 00h=None)
  8    Reserved (must be 00h)... unclear... OR... 4th (of 7) skip info's...?
  8    4th Track number to skip upon playback (01h..99h, or 00h=None)
  8    5th Track number to skip upon playback (01h..99h, or 00h=None)
  8    6th Track number to skip upon playback (01h..99h, or 00h=None)
Note: Skip intervals are seldom written by recorders and typically ignored by readers.

Subchannel R..W
Subchannels R..W are usually unused, except for some extended formats:
  CD-TEXT in the Lead-In area (see below)
  CD-TEXT in the Data area    (rarely used)
  CD plus Graphics (CD+G)     (rarely used)
Most CDROM drives do not allow to read these subchannels. CD-TEXT was designed by Sony and Philips in 1997, so it should be found only on (some) newer discs. Most CD/DVD players don't support it (the only exception is that CD-TEXT seems to be popular for car hifi equipment). Most record labels don't support CD-TEXT, even Sony seems to have discontinued it on their own records after some years (so CD-TEXT is very rare on original disks, however, CDR software does often allow to write CD-TEXT on CDRs).

Subchannel R..W, when used for CD-TEXT in the Lead-In area
CD-TEXT is stored in the six Subchannels R..W. Of the 12.25 bytes (98 bits) per subchannel, only 12 bytes are used. Together, all 6 subchannels have a capacity of 72 bytes (6x12 bytes) per sector. These 72 bytes are divided into four CD-TEXT fragments (of 18 bytes each). The format of these 18 bytes is:
  00h 1  Header Field ID1: Pack Type Indicator
  01h 1  Header Field ID2: Track Number
  02h 1  Header Field ID3: Sequence Number
  03h 1  Header Field ID4: Block Number and Character Position Indicator
  04h 12 Text/Data Field
  10h 2  CRC-16-CCITT (big-endian) (across bytes 00h..0Fh)
ID1 - Pack Type Indicator:
  80h   Titel      (TEXT)
  81h   Performer  (TEXT)
  82h   Songwriter (TEXT)
  83h   Composer   (TEXT)
  84h   Arranger   (TEXT)
  85h   Message    (TEXT)
  86h   Disc ID    (TEXT?)  (content/format/purpose unknown?)
  87h   Genre      (BINARY) (ID codes unknown?)
  88h   TOC        (BINARY) (content/format/purpose unknown?)
  89h   TOC2       (BINARY) (content/format/purpose unknown?)
  8Ah   Reserved for future
  8Bh   Reserved for future
  8Ch   Reserved for future
  8Dh   Reserved for "content provider" aka "closed information"
  8Eh   UPC/EAN and ISRC Codes (TEXT) (content/format/purpose unknown?)
  8Fh   Blocksize (BINARY) (see below)
ID2 - Track Number:
  00h       Title/Performer/etc. for the Disc
  01h..63h  Title/Performer/etc. for Track 1..99 (Non-BCD) (Bit7=Extension)
ID3 - Sequence Number:
  00h..FFh  Incrementing Number (00h=First 18-byte fragment, 01h=Second, etc.)
ID4 - Block Number and Character Position Indicator:
  Bit7      Character Set      (0=8bit, 1=16bit)
  Bit6-4    Block Number       (0..7 = Language number, as set by "Blocksize")
  Bit3-0    Character Position (0..0Eh=Position, 0Fh=Append to prev fragment)
Example Data (generated with CDRWIN):
  ID TR SQ CH <------------Text/Data------------> -CRC-  <---Text--->
  80 00 00 00 54 65 73 74 44 69 73 6B 54 69 74 6C E2 22  TestDiskTitl
  80 00 01 0C 65 00 54 65 73 74 54 72 61 63 6B 54 C9 1B  e.TestTrackT
  80 01 02 0A 69 74 6C 65 31 00 54 65 73 74 54 72 40 3A  itle1.TestTr
  80 02 03 06 61 63 6B 54 69 74 6C 65 32 00 00 00 80 E3  ackTitle2...
  81 00 04 00 54 65 73 74 44 69 73 6B 50 65 72 66 03 DF  TestDiskPerf
  81 00 05 0C 6F 72 6D 65 72 00 54 65 73 74 54 72 12 A5  ormer.TestTr
  81 01 06 06 61 63 6B 50 65 72 66 6F 72 6D 65 72 BC 5B  ackPerformer
  81 01 07 0F 31 00 54 65 73 74 54 72 61 63 6B 50 AC 41  1.TestTrackP
  81 02 08 0A 65 72 66 6F 72 6D 65 72 32 00 00 00 64 1A  erformer2...
  8F 00 09 00 01 01 02 00 04 05 00 00 00 00 00 00 6D E2  ............
  8F 01 0A 00 00 00 00 00 00 00 00 03 0B 00 00 00 CD 0C  ............
  8F 02 0B 00 00 00 00 00 09 00 00 00 00 00 00 00 FC 8C  ............
  00   ;<--- for some reason, CDRWIN stores an ending 00h byte in .CDT files
Each Text string is terminated by a 00h byte (or 0000h for 16bit character set). If there's still room in the 12-byte data region, then first characters for the next Text string (for the next track) are appended after the 00h byte (if there's no further track, then the remaining bytes should be padded with 00h).
The "Blocksize" (ID1=8Fh) consists of three packs with 24h bytes of data (first 0Ch bytes stored with ID2=00h, next 0Ch bytes with ID2=01h, and last 0Ch bytes with ID2=02h):
  00h  1   Character set (00h,01h,80h,81h,82h = see below)
  01h  1   First track number (usually/always 01h)
  02h  1   Last track number (01h..63h)
  03h  1   1bit-cd-text-in-data-area-flag, 7bit-copy-protection-flags
  04h  16  Number of 18-byte packs for ID1=80h..8Fh
  14h  8   Last sequence number of block 0..7 (or 00h=none)
  1Ch  8   Language codes for block 0..7 (definitions are unknown)
Character Set values (for ID1=8Fh, ID2=00h, DATA[0]=charset):
  00h ISO 8859-1
  01h ISO 646, ASCII
  80h MS-JIS
  81h Korean character code
  82h Mandarin (standard) Chinese character code
  Other = reserved
"In case the same character stings is used for consecutive tracks, character 09h (or 0909h for 16bit charset) may be used to indicate the same as previous track. It shall not used for the first track."

adjust_crc_16_ccitt(addr_len) ;for CD-TEXT and Subchannel Q
  lsb=00h, msb=00h      ;-initial value (zero for both CD-TEXT and Sub-Q)
  for i=0 to len-1      ;-len (10h for CD-TEXT, 0Ah for Sub-Q)
    x = [addr+i] xor msb
    x = x xor (x shr 4)
    msb = lsb xor (x shr 3) xor (x shl 4)
    lsb = x xor (x shl 5)
  next i
  [addr+len+0]=msb xor FFh, [addr+len+1]=lsb xor FFh   ;inverted / big-endian


CDROM Sector Encoding

Audio
  000h 930h Audio Data (2352 bytes) (LeftLsb,LeftMsb,RightLsb,RightMsb)
Mode0 (Empty)
  000h 0Ch  Sync   (00h,FFh,FFh,FFh,FFh,FFh,FFh,FFh,FFh,FFh,FFh,00h)
  00Ch 4    Header (Minute,Second,Sector,Mode=00h)
  010h 920h Zerofilled
Mode1 (Original CDROM)
  000h 0Ch  Sync   (00h,FFh,FFh,FFh,FFh,FFh,FFh,FFh,FFh,FFh,FFh,00h)
  00Ch 4    Header (Minute,Second,Sector,Mode=01h)
  010h 800h Data (2048 bytes)
  810h 4    EDC (checksum across [000h..80Fh])
  814h 8    Zerofilled
  81Ch 114h ECC (error correction codes)
Mode2/Form1 (CD-XA)
  000h 0Ch  Sync   (00h,FFh,FFh,FFh,FFh,FFh,FFh,FFh,FFh,FFh,FFh,00h)
  00Ch 4    Header (Minute,Second,Sector,Mode=02h)
  010h 4    Sub-Header (File, Channel, Submode AND DFh, Codinginfo)
  014h 4    Copy of Sub-Header
  018h 800h Data (2048 bytes)
  818h 4    EDC (checksum across [010h..817h])
  81Ch 114h ECC (error correction codes)
Mode2/Form2 (CD-XA)
  000h 0Ch  Sync   (00h,FFh,FFh,FFh,FFh,FFh,FFh,FFh,FFh,FFh,FFh,00h)
  00Ch 4    Header (Minute,Second,Sector,Mode=02h)
  010h 4    Sub-Header (File, Channel, Submode OR 20h, Codinginfo)
  014h 4    Copy of Sub-Header
  018h 914h Data (2324 bytes)
  92Ch 4    EDC (checksum across [010h..92Bh]) (or 00000000h if no EDC)

encode_sector
  sector[000h]=00h,FFh,FFh,FFh,FFh,FFh,FFh,FFh,FFh,FFh,FFh,00h
  sector[00ch]=bcd(adr/75/60)      ;0..7x
  sector[00dh]=bcd(adr/75 MOD 60)  ;0..59
  sector[00eh]=bcd(adr MOD 75)     ;0..74
  sector[00fh]=mode
  if mode=00h then
    sector[010h..92Fh]=zerofilled
  if mode=01h then
    adjust_edc(sector+0, 800h+10h)
    sector[814h..817h]=00h,00h,00h,00h,00h,00h,00h,00h
    calc_p_parity(sector)
    calc_q_parity(sector)
  if mode=02h and form=1
    sector[012h]=sector[012h] AND (NOT 20h)  ;indicate not form2
    sector[014h..017h]=sector[010h..013h]    ;copy of sub-header
    adjust_edc(sector+10h,800h+8)
    push sector[00ch]           ;\temporarily clear header
    sector[00ch]=00000000h      ;/
    calc_p_parity(sector)
    calc_q_parity(sector)
    pop sector[00ch]            ;-restore header
  if mode=02h and form=2
    sector[012h]=sector[012h] OR 20h         ;indicate form2
    sector[014h..017h]=sector[010h..013h]    ;copy of sub-header
    adjust_edc(sector+10h,914h+8)            ;edc is optional for form2

calc_parity(sector,offs,len,j0,step1,step2)
  src=00ch, dst=81ch+offs, srcmax=dst
  for i=0 to len-1
    base=src, x=0000h, y=0000h
    for j=j0 to 42
      x=x xor GF8_PRODUCT[j,sector[src+0]]
      y=y xor GF8_PRODUCT[j,sector[src+1]]
      src=src+step1, if (step1=2*44) and (src>=srcmax) then src=src-2*1118
    sector[dst+2*len+0]=x AND 0FFh, [dst+0]=x SHR 8
    sector[dst+2*len+1]=y AND 0FFh, [dst+1]=y SHR 8
    dst=dst+2, src=base+step2
calc_p_parity(sector) = calc_parity(sector,0,43,19,2*43,2)
calc_q_parity(sector) = calc_parity(sector,43*4,26,0,2*44,2*43)

adjust_edc(addr,len)
  x=00000000h
  for i=0 to len-1
    x=x xor byte[addr+i], x=(x shr 8) xor edc_table[x and FFh]
  word[addr+len]=x  ;append EDC value (little endian)

init_tables
  for i=0 to FFh
    x=i, for j=0 to 7, x=x shr 1, if carry then x=x xor D8018001h
    edc_table[i]=x
  GF8_LOG[00h]=00h, GF8_ILOG[FFh]=00h, x=01h
  for i=00h to FEh
    GF8_LOG[x]=i, GF8_ILOG[i]=x
    x=x SHL 1, if carry8bit then x=x xor 1dh
  for j=0 to 42
    xx=GF8_ILOG[44-j],  yy=subfunc(xx xor 1,19h)
    xx=subfunc(xx,01h), xx=subfunc(xx xor 1,18h)
    xx=GF8_LOG[xx], yy = GF8_LOG[yy]
    GF8_PRODUCT[j,0]=0000h
    for i=01h to FFh
      x=xx+GF8_LOG[i], if x>=255 then x=x-255
      y=yy+GF8_LOG[i], if y>=255 then y=y-255
      GF8_PRODUCT[j,i]=GF8_ILOG[x]+(GF8_ILOG[y] shl 8)

subfunc(a,b)
  if a>0 then
    a=GF8_LOG[a]-b, if a<0 then a=a+255
    a=GF8_ILOG[a]
  return(a)


CDROM Scrambling

Scrambling
Scambling does XOR the data sectors with random values (done to avoid regular patterns). The scrambling is applied to Data sector bytes[00Ch..92Fh] (not to CD-DA audio sectors, and not to the leading 12-byte Sync mark in Data sectors).
The (de-)scrambling is done automatically by the CDROM controller, so disc images should usually contain unscrambled data (there are some exceptions such like CD-i discs that have audio and data sectors mixed inside of the same track; which may confuse the CDROM controller about whether or not to apply scrambling to which sectors; so one may need to manually XOR the faulty sectors in the disc image).
The scrambling pattern is derived from a 15bit polynomial counter (much like a noise generator in sound chips). The data bits are XORed with the counters low bit, and the counters lower 2bit are XORed with each other, and shifted in to the counters upper bit. To compute 8 bits and once, and store them in a 924h-byte table:
  poly=0001h  ;init 15bit polynomial counter
  for i=0 to 924h-1
    scramble_table[i]=poly AND FFh
    poly=(((poly XOR poly/2) AND 0FFh)*80h) XOR (poly/100h)
  next i
The resulting table content should be:
  01h,80h,00h,60h,00h,28h,00h,1Eh,80h,08h,60h,06h,A8h,02h,FEh,81h,
  80h,60h,60h,28h,28h,1Eh,9Eh,88h,68h,66h,AEh,AAh,FCh,7Fh,01h,E0h,
  etc.
After scrambling, the data is reportedly "shuffled and byte-swapped". Unknown what shuffling means. And unknown what/where/why byte-swapping is done (it does reportedly swap each two bytes in the whole(?) 930h-byte (data-?) sector; which might date back to different conventions for disc images to contain "16bit audio samples" in big- or little-endian format).


CDROM XA Subheader, File, Channel, Interleave

The Sub-Header for normal data sectors is usually 00h,00h,08h,00h (some PSX sectors have 09h instead 08h, indicating the end of "something" or so?

1st Subheader byte - File Number (FN)
  0-7 File Number    (00h..FFh) (for Audio/Video Interleave, see below)

2nd Subheader byte - Channel Number (CN)
  0-4 Channel Number (00h..1Fh) (for Audio/Video Interleave, see below)
  5-7 Should be always zero
Whilst not officially allowed, PSX Ace Combat 3 Electrosphere does use Channel=FFh for unused gaps in interleaved streaming sectors.

3rd Subheader byte - Submode (SM)
  0   End of Record (EOR) (all Volume Descriptors, and all sectors with EOF)
  1   Video     ;\Sector Type (usually ONE of these bits should be set)
  2   Audio     ; Note: PSX .STR files are declared as Data (not as Video)
  3   Data      ;/Note: VCD videos start with empty sectors, all 3 bits cleared
  4   Trigger            (for application use)
  5   Form2              (0=Form1/800h-byte data, 1=Form2, 914h-byte data)
  6   Real Time (RT)
  7   End of File (EOF)  (or end of Directory/PathTable/VolumeTerminator)
The EOR bit is set in all Volume Descriptor sectors, the last sector (ie. the Volume Descriptor Terminator) additionally has the EOF bit set. Moreover, EOR and EOF are set in the last sector of each Path Table, and last sector of each Directory, and last sector of each File.

4th Subheader byte - Codinginfo (CI)
When used for Data sectors:
  0-7 Reserved (00h)
When used for XA-ADPCM audio sectors:
  0-1 Mono/Stereo     (0=Mono, 1=Stereo, 2-3=Reserved)
  2-2 Sample Rate     (0=37800Hz, 1=18900Hz, 2-3=Reserved)
  4-5 Bits per Sample (0=Normal/4bit, 1=8bit, 2-3=Reserved)
  6   Emphasis        (0=Normal/Off, 1=Emphasis)
  7   Reserved        (0)

Audio/Video Interleave (Multiple Files/Channels)
The CDROM drive mechanics are working best when continously following the data spiral on the disk, that works fine for uncompressed Audio Data at normal speed, but compressed Audio Data the disk is spinning much too fast. To avoid the drive to need to pause reading or to do permanent backwards seeking, CD-XA allows to store data interleaved in separate files/channels. With common interleave values like so:
  Interleave   Data Format
  1/1 (none)   44100Hz Stereo CD Audio at normal speed
  1/8          37800Hz Stereo ADPCM compressed Audio at double speed
  1/16         18900Hz Stereo ADPCM compressed Audio at double speed
  1/16         37800Hz Mono   ADPCM compressed Audio at double speed
  1/32         18900Hz Mono   ADPCM compressed Audio at double speed
  7/8          15fps 320x224 pixel MDEC compressed Videos at double speed
  Unknown if 1/16 and 1/32 interleaves are actually possible (the PSX cdrom
  controller seems to overwrite the IC303 sector buffer entries once every
  eight sectors, so ADPCM data may get destroyed on interleaves above 1/8).
  (Crash Team Racing uses 37800Hz Mono at Double speed, so 1/16 must work).
For example, 1/8 means that the controller processes only each 8th sector (each having the same File Number and Channel Number), and ignores the next 7 sectors (which must have other File Number and/or other Channel Number). There are various ways to arrange multiple files or channels, for example,
  one file with eight 1/8 audio channels
  one file with one 1/8 audio channels, plus one 7/8 video channel (*)
  one file with one 1/8 audio channels, plus 7 unused channels
  eight different files with one 1/8 audio channel each
  etc.
(*) If the Audio and Video data belongs together then both should use the SAME channel.
Note: Above interleave values are assuming that PSX Game Disks are always running at double speed (that's fastest for normal data files, and ADPCM files are usually using the same speed; otherwise it'd be neccessary to change the drive speed everytime when switching between Data to ADPCM modes).
Note: The file/channel numbers can be somehow selected with the Setfilter command. No idea if the controller is automatically switching to the next channel or so when reaching the end of the file?

Unused sectors in Interleave
There are different ways to mark unused sectors in interleaved streams. Ace Combat 3 uses Channel=FFh=Invalid. Tron Bonne uses Submode=00h=Nothing (notably, that game has a 74Mbyte XA file that leaves about 75% unused).
  Subheader bytes: 01h,FFh,64h,01h   ;Ace Combat 3 Electrosphere
  Subheader bytes: 01h,00h,00h,00h   ;Misadventures of Tron Bonne (XA\*.XA)

Real Time Streaming
With the above Interleave, files can be played continously at real time - that, unless read-errors do occur. In that case the drive controller would usually perform time-consuming error-correction and/or read-retries. For video/audio streaming the resulting delay would be tendencially more annoying as than processing or skipping the incorrect data.
In such cases the drive controller is allowed to ignore read errors; that probably on sectors that have the Real Time (RT) flag set in their subheaders. The controller is probably doing some read-ahead buffering (so, if it has buffered enough data, then it may still perform read retries and/or error correction, as long as it doesn't affect real time playback).


CDROM XA Audio ADPCM Compression

CD-ROM XA ADPCM is used for Audio data compression. Each 16bit sample is encoded in 4bit nibbles; so the compression rate is almost 1:4 (only almost 1:4 because there are 16 header bytes within each 128-byte portion). The data is usually/always stored on 914h-byte sectors (without error correction).

Subheader
The Subheader (see previous chapter) contains important info for ADPCM: The file/channel numbers for Interleaved data, and the codinginfo flags: mono/stereo flag, 37800Hz/18900Hz sampling rate, 4bit/8bit format, and emphasis.

ADPCM Sectors
Each sector consists of 12h 128-byte portions (=900h bytes) (the remaining 14h bytes of the sectors 914h-byte data region are 00h filled).
The separate 128-byte portions consist of a 16-byte header,
  00h..03h  Copy of below 4 bytes (at 04h..07h)
  04h       Header for 1st Block/Mono, or 1st Block/Left
  05h       Header for 2nd Block/Mono, or 1st Block/Right
  06h       Header for 3rd Block/Mono, or 2nd Block/Left
  07h       Header for 4th Block/Mono, or 2nd Block/Right
  08h       Header for 5th Block/Mono, or 3rd Block/Left  ;\unknown/unused
  09h       Header for 6th Block/Mono, or 3rd Block/Right ; for 8bit ADPCM
  0Ah       Header for 7th Block/Mono, or 4th Block/Left  ; (maybe 0, or maybe
  0Bh       Header for 8th Block/Mono, or 4th Block/Right ;/copy of above)
  0Ch..0Fh  Copy of above 4 bytes (at 08h..0Bh)
followed by twentyeight data words (4x28-bytes),
  10h..13h  1st Data Word (packed 1st samples for 2-8 blocks)
  14h..17h  2nd Data Word (packed 2nd samples for 2-8 blocks)
  18h..1Bh  3rd Data Word (packed 3rd samples for 2-8 blocks)
  ...       Nth Data Word (packed Nth samples for 2-8 blocks)
  7Ch..7Fh  28th Data Word (packed 28th samples for 2-8 blocks)
and then followed by the next 128-byte portion.
The "Copy" bytes are allowing to repair faulty headers (ie. if the CDROM controller has sensed a read-error in the header then it can eventually replace it by the copy of the header).

XA-ADPCM Header Bytes
  0-3   Shift  (0..12) (0=Loudest) (13..15=Reserved/Same as 9)
  4-5   Filter (0..3) (only four filters, unlike SPU-ADPCM which has five)
  6-7   Unused (should be 0)
Note: The 4bit (or 8bit) samples are expanded to 16bit by left-shifting them by 12 (or 8), that 16bit value is then right-shifted by the selected 'shift' amount. For 8bit ADPCM shift should be 0..8 (values 9..12 will cut-off the LSB(s) of the 8bit value, this works, but isn't useful). For both 4bit and 8bit ADPCM, reserved shift values 13..15 will act same as shift=9).

XA-ADPCM Data Words (32bit, little endian)
  0-3   Nibble for 1st Block/Mono, or 1st Block/Left  (-8h..+7h)
  4-7   Nibble for 2nd Block/Mono, or 1st Block/Right (-8h..+7h)
  8-11  Nibble for 3rd Block/Mono, or 2nd Block/Left  (-8h..+7h)
  12-15 Nibble for 4th Block/Mono, or 2nd Block/Right (-8h..+7h)
  16-19 Nibble for 5th Block/Mono, or 3rd Block/Left  (-8h..+7h)
  20-23 Nibble for 6th Block/Mono, or 3rd Block/Right (-8h..+7h)
  24-27 Nibble for 7th Block/Mono, or 4th Block/Left  (-8h..+7h)
  28-31 Nibble for 8th Block/Mono, or 4th Block/Right (-8h..+7h)
or, for 8bit ADPCM format:
  0-7   Byte for 1st Block/Mono, or 1st Block/Left    (-80h..+7Fh)
  8-15  Byte for 2nd Block/Mono, or 1st Block/Right   (-80h..+7Fh)
  16-23 Byte for 3rd Block/Mono, or 2nd Block/Left    (-80h..+7Fh)
  24-31 Byte for 4th Block/Mono, or 2nd Block/Right   (-80h..+7Fh)

decode_sector(src)
  src=src+12+4+8   ;skip sync,header,subheader
  for i=0 to 11h
   for blk=0 to 3
    IF stereo ;left-samples (LO-nibbles), plus right-samples (HI-nibbles)
      decode_28_nibbles(src,blk,0,dst_left,old_left,older_left)
      decode_28_nibbles(src,blk,1,dst_right,old_right,older_right)
    ELSE      ;first 28 samples (LO-nibbles), plus next 28 samples (HI-nibbles)
      decode_28_nibbles(src,blk,0,dst_mono,old_mono,older_mono)
      decode_28_nibbles(src,blk,1,dst_mono,old_mono,older_mono)
    ENDIF
   next blk
   src=src+128
  next i
  src=src+14h+4    ;skip padding,edc

decode_28_nibbles(src,blk,nibble,dst,old,older)
  shift  = 12 - (src[4+blk*2+nibble] AND 0Fh)
  filter =      (src[4+blk*2+nibble] AND 30h) SHR 4
  f0 = pos_xa_adpcm_table[filter]
  f1 = neg_xa_adpcm_table[filter]
  for j=0 to 27
    t = signed4bit((src[16+blk+j*4] SHR (nibble*4)) AND 0Fh)
    s = (t SHL shift) + ((old*f0 + older*f1+32)/64)
    s = MinMax(s,-8000h,+7FFFh)
    halfword[dst]=s, dst=dst+2, older=old, old=s
  next j

Pos/neg Tables
  pos_xa_adpcm_table[0..4] = (0, +60, +115, +98, +122)
  neg_xa_adpcm_table[0..4] = (0,   0,  -52, -55,  -60)
Note: XA-ADPCM supports only four filters (0..3), unlike SPU-ADPCM which supports five filters (0..4).

Old/Older Values
The incoming old/older values are usually that from the previous part, or garbage (in case of decoding errors in the previous part), or whatever (in case there was no previous part) (ie. maybe zero on power-up?) (and maybe there's also a way to reset the values to zero at the begin of a new file, or *maybe* it's silently done automatically when issuing seek commands?).

25-point Zigzag Interpolation
The CDROM decoder is applying some weird 25-point zigzag interpolation when resampling the 37800Hz XA-ADPCM output to 44100Hz. This part is different from SPU-ADPCM (which uses 4-point gaussian pitch interpolations). For example, XA-ADPCM interpolation applied to a square wave looks like this:
                                                 .            .
           .--------------.                      | |        | |
           |              |                     .'.'.'----'.'.'.
           |              |                     | |          | |
           |              |                     |              |
           | Decompressed |                     |    Final     |
           |   XA-ADPCM   |                     |   XA-ADPCM   |
           |   Waveform   |                     |    Output    |
           |              |                   | |              | |
           |              |             ---.'.'.'              '.'.'.---
   --------'              '--------          | |                | |
                                               '                '
The zigzagging does produce some (inaudible) 22050Hz noise, and does produce some low-pass (?) filtering ("sinc filter"). The effect can be reproduced somewhat like so:
  Output37800Hz(sample):
    ringbuf[p AND 1Fh]=sample, p=p+1, sixstep=sixstep-1
    if sixstep=0
      sixstep=6
      Ouput44100Hz(ZigZagInterpolate(p,Table1))
      Ouput44100Hz(ZigZagInterpolate(p,Table2))
      Ouput44100Hz(ZigZagInterpolate(p,Table3))
      Ouput44100Hz(ZigZagInterpolate(p,Table4))
      Ouput44100Hz(ZigZagInterpolate(p,Table5))
      Ouput44100Hz(ZigZagInterpolate(p,Table6))
      Ouput44100Hz(ZigZagInterpolate(p,Table7))
    endif
  ZigZagInterpolate(p,TableX):
    sum=0
    for i=1 to 29, sum=sum+(ringbuf[(p-i) AND 1Fh]*TableX[i])/8000h, next i
    return MinMax(sum,-8000h,+7FFFh)
  Table1, Table2, Table3, Table4, Table5, Table6, Table7  ;Index
    0     , 0     , 0     , 0     , -0001h, +0002h, -0005h  ;1
    0     , 0     , 0     , -0001h, +0003h, -0008h, +0011h  ;2
    0     , 0     , -0001h, +0003h, -0008h, +0010h, -0023h  ;3
    0     , -0002h, +0003h, -0008h, +0011h, -0023h, +0046h  ;4
    0     , 0     , -0002h, +0006h, -0010h, +002Bh, -0017h  ;5
    -0002h, +0003h, -0005h, +0005h, +000Ah, +001Ah, -0044h  ;6
    +000Ah, -0013h, +001Fh, -001Bh, +006Bh, -00EBh, +015Bh  ;7
    -0022h, +003Ch, -004Ah, +00A6h, -016Dh, +027Bh, -0347h  ;8
    +0041h, -004Bh, +00B3h, -01A8h, +0350h, -0548h, +080Eh  ;9
    -0054h, +00A2h, -0192h, +0372h, -0623h, +0AFAh, -1249h  ;10
    +0034h, -00E3h, +02B1h, -05BFh, +0BCDh, -16FAh, +3C07h  ;11
    +0009h, +0132h, -039Eh, +09B8h, -1780h, +53E0h, +53E0h  ;12
    -010Ah, -0043h, +04F8h, -11B4h, +6794h, +3C07h, -16FAh  ;13
    +0400h, -0267h, -05A6h, +74BBh, +234Ch, -1249h, +0AFAh  ;14
    -0A78h, +0C9Dh, +7939h, +0C9Dh, -0A78h, +080Eh, -0548h  ;15
    +234Ch, +74BBh, -05A6h, -0267h, +0400h, -0347h, +027Bh  ;16
    +6794h, -11B4h, +04F8h, -0043h, -010Ah, +015Bh, -00EBh  ;17
    -1780h, +09B8h, -039Eh, +0132h, +0009h, -0044h, +001Ah  ;18
    +0BCDh, -05BFh, +02B1h, -00E3h, +0034h, -0017h, +002Bh  ;19
    -0623h, +0372h, -0192h, +00A2h, -0054h, +0046h, -0023h  ;20
    +0350h, -01A8h, +00B3h, -004Bh, +0041h, -0023h, +0010h  ;21
    -016Dh, +00A6h, -004Ah, +003Ch, -0022h, +0011h, -0008h  ;22
    +006Bh, -001Bh, +001Fh, -0013h, +000Ah, -0005h, +0002h  ;23
    +000Ah, +0005h, -0005h, +0003h, -0001h, 0     , 0       ;24
    -0010h, +0006h, -0002h, 0     , 0     , 0     , 0       ;25
    +0011h, -0008h, +0003h, -0002h, +0001h, 0     , 0       ;26
    -0008h, +0003h, -0001h, 0     , 0     , 0     , 0       ;27
    +0003h, -0001h, 0     , 0     , 0     , 0     , 0       ;28
    -0001h, 0     , 0     , 0     , 0     , 0     , 0       ;29
The above formula/table gives nearly correct results, but with small rounding errors in some cases - possibly due to actual rounding issues, or due to factors with bigger fractional portions, or due to a completely different formula...
Probably, the hardware does actually do the above stuff in two steps: first, applying a zig-zag filter (with only around 21-points) to the 37800Hz output, and then doing 44100Hz interpolation (2-point linear or 4-point gaussian or whatever) in a second step.
That two-step theory would also match well for 18900Hz resampling (which has lower-pitch zigzag, and gets spread across about fifty 44100Hz samples).

XA-ADPCM Emphasis
With XA-Emphasis enabled in Sub-header, output will appear as so:
           .------------.                           ....-----.
           |            |                        .''         |
           |    Raw     |                       .'    XA     |
           |   ADPCM    |                       |  Emphasis  '.
           |  Waveform  |                       |   Output    '..
   --------'            '----------     --------'                ''''---
The exact XA-Emphasis formula is unknown (maybe it's just same as for CD-DA's SUBQ emphasis). Additionally, zig-zag interpolation is applied (somewhere before or after applying the emphasis stuff).
Note: The Emphasis feature isn't used by any known PSX games.

Uninitialized Six-step Counter
The hardware does contain some six-step counter (for interpolating 37800Hz to 44100Hz, ie. to insert one extra sample after each six samples). The 900h-byte sectors contain a multiple of six samples, so the counter will be always same before & after playing a sector. However, the initial counter value on power-up is uninitialized random (and the counter will fallback to that initial random setting after each 900h-byte sector).

RIFF Headers (on PCs)
When reading files that consist of 914h-byte sectors on a PC, the PC seems to automatically insert a 2Ch-byte RIFF fileheader. Like so, for ADPCM audio files:
  00h 4   "RIFF"
  04h 4   Total Filesize (minus 8)
  08h 8   "CDXAfmt "
  10h 4   Size of below stuff (10h)
  14h 14  Stuff (looks like the "LEN_SU" region from XA-Directory Record)
  22h 2   Zero  (probably just dummy padding for 32bit alignment)
  24h 4   "data"
  28h 4   Size of following data (usually N*930h)
That RIFF stuff isn't stored on the CDROM (at least not in the file area) (however, some of that info, like the "=UXA" stuff, is stored in the directory area of the CDROM).
After the RIFF header, the normal sector data is appended, that, with the full 930h bytes per sector (ie. the 914h data bytes preceeded by sync bytes, header, subheader, and followed by the EDC value).
The Channel Interleave doesn't seem to be resolved, ie. the Channels are kept arranged as how they are stored on the CDROM. However, File Interleave <should> be resolved, ie. other Files that "overlap" the file shouldn't be included in the file.


CDROM ISO Volume Descriptors

System Area (prior to Volume Descriptors)
The first 16 sectors on the first track are the system area, for a Playstation disk, it contains the following:
  Sector 0..3   - Zerofilled (Mode2/Form1, 4x800h bytes, plus ECC/EDC)
  Sector 4      - Licence String
  Sector 5..11  - Playstation Logo (3278h bytes) (remaining bytes FFh-filled)
  Sector 12..15 - Zerofilled (Mode2/Form2, 4x914h bytes, plus EDC)
Of which, the Licence String in sector 4 is,
  000h 32    Line 1      ("          Licensed  by          ")
  020h 32+6  Line 2 (EU) ("Sony Computer Entertainment Euro"," pe   ") ;\either
  020h 32+1  Line 2 (JP) ("Sony Computer Entertainment Inc.",0Ah)      ; one of
  020h 32+6  Line 2 (US) ("Sony Computer Entertainment Amer","  ica ") ;/these
  041h 1983  Empty (JP)    (filled by repeating pattern 62x30h,1x0Ah, 1x30h)
  046h 1978  Empty (EU/US) (filled by 00h-bytes)
The Playstation Logo in sectors 5..11 contains data like so,
  0000h ..   41h,00h,00h,00h,00h,00h,00h,00h,01h,00h,00h,00h,1Ch,23h,00h,00h
  0010h ..   51h,01h,00h,00h,A4h,2Dh,00h,00h,99h,00h,00h,00h,1Ch,00h,00h,00h
  0020h ..   ...
  3278h 588h FF-filled (remaining bytes on sector 11)
the Logo contains a .TMD header, polygons, vertices and normals for the "PS" logo (which is displayed when booting from CDROM). Some BIOS versions are comparing these 3278h bytes against an identical copy in ROM, and refuse to boot if the data isn't 1:1 the same:
- NTSC US/ASIA BIOS always accepts changed logos.
- PAL EU BIOS accepts changed logos up to v3.0E (and refuses in v4.0E and up).
- NTSC JP BIOS never accepts changed logos (and/or changed license strings?).
Note: A region-patch-modchip causes PAL BIOS to behave same as US/ASIA BIOS.

Volume Descriptors (Sector 16 and up)
Playstation disks usually have only two Volume Descriptors,
  Sector 16    - Primary Volume Descriptor
  Sector 17    - Volume Descriptor Set Terminator

Primary Volume Descriptor (sector 16 on PSX disks)
  000h 1    Volume Descriptor Type        (01h=Primary Volume Descriptor)
  001h 5    Standard Identifier           ("CD001")
  006h 1    Volume Descriptor Version     (01h=Standard)
  007h 1    Reserved                      (00h)
  008h 32   System Identifier             (a-characters) ("PLAYSTATION")
  028h 32   Volume Identifier             (d-characters) (max 8 chars for PSX?)
  048h 8    Reserved                      (00h)
  050h 8    Volume Space Size             (2x32bit, number of logical blocks)
  058h 32   Reserved                      (00h)
  078h 4    Volume Set Size               (2x16bit) (usually 0001h)
  07Ch 4    Volume Sequence Number        (2x16bit) (usually 0001h)
  080h 4    Logical Block Size in Bytes   (2x16bit) (usually 0800h) (1 sector)
  084h 8    Path Table Size in Bytes      (2x32bit) (max 800h for PSX)
  08Ch 4    Path Table 1 Block Number     (32bit little-endian)
  090h 4    Path Table 2 Block Number     (32bit little-endian) (or 0=None)
  094h 4    Path Table 3 Block Number     (32bit big-endian)
  098h 4    Path Table 4 Block Number     (32bit big-endian) (or 0=None)
  09Ch 34   Root Directory Record         (see next chapter)
  0BEh 128  Volume Set Identifier         (d-characters) (usually empty)
  13Eh 128  Publisher Identifier          (a-characters) (company name)
  1BEh 128  Data Preparer Identifier      (a-characters) (empty or other)
  23Eh 128  Application Identifier        (a-characters) ("PLAYSTATION")
  2BEh 37   Copyright Filename            ("FILENAME.EXT;VER") (empty or text)
  2E3h 37   Abstract Filename             ("FILENAME.EXT;VER") (empty)
  308h 37   Bibliographic Filename        ("FILENAME.EXT;VER") (empty)
  32Dh 17   Volume Creation Timestamp     ("YYYYMMDDHHMMSSFF",timezone)
  33Eh 17   Volume Modification Timestamp ("0000000000000000",00h)
  34Fh 17   Volume Expiration Timestamp   ("0000000000000000",00h)
  360h 17   Volume Effective Timestamp    ("0000000000000000",00h)
  371h 1    File Structure Version        (01h=Standard)
  372h 1    Reserved for future           (00h-filled)
  373h 141  Application Use Area          (00h-filled for PSX and VCD)
  400h 8    CD-XA Identifying Signature   ("CD-XA001" for PSX and VCD)
  408h 2    CD-XA Flags (unknown purpose) (00h-filled for PSX and VCD)
  40Ah 8    CD-XA Startup Directory       (00h-filled for PSX and VCD)
  412h 8    CD-XA Reserved                (00h-filled for PSX and VCD)
  41Ah 345  Application Use Area          (00h-filled for PSX and VCD)
  573h 653  Reserved for future           (00h-filled)

Volume Descriptor Set Terminator (sector 17 on PSX disks)
  000h 1    Volume Descriptor Type    (FFh=Terminator)
  001h 5    Standard Identifier       ("CD001")
  006h 1    Terminator Version        (01h=Standard)
  007h 2041 Reserved                  (00h-filled)

Boot Record (none such on PSX disks)
  000h 1    Volume Descriptor Type    (00h=Boot Record)
  001h 5    Standard Identifier       ("CD001")
  006h 1    Boot Record Version       (01h=Standard)
  007h 32   Boot System Identifier    (a-characters)
  027h 32   Boot Identifier           (a-characters)
  047h 1977 Boot System Use           (not specified content)

Supplementary Volume Descriptor (none such on PSX disks)
  000h 1    Volume Descriptor Type (02h=Supplementary Volume Descriptor)
  001h ..   Same as for Primary Volume Descriptor (see there)
  007h 1    Volume Flags           (8bit)
  008h ..   Same as for Primary Volume Descriptor (see there)
  058h 32   Escape Sequences       (32 bytes)
  078h ..   Same as for Primary Volume Descriptor (see there)
In practice, this is used for Joliet:
CDROM Extension Joliet

Volume Partition Descriptor (none such on PSX disks)
  000h 1    Volume Descriptor Type      (03h=Volume Partition Descriptor)
  001h 5    Standard Identifier         ("CD001")
  006h 1    Volume Partition Version    (01h=Standard)
  007h 1    Reserved                    (00h)
  008h 32   System Identifier           (a-characters) (32 bytes)
  028h 32   Volume Partition Identifier (d-characters) (32 bytes)
  048h 8    Volume Partition Location   (2x32bit) Logical Block Number
  050h 8    Volume Partition Size       (2x32bit) Number of Logical Blocks
  058h 1960 System Use                  (not specified content)

Reserved Volume Descriptors (none such on PSX disks)
  000h 1    Volume Descriptor Type    (04h..FEh=Reserved, don't use)
  001h 2047 Reserved                  (don't use)


CDROM ISO File and Directory Descriptors

The location of the Root Directory is described by a 34-byte Directory Record being located in Primary Volume Descriptor entries 09Ch..0BDh. The data therein is: Block Number (usually 22 on PSX disks), LEN_FI=01h, Name=00h, and, LEN_SU=00h (due to the 34-byte limit).

Format of a Directory Record
  00h 1      Length of Directory Record (LEN_DR) (33+LEN_FI+pad+LEN_SU) (0=Pad)
  01h 1      Extended Attribute Record Length (usually 00h)
  02h 8      Data Logical Block Number (2x32bit)
  0Ah 8      Data Size in Bytes        (2x32bit)
  12h 7      Recording Timestamp       (yy-1900,mm,dd,hh,mm,ss,timezone)
  19h 1      File Flags 8 bits         (usually 00h=File, or 02h=Directory)
  1Ah 1      File Unit Size            (usually 00h)
  1Bh 1      Interleave Gap Size       (usually 00h)
  1Ch 4      Volume Sequence Number    (2x16bit, usually 0001h)
  20h 1      Length of Name            (LEN_FI)
  21h LEN_FI File/Directory Name ("FILENAME.EXT;1" or "DIR_NAME" or 00h or 01h)
  xxh 0..1   Padding Field (00h) (only if LEN_FI is even)
  xxh LEN_SU System Use (LEN_SU bytes) (see below for CD-XA disks)
LEN_SU can be calculated as "LEN_DR-(33+LEN_FI+Padding)". For CD-XA disks (as used in the PSX), LEN_SU is 14 bytes:
  00h 2      Owner ID Group  (whatever, usually 0000h, big endian)
  02h 2      Owner ID User   (whatever, usually 0000h, big endian)
  04h 2      File Attributes (big endian):
               0   Owner Read    (usually 1)
               1   Reserved      (0)
               2   Owner Execute (usually 1)
               3   Reserved      (0)
               4   Group Read    (usually 1)
               5   Reserved      (0)
               6   Group Execute (usually 1)
               7   Reserved      (0)
               8   World Read    (usually 1)
               9   Reserved      (0)
               10  World Execute (usually 1)
               11  IS_MODE2        (0=MODE1 or CD-DA, 1=MODE2)
               12  IS_MODE2_FORM2  (0=FORM1, 1=FORM2)
               13  IS_INTERLEAVED  (0=No, 1=Yes...?) (by file and/or channel?)
               14  IS_CDDA         (0=Data or ADPCM, 1=CD-DA Audio Track)
               15  IS_DIRECTORY    (0=File or CD-DA, 1=Directory Record)
             Commonly used Attributes are:
               0D55h=Normal Binary File (with 800h-byte sectors)
               1555h=VCD movie or Junk  (fade to black .DPS and .XA files)
               2555h=Uncommon           (wipeout .AV files) (MODE1 ??)
               4555h=CD-DA Audio Track  (wipeout .SWP files, alone .WAV file)
               3D55h=Streaming File     (ADPCM and/or MDEC or so)
               8D55h=Directory Record   (parent-, current-, or sub-directory)
  06h 2      Signature     ("XA")
  08h 1      File Number   (Must match Subheader's File Number)
  09h 5      Reserved      (00h-filled)
Directory sectors do usually have zeropadding at the end of each sector:
  - Directory sizes are always rounded up to N*800h-bytes.
  - Directory entries should not cross 800h-byte sector boundaries.
  There may be further directory entries on the next sector after the padding.
  To deal with that, skip 00h-bytes until finding a nonzero LEN_DR value (or
  slightly faster, upon a 00h-byte, directly jump to next sector instead of
  doing a slow byte-by-byte skip).
  Note: Padding between sectors does rarely happen on PSX discs because the
  PSX kernel supports max 800h bytes per directory (one exception is PSX Hot
  Shots Golf 2, which has an ISO directory with more than 800h bytes; it does
  use a lookup file instead of actually parsing the whole ISO directory).
Names are alphabetically sorted, no matter if the names refer to files or directories (ie. SUBDIR would be inserted between STRFILE.EXT and SYSFILE.EXT). The first two entries (with non-ascii names 00h and 01h) are referring to current and parent directory.

Path Tables
The Path Table contain a summary of the directory names (the same information is also stored in the directory records, so programs may either use path tables or directory records; the path tables are allowing to read the whole directory tree quickly at once, without neeeding to seek from directory to directory).
Path Table 1 is in Little-Endian format, Path Table 3 contains the same data in Big-Endian format. Path Table 2 and 4 are optional copies of Table 1 and 3. The size and location of the tables is stored in Volume Descriptor entries 084h..09Bh. The format of the separate entries within a Path Table is,
  00h 1       Length of Directory Name (LEN_DI) (01h..08h for PSX)
  01h 1       Extended Attribute Record Length  (usually 00h)
  02h 4       Directory Logical Block Number    (LBA)
  06h 2       Parent Directory Number           (0001h and up)
  08h LEN_DI  Directory Name (d-characters, d1-characters) (or 00h for Root)
  xxh 0..1    Padding Field (00h) (only if LEN_FI is odd)
The first entry (directory number 0001h) is the root directory, the root doesn't have a name, nor a parent (the name field contains a 00h byte, rather than ASCII text, LEN_DI is 01h, and parent is 0001h, making the root it's own parent; ignoring the fact that incest is forbidden in many countries).
The next entries (directory number 0002h and up) (if any) are sub-directories within the root (sorted in alphabetical order, and all having parent=0001h). The next entries are sub-directories (if any) of the first sub-directory (also sorted in alphabetical order, and all having parent=0002h). And so on.
PSX disks usually contain all four tables (usually on sectors 18,19,20,21).
Note: The Path Table contains only the starting LBA of the directories, but not their Size (however, the Size can be obtained by looking at the first entry in each directory; that with Name=00h, which contain info on the directory itself).

Format of an Extended Attribute Record (none such on PSX disks)
If present, an Extended Attribute Record shall be recorded over at least one Logical Block. It shall have the following contents.
  00h 4       Owner Identification (numerical value)  ;\used only if
  04h 4       Group Identification (numerical value)  ; File Flags Bit4=1
  08h 2       Permission Flags (16bit, little-endian) ;/
  0Ah 17      File Creation Timestamp      ("YYYYMMDDHHMMSSFF",timezone)
  1Bh 17      File Modification Timestamp  ("0000000000000000",00h)
  2Ch 17      File Expiration Timestamp    ("0000000000000000",00h)
  3Dh 17      File Effective Timestamp     ("0000000000000000",00h)
  4Eh 1       Record Format                (numerical value)
  4Fh 1       Record Attributes            (numerical value)
  50h 4       Record Length                (numerical value)
  54h 32      System Identifier            (a-characters, a1-characters)
  74h 64      System Use                   (not specified content)
  B4h 1       Extended Attribute Record Version (numerical value)
  B5h 1       Length of Escape Sequences   (LEN_ESC)
  B6h 64      Reserved for future standardization (00h-filled)
  F6h 4       Length of Application Use    (LEN_AU)
  FAh LEN_AU  Application Use
  xxh LEN_ESC Escape Sequences
Unknown WHERE that data is located... the Directory Records can specify the Extended Attribute Length, but not the location... maybe it's meant to be located in the first some bytes or blocks of the File or Directory...?


CDROM ISO Misc

Both Byte Order
All 16bit and 32bit numbers in the ISO region are stored twice, once in Little-Endian order, and then in Big-Endian Order. For example,
  2x16bit value 1234h     ---> stored as 34h,12h,12h,34h
  2x32bit value 12345678h ---> stored as 78h,56h,34h,12h,12h,34h,56h,78h
Exceptions are the 16bit Permission Flags which are stored only in Little-Endian format (although the flags are four 4bit groups, so that isn't a real 16bit number), and, the Path Tables are stored in both formats, but separately, ie. one table contains only Little-Endian numbers, and the other only Big-Endian numbers.

d-characters (Filenames)
  "0..9", "A..Z", and "_"

a-characters
  "0..9", "A..Z", SPACE, "!"%&'()*+,-./:;<=>?_"
Ie. all ASCII characters from 20h..5Fh except "#$@[\]^"

SEPARATOR 1 = 2Eh (aka ".") (extension; eg. "EXT")
SEPARATOR 2 = 3Bh (aka ";") (file version; "1".."32767")

Fixed Length Strings/Filenames
The Volume Descriptors contain a number fixed-length string/filename fields (unlike the Directory Records and Path Tables which have variable lengths). These fields should be padded with SPACE characters if they are empty, or if the string is shorter than the maximum length.
Filename fields in Volume Descriptors are referring to files in the Root Directory. On PSX disks, the filename fields are usually empty, but some disks are mis-using the Copyright Filename to store the Company Name (although no such file exists on the disk).

Volume Descriptor Timestamps
The various timestamps occupy 17 bytes each, in form of
  "YYYYMMDDHHMMSSFF",timezone
  "0000000000000000",00h         ;empty timestamp
The first 16 bytes are ASCII Date and Time digits (Year, Month, Day, Hour, Minute, Second, and 1/100 Seconds. The last byte is Offset from Greenwich Mean Time in number of 15-minute steps from -48 (West) to +52 (East); or actually: to +56 when recursing Kiribati's new timezone.
Note: There Y2K bugs. PSX games manufactured in year 2000 were accidently marked to be created in year 0000. And, "i-mode mo Issho - Doko Demo Issho Tsuika Disc" claims to be from year 1901.

Recording Timestamps
Occupy only 7 bytes, in non-ascii format
  year-1900,month,day,hour,minute,second,timezone
  00h,00h,00h,00h,00h,00h,00h    ;empty timestamp
The year ranges from 1900+0 to 1900+255.

File Flags
If this Directory Record identifies a directory then bit 2,3,7 shall be set to ZERO.
If no Extended Attribute Record is associated with the File Section identified by this Directory Record then bit positions 3 and 4 shall be set to ZERO.
  0  Existence       (0=Normal, 1=Hidden)
  1  Directory       (0=File, 1=Directory)
  2  Associated File (0=Not an Associated File, 1=Associated File)
  3  Record
        If set to ZERO, shall mean that the structure of the information in
        the file is not specified by the Record Format field of any associated
        Extended Attribute Record (see 9.5.8).
        If set to ONE, shall mean that the structure of the information in
        the file has a record format specified by a number other than zero in
        the Record Format Field of the Extended Attribute Record (see 9.5.8).
  4  Restrictions    (0=None, 1=Restricted via Permission Flags)
  5  Reserved        (0)
  6  Reserved        (0)
  7  Multi-Extent    (0=Final Directory Record for the file, 1=Not final)

Permission Flags (in Extended Attribute Records)
  0-3   Permissions for upper-class owners
  4-7   Permissions for normal owners
  8-11  Permissions for upper-class users
  12-15 Permissions for normal users
This is a bit bizarre, an upper-class owner is "an owner who is a member of a group of the System class of user". An upper-class user is "any user who is a member of the group specified by the Group Identification field". The separate 4bit permission codes are:
  Bit0  Permission to read the file    (0=Yes, 1=No)
  Bit1  Must be set (1)
  Bit2  Permission to execute the file (0=Yes, 1=No)
  Bit3  Must be set (1)


CDROM Extension Joliet

Typical Joliet Disc Header
The discs contains two separate filesystems, the ISO one for backwards compatibilty, and the Joliet one with longer filenames and Unicode characters.
  Sector 16 - Primary Volume Descriptor (with 8bit uppercase ASCII ISO names)
  Sector 17 - Secondary Volume Descriptor (with 16bit Unicode Joliet names)
  Sector 18 - Volume Descriptor Set Terminator
  Sector .. - Path Tables and Directory Records (for ISO)
  Sector .. - Path Tables and Directory Records (for Joliet)
  Sector .. - File Data Sectors (shared for ISO and Joliet)
There is no way to determine which ISO name belongs to which Joliet name (except, filenames do usually point to the same file data sectors, but that doesn't work for empty files, and doesn't work for folder names).
The ISO names can be max 31 chars (or shorter for compatibility with DOS short names: Nero does truncate them to max 14 chars "FILENAME.EXT;1", all uppercase, with underscores instead of spaces, and somehow assigning names like "FILENAMx.EXT;1" in case of duplicated short names).

Secondary Volume Descriptor (aka Supplementary Volume Descriptor)
This is using the same format as ISO Primary Volume Descriptor (but with some changed entries).
CDROM ISO Volume Descriptors
Changed entries are:
  000h 1     Volume Descriptor Type (02h=Supplementary instead of 01h=Primary)
  007h 1     Volume Flags           (whatever, instead of Reserved)
  008h 2x32  Identifier Strings     (16-char Unicode instead 32-char ASCII)
  058h 32    Escape Sequences       (see below, instead of Reserved)
  08Ch 4x4   Path Tables            (point to new tables with Unicode chars)
  09Ch 34    Root Directory Record  (point to root with Unicode chars)
  0BEh 4x128 Identifier Strings     (64-char Unicode instead 128-char ASCII)
  2BEh 3x37  Filename Strings       (18-char Unicode instead 37-char ASCII)
The Escape Sequences entry contains three ASCII chars (plus 29-byte zeropadding), indicating the ISO 2022 Unicode charset:
  %/@   UCS-2 Level 1
  %/C   UCS-2 Level 2
  %/E   UCS-2 Level 3

Directory Records and Path Tables
This is using the standard ISO format (but with 16bit Unicode characters instead of 8bit ASCII chars).
CDROM ISO File and Directory Descriptors

File and Directory Name Characters
All characters are stored in 16bit Big Endian format. The LEN_FI filename entry contains the length in bytes (ie. numchars*2). Characters 0000h/0001h are current/parent directory. Characters 0020h and up can be used for file/directory names, except six reserved characters: */:;?\
All names must be sorted by their character numbers, padded with zero (without attempting to merge uppercase, lowercase, or umlauts to nearby locations).

File and Directory Name Length
  max 64 chars according to original Joliet specs from 1995
  max 110 chars (on standard CDROMs, with LEN_SU=0)
  max 103 chars (on CD-XA discs, with LEN_SU=14)
Joliet Filenames include ISO-style version suffices (usually ";1", so the actual filename lengths are two chars less than shown above).
The original 64-char limit was perhaps intended to leave space for future extensions in the LEN_SU region. The 64-char limit can cause problems with verbose names (eg. "Interpreter - Title (version).mp3"). Microsoft later changed the limit to up to 110 chars.
The 110/103-char limit is caused by the 8bit "LEN_DR=(33+LEN_FI+pad+LEN_SU)" entry in the Directory Records.
Joliet allows to exceed the 8-level ISO directory nesting limit, however, it doesn't allow to exceed the 240-byte (120-Unicode-char) limit in ISO 9660 section 6.8.2.1 for the total "path\filename" lengths.

Official Specs
Joliet Specification, CD-ROM Recording Spec ISO 9660:1988, Extensions for Unicode Version 1; May 22, 1995, Copyright 1995, Microsoft Corporation
  http://littlesvr.ca/isomaster/resources/JolietSpecification.html


CDROM Problems and Repair

Testing
Use official pressed retail discs (without heavy scratches):
 - A PSX game disc (for the correct region)
 - A regular Audio disc to check if the drive can read anything at all
Don't rely on CDRs for testing. They may be burned at poor quality, they may decay over time, and they'll only work with modchips anyways.

Cleaning
A good first step is cleaning the lens. Wipe the lens with some liquid, make sure that there aren't any dust or tiny hairs.

Lubrication
That can reportedly help a lot. Check some PSX lubrication guides.
https://www.psxdev.net/forum/viewtopic.php?f=59&t=1113

Laser Adjustments
That's rather frowned upon and could make things worse.

Ed by Ed by
One common problem in old SCPH-100x models is the PSX booting up with the "Licensed by" string being replaced by "ed by ed by".
This is caused by a broken CXD1815Q chip (100pin, IC305, Decoder/FIFO). Replacing the chip with another CXD1815Q does fix the problem (CXD1199BQ are pin-compatible and do also work as replacement).
What is happening internally:
The drive and optics seem to be reading the license string just fine (including for passing through ECC error correction and EDC checksum without read errors). But the broken CXD chip is then somehow corrupting the data, and forwarding the broken string to the MIPS CPU.
The repeated "ed by" is caused by an invalid character in the licence string (the BIOS/GUI is converting the string into two texture snippets, "Licens" and "ed by"), and if there's an invalid char in one snippet then it's instead re-using the other snippet).
https://www.psxdev.net/forum/viewtopic.php?f=24&t=4326


CDROM File Formats

Official PSX File Formars
CDROM File Official Sony File Formats

Executables
CDROM File Playstation EXE and SYSTEM.CNF
CDROM File PsyQ .CPE Files (Debug Executables)
CDROM File PsyQ .SYM Files (Debug Information)
CDROM File COFF Files (Executable/Object with Debug/Linking Information)

Video Files
CDROM File Video Texture Image TIM/PXL/CLT (Sony)
CDROM File Video Texture/Bitmap (Other)
CDROM File Video 2D Graphics CEL/BGD/TSQ/ANM/SDF (Sony)
CDROM File Video 3D Graphics TMD/PMD/TOD/HMD/RSD (Sony)
CDROM File Video STR Streaming and BS Picture Compression (Sony)

Audio Files
CDROM File Audio Single Samples VAG (Sony)
CDROM File Audio Sample Sets VAB and VH/VB (Sony)
CDROM File Audio Sequences SEQ/SEP (Sony)
CDROM File Audio Other Formats
CDROM File Audio Streaming XA-ADPCM
CDROM File Audio CD-DA Tracks
CDROM File Audio MP3/ID3 Tags

Virtual Filesystem Archives
PSX titles are quite often using virtual filesystems, with numerous custom file archive formats.
CDROM File Archives with Filename
CDROM File Archives with Offset and Size
CDROM File Archives with Offset
CDROM File Archives with Size
CDROM File Archives with Chunks
CDROM File Archives with Folders
CDROM File Archives in Hidden Sectors
More misc stuff...
CDROM File Archive HED/DAT/BNS/STR (Ape Escape)
CDROM File Archive WAD.WAD, BIG.BIN, JESTERS.PKG (Crash/Herc/Pandemonium)
CDROM File Archive BIGFILE.BIG (Gex)
CDROM File Archive BIGFILE.DAT (Gex - Enter the Gecko)
CDROM File Archive FF9 DB (Final Fantasy IX)
CDROM File Archive Ace Combat 2 and 3
CDROM File Archive NSD/NSF (Crash Bandicoot 1-3)
CDROM File Archive STAGE.DIR and *.DAT (Metal Gear Solid)
CDROM File Archive DRACULA.DAT (Dracula)
CDROM File Archive Croc 1 (DIR, WAD, etc.)
CDROM File Archive Croc 2 (DIR, WAD, etc.)
CDROM File Archive Alien Resurrection (WAD)
CDROM File Archive Headerless Archives
Using archives can avoid issues with the PSX's poorly implemented ISO filesystem: The PSX kernel supports max 800h bytes per directory, and lacks proper caching for most recently accessed directories (additionally, some archives can load the whole file/directory tree from continous sectors, which could be difficult in ISO filesystems).

Compression
CDROM File Compression

Misc
CDROM File XYZ and Dummy/Null Files

FILENAME.EXT
The BIOS seems to support only (max) 8-letter filenames with 3-letter extension, typically all uppercase, eg. "FILENAME.EXT". Eventually, once when the executable has started, some programs might install drivers for long filenames(?)

The PSX uses the standard CDROM ISO9660 filesystem without any encryption (ie. you can put an original PSX CDROM into a DOS/Windows computer, and view the content of the files in text or hex editors without problems).

Note
MagDemoNN is short for "Official U.S. Playstation Magazine Demo Disc NN"


CDROM File Official Sony File Formats

Official Sony File Formats
https://psx.arthus.net/sdk/Psy-Q/DOCS/Devrefs/Filefrmt.pdf - Sony 1998
  File Formats
    (c) 1998 Sony Computer Entertainment Inc.
    Publication date: November 1998
  Chapter 1: Streaming Audio and Video Data
    STR: Streaming (Movie) Data                               1-3
    BS: MDEC Bitstream Data                                   1-8
    XA: CD-ROM Voice Data                                     1-31
  Chapter 2: 3D Graphics
    RSD: 3D Model Data [RSD,PLY,MAT,GRP,MSH,PVT,COD,MOT,OGP]  2-3
    TMD: Modeling Data for OS Library                         2-24
    PMD: High-Speed Modeling Data                             2-35
    TOD: Animation Data                                       2-40
    HMD: Hierarchical 3D Model, Animation and Other Data      2-49
  Chapter 3: 2D Graphics
    TIM: Screen Image Data                                    3-3
    SDF: Sprite Editor Project File                           3-8
    PXL: Pixel Image Data                                     3-11
    CLT: Palette Data                                         3-14
    ANM: Animation Information                                3-16
    TSQ: Animation Time Sequence                              3-22
    CEL: Cell Data                                            3-23
    BGD: BG Map Data                                          3-27
  Chapter 4: Sound
    SEQ: PS Sequence Data                                     4-3
    SEP: PS Multi-Track Sequence Data                         4-3
    VAG: PS Single Waveform Data                              4-5
    VAB: PS Sound Source Data [VAB and VH/VB]                 4-5
    DA: CD-DA Data                                            4-7
  Chapter 5: PDA and Memory Card
    FAT: Memory Card File System Specification                5-3
Most games are using their own custom file formats. However, VAG, VAB/VH/VB, STR/XA, and TIM are quite popular (because they are matched to the PSX low-level data encoding). Obviously, EXE is also very common (although not officially described in Sony's document).


CDROM File Playstation EXE and SYSTEM.CNF

SYSTEM.CNF
Contains boot info in ASCII/TXT format, similar to the CONFIG.SYS or AUTOEXEC.BAT files for MSDOS. A typical SYSTEM.CNF would look like so:
  BOOT = cdrom:\abcd_123.45;1 arg ;boot exe (drive:\path\name.ext;version)
  TCB = 4                         ;HEX (=4 decimal)   ;max number of threads
  EVENT = 10                      ;HEX (=16 decimal)  ;max number of events
  STACK = 801FFF00                ;HEX (=memtop-256)
The first line specifies the executable to load, from the "cdrom:" drive, "\" root directory, filename "abcd_123.45" (case-insensitive, the real name in the disk directory would be uppercase, ie. "ABCD_123.45"), and, finally ";1" is the file's version number (a rather strange ISO-filesystem specific feature) (the version number should be usually/always 1). Additionally, "arg" may contain an optional 128-byte command line argument string, which is copied to address 00000180h, where it may be interpreted by the executable (most or all games don't use that feature).
Each line in the file should be terminated by 0Dh,0Ah characters... not sure if it's also working with only 0Dh, or only 0Ah...?
The "=" may or may not include spaces (eg. "=" or " = ").
The last line may end with anything like 0Dh,0Ah,0Dh,0Ah, or 0Dh,0Ah,1Ah, or 0Dh,0Ah.

ABCD_123.45
This is a normal executable (exactly as for the .EXE files, described below), however, the filename/extension is taken from the game code (the "ABCD-12345" text that is printed on the CD cover), but, with the minus replaced by an underscore, and due to the 8-letter filename limit, the last two characters are stored in the extension region.
That "XXXX_NNN.NN" naming convention seems to apply for all official licensed PSX games. Wild Arms does unconventionally have the file in a separate folder, "EXE\SCUS_946.06".

PSX.EXE (Boot-Executable) (default filename when SYSTEM.CNF doesn't exist)
XXXX_NNN.NN (Boot-Executable) (with filename as specified in SYSTEM.CNF)
FILENAME.EXE (General-Purpose Executable)
PSX executables are having an 800h-byte header, followed by the code/data.
  000h-007h ASCII ID "PS-X EXE"
  008h-00Fh Zerofilled
  010h      Initial PC                   (usually 80010000h, or higher)
  014h      Initial GP/R28               (usually 0)
  018h      Destination Address in RAM   (usually 80010000h, or higher)
  01Ch      Filesize (must be N*800h)    (excluding 800h-byte header)
  020h      Unknown/Unused ;Addr         (usually 0)  ;\optional overlay?
  024h      Unknown/Unused ;Size         (usually 0)  ;/(not auto-loaded)
  028h      Memfill Start Address        (usually 0) (when below Size=None)
  02Ch      Memfill Size in bytes        (usually 0) (0=None)
  030h      Initial SP/R29 & FP/R30 Base (usually 801FFFF0h) (or 0=None)
  034h      Initial SP/R29 & FP/R30 Offs (usually 0, added to above Base)
  038h-04Bh Reserved for A(43h) Function (should be zerofilled in exefile)
  04Ch-xxxh ASCII marker
             "Sony Computer Entertainment Inc. for Japan area"         ;NTSC
             "Sony Computer Entertainment Inc. for Europe area"        ;PAL
             "Sony Computer Entertainment Inc. for North America area" ;NTSC
             (or often zerofilled in some homebrew files)
             (the BIOS doesn't verify this string, and boots fine without it)
  xxxh-7FFh Zerofilled
  800h...   Code/Data                  (loaded to entry[018h] and up)
The code/data is simply loaded to the specified destination address, ie. unlike as in MSDOS .EXE files, there is no relocation info in the header.
Note: In bootfiles, SP is usually 801FFFF0h (ie. not 801FFF00h as in system.cnf). When SP is 0, the unmodified caller's stack is used. In most cases (except when manually calling DoExecute), the stack values in the exeheader seem to be ignored though (eg. replaced by the SYSTEM.CNF value).
The memfill region is zerofilled by a "relative" fast word-by-word fill (so address and size must be multiples of 4) (despite of the word-by-word filling, still it's SLOW because the memfill executes in uncached slow ROM).
The reserved region at [038h-04Bh] is internally used by the BIOS to memorize the caller's RA,SP,R30,R28,R16 registers (for some bizarre reason, this information is saved in the exe header, rather than on the caller's stack).
Additionally to the initial PC,R28,SP,R30 values that are contained in the header, two parameter values are passed to the executable (in R4 and R5 registers) (however, usually that values are simply R4=1 and R5=0).
Like normal functions, the executable can return control to the caller by jumping to the incoming RA address (provided that it hasn't destroyed the stack or other important memory locations, and that it has pushed/popped all registers) (returning works only for non-boot executables; if the boot executable returns to the BIOS, then the BIOS will simply lockup itself by calling the "SystemErrorBootOrDiskFailure" function.

Relocatable EXE
Fade to Black (CINE.EXR) contains ID "PS-X EXR" (instead "PS-X EXE") and string "PSX Relocable File - Delphine Software Int.", this is supposedly some custom relocatable exe file (unsupported by the PSX kernel).

MSDOS.EXE and WINDOWS.EXE Files
Some PSX discs contain DOS or Windows .EXE files (with "MZ" headers), eg. devkit leftovers, or demos/gimmicks.


CDROM File PsyQ .CPE Files (Debug Executables)

Fileheader
  00h 4   File ID (01455043h aka "CPE",01h)

Chunk 00h: End of File
  00h 1   Chunk ID (00h)

Chunk 01h: Load Data
  00h 1   Chunk ID (01h)
  01h 4   Address (usually 80010000h and up)
  05h 4   Size (LEN)
  09h LEN Data (binary EXE code/data)
Theoretically, this could contain the whole EXE body in a single chunk. However, the PsyQ files are usually containing hundreds of small chunks (with each function and each data item in a separate chunk). For converting CPE to EXE, use "ExeOffset = (CpeAddress AND 1FFFFFFFh)-10000h+800h".

Chunk 02h: Run Address (whatever, optional, usually not used in CPE files)
  00h 1   Chunk ID (02h)
  01h 4   Address
Unknown what this is. It's not the entrypoint (which is set via chunk 03h). Maybe intended to change the default load address (usually 80010000h)?

Chunk 03h: Set Value 32bit (LEN=4) (used for entrypoint)
Chunk 04h: Set Value 16bit (LEN=2) (unused)
Chunk 05h: Set Value 8bit (LEN=1) (unused)
Chunk 06h: Set Value 24bit (LEN=3) (unused)
  00h 1   Chunk ID (03h..06h)
  01h 2   Register (usually 0090h=Initial PC, aka Entrypoint)
  03h LEN Value (8bit..32bit)

Chunk 07h: Select Workspace (whatever, optional, usually not used in CPE)
  00h 1   Chunk ID (07h)
  01h 4   Workspace number (usually 00000000h)

Chunk 08h: Select Unit (whatever, usually first chunk in CPE file)
  00h 1   Chunk ID (08h)
  01h 1   Unit (usually 00h)

Example from LameGuy's sample.cpe:
  0000h 4    File ID ("CPE",01h)
  0004h 2    Select Unit 0            (08h,00h)
  0006h 7    Set Entrypoint 8001731Ch (03h,0090h,8001731Ch)
  000Dh 0Dh  Load   (01h,800195F8h,00000004h,0,0,0,0)
  001Ah ..   Load   (01h,80010000h,0000002Bh,...)
  004Eh ..   Load   (01h,8001065Ch,00000120h,...)
  0177h ...  Load   (01h,8001077Ch,0000012Ch,...)
  02ACh ...  Load   (01h,800108A8h,000000A4h,...)
  ...   ...  Load   (...)
  98F4h ...  Load   (01h,800195F0h,00000008h,...)
  9905h 1    End    (00h)


CDROM File PsyQ .SYM Files (Debug Information)

PsyQ .SYM Files contain debug info, usually bundled with PsyQ .MAP and Psy .CPE files. Those files are generated by PsyQ tools, which appear to be still in use for homebrew PSX titles.
The files are occassionally also found on PSX CDROMs:
  Legacy of Kain PAL version (\DEGUG\NTSC\KAIN2.SYM+MAP+CPE)
  RC Revenge (\RELEASE.SYM)
  Twisted Metal: Small Brawl (MagDemo54: TMSB\TM.SYM)
  Jackie Chan Stuntmaster (GAME_REL.SYM+CPE)
  SnoCross Championship Racing (MagDemo37: SNOCROSS\SNOW.TOC\SNOW.MAP)
  Sled Storm (MagDemo24: DEBUG\MAIN.MAP)
  E.T. Interplanetary Mission (MagDemo54: MEGA\MEGA.CSH\* has SYM+CPE+MAP)

Fileheader .SYM
  00h 4  File ID ("MND",01h)
  04h 4  Whatever (0,0,0,0)    ;TOMB5: 0,02h,0,0
  08h .. Chunks (see below)


 _______________________________ Symbol Chunks ________________________________

Chunk 01h: Symbol (Immediate, eg. memsize, or membase)
Chunk 02h: Symbol (Function Address for Internal & External Functions)
Chunk 05h: Symbol (?)
Chunk 06h: Symbol (?)
  00h 4   Address/Value
  04h 1   Chunk ID (01h/02h/05h/06h)
  05h 1   Symbol Length (LEN)
  06h LEN Symbol (eg. "VSync")


 __________________________ Source Code Line Chunks ___________________________

Chunk 80h: Source Code Line Numbers: Address for 1 Line
  00h 4   Address (for 1 line, starting at current line)
  04h 1   Chunk ID (80h)

Chunk 82h: Source Code Line Numbers: Address for N Lines (8bit)
  00h 4   Address (for N lines, starting at current line)
  04h 1   Chunk ID (82h)
  05h 1   Number of Lines (00h=None, or 02h and up?)

Chunk 84h: Source Code Line Numbers: Address for NN Lines (16bit)
  00h 4   Address (for N lines, starting at current line)
  04h 1   Chunk ID (84h)
  05h 2   Number of Lines (?)

Chunk 86h: Source Code Line Numbers: Address for Line NNN (32bit?)
  00h 4   Address (for 1 line, starting at newly assigned current line)
  04h 1   Chunk ID (84h)
  05h 4   Absolute Line Number (rather than number of lines) (?)

Chunk 88h: Source Code Line Numbers: Start with Filename
  00h 4   Address (start address)
  04h 1   Chunk ID (88h=Filename)
  05h 4   First Line Number (after comments/definitions) (32bit?)
  09h 1   Filename Length (LEN)
  0Ah LEN Filename (eg. "C:\path\main.c")

Chunk 8Ah: Source Code Line Numbers: End of Source Code
  00h 4   Address (end address)
  04h 1   Chunk ID (8Ah)


 __________________________ Internal Function Chunks __________________________

Chunk 8Ch: Internal Function: Start with Filename
  00h 4    Address
  04h 1    Chunk ID (8Ch)
  05h 4    Whatever (1Eh,00h,20h,00h)  ;or 1Eh,00h,18h,00h
  09h 4    Whatever (00h,00h,1Fh,00h)
  0Dh 4    Whatever (00h,00h,00h,C0h)
  11h 4    Whatever (FCh,FFh,FFh,FFh)  ;mask? neg.offset?
  15h 4    Whatever (10h,00h,00h,00h)  <-- line number (32bit?)
  19h 1    Filename Length (LEN1)
  1Ah LEN1 Filename (eg. "C:\path\main.c")
  xxh 1    Symbol Length (LEN2)
  xxh LEN2 Symbol (eg. "VSync")

Chunk 8Eh: Internal Function: End of Function (end of chunk 8Ch)
  00h 4   Address
  04h 1   Chunk ID (8Eh)
  05h 4   Line Number                 <-- line number (32bit?)

Chunk 90h: Internal Function:Whatever90h... first instruction in main func?
Chunk 92h: Internal Function:Whatever92h... last instruction in main func?
Maybe line numbers? Or end of definitions for incoming parameters?
  00h 4   Address
  04h 1   Chunk ID (90h/92h)
  05h 4   Whatever (1Fh,00h,00h,00h)  <-- line number relative to main.start?


 _____________________________ Class/Type Chunks ______________________________

Chunk 94h: Type/Symbol (Simple Types?)
  00h 4   Offset (when used within a structure, or stack-N, or otherwise zero)
  04h 1   Chunk ID (94h)
  05h 2   Class (000Dh=Type.alias, 000Ah=Address, 0001h=Stack, 0002h=Addr)
  07h 2   Type (XX = 8bit,16bit,signed,etc.?)
  09h 4   Zero, or Size in Bytes (for "memblocks")
  0xh 1   Symbol Name Length (LEN)
  0xh LEN Symbol Name (eg. "size_t")

Chunk 96h: Type/Symbol (Complex Structures/Arrays?)
  00h 4   Offset (when used within a structure, otherwise zero)
  04h 1   Chunk ID (96h)
  05h 2   Class (02h=Array,08h=RefToStruct,0Dh=DefineAlias,66h=StructEnd)
  07h 2   Type (0xh=Small, 3xh=WithArrayStuff?) (same/similar as in chunk 94h)
  09h 4     Struct Size in Bytes
  0Dh 2     Array Dimensions (DIM) (0=none) ;eg. [3][4] --> 0002h
  0Fh DIM*4 Array Entries per Dimension     ;eg. [3][4] --> 00000003h,00000004h
  xxh 1     Internal Fake Name Length (LEN1) (0=none)
  xxh LEN1  Internal Fake Name  (eg. ".1fake")
  xxh 1     Symbol Name Length (LEN2)
  xxh LEN2  Symbol Name (eg. "r")


 ______________________________ Class/Type Values _____________________________

Class definition (in chunk 94h) (and somewhat same/similar in chunk 96h)
(looks same/similar as C_xxx class values in COFF files!)
  0001h = Local variable              (with Offset = negative stack offset)
  0002h = Global variable or Function (with Offset = address)
  0008h = Item in Structure           (with Offser = offset within struct)
  0009h = Incoming Function param     (with Offset = index; 0,4,8,etc.)
  000Ah = Type address / struc start? (with Offset = zero)
  000Dh = Type alias                  (with Offset = zero)

Type definition (in chunk 94h/96h)
(maybe lower 4bit=type, and next 4bit=usage/variant?)
(looks same/similar as T_xxx type values in COFF files!)
  0000h =
  0001h =
  0002h =
  0003h =                (16bit signed?)
  0004h = int            (32bit signed?)
  0005h =
  0006h =
  0007h =
  0008h = (address)      (32bit unsigned?) (with Definition=000Ah)
  0009h =
  000Ah =
  000Bh =
  000Ch = u_char         (8bit unsigned?)
  000Dh = u_short,ushort (16bit unsigned?)
  000Eh = u_int          (32bit unsigned?)
  000Fh = u_long         (64bit unsigned?) (or rather SAME as above?)
  0021h = function with 0 params, and/or return="nothing"?
  0024h = main function with 2 params, and/or return="int"?
  0052h = argv           (string maybe?)
  0038h = GsOT           (huh?)
  00F8h = GsOT_TAG       (huh?)
  00FCh = PACKET         (huh?)
  ??    = float,bool,string,ptr,packet,(un-)signed8/16/32/64bit,etc
  ??    = custom type/struct (using value 000xh plus "fake" name, or so?)


 __________________________________ .MAP File _________________________________

PsyQ .MAP File
The .SYM file is usually bundled with a .MAP file, which is containing a summary of the symbolic info as ASCII text (but without info on line numbers or data types). For example:
    Start     Stop   Length      Obj Group            Section name
 80010000 80012D5B 00002D5C 80010000 text             .rdata
 80012D5C 800C8417 000B56BC 80012D5C text             .text
 800C8418 800CDAB7 000056A0 800C8418 text             .data
 800CDAB8 800CFB63 000020AC 800CDAB8 text             .sdata
 800CFB64 800D5C07 000060A4 800CFB64 bss              .sbss
 800D5C08 800DD33F 00007738 800D5C08 bss              .bss


  Address  Names alphabetically
 800CFE80 ACE_amount
 800CFB94 AIMenu
 800CDE5C AXIS_LENGTH
 8005E28C AddClippedTri
 8005DFEC AddVertex
 ...


  Address  Names in address order
 00000000 _cinemax_obj
 00000000 _cinemax_header_org
 00000000 _cinemax_org
 00000000 _mcardx_sbss_size
 00000000 _mcardx_org
 ...


CDROM File COFF Files (Executable/Object with Debug/Linking Information)

The PSX is using ECOFF in PSX-SDK (Programmer Tool CDROM), and in official (and homebrew) Net Yaroze Demo CDROMs:
  PSX-SDK (PSYQ\BIN\CLEANMEM and PFLASH)       ;ECOFF little-endian
  PSX-SDK (3RDPARTY\METROWER\SCELIB*\LIB\*.O)  ;ECOFF big-endian !!
  PSX-SDK (PSYQ\BIN\EMU387)  ;for i386         ;COFF (not a playstation binary)
  PSX Net Yaroze (DATA\*\*.FPC\*)              ;ECOFF with TargetID=0162h
  PSX Net Yaroze (DATA\EDGE\*.FPC\OUT.COF)     ;ECOFF corrupt TargetID=0000h
  PSX Net Yaroze (DATA\JAPAN\TERRAI.FPC\*.EXE) ;ECOFF corrupt lacks symtab

CDROM File COFF Files - Overview, Endianness, Detection
CDROM File COFF Files - File Header and Target Machine IDs
CDROM File COFF Files - Optional A.OUT Header
CDROM File COFF Files - Section, Relocation, Line Numbers, Strings
CDROM File COFF Files - Symbol Table
CDROM File COFF Files - References


CDROM File COFF Files - Overview, Endianness, Detection

COFF files contain executables or linker object files with optional debug/linking information (eg. symbols and source code line numbers).
The COFF format was based on older A.OUT format, and was later replaced by ELF. Netherless, COFF is kept in use here and there, including several extensions like ECOFF, TICOFF, XCOFF, plus variants for 32bit or 64bit processors. Being a UNIX based format, it's common to see documentation and source code to use OCTAL numbers (especially in the A.OUT header).

COFF File Structure
  At begin of File                                 File Header
  After File Header                                Optional A.OUT Header
  After Optional A.OUT Header                      Section Header
  At location(s) stored in Section Header entries  Section Data
  At location(s) stored in Section Header entries  Relocation
  At location(s) stored in Section Header entries  Line Numbers
  At location stored in File Header                Symbol Table
  After Symbol Table                               String Table

Endianness
COFF uses undefined endianness. Little-endian appears to be most common. One might also expect the endianness of the executable to match up with that of the COFF headers, however it can mismatch in case of cross-platform development (for example, little-endian Playstation binaries were developed on different computers, some of them using big-endian ECOFF headers).
For detecting the endianess, FileHeader[010h] should be usually 001Ch..0050h, if it reads 1C00h..5000h then the endianess needs to be swapped (theoretically that value could be 0000h, which would require different detection).

Detection
COFF doesn't have any meaningful file ID or file extension, that makes detection difficult: First of, detect the endianess (see above). Then, one could check for a list of known Target IDs (the problem is that there are more than 100 known IDs, and probably more unknown ones). Checking FileHeader[010h] for known values (001Ch, 0038h, 0050h) may be more reliable.
To avoid mis-detection, one should also do error checking on the A.OUT header and Section Headers (eg. the offset and size values shouldn't exceed the size of the COFF file) (but be careful: some files have stripped away symbol tables, but still contain the symtab address and size in FileHeader) (and mind that variants like ECOFF or TICOFF or 64bit require different error checking).


CDROM File COFF Files - File Header and Target Machine IDs

COFF File Header (14h bytes)
  000h 2     Target Machine ID (see below list)
  002h 2     Number of Sections
  004h 4     Timestamp (seconds since 1970)
  008h 4     Symbol Table Offset            (0=None)
  00Ch 4     Symbol Table Number of Entries (0=None)
  010h 2     Optional A.OUT Header Size (usually 001Ch)
  012h 2     Flags

ECOFF File Header (14h bytes)
  000h 08h   Same as standard COFF File Header (see above)
  008h 4     Symbol Table Offset (same as COFF, but uses different format)
  00Ch 4     Symbol Table Header Size (0=None, 60h=ECOFF32) (not Num Entries!)
  010h 2     Optional A.OUT Header Size (usually 38h=ECOFF32, xxh=ECOFF64)
  012h 2     Flags

TICOFF File Header (16h bytes)
  000h 2     TICOFF ID (00C1h=TICOFF1, or 00C2h=TICOFF2)
  002h 12h   Same as standard COFF File Header (see above)
  014h 2     Target Machine ID (located here, instead at [000h])

Target Machine IDs
  0000h pe.h      Unknown (Net Yaroze Demo Disc DATA\EDGE\*.FPC\OUT.COF)
  0088h m68k.h    Motorola 68K? M68      (0210 octal)
  0089h m68k.h    Motorola 68K? M68TV    (0211 octal)
  0097h spraao8   Texas Instruments TMS470
  0098h tic54x.h  Texas Instruments TMS320C5400  TMS320C54X
  0099h spraao8   Texas Instruments TMS320C6000
  009Ch spraao8   Texas Instruments TMS320C5500
  009Dh spraao8   Texas Instruments TMS320C2800
  00A0h maxq.h    MAXQ (whatever that is)
  00A0h spraao8   Texas Instruments MSP430
  00A1h spraao8   Texas Instruments TMS320C5500+
  00A4h psxspx    COFF Xpert Teak DSP (used in Nintendo DSi Sound)
  00C1h ti.h      Texas Instruments TICOFF1 (with TargetID in FileHdr[14h])
  00C2h ti.h      Texas Instruments TICOFF2 (with TargetID in FileHdr[14h])
  0093h tic4x.h   Texas Instruments TMS320C4X/C3X
  0095h tic80.h   Texas Instruments TMS320C80 (MVP)
  010Dh *.h       Lynx all-platform (i386.h, m68k.h, sparc.h) (0415 octal)
  0140h ecoff.h   ECOFF32 MIPS ISA level 3 big-endian
  0142h ecoff.h   ECOFF32 MIPS ISA level 3 little-endian
  014Ch i386.h    Intel i386 (386/486) (pe.h)
  014Dh i860.h    Intel i860 (with AOUTSZ=32)
  0150h m68k.h    Motorola 68K MC68KWR (0520 octal) writeable text segments
  0151h m68k.h    Motorola 68K MC68KRO (0521 octal) readonly shareable text seg
  0152h m68k.h    Motorola 68K MC68KPG (0522 octal) demand paged text segments
  0154h i386.h    Intel 386/486 (I386PTX)
  0156h m68k.h    Motorola 68K MC68KBCS Bull dpx/2   (0526 octal)
  0160h i960.h    Intel 80960 read-only text segments  (with AOUTHDRSZ=32)
  0160h m88k.h    Motorola 88k - 88k BCS executable (0540 octal)
  0160h sparc.h   Sparc (0540 octal)
  0160h ecoff.h   ECOFF32 MIPS R3000 big-endian
  0161h i960.h    Intel 80960 read/write text segments (with AOUTHDRSZ=32)
  0161h m88k.h    Motorola 88k - DG/UX executable (0541 octal)
  0162h ecoff.h   ECOFF32 MIPS R3000 little-endian (pe.h, PSX-SDK, Net Yaroze)
  0163h ecoff.h   ECOFF32 MIPS R4000 ISA level 2 big-endian
  0166h ecoff.h   ECOFF32 MIPS R4000 ISA level 2 little-endian (pe.h, mipspe.h)
  0168h pe.h      ECOFF?? MIPS R10000 ?
  0169h pe.h      ECOFF?? MIPS WCE v2 ?
  016Dh m88k.h    Motorola 88k - Object file (0555 octal)
  0170h we32k.h   we32k without transfer vector
  0171h we32k.h   we32k with transfer vector
  0172h we32k.h   we32k reserved
  0175h i386.h    Intel 386/486 (I386AIX)
  017Ah a29k.h    AMD Am29000 (Byte 0 is MSB) (0572 octal) (a29k.h, or32.h)
  017Bh a29k.h    AMD Am29000 (Byte 0 is LSB) (0573 octal) (a29k.h, or32.h)
  0180h ecoff.h   ECOFF?? MIPS ?
  0183h ecoff.h   ECOFF64 Alpha                             (0603 octal)(Tru64)
  0184h magdir    ECOFF?? Alpha 32-bit (pe.h)
  0185h ecoff.h   ECOFF64 Alpha BSD
  0188h ecoff.h   ECOFF64 Alpha compressed by DEC's tools   (0610 octal)(Tru64)
  018Fh tru64     ECOFF?? Alpha Ucode object file, obsolete (0617 octal)(Tru64)
  0197h apollo.h  Apollo M68K (0627 octal)
  01A2h sh.h      Hitachi SH3 (little-endian Windows CE) (pe.h)
  01A3h magdir    Hitachi SH3 DSP (pe.h)
  01A4h magdir    Hitachi SH4E (pe.h)
  01A6h magdir    Hitachi SH4 (pe.h)
  01A8h magdir    Hitachi SH5 (pe.h)
  01C0h arm.h     ARMv4  (without THUMB) (pe.h)
  01C2h arm.h     ARMv4T (with THUMB) (pe.h)
  01C4h magdir    ARMv7
  01D3h magdir    Matsushita AM33 (pe.h)
  01D8h rs6000.h  XCOFF IBM RS/6000 writeable text segments **chh**(0730 octal)
  01DDh rs6000.h  XCOFF IBM RS/6000 readonly sharable text segments(0735 octal)
  01DFh rs6000.h  XCOFF IBM RS/6000 readonly text segments and TOC (0737 octal)
  01EFh rs6k64.h  XCOFF Aix 4.3 64-bit   ;AOUTHDRSZ=72, AOUTSZ=120 (0757 octal)
  01F0h pe.h      PowerPC 32-bit, little-endian
  01F1h pe.h      PowerPC 32-bit, little-endian, with FPU
  01F2h magdir    PowerPC 64-bit, big-endian
  01F7h rs6k64.h  XCOFF AIX 5+ 64-bit    ;AOUTHDRSZ=72, AOUTSZ=120 (0767 octal)
  0200h ia64.h    Intel/HP Itanium IA-64 https://bdsmovement.net/boycott-hp
  0266h magdir    MIPS16 (pe.h)
  0268h magdir    Motorola 68000 (pe.h)
  0284h magdir    Alpha 64-bit (pe.h)
  0290h magdir    PA-RISC
  0366h magdir    MIPS with FPU (pe.h)
  0466h magdir    MIPS16 with FPU (pe.h)
  0500h sh.h      Hitachi SH (big-endian)
  0520h pe.h      Tricore
  0550h sh.h      Hitachi SH (little-endian)
  0601h magdir    PowerPC 32-bit (big-endian)
  0CEFh magdir    Windows CE Common Executable Format (pe.h)
  0EBCh magdir    EFI byte code (pe.h)
  3A64h magdir    ARM64 (i386 ABI)
  5032h magdir    RISC-V 32-bit
  5064h magdir    RISC-V 64-bit
  5128h magdir    RISC-V 128-bit
  6232h magdir    LoongArch 32-bit
  6264h magdir    LoongArch 64-bit
  6500h w65.h     WDC 65816
  8000h z8k.h     Zilog Z800N
  8300h h8300.h   Hitachi/Renesas H8/300
  8301h h8300.h   Hitachi/Renesas H8/300-H
  8302h h8300.h   Hitachi/Renesas H8/300-S
  8303h h8300.h   Hitachi/Renesas H8/300-HN
  8304h h8300.h   Hitachi/Renesas H8/300-SN
  8500h h8500.h   Hitachi/Renesas H8/500
  8664h magdir    x86-64, AMD64 (pe.h)
  9041h magdir    Mitsubishi M32R (pe.h)
  A641h magdir    ARM64 (x86-64 ABI)
  A64Eh magdir    ARM64 (classic + x86-64 ABI)
  AA64h magdir    ARM64
  ACE1h magdir    OMNI VM (omniprox.dll)
  C000h tic30.h   Texas Instruments TMS320C3X (hmm, maybe endian-swap = 00C0h?)
  C0EEh magdir    COM+ Execution Engine CEE (in object files) (pe.h)
  -     xcoff.h   XCOFF
  -     mcore.h   Motorola MCore
  stub  go32.h    PC running go32 (with 2048-byte stub before COFF hdr)
Duplicated IDs are 00A0h,0160h,0161h.

References for Target Machine IDs
https://opensource.apple.com/source/gdb/gdb-1708/src/include/coff/ (see *.h)
https://raw.githubusercontent.com/file/file/master/magic/Magdir/coff


CDROM File COFF Files - Optional A.OUT Header

The A.OUT Header is somewhat based on older A.OUT files. It is sometimes referred to as "Optional Header", although it's usually always present in COFF files (except, Microsoft wants the A.OUT header to be included only in executable files, not in object files).

COFF a.out header (1Ch bytes)
  000h 2  Aout Type ID (see below)
  002h 2  Version stamp
  004h 4  CODE Size (text size)
  008h 4  DATA Size (initialized data size)
  00Ch 4  BSS Size  (uninitialized data size)
  010h 4  Entrypoint Address
  014h 4  CODE Start Address
  018h 4  DATA Start Address

ECOFF32 a.out header 32bit (MIPS)
  000h 2  Aout Type ID (see below)             ;\
  002h 2  Version stamp                        ;
  004h 4  CODE Size (text size)                ; same as COFF
  008h 4  DATA Size (initialized data size)    ;
  00Ch 4  BSS Size  (uninitialized data size)  ;
  010h 4  Entrypoint Address                   ;
  014h 4  CODE Start Address                   ;
  018h 4  DATA Start Address                   ;/
  01Ch 4  BSS Start Address                    ;\
  020h 4  coff_uint   gpr mask       A000077Eh ; extra stuff
  024h 4  coff_word   cpr mask cop 0 00000000h ; (including flags for general
  028h 4  coff_word   cpr mask cop 1 00000000h ; purpose CPU registers and
  02Ch 4  coff_word   cpr mask cop 2 00000000h ; coprocessor registers)
  030h 4  coff_word   cpr mask cop 3 00000000h ;
  034h 4  coff_long   gp value       001080D0h ;/ <-- what for?

ECOFF64 a.out header 64bit (Alpha)
  000h 2  Aout Type ID (see below)             ;\same as COFF
  002h 2  Version stamp                        ;/
  004h 2  Revision (bldrev)                    ;\extra stuff
  006h 2  Unused (padding)                     ;/
  008h 8  CODE Size (text size)                ;\
  010h 8  DATA Size (initialized data size)    ;
  018h 8  ...coff_long size   ;or bss_size?    ; as ECOFF32, but 64bit wide
  020h 8  Entrypoint Address                   ;
  028h 8  CODE Start Address                   ;
  030h 8  DATA Start Address                   ;
  038h 8  BSS Start Address                    ;/
  040h 4  coff_uint gprmask  (CPU registers)   ;\as ECOFF32, but only 1 copro
  044h ?  coff_word fprmask  (FPU registers)   ;/
  048h 8  coff_long gp_value                   ;-as ECOFF32, but 64bit wide
See also: ia64.h and pe.h, which seem to say AOUTHDRSZ = 108 ?

Aout Type IDs (in AoutHeader[000h])
  0101h (0401 octal)  ARM/SPARC target shlib    (arm.h, sparc.h)
  0104h (0404 octal)  ARM/SPARC object files    (arm.h, sparc.h)
  0107h (0407 octal)  Impure (not demand paged) (*.h)
  0108h (0410 octal)  Pure (also TICOFF)        (*.h)
  010Bh (0413 octal)  Demand paged              (*.h)
  0111h (0421 octal)  Standalone                (*.h)
  0123h (0443 octal)  target shared lib (m68k.h), host shlib (arm.h, sparc.h)
  020Bh (1103 octal)  32-bit image inside 64-bit address space (ia64.h)
  0901h (4401 octal)  Whatever (in Nintendo DSi Sound)


CDROM File COFF Files - Section, Relocation, Line Numbers, Strings

COFF: Section Header(s)
  000h 8    Section Name (max 8 chars, or reference to String Table)
  008h 4    Physical address, aliased s_nlib
  00Ch 4    Virtual address
  010h 4    Section size
  014h 4    File ptr to raw data for section
  018h 4    File ptr to relocation
  01Ch 4    File ptr to line numbers
  020h 2    Number of relocation entries
  022h 2    Number of line number entries
  024h 4    Flags
ECOFF32 uses same Section Header as above, but with "Line Numbers" renamed to "gp histogram" (whatever that is).
ECOFF64 is supposedly similar, but with some 32bit entries replaced by 64bit entries

COFF: Relocation Directives
  000h 4    Address of relocation
  004h 4    Symbol we're adjusting for
  008h 2    Type of relocation (6=ADDR32, 20=REL32)

COFF: Line Numbers
  000h 4    Function name symbol index (when lnno=0)    ... to Symbol Table?
            Address of line number (when lnno=1..N)
  004h 2    Line number within function (or 0=see above)

COFF: String Table (for strings longer than 8 chars)
  000h 4    Size of string table (N)
  004h N-4  String(s), terminated by 00h each
Strings are used for Section Names (in Section Headers), and for names of Functions, Variables, Constants (in Symbol Table). Both Sections and Symbols are using 8-byte entries that can contain strings with 0..8 characters (zeropadded if less than 8 chars). Longer strings are storing a reference to the String Table in those 8-byte entries; there are two ways for doing that:
  Name[0..3]=00000000h, with Name[4..7]=32bit Index in String Table, or
  Name[0..7]="/NNN",zeropadding (ASCII, with NNN=Decimal Index in String Table)
In both cases, the Index should be 4 or higher (because the first 4 bytes of the Symbol Table contain a size entry), Index=0 should be treated as empty string.


CDROM File COFF Files - Symbol Table

Below if for COFF only (ECOFF is somewhat different, starting with a Symbol Table Header, followed by actual symbol entries).

COFF: Symbol Table
  000h 8  Symbol Name (max 8 chars, or reference to String Table)
  008h 4  Symbol Value (depends of Type, eg. the address, if it's a label)
  00Ch 2  Section Number (1..N) (or special values)
             0000h     Undefined (extern) Symbol
             0001h..N  Symbol belongs to Section 1..N
             FFFEh     Debugging Symbol                                  ;\blah
             FFFFh     Absolute Symbol (a constant, not an address)      ;/
  00Eh 2  e_type
  010h 1  e_sclass
  011h 1  e_numaux

e_type - symbol type
The type of the symbol. This is made up of a base type and a derived type. For example, "pointer to int" is "pointer to T" and "int".
  Type      Bits            Meaning
  T_NULL    ---- 0000  00h  No symbol
  T_VOID    ---- 0001  01h  void function argument (not used)
  T_CHAR    ---- 0010  02h  character
  T_SHORT   ---- 0011  03h  short integer
  T_INT     ---- 0100  04h  integer
  T_LONG    ---- 0101  05h  long integer
  T_FLOAT   ---- 0110  06h  floating point
  T_DOUBLE  ---- 0111  07h  double precision float
  T_STRUCT  ---- 1000  08h  structure
  T_UNION   ---- 1001  09h  union
  T_ENUM    ---- 1010  0Ah  enumeration
  T_MOE     ---- 1011  0Bh  member of enumeration
  T_UCHAR   ---- 1100  0Ch  unsigned character
  T_USHORT  ---- 1101  0Dh  unsigned short
  T_UINT    ---- 1110  0Eh  unsigned integer
  T_ULONG   ---- 1111  0Fh  unsigned long
  T_LNGDBL  ---1 0000  10h  long double (special case bit pattern)
  DT_NON    --00 ----  0xh  No derived type
  DT_PTR    --01 ----  1xh  pointer to T             ;aka T=Type ?
  DT_FCN    --10 ----  2xh  function returning T     ;aka T=Type ?
  DT_ARY    --11 ----  3xh  array of T               ;aka T=Type ?
The BTYPE(x) macro extracts the base type from e_type. Note that all DT_* must be shifted by N_BTSHIFT to get actual values, as in:
  e_type = base + derived << N_BTSHIFT;
There are also macros ISPTR, ISFCN, and ISARY that test the upper bits for the derived type.

e_sclass - storage class
This tells where and what the symbol represents.
  Value    Class     Meaning
  00h 0    C_NULL    No entry
  01h 1    C_AUTO    Automatic variable
  02h 2    C_EXT     External (public) symbol - this covers globals and externs
  03h 3    C_STAT    static (private) symbol
  04h 4    C_REG     register variable
  05h 5    C_EXTDEF  External definition
  06h 6    C_LABEL   label
  07h 7    C_ULABEL  undefined label
  08h 8    C_MOS     member of structure
  09h 9    C_ARG     function argument
  0Ah 10   C_STRTAG  structure tag
  0Bh 11   C_MOU     member of union
  0Ch 12   C_UNTAG   union tag
  0Dh 13   C_TPDEF   type definition
  0Eh 14   C_USTATIC undefined static
  0Fh 15   C_ENTAG   enumaration tag
  10h 16   C_MOE     member of enumeration
  11h 17   C_REGPARM register parameter
  12h 18   C_FIELD   bit field
  13h 19   C_AUTOARG auto argument                      ;-blah
  14h 20   C_LASTENT dummy entry (end of block)
  62h 98   blah      "func_start_@@@_3_xxx"                             ;\
  63h 99   blah      "func_end_@@@_3_xxx"                               ;
  64h 100  C_BLOCK   ".bb" or ".eb" - beginning or end of block         ;
  65h 101  C_FCN     ".bf" or ".ef" - beginning or end of function      ;
  66h 102  C_EOS     end of structure                                   ; blah
  67h 103  C_FILE    file name                                          ;
  68h 104  C_LINE    line number, reformatted as symbol                 ;
  69h 105  C_ALIAS   duplicate tag                                      ;
  6Ah 106  C_HIDDEN  ext symbol in dmert public lib                     ;
  6Bh..70h blah      ".ar"                                              ;
  FFh 255  C_EFCN    physical end of function                           ;/

e_numaux - number of auxiliary entries
Each symbol is allowed to have additional data that follows it in the symbol table. This field tells how many equivalent SYMENTs are used for aux entries. For most symbols, this is zero. A value of one allows up to SYMESZ bytes of auxiliary information for that symbol. A non-exhaustive list of auxiliary entries follows, based on the storage class (e_sclass) or type (e_type) of the symbol.

Auxiliary Entries

DT_ARY
  .x_sym.x_misc.x_lnsz.x_size       ;size in bytes (size*count)

T_STRUCT
T_UNION
T_ENUM
  .x_sym.x_tagndx                   ;syment index for list of tags (will point
                                    ;        to C_STRTAG, C_UNTAG, or C_ENTAG)
  .x_sym.x_misc.x_lnsz.x_size       ;size in bytes (size*count)

T_NULL | C_STAT (section symbols, like .text)
  .x_scn.x_scnlen                   ;section length (bytes)
  .x_scn.x_nreloc                   ;number of relocation entries (ushort)
  .x_scn.x_nlinno                   ;number of line numbers (ushort)

C_STRTAG (will be followed by C_MOS's and C_EOS)
C_UNTAG (will be followed by C_MOU's and C_EOS)
C_ENTAG (will be followed by C_MOE's and C_EOS)
  .x_sym.x_x_misc.x_lnsz.x_size     ;the size of the struct/union/enum
  .x_sym.x_fcnary.x_fcn.x_endndx    ;the symbol index after our list

C_EOS
  .x_sym.x_misc.x_lnsz.x_size       ;the size of the struct/union/enum
  .x_sym.x_tagndx                   ;the symbol index of the start of our list

C_FIELD
  .x_sym.x_x_misc.x_lnsz.x_size     ;the number of bits

C_BLOCK
  .x_sym.x_misc.x_lnsz.x_lnno       ;starting line number
  .x_sym.x_fcnary.x_fcn.x_endndx    ;the symbol index after our block (if .bb)

C_FCN
  .x_sym.x_misc.x_lnsz.x_lnno       ;starting line number
  .x_sym.x_misc.x_lnsz.x_size       ;size in bytes

C_FILE
  .x_file.x_fname
  .x_file.x_n.x_zeroes
  .x_file.x_n.x_offset
These three specify the file name, just like the three fields used to specify the symbol name.

Meanings of the Values
  SClass               Meaning of the Value
  C_AUTO,C_ARG         Address of the variable, relative to %ebp
  C_EXT,C_STAT,others  The address of the symbol
  C_REG                The register number assigned to this variable
  C_MOS                Offset of the member from the beginning of the structure
  C_MOE                The value of this enum member
  C_FIELD              The mask for this field
  C_EOS                size of struct/union/enum


CDROM File COFF Files - References

Basic descriptions
  COFF    http://fileformats.archiveteam.org/wiki/COFF
  ECOFF   http://web.archive.org/web/2/http://en.wikipedia.org/wiki/ECOFF

Specific descriptions
  COFF    http://www.delorie.com/djgpp/doc/coff/
  TICOFF  http://www.ti.com/lit/an/spraao8/spraao8.pdf
  ECOFF64 http://web.archive.org/web/20160305114748/http://h41361.www4.hp.com
               /docs/base_doc/DOCUMENTATION/V50A_ACRO_SUP/OBJSPEC.PDF
  XCOFF   http://web.archive.org/web/2/https://www.ibm.com/docs/en/aix
               /7.1?topic=formats-xcoff-object-file-format

Header files (for more variants than in above descriptions):
  https://opensource.apple.com/source/gdb/gdb-1708/src/include/coff/ (see *.h)
For ECOFF check these four header files:
  ecoff.h    ECOFF general structures, excluding symtab
  sym.h      ECOFF symtab structures
  symconst.h ECOFF symtab constants
  alpha.h    ECOFF64 structures and constants

TargetMachineIDs:
  https://raw.githubusercontent.com/file/file/master/magic/Magdir/coff
  https://opensource.apple.com/source/gdb/gdb-1708/src/include/coff/ (see *.h)


CDROM File Video Texture Image TIM/PXL/CLT (Sony)

TIM/PXL/CLT are standard formats from Sony's devkit. TIM is used by many PSX games.
  .TIM   contains Pixel data, and (optional) CLUT data  ;-all in one file
  .PXL   contains Pixel data only                       ;\in two separate files
  .CLT   contains CLUT data only (if any)               ;/

TIM Format
  000h 1  File ID  (always 10h=TIM)
  001h 1  Version  (always 00h)
  002h 2  Reserved (always 0000h) (or 1 or 2 for Compressed TIM, see below)
  004h 4  Flags (bit0-2=Type; see below, bit3=HasCLUT, bit4-31=Reserved/zero)
  ...  .. Data Section for CLUT (Palette), only exists if Flags.bit3=1, HasCLUT
  ...  .. Data Section for Pixels (Bitmap/Texture)
The Type in Flags.bit0-2 can be 0=4bpp, 1=8bpp, 2=16bpp, 3=24bpp, 4=Mixed.
NFL Blitz 2000 (MagDemo26: B2000\DATA\ARTD_G.BIN) does additionally use Type 5=8bit.
The Type value value is only a hint on how to view the Pixel data (the data is copied to VRAM regardless of the type; 4=Mixed is meant to indicate that the data contains different types, eg. both 4bpp & 8bpp textures).
Type 3=24bpp is quite rare, but does exist (eg. Colony Wars (MagDemo02: CWARS\GAME.RSC\DEMO.TIM)).

The format of the CLUT and Pixel Data Section(s) is:
  000h 4  Size of Data Section (Xsiz*2*Ysiz+0Ch)  ;maybe rounded to 4-byte?
  004h 4  Destination Coord    (YyyyXxxxh)  ;Xpos counted in halfwords
  008h 4  Width+Height         (YsizXsizh)  ;Xsiz counted in halfwords
  00Ch .. VRAM Data (to be DMAed to frame buffer)
Note: Above is usually a multiple of 4 bytes, but not always:
Shadow Madness (MagDemo18: SHADOW\DATA\ANDY\LOADSAVE\*.TIM) contains TIM bitmaps with 27x27 or 39x51 halfwords; those files have odd section size & odd total filesize. Gran Turismo 2 (GT2.VOL\arcade\arc_other.tim\0000) also has odd size. Unknown if the CLUT can also have odd size (which would misalign the following Bitmap section).
Bust A Groove (MagDemo18: BUSTGR_A\G_COMMON.DFS\0005) has 0x0 pixel Bitmaps (with CLUT data).

PXL/CLT Format
PXL/CLT is very rare. And oddly, with swapped ID values (official specs say 11h=PXL, 12h=CLT, but the existing games do use 11h=CLT, 12h=PXL).
Used by Granstream Saga (MagDemo10 GS\*)
Used by Bloody Roar 1 (MagDemo06: BL\*)
Used by Bloody Roar 2 (MagDemo22: ASC,CMN,EFT,LON,SND,ST5,STU\*)

CLT Format
  000h 1  File ID  (always 11h=CLT) (although Sony's doc says 12h)
  001h 1  Version  (always 00h)
  002h 2  Reserved (always 0000h)
  004h 4  Flags (bit0-1=Type=2; bit2-31=Reserved/zero)
  ...  .. Data Section for CLUT (Palette)
The .CLT Type should be always 2 (meant to indicate 16bit CLUT entries).

PXL Format
  000h 1  File ID  (always 12h=PXL) (although Sony's doc says 11h)
  001h 1  Version  (always 00h)
  002h 2  Reserved (always 0000h)
  004h 4  Flags (bit0-?=Type; see below, bit?-31=Reserved/zero)
  ...  .. Data Section for Pixels (Bitmap/Texture)
This does probably support the same 5 types as in .TIMs (though official Sony docs claim the .PXL type to be only 1bit wide, but nethertheless claim that PXL can be 4bpp, 8bpp, or 16bpp).

 _______________________________ Compressed TIM _______________________________

Compressed TIMs
Ape Escape (Sony 1999) is using a customized TIM format with 4bpp compression:
CDROM File Compression TIM-RLE4/RLE8
Other than that, TIMs can be compressed via generic compression functions (like LZSS, GZIP), or via bitmap dedicated compression formats (like BS, JPG, GIF).

 ______________________________ Malformed Files _______________________________

Malformed TIMs in BIGFILE.DAT
  Used by Legacy of Kain: Soul Reaver (eg. BIGFILE.DAT\folder04h\file13h)
  Used by Gex - Enter the Gecko (eg. BIGFILE.DAT\file0Fh\LZcompressed)
Malformed TIMs contain texture data preceeded by a dummy 14h-byte TIM header with following constant values:
  10 00 00 00  02 00 00 00  04 00 08 00  00 02 00 00  00 02 00 02  ;<-- this
  10 00 00 00  02 00 00 00  04 00 08 00  00 00 00 00  00 02 00 02  ;<-- or this
The malformed entries include:
  [04h]=Type should indicated the color depth, but it's always 02h=16bpp.
  [08h]=Width*2*Height+0Ch should be 8000Ch, but malformed is 80004h.
  Total filesize should be 80014h, but Gecko files are often MUCH smaller.
Also, destination yloc should be 0..1FFh, but PSX "Lemmings & Oh No! More Lemmings" (FILES\GFX\*.TIM) has yloc=200h (that game also has vandalized .BMP headers with 2-byte alignment padding after ID "BM", whilst pretending that those extra bytes aren't there in data offset and total size entries).

Oversized TIMs
  Used by Pong (MagDemo24: LES02020\*\*.TIM)
  Used by Alien Resurrection (MOVIE\LANGSEL.BIN, PACK.BIN\FEGRUK*.TIM)
Has WxH pix, but section size (and filesize) are +2 bytes bigger than that:
  10 00 00 00 02 00 00 00 0E 00 08 00 C0 01 00 00 00 02 00 02  ;Pong *.TIM
  10 00 00 00 02 00 00 00 0E 00 07 00 00 02 00 00 C0 01 00 02  ;Pong WORLD.TIM
  10 00 00 00 02 00 00 00 0E 80 03 00 00 02 00 01 C0 01 00 01  ;Pong ZONE*.TIM
  10 00 00 00 02 00 00 00 0E 00 02 00 00 00 00 01 00 01 00 01  ;Alien LANGSEL
  10 00 00 00 02 00 00 00 0E 00 02 00 00 03 00 01 00 01 00 01  ;Alien FEGRUK*

Miscomputed Section Size
NBA Basketball 2000 (MagDemo28: FOXBB\TIM\*.TIM) has TIMs with section size "0Ch+Xsiz*Ysiz" instead of "0Ch+Xsiz*2*Ysiz".

NonTIMs in Bloody Roar 1 and 2
  Bloody Roar 1 (CMN\INIT.DAT\000Eh)
  Bloody Roar 2 (CMN\SE00.DAT, CMD\SEL00.DAT\0030h and CMN\VS\VS.DAT\0000h)
This looks somehow TIM-inspired, but has ID=13h.
  13 00 00 00 02 00 00 00 0C 20 00 00 00 00 F8 01 00 01 10 00  ;Bloody Roar 1
  13 00 00 00 02 00 00 00 0C 20 00 00 00 00 00 00 00 01 10 00  ;Bloody Roar 2

Other uncommon/malformed TIM variants
And, Heart of Darkness has a TIM with Size entry set to Xsiz*2*Ysiz+0Eh (instead of +0Ch) (that malformed TIM is found inside of the RNC compressed IMAGES\US.TIM file).
Also, NFL Gameday '99 (MagDemo17: GAMEDAY\PHOTOS.FIL) contains a TIM cropped to 800h-byte size (containing only the upper quarter of the photo).
Also, not directly malformed, but uncommon: Final Fantasy IX contains 14h-byte 0x0 pixel TIMs (eg. FF9.IMG\dir04\file0046\1B-0000\04-0001).
Klonoa (MagDemo08: KLONOA\FILE.IDX\3\2\0..1) has 0x0pix TIM (plus palette).

Malformed CLTs
  Used by Secret of Mana, WM\WEFF\*.CLT
ID is 10h=TIM, Flags=10101009h (should be ID=12h, Flags=02h).


CDROM File Video Texture/Bitmap (Other)

Apart from Sony's TIM (and PXL/CLT) format, there are a bunch of other texture/bitmap formats:

Compressed Bitmaps
  .BS used by several games (and also in most .STR videos)
  .GIF used by Lightspan Online Connection CD
  .JPG used by Lightspan Online Connection CD
  .GIF used by Keitai Henshuu (CompactNetFront browser) (I-Mode)
  .BMP with RLE4 used by Lightspan Online Connection CD (MONOFONT, PROPFONT)
  .BMP with RLE8+Delta also used by Online Connection CD (PROPFONT\ARIA6.BMP)
  .PCX with RLE used by Jampack Vol. 1 (MDK\CD.HED\*.pcx)

Uncompressed Bitmaps
  .BMP
  .BMP used by Mat Hoffman's Pro BMX (MagDemo39: BMX\BMXCD.HED\*)
  .BMP used by Mat Hoffman's Pro BMX (MagDemo48: MHPB\BMXCD.HED\*)
  .BMP used by Thrasher: Skate and Destroy (MagDemo27: SKATE\ASSETS\*.ZAL)
  .BMP used by Dave Mirra Freestyle BMX (MagDemo36,46: BMX\ASSETS\*.ZAL)
  .VRM .IMG .TEX .TIM .RAW .256 .COL .4B .15B .R16 .TPG - raw VRAM data
  "SC" memory card icons

Targa TGA and Paintbrush PCX
CDROM File Video Texture/Bitmap (TGA)
CDROM File Video Texture/Bitmap (PCX)

PSI bitmap - Power Spike (MagDemo43: POWER\GAME.IDX\*.BIZ\*.PSI)
  000h 10h   Name 1 ("FILENAME.BMP", zeropadded)
  010h 10h   Name 2 ("FILENAME.PSI", zeropadded)
  020h 4     Bits per pixel (usually 4, 8, or 16)
  024h 2     Bitmap VRAM Dest.X ?
  026h 2     Bitmap VRAM Dest.Y ?
  028h 2     Bitmap Width in pixels
  02Ah 2     Bitmap Height in pixels
  02Ch 2     Palette VRAM Dest.X ?   ;\zero for 16bpp
  02Eh 2     Palette VRAM Dest.Y ?   ;/
  030h 2     Bitmap Width in Halfwords (PixelWidth*bpp/16)
  032h 2     Palette Size in Halfwords (0, 10h, 100h for 16bpp,4npp,8bpp)
  034h 4     Maybe Bitmap present flag (always 1)
  038h 4     Maybe Palette present flag (0=16bpp, 1=4bpp/8bpp)
  03Ch ..    Bitmap pixels
  ...  ..    Palette (if any, for 4bpp: 16x16bit, for 8bpp: 256x16bit)

JumpStart Wildlife Safari Field Trip (MagDemo52: DEMO\DATA.DAT\*.DAT+*.PSX)
This game does use two different (but nearly identical) bitmap formats (with either palette or bitmap data stored first).
  000h 4     Total Filesize (Width*Height+20Ch)
  004h 2     Bitmap Width
  006h 2     Bitmap Height
  008h 4     Unknown, always 1 (maybe 1=8bpp?)
 In .DAT files (512x192 or 256x64 pix), palette first:
  00Ch 200h  Palette data
  20Ch ..    Bitmap data
 In .PSX files (64x64 pix), bitmap first:
  00Ch ..    Bitmap data
  ...  200h  Palette data
To detect the "palette first" format, check for these conditions(s):
  Filename extension is ".DAT"
  Bitmap Width<>Height (non-square)
  [00Ch..20Bh] has AllMSBs>=80h, and SomeLSBs<80h
Note: The bitmaps are vertically mirrored (starting with bottom-most scanline).

WxH Bitmap (Width*Height)
Used by Alone in the Dark The New Nightmare (FAT.BIN\BOOK,DOC,INTRO,MENU\*)
Used by Rayman (RAY\JUN,MON,MUS\*) (but seems to contain map data, not pixels)
  000h 2   Width  (W)   ;\usually 320x240 (or 512x240 or 80x13)
  002h 2   Height (H)   ;/
  004h ..  Bitmap 16bpp (W*H*2 bytes)

WxHxN bpp Bitmap
Used by Alien Resurrection (MOVIE\*SPLASH.BIN, PACK.BIN\*.TIM)
  000h 2   Width  (W) (140h)
  002h 2   Height (H) (F0h)
  004h 4   Type   (0=15bpp, 1=24bpp)
  008h ..  Bitmap 15bpp/24bpp (W*H*2 or W*H*3 bytes)
  ...  4   Checksum (all bytes above added together)

RAWP Bitmap
Used by Championship Motocross (MagDemo25: SMX\RESHAD.BIN\*) ("RAWP")
  000h 4     ID "RAWP" (this variant has BIG-ENDIAN width/height!)
  004h 2     Width  (usually 280h=640pix or 140h=320pix) (big-endian!!!)
  006h 2     Height (usually 1E0h=480pix or F0h=240pix)  (big-endian!!!)
  008h ..    Bitmap data, 16bpp (width*height*2 bytes)

XYWH Bitmap/Palette (X,Y,Width*Height) (.BIT and .CLT)
Used by CART World Series (MagDemo04: CART\*.BIT and *.BIN\*)
Used by NFL Gameday '98 (MagDemo04: GAMEDAY\BUILD\GRBA.FIL\*)
Used by NFL Gameday '99 (MagDemo17: GAMEDAY\*.BIT and *.FIL\*)
Used by NFL Gameday 2000 (MagDemo27: GAMEDAY\*.BIT)
Used by NCAA Gamebreaker '98 (MagDemo05: GBREAKER\*.BIT and UFLA.BIN\*)
Used by NCAA Gamebreaker 2000 (MagDemo27: GBREAKER\*.BIT and *.FIL\*)
Used by Twisted Metal 4 (MagDemo30: TM4DATA\*.MR,*.IMG\*.bit,*.clt)
  000h 2   VRAM.X             (X) (0..3FFh)
  002h 2   VRAM.Y             (Y) (0..1FFh)
  004h 2   Width in halfwords (W) (1..400h)
  006h 2   Height             (H) (1..200h)
  008h ..  Bitmap or Palette data (W*H*2 bytes)

Viewpoint (VIEW.DIR\*\FORM.IFF\*.SPRT) (sprites and bitmaps)
  000h 2    Bitmap Width  (min 2)
  002h 2    Bitmap Height (min 1)
  004h 2    Hotspot X (signed)
  006h 2    Hotspot Y (signed)
  008h 08h  Zerofilled
  010h 4    Bitmap Size (Width*Height*bpp/8, or less when compressed)
  014h 2    Color Depth (1=8bpp, 2=16bpp)
  016h 2    Compression Method (0=None, 1=LZ+RLE+DELTA, 2=LZSS.32, 3=LZSS.8)
  018h ..   Bitmap pixels
16bpp is used in VIEW.DIR\fonts and VIEW.DIR\screens, 8bpp is using in VIEW.DIR\streams, 8bpp SPRT's are often (not always) bundled with a 200h-byte CLUT chunk. For the compression methods, see:
CDROM File Compression LZSS.8/32 and LZ+RLE+DELTA (Viewpoint)

Viewpoint (VIEW.DIR\streams\FORM.IFF\*.VCBG) (16x512pix BG slices)
  0000h 200h  Palette                  ;\upper half
  0200h 1000h Bitmap (16x256x8bpp)     ;/
  1200h 200h  Palette                  ;\lower half
  1400h 1000h Bitmap (16x256x8bpp)     ;/

Doom (PSXDOOM\ABIN\PSXDOOM.WAD\*\*, PSXDOOM\*\*.IMG\*)
  000h 2     Hotspot X (signed) (usually 0)
  002h 2     Hotspot Y (signed) (usually 0)
  004h 2     Width in bytes
  006h 2     Height
  008h ..    Bitmap 8bpp (Width*Height bytes)
Most files have Hotspot X=0,Y=0, WAD\LOADING has X=FF80h,Y=FF8Ah, and WAD\S\* has X=0..Width, Y=0..Height+1Ah (eg. S\BKEY*, S\BFG*, S\PISFA0 have large Y).
The files do not contain any palette info... maybe 2800h-byte PLAYPAL does contain the palette(s)?

Lemmings & Oh No! More Lemmings (FILES\GFX\*.BOB, FILES\SMLMAPS\*.BOB)
  000h 2       Width
  002h 2       Height
  004h 100h*3  Palette 24bit RGB888
  304h ..      Bitmap 8bpp (Width*Height bytes)
  ..   (1700h) Unknown (only in SMLMAPS\*.BOB, not in GFX\*.BOB)
Apart from .BOB, the FILES\GFX folder also has vandalized .BMP (with ID "BM",00h,00h) and corrupted .TIM (with VRAM.Y=200h).

Perfect Assassin (DATA.JFS\DATA\*.BM)
  000h 4      Format 1 (0=8bpp, 1=16bpp)
  004h 4      Format 2 (1=8bpp, 2=16bpp)
  008h 4      Width in pixels
  00Ch 4      Height in pixels
  010h ..     Bitmap Data
  ...  (300h) Palette 18bit RGB666 (R,G,B range 00h..3Fh) (only if format 8bpp)

One (DIRFILE.BIN\*.VCF)
  000h 4     Unknown (always 1)
  004h 4     Unknown (always 8)
  008h 4     Unknown (always 2) (maybe 2=16bpp?)
  00Ch 4     Width in pixels (3Ah, 140h, or 280h)
  010h 4     Height          (3Ah, or F0h)
  014h ..    Bitmap 16bpp (Width*Height*2 bytes)

One (DIRFILE.BIN\*.VCK and DIRFILE.BIN\w*\sect*.bin\TEXTURE 001)
  000h 2     Number if Files (N)
  002h 2     Number of VRAM.Slots (less or equal than Number of Files)
  004h 4     ID "BLK0"
  008h N*10h File List
  ...  ..    1st File Bitmap
  ...  ..    1st File Palette (20h/200h/0 bytes for 4bpp/8bpp/16bpp)
  ...  ..    2nd File Bitmap
  ...  ..    2nd File Palette (only if PaletteID=FileNo=1)
  ...  ..    3rd File Bitmap
  ...  ..    3rd File Palette (only if PaletteID=FileNo=2)
  ...  ..    etc.
File List entries:
  000h 2     VRAM.X in halfwords (0..1Fh, +bit15=Blank)  ;\within current
  002h 2     VRAM.Y              (0..3Fh)                ;/VRAM.Slot
  004h 2     Width in pixels (max 80h/40h/20h for 4bpp/8bpp/16bpp)
  006h 2     Height          (max 40h)
  008h 2     VRAM.Slot       (0,1,2,3,...,NumSlots-1)
  00Ah 2     Unknown         (0,1,2,4 in *.vck, 4 in sect*.bin)
  00Ch 2     Color Depth     (0=4bpp, 1=8bpp, 2=16bpp)
  00Eh 2     Palette ID      (0..FileNo-1=Old, FileNo=New, FFFFh=None/16bpp)
  NumFiles-1, or ID of already used palette)
Note: VRAM.Slots are 20h*40h halfwords.
Bitmaps can either have newly defined palettes (when PaletteID=FileNo), or re-use previously defined "old" palettes (when PaletteID<FileNo).
The Blank flag allows to define a blank region (for whatever purpose), the file doesn't contain any bitmap/palette data for such blank regions.

BMR Bitmaps
These are 16bpp bitmaps, stored either in uncompressed .BMR files, or in compressed .RLE files:
CDROM File Compression RLE_16
  Apocalypse (MagDemo16: APOC\CD.HED\*.RLE and *.BMR)
  Spider-Man 1 older version (MagDemo31: SPIDEY\CD.HED\*.RLE)
  Spider-Man 1 newer version (MagDemo40: SPIDEY\CD.HED\*.RLE and .BMR)
  Spider-Man 2 (MagDemo50: HARNESS\CD.HED\*.RLE)
  Tony Hawk's Pro Skater (MagDemo22: PROSKATE\CD.HED\*.BMR)
The width/height for known filesizes are:
  33408h bytes --> 512x205pix, 16bpp (Apocalypse warning.rle)
  3C008h bytes --> 512x240pix, 16bpp (most common)
  96008h bytes --> 640x480pix, 16bpp (tony hawk's pro skater)
Most of the older BMR files (in Apocalypse) have valid 8-byte headers:
  000h 2     Unknown (FFA0h) (ID for files with valid headers?)
  002h 2     Dest.Y (usually 0) (11h=(240-205)/2 in Apocalypse warning.rle)
  004h 2     Width  (usually 200h=512pix)
  006h 2     Height (usually F0h=240pix) (CDh=205pix in Apocalypse warning.rle)
  008h ..    Bitmap data, 16bpp (width*height*2 bytes)
Most or all newer BMR files (in Apocalypse "loadlogo.rle", and in all files in Spider-Man 1, Spider-Man-2, Tony Hawk's Pro Skater) have the 8-byte header replaced by unused 8-byte at end of file:
  000h ..    Bitmap data, 16bpp (width*height*2 bytes)
  ..   8     Unused (garbage or extra pixels, not transferred to VRAM)
BUG: The bitmaps in all .BMR files (both with/without header) are distorted: The last 4-byte (rightmost 2pix) of each scanline should be actually located at the begin of the scanline, and the last scanline is shifted by an odd amount of bytes (resulting in nonsense 16bpp pixel colors); Spider-Man is actually displaying the bitmap in that distorted form (although it does mask off some glitches: one of the two bad rightmost pixels is replaced by a bad black leftmost pixel, and glitches in upper/lower lines aren't visible on 224-line NTSC screens).

Croc 1 (retail: *.IMG) (retail only, not in MagDemo02 demo version)
Croc 2 (MagDemo22: CROC2\CROCII.DIR\*.IMG)
Disney's The Emperor's New Groove (MagDemo39: ENG\KINGDOM.DIR\*.IMG)
Disney's Aladdin in Nasira's Rev. (MagDemo46: ALADDIN\ALADDIN.DIR\*.IMG)
Harry Potter and the Philosopher's Stone (POTTER.DIR\*.IMG, REFLECT.DAT)
Harry Potter and the Chamber of Secrets (POTTER.DIR\*.IMG, REPORT.IMG\*)
Contains raw 16bpp bitmaps, with following sizes:
  150h   bytes = 12x14x16bpp     ;Potter/Chamber                ;\
  25800h bytes = 320x240x16bpp   ;Croc 1 (retail version)       ;
  34800h bytes = 448x240x16bpp   ;Potter/Chamber                ; 16bpp
  38000h bytes = 448x256x16bpp   ;Potter/Philosopher            ;
  3C000h bytes = 512x240x16bpp   ;common                        ;
  40000h bytes = 512x256x16bpp   ;Potter/Philosopher            ;
  96000h bytes = 640x480x16bpp   ;common                        ;/
The Potter games additionally have .IMG files with 8bpp and 4bpp (with leading 200h-byte or 20h-byte CLUTs):
  600h bytes   = 32x32x8bpp      ;Potter/Philosopher            ;\
  1A00h bytes  = 96x64x8bpp      ;Potter/Chamber                ;
  2600h bytes  = 96x96x8bpp      ;Potter/Chamber                ; 8bpp, with
  5200h bytes  = 256x80x8bpp     ;Potter/Philosopher            ; leading 200h
  6200h bytes  = 128x192x8bpp    ;Potter/Philosopher            ; byte clut
  7A00h bytes  = 320x96x8bpp     ;Potter/Chamber                ;
  C200h bytes  = 128x384x8bpp    ;Potter/Philosopher            ;
  A734h bytes  = 218x194x8bpp    ;Potter/Philosopher            ;
  11A00h bytes = 448x160x8bpp    ;Potter/Philosopher            ;
  1E200h bytes = 513x240x8bpp    ;Potter/Philosopher            ;
  20200h bytes = 512x256x8bpp    ;Potter/Philosopher            ;
  20300h bytes = 513x256x8bpp    ;Potter/Philosopher            ;/
  120h bytes   = 32x16x4bpp      ;Potter/Chamber                ;\4bpp, with
  260h bytes   = 48x24x4bpp      ;Potter/Chamber                ; leading 20h
  340h bytes   = 40x40x4bpp      ;Potter/Chamber                ; byte clut
  820h bytes   = 128x32x4bpp     ;Potter/Chamber                ;/
  1020h bytes  = 128x64x4bpp     ;Potter/Philosopher+Chamber
Potter Notes: REFLECT.DAT is also an .IMG file. SECURITY.IMG is an ASCII file, KEEP.IMG also looks like ASCII (not .IMG). REPORT.IMG contains several 4bpp .IMGs badged together (each with their own palette, the separate file sizes are 260h, 3x120h, 8x260h = 18C0h total).
Note: The 16bpp .IMG format is about same as .BMR files (but without the 8-byte header, and without distorted scanlines).

Mat Hoffman's Pro BMX (MagDemo39: BMX\FE.WAD+STR\*.BIN) (Activision)
Mat Hoffman's Pro BMX (MagDemo48: MHPB\FE.WAD+STR\*.BIN) (Shaba/Activision)
  000h 2     Bits per pixel (4 or 8)
  002h 2     Bitmap Width in pixels
  004h 2     Bitmap Height in pixels
  006h 2     Zero
  008h N*2   Palette (with N=(1 SHL bpp))
  ...  ..    Bitmap (with Width*Height*bpp/8 bytes)
  ...  (..)  Zeropadding to 4-byte boundary (old version only)
The trailing alignment padding exists only in old demo version (eg. size of 78x49x8bpp "coreypp.bin" is old=10F8h, new=10F6h).

E.T. Interplanetary Mission (MagDemo54: MEGA\MEGA.CSH\*)
  000h 2     Type (0=4bpp, 1=8bpp, 2=16bpp)
  002h 2     Unknown (usually 0000h, or sometimes CCCCh)
  004h 2     Bitmap Width in pixels
  006h 2     Bitmap Height in pixels
  008h 200h  Palette (always 200h-byte, even for 4bpp or 16bpp)
  208h ..    Bitmap (Width*Height*bpp/8 bytes)
Palette is 00h-or-CCh-padded when 4bpp, or CCh-filled when 16bpp.
Note: Some files contain two or more such bitmaps (of same or different sizes) badged together.

EA Sports: Madden NFL '98 (MagDemo02: TIBURON\*.DAT\*)
EA Sports: Madden NFL 2000 (MagDemo27: MADN00\*.DAT\*)
EA Sports: Madden NFL 2001 (MagDemo39: MADN01\*.DAT\*)
This format is used in various EA Sports Madden .DAT archives, it contains standard TIMs with extra Headers/Footers.
  000h 4     Offset to TIM (1Ch) (Hdr size)    (1Ch)               ;\
  004h 4     Offset to Footer    (Hdr+TIM size)(123Ch,1A3Ch,1830h) ;
  008h 2     Bitmap Width in pixels      (40h or 60h or 30h)       ;
  00Ah 2     Bitmap Height in pixels     (40h)                     ;
  00Ch 4     Unknown, always 01h         (01h)                     ; Header
  010h 4     Unknown, always 23h         (23h)                     ; 1Ch bytes
  014h 2     Unknown, always 0101h       (101h)                    ;
  016h 1     Bitmap Width in pixels      (40h or 60h or 30h)       ;
  017h 1     Bitmap Height in pixels     (40h)                     ;
  018h 4     Unknown, always 00h         (0)                       ;/
  01Ch ..    TIM (Texture, can be 4bpp, 8bpp, 16bpp)               ;-TIM
  ...  4     Unknown, always C0000222h   (C0000222h)               ;\
  ...  2     Unknown, always 0001h       (0001h)                   ;
  ...  1     Bitmap Width in pixels      (40h or 60h or 30h)       ; Footer
  ...  1     Bitmap Height in pixels     (40h)                     ; 12h bytes
  ...  4     Unknown, always 78000000h   (78000000h)               ;
  ...  6     Unknown                     (0,0,80h,0,0,0)           ;/
Purpose is unknown; the 8bit Width/Height entries might be TexCoords.
The PORTRAITS.DAT archives are a special case:
  Madden NFL '98 (MagDemo02: TIBURON\PORTRAIT.DAT) (48x64, 16bpp)
  Madden NFL 2000 (MagDemo27: MADN00\PORTRAIT.DAT) (96x64, 8bpp plus palette)
  Madden NFL 2001 (MagDemo39: MADN01\PORTRAIT.DAT) (64x64, 8bpp plus palette)
Those PORTRAITS.DAT don't have any archive header, instead they do contain several images in the above format, each one zeropadded to 2000h-byte size.

989 Sports: NHL Faceoff '99 (MagDemo17: FO99\*.KGB\*.TEX)
989 Sports: NHL Faceoff 2000 (MagDemo28: FO2000\*.TEX)
989 Sports: NCAA Final Four 2000 (MagDemo30: FF00\*.TEX)
  000h 0Ch  ID "TEX PSX ",01h,00h,00h,00h    ;used in 989 Sports games
  00Ch 4    Number of Textures
  010h 4    Total Filesize
  014h 4    Common Palette Size    (0=200h, 1=None, 2=20h)
  018h (..) Common Palette, if any (0,20h,200h bytes)
  ...  ..   Texture(s)
 Texture format:
  000h 10h  Filename (eg. "light1", max 16 chars, zeropadded if shorter)
  010h 4    Width in pixels  (eg. 40h)
  014h 4    Height           (eg. 20h or 40h)
  018h 4    Unknown          (always 0)
  01Ch 4    Number of Colors (eg. 10h, 20h or 100h)
  020h ..   Bitmap (4bpp when NumColors<=10h, 8bpp when NumColors>10h)
  ...  (..) Palette (NumColors*2 bytes, only present if Common Palette=None)
The .TEX files may be in ISO folders, KGB archives, DOTLESS archives. And, some are stored in headerless .DAT/.CAT archives (which start with ID "TEX PSX ", but seem to have further files appended thereafter).

Electronic Arts .PSH (SHPP)
FIFA - Road to World Cup 98 (with chunk C0h/C1h = RefPack compression)
NCAA March Madness 2000 (MagDemo32: MM2K\*.PSH)
Need for Speed 3 Hot Pursuit (*.PSH, ZLOAD*.QPS\RefPack.PSH)
ReBoot (DATA\*.PSH) (with chunk 6Bh)
Sled Storm (MagDemo24: DEBUG,ART,ART2,ART3,SOUND\*.PSH) (with Comment, Mipmap)
WCW Mayhem (MagDemo28: WCWDEMO\*.BIG\*.PSH) (with chunk C0h/C1h = RefPack)
  000h 4    ID "SHPP"
  004h 4    Total Filesize (or Filesize-0Ch, eg. FIFA'98 ZLEG*.PSH)
  008h 4    Number of Textures (N)
  00Ch 4    ID "GIMX"
  010h N*8  File List
  ...  ..   Data (each File contains a Bitmap chunk, and Palette chunk, if any)
 File List entries:
  000h 4    Name (ascii) (Mipmaps use the same name for each mipmap level)
  004h 4    Offset from begin of archive to first Chunk of file
  Caution: Most PSH files do have the above offsets sorted in increasing order,
  but some have UNSORTED offsets, eg. Sled Storm (MagDemo24: ART3\LOAD1.PSH),
  so one cannot easily compute sizes as NextOffset-CurrOffset.
  Note: Mipmap textures consist of two files with same name and different
  resolution, eg. in Sled Storm (MagDemo24: ART\WORLD0x.PSH)
 Bitmap Chunk:
  000h 1    Chunk Type (40h=PSX/4bpp, 41h=PSX/8bpp, 42h=PSX/16bpp)
  001h 3    Offset from current chunk to next chunk (000000h=None)
  004h 2    Bitmap Width in pixels (can be odd, pad lines to 2-byte boundary)
  006h 2    Bitmap Height
  008h 2    Center X   (whatever that is)
  00Ah 2    Center Y   (whatever that is)
  00Ch 2    Position X (whatever that is, plus bit12-15=flags?)
  00Eh 2    Position Y (whatever that is, plus bit12-15=flags?)
  010h ..   Bitmap data (each scanline is padded to 2-byte boundary)
  ...  ..   Padding to 8-byte boundary
 Compressed Bitmap Chunk:
  000h 1    Chunk Type (C0h=PSX/4bpp, C1h=PSX/8bpp, and probably C2h=PSX/16bpp)
  001h 0Fh  Same as in Chunk 40h/41h/42h (see there)
  010h ..   Compressed Bitmap data (usually/always with Method=10FBh)
  ...  ..   Padding to 8-byte boundary
 Palette Chunk (if any) (only for 4bpp/8bpp bitmaps, not for 16bpp):
  000h 1    Chunk Type (23h=PSX/Palette)
  001h 3    Offset from current chunk to next chunk (000000h=None)
  004h 2    Palette Width in halfwords (10h or 100h)
  006h 2    Palette Height             (1)
  008h 2    Unknown (usually same as Width) (or 80D0h or 9240h)
  00Ah 2    Unknown (usually 0000h)         (or 0001h or 0002h)
  00Ch 2    Unknown (usually 0000h)
  00Eh 2    Unknown (usually 00F0h)
  010h ..   Palette data (16bit per color)
  Note: The odd 80D0h,0001h values occur in Sled Storm ART\WORKD00.PSH\TBR1)
 Unknown Chunk (eg. ReBoot (DATA\AREA15.PSH\sp*))
  000h 1    Chunk Type (6Bh)
  001h 3    Offset from current chunk to next chunk (000000h=None)
  004h 8    Unknown (2C,00,00,3C,03,00,00,00)
  00Ch -    For whatever reason, there is no 8-byte padding here
 Comment Chunk (eg. Sled Storm (MagDemo24: ART\WORLD0x.PSH))
  000h 1    Chunk Type (6Fh=PSX/Comment)
  001h 3    Offset from current chunk to next chunk (000000h=None)
  004h ..   Comment ("Saved in Photoshop Plugin made by PEE00751@...",00h)
  ...  ..   Zeropadding to 8-byte boundary
 Unknown Chunk (eg. Sled Storm (MagDemo24: ART\WORLD09.PSH\ADAA))
  000h 1    Chunk Type (7Ch)
  001h 3    Offset from current chunk to next chunk (000000h=None)
  004h 2Ch  Unknown (reportedly Hot spot / Pix region, but differs on PSX?)
The whole .PSH file or the bitmap chunks can be compressed:
CDROM File Compression EA Methods
Variants of the .PSH format are also used on PC, PS2, PSP, XBOX (with other Chunk Types for other texture/palette formats, and for optional extra data). For details, see: http://wiki.xentax.com/index.php/EA_SSH_FSH_Image

Destruction Derby Raw (MagDemo35: DDRAW\*.PCK,*.FNT,*.SPR)
This format can contain one single Bitmap, or a font with several small character bitmaps.
  000h 2     ID "BC"                                        ;\
  002h 1     Color Depth (1=4bpp, 2=8bpp, 4=16bpp)          ; Header
  003h 1     Type        (40h=Bitmap, C0h=Font)             ;/
  ...  (2)   Palette Unknown (0 or 1)                       ;\only if Bitmap
  ...  (2)   Palette Unknown (1)                            ; 4bpp or 8bpp
  ...  (..)  Palette data (20h or 200h bytes for 4bpp/8bpp) ;/
  ...  2     Bitmap Number of Bitmaps-1 (N-1)               ;\
  ...  2     Bitmap Width in pixels                         ;
  ...  2     Bitmap Height in pixels                        ; Bitmap(s)
  ...  N*1   Bitmap Tilenumbers (eg. "ABCDEFG..." for Fonts);
  ...  N*1   Bitmap Proportional Font widths? (0xh or FFh)  ;
  ...  N*BMP Bitmap(s) for all characters                   ;/
  ...  (20h) Palette Data (20h bytes for 4bpp)              ;-only if Font/4bpp
All bitmap scanlines are padded to 2-byte boundary, eg. needed for:
  INGAME1\BOWL2.PTH\SPRITES.PTH\ST.SPR    30x10x4bpp: 15 --> 16 bytes/line
  INGAME1\BOWL2.PTH\SPRITES.PTH\STOPW.SPR 75x40x4bpp: 37.5 --> 38 bytes/line
The BC files are usually compressed (either in PCK file, or in the compressed DAT portion of a PTH+DAT archive).

Cool Boarders 2 (MagDemo02: CB2\DATA*\*.FBD)
  000h 2    ID ("FB")                                ;\File Header
  002h 2    Always 1 (version? 4bpp? num entries?)   ;/
  004h 2    Palette VRAM Dest X (eg. 300h)           ;\
  006h 2    Palette VRAM Dest Y (eg. 1CCh,1EDh,1FFh) ; Palette Header
  008h 2    Palette Width in halfwords (eg. 100h)    ; (all zero when unused)
  00Ah 2    Palette Height (eg. 1 or 0Dh)            ;/
  00Ch 2    Bitmap VRAM Dest X (eg. 140h or 200h)    ;\
  00Eh 2    Bitmap VRAM Dest Y (eg. 0 or 100h)       ; Bitmap Header
  010h 2    Bitmap Width in halfwords                ;
  012h 2    Bitmap Height                            ;/
  ...  ..   Palette Data (if any)                    ;-Palette Data
  ...  ..   Bitmap Data                              ;-Bitmap Data
The bitmap data seems to be 4bpp and/or 8bpp, but it's hard to know the correct palette (some files have more than 16 or 256 palette colors, or don't have any palette at all).

Alien Resurrection Textures (PACK.BIN\*.WAD\*.TXF and PACK.BIN\*.TXF)
  000h 2       Always 302h
  002h 2       Number of Texture Slices           (N)
  004h 4       Number of 1-byte Footer entries    (F1) (0..6xxh)
  008h 4       Total Size of Footer               (F1+F2*10h+F3*4)
  00Ch 2       Unknown                            (0 or 1)
  00Eh 2       Number of 10h-byte Footer entries  (F2) (0..7Eh)
  010h 2       Number of 4-byte Footer entries    (F3) (0..25h)
  012h 2       Zero (or does below list already start here?)
  014h N*8     Texture Slice Dest Coords (4x16bit: 0,X,Y,0)?
  ...  ..      Zeropadding to 800h-byte boundary
  800h N*8000h Texture Slice Data (64x256 halfwords each)
  ...  F1*1    Footer 1-byte entries   (unknown content)
  ...  F2*10h  Footer 10h-byte entries (unknown content)
  ...  F3*4    Footer 4-byte entries   (unknown content)
Most or all of the 64x256 halfword slices seem to be 4bpp (256x256 pixels).
Unknown if the file contains palettes (in the slices themselves, or in footer)?
Note: TXF[10h] is same as WAD[04h].


CDROM File Video Texture/Bitmap (TGA)

Targa TGA
  000h 1   Image ID Size (00h..FFh, usually 0=None)      ;0
  001h 1   Palette Present Flag (0=None, 1=Present)      ;0            iv=1
  002h 1   Data Type code (0,1,2,3,9,10,11,32,33)        ;NEBULA=2     iv=1
  003h 2   Palette First Color (usually 0)               ;0            iv=0
  005h 2   Palette Number of Colors (usually 100h)       ;0            iv=100h
  007h 1   Palette Bits per Color (16,24,32, usually 24) ;0            iv=18h
  008h 2   Bitmap X origin (usually 0)                   ;0
  00Ah 2   Bitmap Y origin (usually 0)                   ;0
  00Ch 2   Bitmap Width                                  ;NEBULA=20h LOGO=142h
  00Eh 2   Bitmap Height                                 ;NEBULA=20h
  010h 1   Bitmap Bits per Pixel (8,16,24,32 exist?)     ;NEBULA=18h   iv=8
  011h 1   Image Descriptor (usually 0)                  ;0
  012h ..  Image ID Data (if any, len=[00h], usually 0=None)
  ...  ..  Palette
  ...  ..  Bitmap
  ...  1Ah Footer (8x00h, "TRUEVISION-XFILE.", 00h) (not present in iview)
Data Type [02h]:
  00h = No image data included  ;-Unknown purpose
  01h = Color-mapped image      ;\
  02h = RGB image               ; Uncompressed
  03h = Black and white image   ;/
  09h = Color-mapped image      ;\Runlength
  0Ah = RGB image               ;/
  0Bh = Black and white image   ;-Unknown compression method
  20h = Color-mapped image      ;-Huffman+Delta+Runlength
  21h = Color-mapped image      ;-Huffman+Delta+Runlength+FourPassQuadTree
The official specs do list the above 9 types, but do describe only 4 types in detail (type 01h,02h,09h,0Ah).
  Type 01h and 09h lack details on supported bits per pixel (8bpp with 100h
    colors does exist; unknown if less (or more) than 8bpp are supported,
    and if so, in which bit order.
  Type 02h and 0Ah are more or less well documented.
  Type 03h has unknown bit-order, also unknown if/how it differs from type
    01h with 1bpp.
  Type 0Bh, 20h, 21h lack any details on the compression method.
TGA's are used by a couple of PSX games/demos (all uncompressed):
  16bpp: Tomb Raider 2 (MagDemo01: TOMBRAID\*.RAW)
  24bpp: Tomb Raider 2 (MagDemo05: TOMB2\*.TGA)
  24bpp: Colony Wars Venegance (MagDemo14: CWV\GAME.RSC\NEBULA*.TGA, *SKY.TGA)
  24bpp: Colony Wars Red Sun (MagDemo31: CWREDSUN\GAME.RSC\000A\*)
  16bpp: Colony Wars Venegance (MagDemo14: CWV\GAME.RSC\LOGO.DAT)
  16bpp: X-Men: Mutant Academy (MagDemo50: XMEN2\*)
  16bpp: Disney's Tarzan (MagDemo42: TARZAN\*)
  8bpp+Wrong8bitAttr: SnoCross Championship Racing (MagDemo37: SNOCROSS\*.TGA)
  16bpp+WrongYflip: SnoCross Championship Racing (MagDemo37: SNOCROSS\*.TGA)
For whatever reason, TGA is still in use on newer consoles:
  32bpp: 3DS AR Games (RomFS:\i_ar\tex\hm*.lz77


CDROM File Video Texture/Bitmap (PCX)

PC Paintbrush .PCX files (ZSoft)
Default extension is .PCX (some tools did use .PCX for the "main" image, and .PCC for smaller snippets that were clipped/cropped/copied from from a large image).
  000h 1    File ID (always 0Ah=PCX/ZSoft)
  001h 1    Version (0,2,3,4,5)
  002h 1    Compression (always 01h=RLE) (or inofficial: 00h=Uncompressed)
  003h 1    Bits per Pixel (per Plane) (1, 2, 4, or 8)
  004h 2    Window X1   ;\
  006h 2    Window Y1   ; Width  = X2+1-X1
  008h 2    Window X2   ; Height = Y2+1-Y1
  00Ah 2    Window Y2   ;/
  00Ch 2    Horizontal Resolution in DPI  ;\often square, but can be also zero,
  00Eh 2    Vertical Resolution in DPI    ;/or screen size, or other values
  010h 30h  EGA/VGA Palette (16 colors, 3-byte per color = R,G,B) (or garbage)
  010h 1    CGA: Bit7-4=Background Color (supposedly IRGB1111 ?)
  013h 1    CGA: Bit7:0=Color,1=Mono,Bit6:0=Yellow,1=White,Bit5:0=Dim,1=Bright
  014h 1    Paintbrush IV: New CGA Color1 Green  ;\weird new way to encode CGA
  015h 1    Paintbrush IV: New CGA Color1 Red    ;/palette in these two bytes
  040h 1    Reserved (00h) (but is 96h in animals.pcx)
  041h 1    Number of color planes (1=Palette, 3=RGB, or 4=RGBI)
  042h 2    Bytes per Line (per plane) (must be N*2) (=(Width*Bits+15)/16*2)
  044h 2    PaletteInfo? (0000h/xxxxh=Normal, 0001h=Color/BW, 0002h=Grayscale)
  046h 2    Horizontal screen size in pixels  ;\New fields, found only
  048h 2    Vertical screen size in pixels    ;/in Paintbrush IV/IV Plus
  04Ah 36h  Reserved (zerofilled) (or garbage in older files, custom in MGS)
  080h ..   Bitmap data (RLE compressed)
  ...  1    VGA Palette ID (0Ch=256 colors)                      ;\when 8bpp
  ..   300h VGA Palette (256 colors, 3-byte per color  = R,G,B)  ;/
Decoding PCX files is quite a hardcore exercise due to a vast amount of versions, revisions, corner cases, incomplete & bugged specifications, and inofficial third-party glitches.

PCX Versions
  00h = Version 2.5 whatever ancient stuff
  02h = Version 2.8 with custom 16-color palette
  03h = Version 2.8 without palette (uses fixed CGA/EGA palette)
  04h = Version ?.? without palette (uses fixed CGA/EGA palette)
  05h = Version 3.0 with custom 16-color or 256-color palette or truecolor
NOTE: Version[01h]=05h with PaletteInfo[44h]=0001h..0002h is Paintbrush IV?

Known PCX Color Depths
  planes=1, bits=1  P1        ;1bit, HGC 2 color (iview and paint shop pro 2)
  planes=1, bits=2  P2        ;2bit, CGA 4 color (with old/new palette info)
  planes=3, bits=1  RGB111    ;3bit, EGA 8 color (official samples)  ;\version
  planes=4, bits=1  IRGB1111  ;4bit, EGA 16 color (paint shop pro 2) ;/03h..04h
  planes=1, bits=4  P4        ;4bit, BMP 16 color (iview)
  planes=1, bits=8  P8        ;8bit, VGA 256 color palette
  planes=1, bits=8  I8        ;8bit, VGA 256 level grayscale (gmarbles.pcx)
  planes=3, bits=8  BGR888    ;24bit, truecolor (this is official 24bit format)
 ;planes=1, bits=24 BGR888 ?  ;24bit, reportedly exists? poor compression
 ;planes=4, bits=4  ABGR4444  ;16bit, wikipedia-myth? unlikely to exist
 ;planes=4, bits=8  ABGR8888  ;32bit, truecolor+alpha (used in abydos.dcx\*)

Width and Height
These are normally calculated as so:
  Width  = X2+1-X1      ;width for normal files
  Height = Y2+1-Y1      ;height for normal files
However, a few PCX files do accidentally want them to be calculated as so:
  Width  = X2-X1        ;width for bugged files
  Height = Y2-Y1        ;height for bugged files
Files with bugged width can be (sometimes) detected as so:
  (Width*Bits+15)/16*2) > BytesPerLine
Files with bugged height can be detected during decompression:
  BeginOfLastScanline >= Filesize (or Filesize-301h for files with palette)
Bugged sample files are SAMPLE.DCX, marbles.pcx and gmarbles.pcx. RLE decompression may crash when not taking care of such files.

Color Planes and Palettes
The official ZSoft PCX specs are - wrongly - describing planes as:
  plane0 = red         ;\
  plane1 = green       ; this is WRONG, NONSENSE, does NOT exist
  plane2 = blue        ;
  plane3 = intensity   ;/
The 8-color and 16-color EGA images are actually using plane0,1,2,(3) as bit0,1,2,(3) of the EGA color number; which implies plane0=blue (ie. red/blue are opposite of the ZSoft document).
The truecolor and truecolor+alpha formats have plane0..2=red,green,blue (as described by ZSoft), but they don't have any intensity plane (a few files are using plane3=alpha).

Mono 2-Color Palette
This format was intended for 640x200pix 2-color CGA graphics, it's also common for higher resolution FAX or print images. The general rule for these files is to use this colors:
  color0=black
  color1=white
There are rumours that color1 could be changed to any of the 16 CGA colors (supposedly via [10h].bit7-4, but most older & newer 2-color files have that byte set to 00h, so one would end up with black-on-black).
Some newer 2-color files contain RGB palette entries [10h]=000000h, [13h]=FFFFFFh (and [16h..3Fh]=00h-filled or FFh-filled).
Iview does often display 2-color images with color1=dark green (somewhat mysteriously; it's doing that even for files that don't contain any CGA color numbers or RGB palette values that could qualify as dark green).

4-Color Palettes
This format was intended for 320x200pix 4-color CGA graphics, and the palette is closely bound to colors available in CGA graphics modes. Color0 is defined in [10h], and Color1-3 were originally defined in [13h], and later in [14h,15h]:
  color0=[10h].bit7-4  ;(Color0 IRGB)  ;CGA Port 3D9h.bit3-0 (usually 0=black)
  bright=[13h].bit5                    ;CGA Port 3D9h.bit4    ;\
  palette=[13h].bit6                   ;CGA Port 3D9h.bit5    ; old method
  if [13h].bit7 then palette=2         ;CGA Port 3D8h.bit2    ;/
  if [01h]=05h and [44h]=0001h then                           ;\new "smart"
    if [14h]>200 or [15h]>200 then bright=1, else bright=0    ; method used in
    if [14h]>[15h] then palette=0 else palette=1              :/Paintbrush IV
  if palette=0 and bright=0 then color1..3=02h,04h,06h  ;\green-red-yellow
  if palette=0 and bright=1 then color1..3=0Ah,0Ch,0Eh  ;/
  if palette=1 and bright=0 then color1..3=03h,05h,07h  ;\cyan-magenta-white
  if palette=1 and bright=1 then color1..3=0Bh,0Dh,0Fh  ;/
  if palette=2 and bright=0 then color1..3=03h,04h,07h  ;\cyan-red-white
  if palette=2 and bright=1 then color1..3=0Bh,0Ch,0Fh  ;/
Palette=2 uses some undocumented CGA glitch, it was somewhat intended to output grayscale by disabling color burst on CGA hardware with analog composite output, but actually most or all CGA hardware is having digital 4bit IRGB output, which outputs cyan-red-white.
The new "smart" method is apparently trying to detect if [13h-1Bh] contains RGB values with Color1=Green or Cyan, and to select the corresponding CGA palette; unfortunately such PCX files are merely setting [14h,15h] to match up with the "smart" formula, without actually storing valid RGB values in [13h-1Bh].

8-Color and 16-Color, with fixed EGA Palettes (version=03h or 04h)
These images have 3 or 4 planes. Plane0-3 correspond to bit0-3 of the EGA color numbers (ie. blue=plane0, green=plane1, red=plane2, and either intensity=plane3 for 16-color, or intensity=0 for 8-color images).
Some 8-Color sample images (with version=03h and 04h) can be found bundled with PC Paintbrush Plus 1.22 for Windows. A 16-color sample called WINSCR.PCX can be found elsewhere in internet.
Caution 1: Official ZSoft specs are wrongly claiming plane0=red and plane2=blue; this is wrong (although Paint Shop Pro 2 is actually implementing it that way) (whilst MS Paint for Win95b can properly display them) (most other tools are trying to read a palette from [10h..3Fh], which is usually garbage filled in version=03h..04h).
Caution 2: The standard EGA palette is used for version=03h..04h (many docs claim it to be used for version=03h only).

16-Color, with custom EGA/VGA Palettes (version=02h or 05h)
These can have 1 plane with 4 bits, or 4 planes with 1 bit. Header[10h..3Fh] contains a custom 16-color RGB palette with 3x8bit per R,G,B.
Classic VGA hardware did only use the upper 6bit of the 8bit values.
Classic EGA hardware did only use the upper 2bit of the 8bit values (that, only when having a special EGA monitor with support for more than 16 colors).

256-Color VGA Palettes (version=05h)
These have 1 plane with 8 bits. And a 256-color RGB palette with 3x8bit per R,G,B appended at end of file.
The appended 256-color palette should normally exist only in 256-color images, some PCX tools are reportedly always appending the extra palette to all version=05h files (even for 2-color files).

256-Level Grayscale Images (version=05h and [44h]=0002h)
The most obvious and reliable way is to use a palette with grayscale RGB values. However, Paintbrush IV is explicetly implementing (or ignoring?) an obscure grayscale format with following settings:
  [01h]=version=05h, and [44h]=0002h=grayscale
That settings are used in a file called gmarbles.pcx (which does contain a 256-color RGB palette with gray RGB values, ie. one can simply ignore the special settings, and display it as normal 256-color image).

Default 16-color CGA/EGA Palettes
  Color  Name                     IRGB1111 RGB222 RGB888   Windows
  00h    dark black               0000     000    000000   000000
  01h    dark blue                0001     002    0000AA   000080
  02h    dark green               0010     020    00AA00   008000
  03h    dark cyan                0011     022    00AAAA   008080
  04h    dark red                 0100     200    AA0000   800000
  05h    dark magenta             0101     202    AA00AA   800080
  06h    dark yellow (brown)      0110     210!!  AA5500!! 808000
  07h    dark white (light gray)  0111     222    AAAAAA   C0C0C0!!
  08h    bright black (dark gray) 1000     111    555555   808080!!
  09h    bright blue              1001     113    5555FF   0000FF
  0Ah    bright green             1010     131    55FF55   00FF00
  0Bh    bright cyan              1011     133    55FFFF   00FFFF
  0Ch    bright red               1100     311    FF5555   FF0000
  0Dh    bright magenta           1101     313    FF55FF   FF00FF
  0Eh    bright yellow            1110     331    FFFF55   FFFF00
  0Fh    bright white             1111     333    FFFFFF   FFFFFF
Some notes on number of colors:
 CGA supports 16 colors in text mode (but only max 4 colors in graphics mode).
 EGA supports the same 16 colors as CGA in both text and graphics mode.
 EGA-with-special-EGA-monitor supports 64 colors (but only max 16 at once).
 VGA supports much colors (but can mimmick CGA/EGA colors, or similar colors)
CGA is using a 4pin IRGB1111 signal for up to 16 colors in text mode (max 4 colors in graphics mode), and CGA monitors contain some circuitry to convert "dark yellow" to "brown" (though cheap CGA clones may display it as "dark yellow").
EGA can display CGA colors (with all 16 colors in graphics mode). EGA-with-special-EGA-monitor uses 6pin RGB222 signals for up to 64 colors (but not more than 16 colors at once).
Windows is also using those 16 standard colors (when not having any VGA driver installed, and also in 256-color VGA mode, in the latter case the 16 standard colors are held to always available (even if different tasks are trying to simultanously display different images with different palettes).
However, Windows has dropped brown, and uses non-pastelized bright colors.

PCX files in PSX games
  .PCX with RLE used by Jampack Vol. 1 (MDK\CD.HED\*.pcx)
  .PCX with RLE used by Hot Wheels Extreme Racing (MagDemo52: US_01293\MISC\*)
  .PCX with RLE used by Metal Gear Solid (slightly corrupted PCX files)

PCX files in PSX Metal Gear Solid (MGS)
MGS is storing some extra data at [4Ah..57h] (roughly resembling the info in TIM files).
  04Ah 2    Custom MGS ID (always 3039h)
  04Ch 2    Display Mode? (08h/18h=4bit, 09h/19h=8bit)
  04Eh 2    Bitmap X-coordinate in VRAM (reportedly "divided by 2" ???)
  050h 2    Bitmap Y-coordinate in VRAM
  052h 2    Palette X-coordinate in VRAM
  054h 2    Palette Y-coordinate in VRAM
  056h 2    Palette number of actually used colors (can be less than 16/256)
  058h 28h  Reserved (zerofilled)
  080h ..   Bitmap data (RLE compressed)
  ...  1    VGA Palette ID (0Ch=256 colors)                      ;\when 8bpp
  ..   300h VGA Palette (256 colors, 3-byte per color  = R,G,B)  ;/
  ..   ..   Padding to 4-byte boundary, ie. palette isn't at filesize-301h !!!
MGS has filesize padded to 4-byte boundary. That is causing problems for files with 256-color palette: The official way to find the palette is to stepback 301h bytes from end of file, which won't work with padding. To find the MGS palette, one must decompress the whole bitmap, and then expect the 301h-byte palette to be located after the compressed data.
As an extra oddity, MGS uses non-square ultra-high DPI values.

DCX Archives
DCX archives contain multiple PCX files (eg. multi-page FAX documents). The standard format is as so:
  0000h 4     ID (3ADE68B1h) (987654321 decimal)
  0004h 4000h File List (32bit offsets) (max 1023 files, plus 0=End of List)
  1004h ..    File Data area (PCX files)
However, some files have the first PCX at offset 1000h (ie. the list is only 3FFCh bytes tall). Reportedly there are also files that start with yet smaller offsets (for saving space when the file list contains fewer entries).
The PCX filesize is next-curr offset (or total-curr for last file).

References
https://www.fileformat.info/format/pcx/egff.htm


CDROM File Video 2D Graphics CEL/BGD/TSQ/ANM/SDF (Sony)

CEL/BGD/TSQ/ANM/SDF

CEL: Cell Data (official format with 8bit header entries)
This does merely translate Tile Numbers to VRAM Addresses and Attributes (with the actual VRAM bitmap data usually being stored in .TIM files).
  000h 1   File ID (22h)
  001h 1   Version (3)
  002h 2   Flag (bit15=WithAttr, bit14=AttrDataSize:0=8bit,1=16bit, bit13-0=0)
  004h 2   Number of cell data items (in cell units) (N)
  006h 1   Sprite Editor Display Window Width  (in cell units)
  007h 1   Sprite Editor Display Window Height (in cell units)
  008h ..  Cell Data[N] (64bit entries)
  ...  ..  Cell Attr[N] (0bit/8bit/16bit user data? depending on Flag)
Cell Data:
  0-7   Tex Coord X (8bit)
  8-15  Tex Coord Y (8bit)
  16-21 Clut X      (6bit)
  22-30 Clut X      (9bit)
  31    Semi-transparency enable        ;-only in Version>=3
  32    Vertical Reversal   (Y-Flip)    ;\only in Version=0 and Version>=2
  33    Horizontal Reversal (X-Flip)    ;/
  34-47 Unused
  48-52 Texture Page (5bit)
  53-54 Semi Transparency     (0=B/2+F/2, 1=B+F, 2=B-F, 3=B+F/4)
  55-56 Texture page colors   (0=4bit, 1=8bit, 2=15bit, 3=Reserved)
  57-60 Sprite Editor Color Set Number  ;\
  61    Unused                          ; only in Version>=3
  62-63 Sprite Editor TIM Bank          ;/     XXX else hardcoded?
This is used in R-Types, CG.1\file3Dh\file00h, but [6,7] are 16bit wide! And there are a LOT of ZEROes appended (plus FFh-padding due to CG.1 archive size units).
Used by R-Types (CG.1\file07h\file01h, size 08h*04h, with 8bit attr)
Used by R-Types (CG.1\file07h\file03h, size 10h*08h, with 16bit attr)
Used by R-Types (CG.1\file07h\file05h, size 04h*04h, with 16bit attr)
Used by Tiny Tank (MagDemo23: TINYTANK\TMD05.DSK\*.CEL, size 08h*05h)
Used by PSX-SDK: Programmer Tool CDROM (PSX\SAMPLE\GRAPHICS\BG\*\*.CEL)

CEL16: Inofficial CEL hack with 16bit entries and more extra data (R-Types)
This is an inofficial hack used by R-Types, the game does use both the official CEL and inofficial CEL16 format.
  000h 1   File ID (22h)        ;\same as in official CEL version
  001h 1   Version (3)          ;/
  002h 2   Flag (...unknown meaning in this case...?)           ;<-- ?
  004h 2   Number of cell data items (in cell units) (N)
  006h 2   Sprite Editor Display Window Width  (in cell units)  ;<-- 16bit!
  008h 2   Sprite Editor Display Window Height (in cell units)  ;<-- 16bit!
  00Ah ..  Cell Data[N] (64bit entries)
  ...  ..  Cell Attr[N] (16bit/192bit user data, depending on Flag or so...?)
Used by R-Types (CG.1\file12h\file00h, size 0120h*000Fh with 192bit attr)
Used by R-Types (CG.1\file15h\file00h, size 0168h*000Fh with ? attr)
Used by R-Types (CG.1\file1Ch\file00h, size 00D8h*000Fh with ? attr)

BGD: BG Map Data (official format with 8bit header entries)
  000h 1   File ID (23h)
  001h 1   Version (0)
  002h 2   Flag (bit15=WithAttr, bit14=AttrDataSize:0=8bit,1=16bit, bit13-0=0)
  004h 1   BG Map Width  (in cell units) (W)
  005h 1   BG Map Height (in cell units) (H)
  006h 1   Cell Width    (in pixels)
  007h 1   Cell Height   (in pixels)
  008h ..  BG Map Data[W*H] (16bit cell numbers)
  ...  ..  BG Map Attr[W*H] (0bit/8bit/16bit user data? depending on Flag)
Used by R-Types (CG.1\file07h\file00h, official BGD format)
Used by Cardinal Syn (MagDemo03,09: SYN\SONY\KROLOGO.WAD\*.BGD)
Used by Tiny Tank (MagDemo23: TINYTANK\TMD05.DSK\*.BGD, with 8bit entries)
Used by Reel Fishing (*.PAK\..\*)
Used by PSX-SDK: Programmer Tool CDROM (PSX\SAMPLE\GRAPHICS\BG\*\*.BGD)

BGD16: Inofficial BGD hack with 16bit entries (R-Types)
This is an inofficial hack used by R-Types, the game does use both the official BGD and inofficial BGD16 format. Apparently invented to support bigger BG Map Widths for huge sidescrolling game maps.
  000h 1   File ID (23h)        ;\same as in official BGD version
  001h 1   Version (0)          ;/
  002h 2   Flag (bit15=WithAttr, bit14=AttrDataSize:0=8bit,1=16bit, bit13-0=0)
  004h 2   BG Map Width  (in cell units) (W)                    ;<-- 16bit!
  006h 2   BG Map Height (in cell units) (H)                    ;<-- 16bit!
  008h 2   Cell Width    (in pixels)                            ;<-- 16bit!
  00Ah 2   Cell Height   (in pixels)                            ;<-- 16bit!
  00Ch ..  BG Map Data[W*H] (16bit cell numbers)
  ...  ..  BG Map Attr[W*H] (0bit/8bit/16bit user data? depending on Flag)
  ...  ..  FFh-padding (in case being stored in R-Types' DOT1 archives)
Used by R-Types (CG.1\file3Ch\file00h, inofficial BGD16 format)

TSQ: Animation Time Sequence
  000h 1   File ID (24h)
  001h 1   Version (1=normal) (but see below notes on older versions)
  002h 2   Number of Sequence data entries (N)
  004h N*8 Sequence Data (64bit per entry)
Sequence entries (same format as in ANM files):
  000h 2   Sprite Group Number to be displayed
  002h 1   Display Time (can be 0)
  003h 1   Attribute/unused (bit0-3=Zero, bit4-7=User defined; version>=1 only)
  004h 2   Hotspot X Coordinate (usually 0, or maybe can be +/-NNN ?)
  006h 2   Hotspot Y Coordinate (usually 0, or maybe can be +/-NNN ?)
There aren't any known games using .TSQ files. The Tron Bonne source code leak includes a set of ANM/CEL/BGD/TSQ files, but those files aren't actually used in the retail version.

ANM: Animation Information
  000h 1   File ID (21h)
  001h 1   Version (3=normal) (but see below notes on older versions)
  002h 2   Flag (bit0-1=TPF, bit2-11=0, bit12-15=CLT)
            0-1   TPF PixFmt (0=4bpp, 1=8bpp, 2/3=Reserved)   ;version>=2 only
            2-11  -   Reserved (0)
            12-15 CLT Number of CLUT Groups, for color animation
  004h 2   Number of Sprites Groups
  006h 2   Number of Sequences (N) (can be 0=None)
  008h N*8 Sequence(s) (64bit per entry)  ;Num=[004h]
  ...  ..  Sprite Group(s)                ;Num=[006h]
  ...  ..  CLUT Group(s)                  ;Num=[002h].bit12-15
Sequence entries (same format as in TSQ files):
  000h 2   Sprite Group Number to be displayed (range 0..AnimHdr[004h]-1)
  002h 1   Display Time (can be 00h or 0Ah or whatever)
  003h 1   Attribute/unused (bit0-3=Zero, bit4-7=User defined; version>=3 only)
  004h 2   Hotspot X Coordinate (usually 0, or maybe can be +/-NNN ?)
  006h 2   Hotspot Y Coordinate (usually 0, or maybe can be +/-NNN ?)
Sprite Group entries (a "Group" represents a metatile for an animation frame):
  000h 4   Number of Sprites in this Sprite Group ("sprites per metatile")
  004h ..  Sprite(s), 10h or 14h bytes each (see below)
 Sprites:
  000h 1   Tex Coord X (8bit)
  001h 1   Tex Coord Y (8bit)
  002h 1   Offset X from Hotspot within frame (maybe vertex x ?)
  003h 1   Offset Y from Hotspot within frame (maybe vertex y ?)
  004h 2   CBA Clut Base (bit0-5=ClutX, Bit6-14=ClutY, bit15=SemiTransp)
  006h 2   FLAGs (bit0-4, bit5-6, bit7-8, bit9, bit10, bit11, bit12-15)
            0-4   TPN Texture Page Number
            5-6   ABR Semi-Transparency Rate
            7-8   TPF Pixel depth (0=4bpp, 1=8bpp, 2=16bpp)
            9     -   Reserved
            10    RSZ Scaling  (0=No, 1=Scaled)
            11    ROT Rotation (0=No, 1=Rotated)
            12-15 THW Texture Width/Height div8 (or 0=Custom Width/Height)
  008h (2) Custom Texture Width      ;\only present if
  ...  (2) Custom Texture Height     ;/FLAGs.bit12-15=0=CustomSize
  ...  2   Angle of Rotation (in what units?)
  ...  2   Sprite Editor info (bit0-7=0..1?, bit8-13=ClutNo, bit14-15=TimBank)
  ...  2   Scaling X (for Vertex?) (as whatever fixed point number) (eg. 1000h)
  ...  2   Scaling Y (for Vertex?) (as whatever fixed point number) (eg. 1000h)
CLUT Group entries:
  000h 4   CLUT size in bytes (Width*Height*2+0Ch)
  004h 2   Clut X Coordinate
  006h 2   Clut Y Coordinate
  008h 2   Clut Width
  00Ah 2   Clut Height
  00Ch ..  CLUT entries (16bit per entry, Width*Height*2 bytes)
Note: ALICE.PAC\MENU.PAC\CON00.ANM has NumSequences=0 and NumSpriteGroups=2Dh (unknown if/how that is animated, maybe it has 2Dh static groups? or the groups are played in order 0..2Ch with display time 1 frame each?).
Used by Alice in Cyberland (ALICE.PAC\*.ANM) (ANM v3)
Unknown if there are any other games are using that format.

SDF: Sprite Editor Project File
This is an ASCII text file for "artist boards" with following entries:
  TIM0 file0.tim             ;\
  TIM1 file1.pxl file1.clt   ; four TIM banks (with TIM or PXL/CLT files)
  TIM2                       ; (or no filename for empty banks)
  TIM3                       ;/
  CEL0 file0.cel             ;-one CEL (with CEL, or no filename if none)
  MAP0 file0.bgd             ;\
  MAP1 file1.bgd             ; four BG MAP banks (with BGD filenames)
  MAP2                       ; (or no filename for empty banks)
  MAP3                       ;/
  ANM0 file0.anm             ;-one ANM (with ANM, or no filename if none)
  DISPLAY n       ;0-3=256/320/512/640x240, 4-7=256/320/512/640x480
  COLOR n         ;0=4bpp, 1=8bpp  ;docs are unclear, is it COLORn or COLOR n?
  ADDR0 texX texY clutX clutY numColorSets ;\
  ADDR1 texX texY clutX clutY numColorSets ; four texture/palette offsets
  ADDR2 texX texY clutX clutY numColorSets ; for the corresponding TIM banks
  ADDR3 texX texY clutX clutY numColorSets ;/ (or whatever for empty banks?)


CDROM File Video 3D Graphics TMD/PMD/TOD/HMD/RSD (Sony) 

 ____________________________________ TMD _____________________________________

TMD - Modeling Data for OS Library
  000h 4     ID (00000041h)
  004h 4     Flags (bit0=FIXP, bit1-31=Reserved/zero)
  008h 4     Number of Objects (N)     ;"integral value" uh?
  00Ch N*1Ch Object List (1Ch-byte per entry)
  ...  ..    Data (Vertices, Normals, Primitives)
Object List entries:
  000h 4    Start address of a Vertex     ;\Address values depend on the
  004h 4    Number of Vertices            ; file header's FIXP flag:
  008h 4    Start address of a Normal     ;  FIXP=0 Addr from begin of Object
  00Ch 4    Number of Normals             ;  FIXP=1 Addr from begin of TMD File
  010h 4    Start address of a Primitive  ;
  014h 4    Number of Primitives          ;/
  018h 4    Scale (signed shift value, Pos=SHL, Neg=SHR) (not used by LIBGS)
Vertex entries (8-byte):
  000h 2    Vertex X (signed 16bit)
  002h 2    Vertex Y (signed 16bit)
  004h 2    Vertex Z (signed 16bit)
  006h 2    Unused
Normal entries (8-byte) (if any, needed only for computing light directions):
  000h 2    Normal X (fixed point 1.3.12)
  002h 2    Normal Y (fixed point 1.3.12)
  004h 2    Normal Z (fixed point 1.3.12)
  006h 2    Unused
Primitive entries (variable length):
  000h 1    Output Size/4 of the GPU command (after GTE conversion)
  001h 1    Input Size/4 of the Packet Data in the TMD file
  002h 1    Flag
              0   Light source calculation (0=On, 1=Off)
              1   Clip Back (0=Clip, 1=Don't clip) (for Polygons only)
              2   Shading (0=Flat, 1=Gouraud)
                   (Valid only for the polygon not textured,
                   subjected to light source calculation)
              3-7 Reserved (0)
  003h 1    Mode (20h..7Fh) (same as GP0(20h..7Fh) command value in packet)
  004h ..   Packet Data
Packet Data (for Polygons)
  000h 4   GPU Command+Color for that packet (CcBbGgRrh), see GP0(20h..3Fh)
  ... (4)  Texcoord1+Palette (ClutYyXxh)               ;\
  ... (4)  Texcoord2+Texpage (PageYyXxh)               ; only if Mode.bit2=1
  ... (4)  Texcoord3         (0000YyXxh)               ;
  ... (4)  Texcoord4         (0000YyXxh) ;-quad only   ;/
  ... (4)  Color2 (00BbGgRrh)                          ;\
  ... (4)  Color3 (00BbGgRrh)                          ; only if Flag.bit2=1
  ... (4)  Color4 (00BbGgRrh) ;-quad only              ;/
  ... (2)  Normal1 (index in Normal list?)  ;always, unless Flag.bit0=1
  ...  2   Vertex1 (index in Vertex list?)
  ... (2)  Normal2 (index in Normal list?)             ;-only if Mode.bit4=1
  ...  2   Vertex2 (index in Vertex list?)
  ... (2)  Normal3 (index in Normal list?)             ;-only if Mode.bit4=1
  ...  2   Vertex3 (index in Vertex list?)
  ... (2)  Normal4 (index in Normal list?) ;\quad only ;-only if Mode.bit4=1
  ...  2   Vertex4 (index in Vertex list?) ;/
  ... (2)  Unused zeropadding (to 4-byte boundary)
Packet Data (for Lines)
  000h 4   GPU Command+Color for that packet (CcBbGgRrh), see GP0(40h,50h)
  ... (4)  Color2 (00BbGgRrh)                          ;-only if Mode.bit4=1
  ...  2   Vertex1 (index in Vertex list?)
  ...  2   Vertex2 (index in Vertex list?)
Packet Data (for Rectangle/Sprites)
  000h 4   GPU Command+Color for that packet (CcBbGgRrh), see GP0(60h..7Fh)
  ...  ..  Unknown, reportedy "with 3-D coordinates and the drawing
           content is the same as a normal sprite."
Note: Objects should usually contain Primitives and Vertices (and optionally Normals), however, N2O\SHIP.TMD does contain some dummy Objects with Number of Vertices/Normals/Primitives all set to zero.
Used by Playstation Logo (in sector 5..11 on all PSX discs, 3278h bytes)
Used by ...???model???... (MagDemo54: MODEL\*.BIN\*.TMD)
Used by Alice in Cyberland (ALICE.PAC\xxx_TM*.FA\*.TMD)
Used by Armored Core (MagDemo02: AC10DEMP\MS\MENU_TMD.T\*)
Used by Bloody Roar 1 (MagDemo06: CMN\EFFECT.DAT\0005h)
Used by Deception III Dark Delusion (MagDemo33: DECEPT3\K3_DAT.BIN\056A,0725\*)
Used by Gundam Battle Assault 2 (DATA\*.PAC\*)
Used by Hear It Now (Playstation Developer's Demo) (*.TMD and FISH.DAT).
Used by Jersey Devil (MagDemo10: JD\*.BZZ\*)
Used by Klonoa (MagDemo08: KLONOA\FILE.IDX\*)
Used by Legend of Dragoon (MagDemo34: LOD\DRAGN0.BIN\16xxh)
Used by Macross VF-X 2 (MagDemo23: VFX2\DATA01\*.TMD)
Used by Madden NFL '98 (MagDemo02: TIBURON\MODEL01.DAT\*)
Used by No One Can Stop Mr. Domino (MagDemo18: DATA\*, .TMD and DOT1\TMD)
Used by O.D.T. (MagDemo17: ODT\*.LNK\*)
Used by Parappa (MagDemo01: PARAPPA\COMPO01.INT\3\*.TMD)
Used by Resident Evil 1 (PSX\ITEM_M1\*.DOR\0001)
Used by Starblade Alpha (FLT\SB2.DAT\* and TEX\SB2.DAT\*)
Used by Tiny Tank (MagDemo23: TINYTANK\TMD*.DSK\*.TMD)
Used by WCW/nWo Thunder (MagDemo19: THUNDER\RING\*.TMD)
Used by Witch of Salzburg (the MODELS\*.MDL\*.TMD)
Used by Scooby Doo and the Cyber Chase (MagDemo54: MODEL\*\*)
Used by Vampire Hunter D (ETC\*.TMD and EFFECT\*.TMD and EFFECT\*.MPK\*)

 ____________________________________ PMD _____________________________________

PMD - High-Speed Modeling Data
This is about same as TMD, with less features, intended to work faster.
  000h 4    ID (00000042h)
  004h 4    Offset to Primitives
  008h 4    Offset to Shared Vertices (or 0=None)
  00Ch 4    Number of Objects
  010h ..   Objects         (4+N*4 bytes each, with offsets to Primitives)
  ...  ..   Primitives
  ...  ..   Shared Vertices (8-bytes each, if any)
Vertex entries (8-byte):
  000h 2    Vertex X (signed 16bit)
  002h 2    Vertex Y (signed 16bit)
  004h 2    Vertex Z (signed 16bit)
  006h 2    Unused
Objects:
  000h 4    Number of Primitives
  004h N*4  Offsets to Primitives ... maybe relative to hdr[004h] ?
Primitives:
  000h 2    Number of Packets
  002h 2    Type flags
             0    Polygon   (0=Triangle, 1=Quadrilateral)
             1    Shading   (0=Flat, 1=Gouraud)           ;uh, with ONE color?
             2    Texture   (0=Texture-On, 1=Texture-Off) ;uh, withoutTexCoord?
             3    Shared    (0=Independent vertex, 1=Shared vertex)
             4    Light source calculation (0=Off, 1=On)  ;uh, withoutNormal?
             5    Clip      (0=Back clip, 1=No back clip)
             6-15 Reserved for system
  004h ...  Packet(s)
Packet entries, when Type.bit3=0 (independent vertex):
  000h 4   GPU Command+Color for that packet (CcBbGgRrh), see GP0(20h..7Fh)
  004h 8   Vertex1 (Xxxxh,Yyyyh,Zzzzh,0000h)
  00Ch 8   Vertex2 (Xxxxh,Yyyyh,Zzzzh,0000h)
  014h 8   Vertex3 (Xxxxh,Yyyyh,Zzzzh,0000h)
  01Ch (8) Vertex4 (Xxxxh,Yyyyh,Zzzzh,0000h) ;<-- only when Type.bit0=1 (quad)
Packet entries, when Type.bit3=1 (shared vertex):
  000h 4   GPU Command+Color for that packet (CcBbGgRrh), see GP0(20h..7Fh)
  004h 4   Offset to Shared Vertex1    ;offsets are
  008h 4   Offset to Shared Vertex2    ;"from the start of a row"
  00Ch 4   Offset to Shared Vertex3    ;aka from "Packet+04h" ?
  010h (4) Offset to Shared Vertex4          ;<-- only when Type.bit0=1(quad)
Unknown if/how Texture/Light is implemented... without TexCoords/Normals?
Unknown if/how Gouraud is implemented... with ONE color and without Normals?
Used only by a few games:
  Cool Boarders 2 (MagDemo02: CB2\DATA3\*.PMD)
  Cardinal Syn (MagDemo03,09: SYN\*\*.WAD\*.PMD)    (4-byte hdr plus PMD file)
  Sesame Streets Sports (MagDemo52: SSS\LV*\*MRG\*) (4-byte hdr plus PMD file)
  PSX-SDK: Programmer Tool CDROM (PSX\SAMPLE\GRAPHICS\PMD\*.PMD)
Unknown if/which other games are using the PMD format.

 ____________________________________ TOD _____________________________________

TOD - Animation Data
  000h 1    ID (50h)
  001h 1    Version (0)
  002h 2    Resolution (time per frame in 60Hz units, can be 0) (60Hz on PAL?)
  004h 4    Number of Frames
  008h ..   Frame1
  ...  ..   Frame2
  ...  ..   Frame3
  ...  ..   etc.
Frames:
  000h 2    Frame Size in words (ie. size/4)
  002h 2    Number of Packets (can be 0=None, ie. do nothing this frame)
  004h 4    Frame Number (increasing 0,1,2,3,..)
  008h ...  Packet(s)
Packet:
  000h 2    Object ID
  002h 1    Type/Flag (bit0-3=Type, bit4-7=Flags)
  003h 1    Packet Size ("in words (4 bytes)")
  004h ...  Packet Data
XXX... in Sony's doc.
Used by Witch of Salzburg (ANIM\ANM0\ANM0.TOD) (oddly with [02h]=0000h)
Used by Parappa (MagDemo01: PARAPPA\COMPO01.INT\3\*.TOD)
Used by Macross VF-X 2 (MagDemo23: VFX2\DATA01\*.TOD and *.TOX)
Used by Alice in Cyberland (ALICE.PAC\xxx_T*.FA\*.TOD)
Used by PSX-SDK: Programmer Tool CDROM (PSX\SAMPLE\GRAPHICS\TOD\JANKEN\*\*.TOD)
Unknown if/which other games are using the TOD format.

 ____________________________________ HMD _____________________________________

HMD - Hierarchical 3D Model, Animation and Other Data
  000h 4    ID (00000050h)   ;same as in TOD, which CAN ALSO have MSBs=zero(!)
  004h 4    MAP FLAG (0 or 1, set when mapped via GsMapUnit() function)
  008h 4    Primitive Header Section pointer (whut?)
  00Ch 4    Number of Blocks
  010h 4*N  Pointers to Blocks
  ...       Primitive Header section    (required)
  ...       Coordinate section          (optional)
  ...       Primitive section           (required)
This format is very complicated, see Sony's "File Formats" document for details.
.HMD used by Brunswick Bowling (MagDemo13: THQBOWL\*).
.HMD used by Soul of the Samurai (MagDemo22: RASETSU\0\OPT01T.BIN\0\0\*)
.HMD used by Bloody Roar 2 (MagDemo22: LON\LON*.DAT\*, ST5\ST*.DAT\02h..03h)
.HMD used by Ultimate Fighting Championship (MagDemo38: UFC\CU00.RBB\6Bh..EFh)
.HMD used by PSX-SDK: Programmer Tool CDROM (PSX\SAMPLE\GRAPHICS\HMD\DATA\..)
Unknown if/which games other are using the HMD format.

 ____________________________________ RSD _____________________________________

RSD Files (RSD,PLY,MAT,GRP,MSH,PVT,COD,MOT,OGP)
RSD files consist of a set of several files (RSD,PLY,MAT,etc). The files contain the "polygon source code" in ASCII text format, generated from Sony's "SCE 3D Graphics Tool". For use on actual hardware, the "RSDLINK" utility can be used to convert them to binary (TMD, PMD, TOD?, HMD?) files.
  .RSD Main project file
  .PLY Polygon Vertices (Vertices, Normals, Polygons)
  .MAT Polygon Material (Color, Blending, Texture)
  .GRP Polygon Grouping
  .MSH Polygon Linking                   ;\
  .PVT Pivot Rotation center offsets     ; New Extended
  .COD Vertex Coordinate Attributes      ; (since RSD version 3)
  .MOT Animation Information             ;/
  .OGP Vertex Object Grouping            ;-Sub-extended
All of the above files are in ASCII text format. Each file is starting with a "@typYYMMDD" string in the first line of the file, eg. "@RSD970401" for RSD version 3. Vertices are defined as floating point values (as ASCII strings).
There's more info in Sony's "File Formats" document, but the RSD stuff isn't used on retail discs. Except:
  RSD/GRP/MAT/PLY (and DXF=whatever?) used on Yaroze disc (DTL-S3035)


CDROM File Video STR Streaming and BS Picture Compression (Sony)

STR Files (movie streams)
CDROM File Video Streaming STR (Sony)
CDROM File Video Streaming STR Variants
CDROM File Video Streaming Framerate
CDROM File Video Streaming Audio
CDROM File Video Streaming Chunk-based formats
CDROM File Video Streaming Mis-mastered files
Apart from the 20h-byte STR headers, movies basically consist of a series of BS files (see below).

BS Files (Huffman compressed MDEC codes)
BS stands for bitstream, which might refer to the use in STR files, or to the Huffman bitstreams.
CDROM File Video BS Compression Versions
CDROM File Video BS Compression Headers
The header is followed by the bitstream...
  v1/v2/v3/ea/iki --> first bit in bit15 of first halfword (good for psx)
  v0              --> first bit in bit7 of first byte (not so good for psx)
  (to use the same decoder for all version: swap each 2 bytes in v0)
For each block, the bitstream contains one DC value, up to 63 AC values, terminated by EOB (end of block).
CDROM File Video BS Compression DC Values
CDROM File Video BS Compression AC Values
Apart from being used in STR movies, BS can be also used to store single pictures:
CDROM File Video BS Picture Files

Wacwac (similar as BS, but with completely different Huffman codes)
CDROM File Video Wacwac MDEC Streams

Credits
Thanks to Michael Sabin for info on various STR and BS variants:
https://github.com/m35/jpsxdec/


CDROM File Video Streaming STR (Sony)

.STR Sectors (with 20h-byte headers) (for MDEC Movies, or User data)
  000h 2    StStatus (0160h) (RV6Rh; R=Reserved=0, V=Version=1, 6=Fixed ID)
  002h 2    StType (0000h..7FFFh=User Defined, 8000h..FFFFh=System; 8001h=MDEC)
  004h 2    StSectorOffset (Sector number in the frame, 0=First)
  006h 2    StSectorSize   (Number of sectors in the frame) (eg. 4 or 5)
  008h 4    StFrameNo      (Frame number, 1=First) (except Viewpoint=0)
  00Ch 4    StFrameSize    (in bytes, in this frame, excluding headers/padding)
 When StType=0000h..7FFFh:
  010h 10h  StUser         (user defined data)
  020h 7E0h User data      (more user defined data)
 When StType=8001h=MDEC (the only system defined type) (with StStatus=0160h):
  010h 2    StMovieWidth                  (eg. 0140h)
  012h 2    StMovieHeight                 (eg. 00F0h)
  014h 4    StHeadM (reserved for system) (eg. 38000720h) ;\same as [020h-027h]
  018h 4    StHeadV (reserved for system) (eg. 00020001h) ;/from 1st STR sector
  01Ch 4    Unspecified                   (eg. 00000000h) (except Viewpoint<>0)
  020h 7E0h Data (in BS format) (or padding, when image is smaller than frame)
The default file extension .STR is used by various games (though some games use other extensions, the .FMV files in Tomb Raider do also contain standard 20h-byte .STR sector headers).

Video Frames
The video frames consist of BS compressed images (that is, all sectors have STR headers at 000h..01Fh, and the first sector of each frame does additionally contain a standard BS fileheader at offset 020h..027h).
  See "CDROM File Video BS Compression" chapters
Less common, there is also a format for streaming polygon animations instead of BS compressed bitmaps:
CDROM File Video Polygon Streaming

STR Resolution
The Width/Height entries are almost always multiples of 16 pixels. But there are a few exceptions:
  Height=260 (104h) in Star Wars Rebel Assault II, NTSC (S1\L01_PLAY.STR)
  Height=200 (0C8h) in Perfect Assassin (DATA.JFS\CDV\*.STR)
  Height=40  (028h) in Gran Turismo 1 (TITLE.DAT\*, MagDemo10 and MagDemo15)
  Width=232  (0E8h) in Gran Turismo 1 (TITLE.DAT\*, MagDemo10 only)
For such videos, the width/height of MDEC decompression buffer in RAM must be rounded up to multiples of 16 pixels (and the decompressed picture should be cropped to the STR header width/height before forwarding it to VRAM).
Note: The extra scanlines are usually padded with the bottom-most scanline (except, Gran Turismo 1 has gray-padding in lower/right pixels). Ideally, one would repeat the bottom-most pixels in zigzag order.

Subtitles
Metal Gear Solid MGS\ZMOVIE.STR contains subtitles as text strings: The first sector of the .STR file is something custom (without STR header), the remaining movie consists of STR sectors with StType=0001h for subtitles and StType=8001h for picture frames.
Unknown if other games are using the same method, or other methods.
Obviously, subtitles could be also displayed as part of the compressed image, but text strings are much smaller, have better quality, and would also allow to support multiple languages.


CDROM File Video Streaming STR Variants

STR ID Values
  2-byte  0160h         ;Standard STR header
  1-byte  01h           ;Ace Combat 3 Electrosphere
  4-byte  "SMJ",01h     ;Final Fantasy 8, Video
  4-byte  "SMN",01h     ;Final Fantasy 8, Audio/left
  4-byte  "SMR",01h     ;Final Fantasy 8, Audio/righ
  4-byte  0000000xh     ;Judge Dredd
  4-byte  DDCCBBAAh     ;Electronic Arts v2/v3
  4-byte  08895574h     ;Chunk header in 1st sector only, Best Sports (demo)
  4-byte  "Ad10"        ;Chunk header in 1st sector only, Electronic Arts v1
  4-byte  "VLC0"        ;Chunk header in 1st sector only, Electronic Arts v4
  4-byte  "VMNK"        ;Chunk header in 1st sector only, Policenauts
  4-byte  01h,"XSP"     ;Sentient header in 1st sector only
  N-byre  zero(es)      ;Polygons? (in last 150Mbyte of PANEKIT.STR)

STR Type values (for videos that do have STR ID=0160h):
The official definition from Sony's File Formats document is as so;
  0000h..7FFFh=User Defined
  8000h..FFFFh=System (with 8001h=MDEC being the only officially defined type)
In practice, the following values are used (of which, 8001h is most common).
  0000h=Polygon Video, Wacwac as Polygon Stream
  0000h=Polygon Video?, Army Men Air Attack 2 (MagDemo40: AMAA2\*.PMB)
  0000h=MDEC Video, Alice in Cyberland
  0001h=MDEC Video, Ridge Racer Type 4 (PAL version, 320x176 pix)
  0001h=Whatever extra data for XA-ADPCM streams (Bits Laboratory games)
  0001h=Whatever non-audio waverform? (3D Baseball)
  0001h=Subtitles, Metal Gear Solid MGS\ZMOVIE.STR
  0002h=Software-rendered video (without using MDEC/GTE) (Cyberia)
  0002h=MDEC Video, Wacwac with IntroTableSet
  0003h=MDEC Video, Wacwac with EndingTableSet
  0004h=MDEC Video, Final Fantasy 9 (MODE2/FORM2)
  0008h=SPU-ADPCM, AKAO audio (Final Fantasy 9)
  0000h=SPU-ADPCM, AKAO audio (Chrono Cross Disc 1, Legend of Mana)
  0001h=SPU-ADPCM, AKAO audio (Chrono Cross Disc 1, Legend of Mana)
  0100h=SPU-ADPCM, AKAO audio (Chrono Cross Disc 2)
  0101h=SPU-ADPCM, AKAO audio (Chrono Cross Disc 2)
  0000h=Whatever special, channel 0 header (Nightmare Project: Yakata)
  0400h=Whatever special, channel 1 header (Nightmare Project: Yakata)
  0001h=Whatever special, channel 0 data   (Nightmare Project: Yakata)
  0401h=Whatever special, channel 1 data   (Nightmare Project: Yakata)
  5349h=MDEC Video, Gran Turismo 1 and 2 (with BS iki)
  0078h=MDEC Ending Dummy  (Mat Hoffman's Pro BMX (MagDemo48: MHPB\SHORT.STR)
  5673h=MDEC Leading Dummy (Mat Hoffman's Pro BMX (MagDemo48: MHPB\SHORT.STR)
  8001h=MDEC Video, Standard MDEC (most common type value)
  8001h=Polygon Video (Ape Escape) (same ID as standard MDEC)
  8001h=Eagle One: Harrier Attack various types (MDEC and other data)
  8001h=Dance series SPU-ADPCM streaming (with STR[1Ch]=DDCCBBAAh)
  8101h=MDEC Video, Standard MDEC plus bit8=FlagDisc2 (Chrono Cross Disc 2)
  8x01h=Whatever  ;\i-mode mo Issho - Doko Demo Issho Tsuika Disc (*.STR)
  9x01h=Whatever  ;/contains XA-ADPCM, and odd STR headers, with x=0h,4h,8h,Ch


 ______________________________________________________________________________

Leading XA-ADPCM
Most movies start with STR video sectors. But a few games start with XA-ADPCM:
  Ace Combat 3 Electrosphere (*.SPB)
  Alice in Cyber Land (*.STR)
  Judge Dredd (*.IXA) ;and very small 4-byte STR header
  ReBoot (MOVIES\*.WXA)
Also, Aconcagua (Wacwac) has XA-ADPCM before Video (but, yet before that, it has 150 leading zerofilled sectors).
Also, Porsche Challenge (SRC\MENU\STREAM\*.STR) starts with corrupted Subheaders, which may appear as leading XA-ADPCM (depending on how to interprete the corrupted header bits).

Leading SPU-ADPCM
  EA videos     ;\
  Crusader      ; chunks
  Policenauts   ;/
  AKAO videos

Metal Gear Solid (MGS\ZMOVIE.STR, 47Mbyte)
This is an archive dedicated to STR movies (with number of frames instead of filesize entries). Metal Gear Solid does also have cut-scenes with polygon animations (but those are supposedly stored elsewhere?).
  000h 4    Number of entries (4)
  004h N*8  File List
  ...  ..   Zerofilled
File List entries:
  000h 2    Unknown... decreasing values?
  002h 2    Number of Frames (same as last frame number in STR header)
  004h 4    Offset/800h (to begin of STR movie, with subtiltes in 1st sector)
Disc 1 has four movies: The first one has a bit more than 12.5 sectors/frame, the other three have a bit more than 10 sectors/frame (eg. detecting the archive format could be done checking for entries wirh 8..16 sectors/frame).
Example, from Disc 1:
  04 00 00 00
  ED 97 9E 01  01 00 00 00 ;num sectors=1439h ;div19Eh=C.81h ;97EDh-6137h=36B6h
  37 61 86 01  3A 14 00 00 ;num sectors=0F41h ;div186h=A.03h ;6137h-38D0h=2867h
  D0 38 10 03  7B 23 00 00 ;num sectors=1EA1h ;div310h=A.00h ;38D0h-2302h=15CEh
  02 23 73 02  1C 42 00 00 ;num sectors=1881h ;div273h=A.01h ;2302h-0000h=2302h
The files in the ZMOVIE.STR archive start with subtitles in 1st sector (this is usually/always only one single sector for the whole movie):
  000h 2    STR ID   (0160h)                                       ;\
  002h 2    STR Type (0001h=Subtitles)                             ;
  004h 2    Sector number within Subtitles (0)                     ; STR
  006h 2    Number of Sectors with Subtitles (1)                   ; header
  008h 4    Frame number (1)                                       ;
  00Ch 4    Data size counted in 4-byte units (same as [02Ch]/4)   ;
  010h 10h  Zerofilled                                             ;/
  020h 4    Unknown (2)                                            ;\
  024h 4    Unknown (1AAh, 141h, or 204h)                          ; Data
  028h 4    Unknown (00100000h)                                    ; part
  02Ch 4    Size of all Subtitle entries in bytes plus 10h         ;
  030h ..   Subtitle entries                                       ;/
  ...  ..   Zeropadding to 800h-byte boundary                      ;-padding
Subtitle entries:
  000h 4    Offset from current subtitle to next subtitle (or 0=Last subtitle)
  004h 4    First Frame number when to display the subtitle?
  008h 4    Number of frames when to display the subtitle?
  00Ch 4    Zero
  010h ..   Text string, terminated by 00h
  ...  ..   Zeropadding to 4-byte boundary
The text strings are ASCII, with special 2-byte codes (80h,7Bh=Linebreak, 1Fh,20h=u-Umlaut, etc).

 ________________________ STR with extra Header/Footer ________________________

Fade to Black (VIDEO*\*.DPS)
This contains a standard STR video, but with additional header/footer (and addly using ISO directory entries with attr=1555h, which would imply MODE1).
  0000h 1 sector      DPS Header                                   ;\header
  0800h 4 sectors     Zerofilled                                   ;/
  2800h many sectors  STR video  (interleaved with XA-ADPCM audio) ;\video
  ...   some sectors  Zerofilled (interleaved with XA-ADPCM audio) ;/
  ...   10 sectors    END markers                                  ;-footer
 DPS Header (in first sector):
  000h 4    File ID  ("DPS",00h)
  004h 0Ch  Zerofilled
  010h 2    Width    (140h)                                     ;\same as in
  012h 2    Height   (0A0h or 0D0h) (and maybe other for NTSC?) ;/STR headers
  014h 08h  Zerofilled
  01Ch 4    Number of video frames
  020h 7E0h Zerofilled
 End Marker (repeated in last 10 sectors):
  000h 2    STR ID   (0160h)
  002h 2    STR Type (8001h, same as MDEC)
  004h 0Ch  Zerofilled
  010h 4    End ID   ("END",00h)
  014h 7ECh Zerofilled


 ________________________ Customized STR Video Headers ________________________

Viewpoint (with slightly modified STR header)
  008h 4    Frame number (0=First)                      ;<-- instead of 1=First
  01Ch 2    Unknown (always D351h)                      ;<-- instead of zero
  01Eh 2    Number of Frames in this STR file           ;<-- instead of zero

Capcom games
Resident Evil 2 (ZMOVIE\*.STR, PL0\ZMOVIE\*.STR)
Super Puzzle Fighter II Turbo (STR/CAPCOM15.STR)
  01Ch 4    Sector number of 1st sector of current frame  ;<-- instead of zero

Chrono Cross Disc 2 Video
Chrono Cross Disc 1 does have normal STR headers, but Disc 2 has Type.bit8 toggled:
  002h 2    STR Type (8101h=Disc 2)                       ;<-- instead of 8001h
And, the Chrono Cross "final movie" does reportedly have "additional properties". Unknown, what that means, it does probably refer to the last movie on Chrono Cross Disc 2, which is quite huge (90Mbyte), and has lower resolution (160x112), and might have whatever "additional properties"?

Need for Speed 3
Need for Speed 3 Hot Pursuit (MOVIES\*.XA, contains videos, not raw XA-ADPCM)
Jackie Chan Stuntmaster (FE\MOVIES\*.STR)
With slightly modified STR headers:
  014h 4    Number of Frames (..excluding last some frames?) ;-instead BS[0..3]
  018h 4    Unlike the above modified entry, this is normal  ;-copy of BS[4..7]

ReBoot (MOVIES\*.WXA)
This has leading XA-ADPCM, and customized STR header:
  014h 2    Type (0000h=Normal, 01FFh=Empty frames at end of video)
  016h 2    Number of Frames (excluding empty ones at end of video)
  018h 8    Zerofilled

Gran Turismo 1 (230Mbyte STREAM.DAT) and Gran Turismo 2 (330Mbyte STREAM.DAT)
These two games use BS iki format, and (unlike other iki videos) also special STR headers:
  002h 2    STR Type (5349h) ("IS")         ;-special (instead 8001h)
  010h 2    Total number of frames in video ;-special (instead width)
  012h 2    Flags (bit15=1st, bit14=last)   ;-special (instead height)
  014h 8    Zero                            ;-special (instead BS header copy)
  020h 7E0h Data (in BS iki format)         ;-BS iki header (with width/height)
Caution: The STR header values aren't constant throughout the frame:
  Namely, flags in [012h] are toggled on first/last sector of each frame,
  and of course [04h] does also increase per sector.

PGA Tour 96, 97, 98 (VIDEO\..\*.XA and ZZBUFFER\*.STR)
Used by all movies in PGA Tour 96, 97 (and for the ZZBUFFER\BIGSPY.STR dummy padding movie in PGA Tour 98).
The videos have normal BS v2 data, but the Frame Size entry is 8 smaller than usually. As workaround, always load [0Ch]+8 for all movies with standard STR headers (unless that would exceed [06h]*7E0h).
  00Ch 4    Frame Size-8 (ie. excluding 8-byte BS header)  ;instead of Size-0
The padding videos in ZZBUFFER folder have additional oddities in STR header:
  ZZBUFFER\SPY256.STR    [14h..1Fh]=normal copy of 8-byte BS v2 header and zero
  ZZBUFFER\SPYGLASS.STR  [14h..1Fh]=zerofilled                          ;\BS v1
  ZZBUFFER\SPYTEST.STR   [14h..1Fh]=00 00 10 00 00 00 00 09 00 00 07 EE ;/
  ZZBUFFER\BIGSPY.STR    Used in PGA Tour 98 (instead of above three files)
SPYTEST.STR has nonsense quant values exceeding the 0000h..003Fh range (first frame has quant=00B1h, and later frames go as high as quant=FFxxh, that kind of junk is probably unrelated to BS fraquant). The oddities for SPYTEST.STR do also occur in some frames in PGA Tour 98 BIGSPY.STR. Anyways, those ZZBUFFER files seem to be only unused padding files.

Alice in Cyber Land (*.STR)
Note: First sector contains XA-ADPCM audio (video starts in 2nd sector).
 STR Sector Header:
  002h 2    STR Type (0000h=Alice in Cyber Land video)            ;-special
  008h 4    Frame number (1=First) (bit15 set in last frame, or FFFFh)
  010h 10h  Zerofilled (instead width/height and BS header copy)  ;-special
  020h 7E0h Data (in BS v2 format)
Frames are always 320x240.
The frame number of the last used frame of a movie has the bit15 set. After that last frame, there are some empty frame(s) with frame number FFFFh.
For some reason there are "extra audio sectors in between movies" (uh?).
Many of the movies have a variable frame rate. All movies contain frames sequences that match one of the following frame rates: 7.5 fps, 10 fps, 15 fps, 30 fps.

Encrypted iki (Panekit - Infinitive Crafting Toy Case)
  014h 8    Copy of decrypted BS header (instead of encrypted BS header)

Princess Maker: Yumemiru Yousei (PM3.STR)
Parappa (Japanese Demo version only) (S0/GUIDE.STR)
These files do have BS ID=3000h (except, the first and last some frames have normal ID=3800h). The STR header is quite normal (apart from reflecting the odd BS ID):
  016h 2    Copy of BS ID, 3000h in most frames (instead of 3800h)
  020h 7E0h Data (in BS format, also with BS ID 3000h, instead of 3800h)

Starblade Alpha and Galaxian 3
These movies have Extra stuff in the data section. The STR header is quite normal (apart from reflecting the Extra stuff):
  00Ch 4    Frame Size in bytes (=size of ExtraHeader + BsData + ExtraData)
  014h 4    Copy of Extra Header        ;instead of BS[0..3]
  018h 4    Copy of BS[0..3]            ;instead of BS[4..7]
  020h 7E0h Data (ExtraHeader + BsData + ExtraData)
The data part looks as so:
  000h 2    Size of BS Data area    (S1)        ;\Extra Header
  002h 2    Size of Extra Data area (S2)        ;/
  004h S1   BS Data (in BS v3 format)           ;-BS Data
  ..   S2   Extra Data (unknown purpose)        ;-Extra Data
Note: Starblade Alpha does use that format for GAMEn.STR and NAME.STR in FLT and TEX folders (the other movies in that game are in normal STR format).

Largo Winch: Commando SAR (FMV\NSPIN_W.RNG)
This is a somewhat "normal" movie, without audio, and with the STR headers moved to the begin of the file:
  000h Nx20h   STR Headers  ;size = filesize/800h*20h
  ...  Nx7E0h  Data         ;size = filesize/800h*7E0h
Note: The movie contains the rotating "W" logo, which is looped in Start screen.

Player Manager (1996, Anco Software) (FILMS\1..3\*.STR)
  006h 2    Number of Sectors in this Frame-1 (8..9 = 9..10 sectors)
  00Ch 4    Frame Size in bytes               (8..9*7E0h = 3F00h or 46E0h)
  010h 2    Bitmap Width                      (always F0h)
  012h 2    Bitmap Width                      (always 50h)
  014h 0Ch  Zerofilled (instead copy of BS header or copy of Extra header)
  020h 7E0h Data (Extra Stuff, BS v2 data, plus Unused stuff)
The data part occupies 9-10 sectors, consisting of:
  0000h Extra Stuff   (7E0h bytes, whatever, often starts with 00,FF,00,FF,..)
  07E0h BS v2 data    (3720h or 3F00h bytes, including FFh-padding)
  ...   Unused Sector (7E0h bytes, same as in previous frame or zerofilled)
The compressor tries to match the picture quality to the number of sectors per frame, but it's accidentally leaving the last sector unused:
  For 9 sectors:  Only 1..7 are used, sector 8 is same as in previous frame
  For 10 sectors: Only 1..8 are used, sector 9 is zerofilled
Apart from the odd format in FILMS\1..3\*.STR, the game does also have normal videos in FILMS\*.STR.

Chiisana Kyojin Microman (DAT\STAGE*\*.MV)
The .MV files have 5 sectors/frame: Either 5 video sectors without audio, or 4-5 video sectors plus XA-ADPCM audio (in the latter case, audio is in each 8th sector (07h,0Fh,17h,1Fh,etc), hence having filesize rounded up to N*8 sectors):
  Filesize = 800h*((NumberOfFrames*5))             ;5 sectors, no xa-adpcm
  Filesize = 800h*((NumberOfFrames*5+7) AND not 7) ;4-5 sectors, plus xa-adpcm
Caution: The STR header values aren't constant throughout the frame:
  Sector 0: [10h] = Number of Frames,   [12h]=Junk
  Sector 1: [10h] = Junk,               [12h]=0
  Sector 2: [10h] = Junk,               [12h]=Junk
  Sector 3: [10h] = Junk,               [12h]=Same as below (Bitmap Height)
 Below ONLY when having 5 sectors per frame:
  Sector 4: [10h] = Bitmap Width (140h) [12h]=Bitmap Height (D0h)
 That is, frames with 4 sectors do NOT have any Bitmap Width entry
 (the duplicated Height entry in sector 3 exists, so one could compute
 Width=NumMacroBlocks*100h/Height, or assume fixed Width=320, Height=208).
The Junk values can be zero, or increase/decrease during the movie, some or all of them seem to be sign-expanded from 12bit (eg. increasing values can wrap from 07xxh to F8xxh).
Apart from the odd DAT\STAGE*\*.MV files, the game does also have .STR files with normal STR headers and more sectors per frame (DAT\STAGE16,21,27\*.STR, DAT\OTHER\*.STR, DAT\OTHER\CM\*.STR, and MAT\DAT\*.STR).

Black Silence padding
Used by Bugriders: The Race of Kings (MOVIE\*XB.STR)
Used by Rugrats Studio Tour (MagDemo32: RUGRATS\DATA\OPEN\*B.STR)
  Each movie file is followed by dummy padding file. For example, in Bugriders:
  MOVIE\*XA.STR  Movie clip             (with correct size, 320x192)
  MOVIE\*XB.STR  Black Silence padding  (wrong size 640x192, should be 320x192)
The names are sorted alphabetically and exist in pairs (eg. CHARMXA.STR and CHARMXB.STR), and the disc sectors are following the same sort order.
The padding files contain only black pixels and silent XA-ADPCM sectors, with following unique STR header entries, notably with wrong Width entry (the MDEC data contains only 320x192 pixels).
  00Ch 4    Frame Size    (087Ch)
  010h 2    Bitmap Width  (wrongly set to 640, should be 320)
  012h 2    Bitmap Height (192)
  014h 2    MDEC Size     (05A0h)
  016h 2    BS ID         (3800h)
  018h 2    BS Quant      (0001h)
  01Ah 2    BS Version    (0002h)
  Filesize is always 44Fh sectors (about 2.2Mbyte per *XB.STR file)
The huge 7 second padding is a very crude way to avoid the next movie to be played when not immediately pausing the CDROM at end of current movie.

Ridge Racer Type 4 (only PAL version) (R4.STR)
The 570Mbyte R4.STR file contains XA-ADPCM in first three quarters, and two STR movies in last quarter:
  1st NTSC/US movie: 320x160 pix, 0F61h frames, 4-5 sectors/frame, normal STR
  1st PAL/EUR movie: 320x176 pix, 0CD0h frames, 5-6 sectors/frame, special STR
  2nd NTSC/US movie: 320x160 pix, 1D6Ah frames, 4-5 sectors/frame, normal STR
  2nd PAL/EUR movie: 320x160 pix, 18B5h frames, 5-6 sectors/frame, normal STR
As seen above, the PAL movies have lower framerate. And, the 1st PAL movie has higher resolution, plus some other customized STR header entries:
  002h 2    STR Type (0001h=Custom, 176pix PAL video)         ;instead of 8001h
  006h 2    Number of Sectors in this Frame (always 5..6)
  00Ch 4    Frame Size (always 2760h or 2F40h, aka 7E0h*5..6)
  012h 2    Bitmap Height (00B0h, aka 176 pixels)             ;instead of 00A0h
  014h 8    Zerofilled                                        ;instead BS[0..7]
  020h 7E0h Data (in BS v3 format, plus FFh-padding)
That is, the special video is standard MDEC, the only problem is detecting it as such (despite of the custom STR Type entry).

Mat Hoffman's Pro BMX (MagDemo48: MHPB\SHORT.STR)
This contains a normal MDEC movie, but with distorted "garbage" in first and last some sectors.
  1st sector          STR Type 5673h (Leading Dummy)                ;\
  2nd sector          STR Type 8001h (distorted/empty MDEC)         ; junk
  3rd..6th sector     STR Type 8001h (distorted/garbage MDEC)       ;/
  7th sector and up   STR Type 8001h (normal MDEC, with odd [01Ch]) ;-movie
  Last 96h sectors    STR Type 0078h (Ending Dummy)                 ;-junk
1st Sector:
  002h 2    STR Type (5673h=Leading Dummy)
  004h 4    Whatever (0004000Ch)
  008h 4    Whatever (0098967Fh)
  00Ch 4    Frame Size (always 100h)
  010h 7F0h EAh-filled
2nd Sector:
  002h 2    STR Type (8001h=Normal MDEC ID, but content is empty)
  004h 4    Whatever (0004000Ch)        ;\
  008h 4    Whatever (0098967Fh)        ; same as in 1st sector
  00Ch 4    Frame Size (always 100h)    ; (but ID at [002h] differes)
  010h 7F0h EAh-filled                  ;/
3rd-6th Sector:
  002h 2    STR Type (8001h=Normal MDEC ID, but content is distorted)
  004h 2    Sector number within current Frame (always 0)
  006h 2    Number of Sectors in this Frame (always 1)
  008h 4    Frame number (increasing, 1..4 for 3rd..6th sector)
  00Ch 4    Frame Size (always 7D0h)
  010h 10h  EAh-filled
  020h 7D0h Unknown (random/garbage?)
  7F0h 10h  EAh-filled
7th Sector and up (almost standard MDEC):
 Caution: The STR header values aren't constant throughout the frame:
 Entry entry [01Ch] is incremented per sector (or wraps to 0 in new section).
  01Ch 4    Increasing sector number (within current movie section or so)
Last 96h Sectors:
  002h 2    STR Type (0078h=Ending Dummy)
  004h 2    Sector number within current Frame (always 0)
  006h 2    Number of Sectors in this Frame (always 1)
  008h 4    Frame number (increasing, in last 96h sectors)
  00Ch 4    Frame Size (always 20h)
  010h 2    Bitmap Width  (always 40h)
  012h 2    Bitmap Height (always 40h)
  014h 7ECh Zerofilled

Final Fantasy VII (FF7) (MOVIE\*.MOV and MOVIE\*.STR)
These movies have Extra stuff in the data section. The STR header is quite normal (apart from reflecting the Extra stuff):
  00Ch 4    Frame Size in bytes (including 28h-byte extra stuff)
  014h 8    Copy of Extra data [0..7]           :-instead of BS header[0..7]
  020h 7E0h Data (ExtraData + BsData)
The data part looks as so:
  000h 28h  Extra data (unknown purpose, reportedly "Camera data" ... whut?)
  028h ..   BS Data (in BS v1 format)

Final Fantasy IX (FF9) (*.STR and *.MBG)
There are several customized STR header entries:
  002h 2    STR Type (0004h=FF9/Video)                      ;instead of 8001h
  004h 2    Sector number within current Frame (02h..num-1) (2..9 for video)
  006h 2    Total number of Audio+Video sectors in this frame (always 0Ah)
  00Ch 4    Frame Size/4 (of BS data, excluding MBG extra)  ;instead of Size/1
  014h 8    Copy of BS[0..7] from 8th video sector          ;instead 1st sector
  01Ch 2    Usually 0000h (or 0004h in some MBG sectors)    ;inszead of 0000h
  01Eh 2    Usually 0000h (or 3xxxh in some MBG sectors)    ;inszead of 0000h
  020h 8F4h Data (in BS v2 format, plus MBG extra data, if any)
Caution: The STR header values aren't constant throughout the frame:
  Namely, entry [1Ch..1Fh]=nonzero occurs only on the sector that does contain
  the end of BS data (=and begin of MBG extra data), and of course [04h] does
  also increase per sector.
Sector ordering has BS data snippets arranged backwards, for example, if BS data does occupy 2.5 sectors:
  [04h]=00h-01h 1st-2nd audio sector, SPU-ADPCM (see Audio streaming chapter)
  [04h]=02h-06h 1st-5th video sector, unused, [020h..913h] is FFh-filled
  [04h]=07h     6th video sector, contains end of BS data and MBG extra, if any
  [04h]=08h     7th video sector, contains middle of BS data
  [04h]=09h     8th video sector, contains begin of BS data
Sector type/size, very unusually with FORM2 sectors:
  Audio sectors are MODE2/FORM1 (800h bytes, with error correction)
  Video sectors are MODE2/FORM2 (914h bytes, without error correction)
Huffman codes are standard BS v2, with one odd exception: MDEC 001Eh/03E1h (run=0, level=+/-1Eh) should be usually encoded as 15bit Huffman codes, FF9 is doing that for 001Eh, but 03E1h is instead encoded as 22bit Escape code:
  000000000100010         MDEC=001Eh (run=0, level=+1Eh) ;-normal (used)
  000000000100011         MDEC=03E1h (run=0, level=-1Eh) ;-normal (not used)
  0000010000001111100001  MDEC=03E1h (run=0, level=-1Eh) ;-escape (used)
There are two movie variants: *.STR and *.MBG. Most MBG files (except SEQ02\MBG102.MBG) contain extra MBG info in [01Ch..01Fh] and extra MBG data appended after the BS data. If present, the appended MBG data is often/always(?) just these 28h-bytes:
  FF FF FF FF FE FF FE 41 AD AD AD AD AD AD AD AD
  AD AD AD AD AD AD AD AD AD AD AD AD AD AD AD AD
  AD AD AD AD AD AD AD AD
  (followed by FF's, which might be padding, or part of the extra data)
Unknown if some sectors contain more/other MBG data, perhaps compressed BG pixel-depth values for drawing OBJs in front/behind BG pixels?

 _______________________ Non-standard STR Video Headers _______________________

Final Fantasy VIII (FF8)
Video frames are always 320x224. The video frames are preceeded by two SPU-ADPCM audio sectors.
  000h 4    ID "SMJ",01h=Video
  004h 1    Sector number within current Frame (02h..num-1) (2..9 for video)
  005h 1    Total number of Audio+Video sectors in this frame, minus 1 (9)
  006h 2    Frame number (0=First)
  008h 7F8h Data (in BS v2 format)

Ace Combat 3 Electrosphere (in 520Mbyte ACE.SPH/SPB archive)
The videos start with one XA-ADPCM sector, followed by the first Video sector.
 STR Sector Header:
  000h 1    Always 01h
  001h 1    Sector number within current Frame (00h..num-1) (8bit)
  002h 2    Number of Sectors in this Frame
  004h 2    Unknown (1 or 3)
  006h 2    Frame number (decreasing, 0=Last)
  008h 2    Bitmap Width in pixels    ;\130hxE0h or 140hxB0h or 80hx60h
  00Ah 2    Bitmap Height in pixels   ;/
  00Ch 4    Zero
  010h 2    Zero, or decreasing timer (decreases approx every 2 sectors)
  012h 2    Zero, or decreasing timer (decreases approx every 1 sector)
  014h 3    Zero
  017h 1    Zero, or increases with step 2 every some hundred sectors
  018h 2    Zero, or Timer (increments when [1Ah] wraps from 04h to 01h)
  01Ah 1    Zero, or Timer (increments when [1Bh] wraps from 5Fh to 00h]
  01Bh 1    Zero, or Timer (increments approx every 1 sector)
  01Ch 2    Zero, or Whatever (changes to whatever every many hundred sectors)
  01Eh 2    Zero, or 0204h
  020h 7E0h Data (in BS v3 format)
Caution: The STR header values aren't constant throughout the frame:
  Namely, entry [10h..1Fh] can change within the frame (happens in japanese
  version), and of course [01h] does also increase per sector.
The Japanese version may be the only game that has two streaming videos running in parallel on different channels.
That means, non-japanese version is different...?

Judge Dredd (1998, Gremlin) (CUTS\*.IXA and LEVELS\*\*.IXA)
This is a lightgun-game with "interactive movies". The gameplay consists of running on a fixed path through a scene with pre-recorded background graphics, the only player interaction is aiming the gun at other people that show up in that movie scene. There are two movie types:
  LEVELS\*\*.IXA  - Interactive gameplay movies
  CUTS\*.IXA      - Non-interactive cut-scene movies
Both CUTS and LEVELS have unusually small 4-byte STR headers:
  000h 4    Sector number within current Frame (LEVELS=0..8, or CUTS=0..9)
  004h 7FCh Data (see below)
Data for CUTS is 320x240pix (10 sectors per frame):
  Note: CUTS videos have 2 leading XA-ADPCM sectors
  000h ..   BS Data (in BS v2/v3 format)                        ;-BS picture
Data for LEVELS is 320x352pix plus extra stuff (9 sectors per frame):
  Note: LEVELS videos have 1 leading XA-ADPCM sector
  000h 4    Offset to BS Data (always 28h)                      ;\
  004h 4*6  Offsets to Extra Stuff 1..6                         ; extra header
  01Ch 0Ch  Zerofilled                                          ;/
  028h ..   BS Data (in BS v2/v3 format)                        ;-BS picture
  ...  ..   Extra Stuff 1..6                                    ;-extra data
The unusual 320x352pix resoltution contains a 320x240pix BG image, with additional 320x112pix texture data appended at the bottom.
Extra Stuff 1..6 does supposedly contain info for animating enemies and/or backgrounds.

______________________________________________________________________________

iki
The .iki video format (found in files with .IKI or .IK2 extension) is used in several games made by Sony. iki movie sectors have some different properties:
  * There are only as many iki video sectors as needed to hold all the
    frame's data. Remaining sectors are null.
  * The first sector's Submode.Channel starts at zero, then increments for
    each sector after that, and resets to zero after an audio sector.
  * IK2 videos can also have variable frame rates that are very inconsistent.


CDROM File Video Streaming Framerate

According to Sony, BS encoded 320x240pix videos can be played at 30fps (with cdrom running at double speed).

STR Frame Rate
As a general rule, the frame rate is implied in CDROM rotation speed (150 or 75 sectors per second, minus the audio sectors, divided by the number of sectors per video frame).

Fixed/Variable Framerates
The frame can drop on video frames that contain more sectors than usually. Video frames that require fewer sectors than often padded with zerofilled sectors. However, some games don't have that padding, so they could end up reeceiving up to 150 single-sector frames per second; the actual framerate is supposedly slowed down to 60Hz or less via Vblank timer (and with the CDROM reading getting paused when the read-ahead buffer gets full).

Audio Samplerate
XA-ADPCM audio contains samplerate info (in the FORM2 subheader), the samplerate versus amount of audio sectors can be used to compute the CDROM rotation speed.
There are two exceptions: Some movies don't have any audio at all, and some movies use SPU-ADPCM instead of XA-ADPCM. In the latter case, the SPU Pitch (samplerate) may (or may not) be found somewhere in the audio sector headers.

CDROM Rotation speed
As said above, the speed can be often detected via audio sample rate. Otherwise, the general rule is that most PSX games are used 2x speed (150 sectors/second). But, there are a few games with 1x speed (see below).

CDROM Single speed (75 sectors/frame)
Here are probably most of the USA games with videos at 1x speed.
  007 - The World Is Not Enough
  1Xtreme
  Arcade Party Pak
  Atari Anniversary Edition Redux
  Blast Radius
  Blue's Clues - Blue's Big Musical
  Chessmaster II
  Chronicles of the Sword
  Civilization II
  Colin McRae Rally
  Creatures - Raised in Space
  Cyberia
  Demolition Racer
  Dune 2000
  ESPN Extreme Games
  FIFA Soccer 97
  Fade to Black
  Family Connection - A Guide to Lightspan
  Fear Effect
  Fox Hunt
  Interactive CD Sampler Volume 1
  Jade Cocoon - Story of the Tamamayu
  Jeopardy! 2nd Edition
  Juggernaut
  Krazy Ivan
  MTV Sports - Skateboarding featuring Andy Macdonald
  MTV Sports - T.J. Lavin's Ultimate BMX
  Medal of Honor
  Medal of Honor - Underground
  Official U.S. PlayStation Magazine Demo Disc 23
  Planet of the Apes
  PlayStation Underground Number 2
  Shockwave Assault
  Starblade Alpha
  Starwinder - The Ultimate Space Race
  Str.at.e.s. 1 - Match-A-Batch
  Str.at.e.s. 5 - Parallel Lives!
  Str.at.e.s. 7 - Riddle Roundup!
  The X-Files
  Top Gun - Fire at Will!
  Um Jammer Lammy
  Uprising X
  Wheel of Fortune - 2nd Edition
  Williams Arcade's Greatest Hits


CDROM File Video Streaming Audio

Audio Stream
STR movies are usually interleaved with XA-ADPCM sectors (the audio sectors are automatically decoded by the CDROM hardware and consist of raw ADPCM data without STR headers).
CDROM File Audio Streaming XA-ADPCM
However, there are also movies without audio. And a few movies with SPU-ADPCM audio.

SPU-ADPCM in Chunk-based formats
CDROM File Video Streaming Chunk-based formats

SPU-ADPCM in Chrono Cross/Legend of Mana Audio Sector
Chrono Cross Disc 1 (HiddenDirectory\1793h..17A6h)
Chrono Cross Disc 2 (HiddenDirectory\1793h..179Dh)
Legend of Mana (MOVIE\*.STR, except some movies without audio)
  000h 2    STR ID   (0160h)
  002h 2    STR Type (0000h, 0001h, 0100h, or 0101h)
              0000h=Legend of Mana, Audio normal sectors
              0001h=Legend of Mana, Audio sectors near end of movie
              0000h=Chrono Cross Disc 1, Audio.left?
              0001h=Chrono Cross Disc 1, Audio.right?
              0100h=Chrono Cross Disc 2, Audio.left?
              0101h=Chrono Cross Disc 2, Audio.right?
  004h 2    Sector number in Frame (0=Audio.left?, 1=Audio.right?)
  006h 2    Number of Audio sectors in this frame (always 2)
  008h 4    Frame number (1=First)
  00Ch 4    Unused (Chrono: FFh-filled or Mana: 00000FC0h=2x7E0h=Framesize?)
  010h 10h  Unused (Chrono: FFh-filled or Mana: 00h-filled)
  020h 60h  Unused (FFh-filled)
  080h 4    ID "AKAO"
  084h 4    Frame number (0=First)
  088h 8    Unused (zerofilled)
  090h 4    Remaining Time (step 690h) (can get stuck at 0340h or 0B20h at end)
  094h 4    Zero
  098h 4    Unknown (11h)
  09Ch 4    Pitch (1000h=44100Hz)
  0A0h 4    Number of bytes of audio data (always 690h)
  0A4h 2Ch  Unused (zerofilled)
  0D0h 690h Audio  (10h-byte SPU-ADPCM blocks) (1680 bytes)
  760h A0h  Unused (10h-byte SPU-ADPCM blocks with flag=03h and other bytes=0)
Note: The Chrono/Mana STR files start with Audio frames in first sector (except, some Legend of Mana movies don't have any Audio, and do start with Video frames).

SPU-ADPCM in Final Fantasy VIII (FF8)
  000h 4    ID "SMN",01h=Audio/left, "SMR",01h=Audio/right
  004h 1    Sector number in Frame (0=Audio.left, 1=Audio.right)
  005h 1    Total number of Audio+Video sectors in this frame, minus 1 (1 or 9)
  006h 2    Frame number (0=First)
  008h E8h  Unknown (camera data?) (232 bytes)
  0F0h 6    Audio ID (usually "MORIYA", sometimes "SHUN.M")
  0F6h 0Ah  Unknown (10 bytes) (reportedly 10 bytes at offset 250 = FAh ?????)
  100h 4    ID "AKAO"
  104h 4    Frame number (0=First)
  108h 14h  Unknown (20 bytes)
  11Ch 4    Pitch (1000h=44100Hz)
  120h 4    Number of bytes of audio data (always 690h)
  124h 2Ch  Unknown (44 bytes)
  150h 20h  Unknown (32 bytes)
  170h 690h SPU-ADPCM Audio data (690h bytes)
There is one special case on disc 1: a movie with no video. Each 'frame' consists of two sectors: the first is the left audio channel, the second is the right audio channel.

SPU-ADPCM in Final Fantasy IX (FF9) (*.STR and *.MBG)
The FF9 audio sectors are normal MODE2/FORM1 sectors (unlike the FF9 video sectors, which are MODE2/FORM2).
  000h 2    STR ID   (0160h)
  002h 2    STR Type (0008h=FF9/Audio)
  004h 2    Sector number in Frame (0=Audio.left, 1=Audio.right)
  006h 2    Total number of Audio+Video sectors in this frame (always 0Ah)
  008h 4    Frame number (1=First)
  00Ch 4    Zero
  010h 1    Audio flag? (00h=No Audio, 01h=Audio)
  011h 4Fh  Zerofilled --- XXX or whatever (when above is 00h)
  060h 4    Number of Frames in this STR file
  064h 1Ch  EEh-filled
 Below 780h bytes are all zerofilled when [10h]=00h (no audio)
 Below 780h bytes are reportedly all ABh-filled "in the last frame of a movie
 on Disc 4" (unknown which movie, and if that occurs in other movies, too)
  080h 4    ID "AKAO"
  084h 4    Frame number (0=First)
  088h 14h  Unknown (20 bytes)
  09Ch 4    Pitch (116Ah=48000Hz) (or 1000h=44100Hz in final movie)
  0A0h 4    Number of bytes of audio data (0, 720h, 730h, or 690h=final movie)
  0A4h 2Ch  Unknown (44 bytes)
  0D0h 730h SPU-ADPCM audio (plus leftover/padding when less than 730h bytes)

Dance series SPU-ADPCM streaming (bigben interactive, DATA.PAK\stream\*.str)
This format is used for raw SPU-ADPCM streaming (without video).
SLES-04121 Dance: UK
SLES-04161 Dance: UK eXtra TraX
SLES-04129 Dance Europe
SLES-04162 All Music Dance! (Italy)
  000h 2    STR ID   (0160h)
  002h 2    STR Type (8001h, same as MDEC)
  004h 2    Sector number within current Frame (0000h..num-1)
  006h 2    Number of Sectors in this Frame (always 9)
  008h 4    Frame number (0=First)
  00Ch 4    Frame Size in bytes (always 4000h)
  010h 4    Whatever (always 00A000A0h, would be width/height if it were video)
  014h 8    Zerofilled
  01Ch 4    Special ID (always DDCCBBAAh for Dance audio)
  020h 7E0h Data (in SPU-ADPCM format, mono, 22200Hz aka Pitch=07F5h)
Note: Sector 0..8 contain 9*7E0h=46E0h bytes data per frame, but only 4000h bytes are used (the last 6E0h bytes in sector 8 are same as in sector 7).

Raw SPU-ADPCM Streaming
Some games are using raw SPU-ADPCM for streaming. That is, the file is basically a normal .VB file, but it can be dozens of megabytes tall (ie. too large to be loaded into RAM all at once).
  Disney's The Emperor's New Groove (MagDemo39: ENG\STREAM\*.CVS)
  Disney's Aladdin in Nasira's Revenge (MagDemo46: ALADDIN\STREAM\*.CVS)


CDROM File Video Streaming Chunk-based formats

Electronic Arts
EA videos are chunk based (instead of using 20h-byte .STR headers). The next chunk starts right at the end of the previous chunk (without padding to sector boundaries).

Electronic Arts v1
Wing Commander III: Heart of the Tiger (MOVIES1.LIB\*.wve) (1995, EA/Origin)
 STR Sector Header:
  No STR Sector header (first sector starts directly with "Ad10" chunk)
 Video Chunks (MDEC):
  000h 4    Chunk ID "MDEC"                           ;\
  004h 4    Chunk Size (2xx0h)           (big-endian) ;
  008h 2    Bitmap Width in pixels       (big-endian) ; custom chunk header
  00Ah 2    Bitmap Height in pixels      (big-endian) ;
  00Ch 2    Unknown (7FFFh)              (big-endian) ;
  00Eh 2    Unknown (AD14h or AD24h)     (big-endian) ;/
  010h ..   Data (in BS v2 format)                    ;-standard BS v2 data
  ...  ..   FFh-Padding (to make Chunk Size a multiple of 10h-byte)
  ...  10h  FFh-Padding (extra padding, INCLUDED in Chunk Size)
 Audio Chunks (Ad10/Ad11) (22050Hz mono, or 22050Hz stereo):
  000h 4    Chunk ID ("Ad10"=normal, "Ad11"=last audio chunk)
  004h 4    Chunk Size (D38h or D28h) (or less in last chunk)   (big-endian)
  008h ..   SPU-ADPCM audio data, mono or stereo (10h bytes per sample block)
 Last STR Sector:
  Last STR sector contains ending MDEC bytes, but can be smaller than 800h.
Audio can be mono or stereo. The intro (stud_loa.wve) is stereo. The briefings are mono. The stereo videos have twice as many Ad10 blocks (and notably, TWO such blocks right at the begin of the file).
  Unknown how the stereo data is arranged (chunks with D38h bytes can't be
  evenly divided into two halves with D30h/2 bytes each).
  -- TODO: Debug SPU DMA length to see what data amount(s) are transferred

Electronic Arts v2
Psychic Detective (1996) (*.MDC) (but not *.300, which are normal STR)
 STR Sector Header:
  000h 4    ID (DDCCBBAAh) (aka AABBCCDDh big-endian)
  004h 4    Sector number within STR file (0=First, up to Filesize/800h-1)
  008h 7F8h Data (video and audio chunks, see below) (first chunk is "Ad10")
 Video Chunks (MDEC):
  000h 4    Chunk ID "MDEC"                           ;\
  004h 4    Chunk Size (1xx0h)           (big-endian) ;
  008h 2    Bitmap Width in pixels       (big-endian) ; custom chunk header
  00Ah 2    Bitmap Height in pixels      (big-endian) ;
  00Ch 4    Frame Number (starting at 0) (big-endian) ;/
  010h ..   Data (in BS v2 format)                    ;-standard BS v2 data
  ...  ..   FFh-Padding (to make Chunk Size a multiple of 10h-byte)
  ...  10h  FFh-Padding (extra padding, NOT included in Chunk Size)
 Audio Chunks (Ad10/Ad11) (22050Hz mono):
  000h 4    Chunk ID ("Ad10"=normal, "Ad11"=last audio chunk)
  004h 4    Chunk Size (D3Ch or D2Ch) (including in last chunk) (big-endian)
  008h 4    Sample number (0 and up, step 1714h or 16F8h)       (big-endian)
  00Ch ..   SPU-ADPCM audio data, mono    (10h bytes per sample block)
  ...  10h  SPU-ADPCM Padding (extra padding, NOT included in Chunk Size)
 Last STR Sector:
  Last STR sector contains ending MDEC bytes, but can be smaller than 800h.
Note: Psychic Detective does render the video in 15bpp mode.

Electronic Arts v3
Crusader: No Remorse (1996 Origin Systems) (MOVIES\*.STR)
Soviet Strike (1996 Electronic Arts)
Battle Stations (1997 Electronic Arts)
Andretti Racing (1996 Electronic Arts)
 STR Sector Header:
  000h 4    ID (DDCCBBAAh) (aka AABBCCDDh big-endian)
  004h 4    Sector number within STR file (0=First, up to Filesize/800h-1)
  008h 7F8h Data (video and audio chunks, see below) (first chunk is "ad20")
 Video Chunks (MDEC):
  000h 4    Chunk ID "MDEC"                           ;\
  004h 4    Chunk Size (...)             (big-endian) ;
  008h 2    Bitmap Width in pixels       (big-endian) ; custom chunk header
  00Ah 2    Bitmap Height in pixels      (big-endian) ;
  00Ch 4    Frame Number (starting at 0) (big-endian) ;/
  010h ..   Data (in BS v2 format)                    ;-standard BS v2 data
 Audio Chunks (ad20/ad21) (22050Hz stereo):
  000h 4    Chunk ID ("ad20"=normal, "ad21"=last audio chunk)
  004h 4    Chunk Size (1A50h or 1A70h)                        (big-endian)
  008h 4    Total number of 2x4bit samples in previous chunks  (big-endian)
  00Ch 2    Unknown (always 800h) (maybe Pitch: 800h=22050Hz)  (big-endian)
  00Eh 2    Unknown (always 200h)                              (big-endian)
  010h ..   SPU-ADPCM audio data, left  (10h bytes per sample block)
  ...  ..   SPU-ADPCM audio data, right (10h bytes per sample block)
 Last STR Sector:
  000h 18h  FFh-filled (aka 8-byte STR header and 10h-byte Chunk header)
  018h -    Nothing (total STR filesize is N*800h+18h bytes)

Electronic Arts v4
 STR Sector Header:
  No STR Sector header (first sector starts directly with "VLC0" chunk)
 VLC0 Chunk (at begin of movie file):
  000h 4    Chunk ID "VLC0"
  004h 4    Chunk Size (always 1C8h)     (big-endian)
  008h 1C0h 16bit MDEC values for E0h huffman AC codes (little-endian)
 MDEC Chunks(video frames):
  000h 4    Chunk ID "MDEC"                           ;\
  004h 4    Chunk Size (...)             (big-endian) ; custom chunk header,
  008h 2    Bitmap Width in pixels       (big-endian) ; instead of STR header
  00Ah 2    Bitmap Height in pixels      (big-endian) ;
  00Ch 4    Frame Number (starting at 0) (big-endian) ;/
  010h ..   Data (in BS v2 format, but using custom Huffman codes from VLC0)
  ...  ..   Zeropadding to 4-byte boundary
 Audio Chunks (au00/au01):
  000h 4    Chunk ID ("au00"=normal, "au01"=last audio chunk)
  004h 4    Chunk Size (...)                                   (big-endian)
  008h 4    Total number of 2x4bit samples in previous chunks  (big-endian)
  00Ch 2    Unknown (always 800h) (maybe Pitch: 800h=22050Hz)  (big-endian)
  00Eh 2    Unknown (always 200h)                              (big-endian)
  010h ..   SPU-ADPCM audio data, left  (0Fh bytes per sample block)
  ...  ..   SPU-ADPCM audio data, right (0Fh bytes per sample block)
  ...  ..   Garbagepadding to 4-byte boundary
  Note: SPU-ADPCM does normally have 10h-byte blocks, but in this case,
  the 2nd byte (with loop flags) is omitted, hence only 0Fh-byte blocks.
 Zero Chunk (zeropadding at end of file, exists only in some EA videos):
  000h ..   Zeropadding

Policenauts (Japan, 1996 Konami) (NAUTS\MOVIE\*.MOV)
 STR Sector Header:
  No STR Sector header (first sector starts directly with "VMNK" chunk)
 First chunk (800h bytes):
  000h 4     ID "VMNK" (aka KNMV backwards, maybe for Konami Video/Movie)
  004h 4     Unknown (01h)
  008h 4     Unknown (01h)
  00Ch 4     Unknown (F0h)
  010h 4     Size of KLBS chunks?          (40000h)
  014h 4     Bitmap X1 (aka left border)?  (16pix, 10h)
  018h 4     Bitmap Y1 (aka upper border)? (16pix, 10h)
  01Ch 4     Bitmap Width                  (288pix, 120h)
  020h 4     Bitmap Height                 (144pix, 90h)
  024h 7E4h  Zerofilled
 Further chunks (40000h bytes, each):
  000h 8     Zerofilled
  008h 4     Chunk ID "KLBS" (aka SBLK backwards, maybe for Stream Block)
  00Ch 4     Chunk Size (usually 40000h)
  010h 4     Number of Name List entries
  014h 4     Number of Name List entries (same as above)
  018h 8     Zerofilled
  020h N*30h Name List
  ...  ..    Data (referenced from Name List)
  ...  ..    Zeropadding (to end of 40000h-byte chunk)
The Name List does resemble a file archive, however, the "filenames" are just Type IDs (eg. all picture frames do have the same name).
 Name List entries:
  000h 8     Zerofilled
  008h 8     Data Type Name (eg. "SCIPPDTS")
  010h 4     Time when to play/display the frame (0 and up)
  014h 4     Time duration for that frame (usually 14h for Picture frames)
  018h 4     Data Offset in bytes (from begin of chunk)
  01Ch 4     Data Size in bytes
  020h 10h   Zerofilled
Data Formats for the different Data Types...
 Type "SDNSHDTS" aka SNDS,STDH - SoundStdHeader (Size=800h, Duration=0)
  000h 4     Maybe Pitch? (800h)                            (big-endian)
  004h 4     Maybe Pitch? (800h)                            (big-endian)
  008h 4     Total SPU-ADPCM size in bytes (for whole .MOV) (big-endian)
  00Ch 4     Unknown (FFFFFFFFh)                            (whatever)
  010h 4     Unknown (00007FFFh)                            (big-endian)
  014h 7ECh  Zerofilled
 Type "SDNSSDTS" aka SNDS,STDS - SoundStdStream (Size=10h..4000h, Duration=9Ch)
  000h 4000h SPU-ADPCM data in 10h-byte blocks (last chunk is less than 4000h)
 Type "SCIPPDTS" aka PICS,STDP - PictureStdPicture (Size=3xxxh, Duration=14h)
  000h 3xxxh Picture Frame (in BS v1 format)
 Type "SCTELLEC" aka ETCS,CELL - ExtraCells? (Size=0Ch, Duration=1)
  000h ..    Maybe subtitle related...?
 Type "SCTEGOLD" aka ETCS,DLOG - ExtraD-log? (Size=19h..31h, Duration=27h..44h)
  000h ..    Maybe subtitle related...?
Note: Total number of 10h-byte SPU-ADPCM blocks can be odd (so the audio seems to be mono).
Apart from the .MOV files, there's also one standard .STR file for the Knnami Intro (with normal STR headers and BS v2 data).

Best Sports Games Ever (DD\*.VLC and MOVIES\*.VLC) (Powerline Demo Disc menu)
This format is used for still images with only frame, and for looping short animation sequences in the Demo Disc Menu. There's no audio.
 Header Chunk:
  000h 4    Fixed ID (74h,55h,89h,08h aka 08895574h)
  004h 2    Bitmap Width           (140h)
  006h 2    Bitmap Height          (100h)
  008h 2    Video Frame Size/4     (17A0h or 13B0h)
  00Ah 2    Number of Video Frames (01h or 32h)
  00Ch 4    Frame End ID (eg. 62DCCACEh) (random?, but stays same within movie)
 Video Frame Chunk(s):
  ...  ..   Data (in BS v1/v2/v3 format)         ;\size = hdr[008h]*4
  ...  ..   FFh-filled (padding to Frame Size)   ;/
  ...  4    Frame End ID (eg. 62DCCACEh)         ;-same value as in hdr[00Ch]
For random access, best is seeking "fpos=N*(Framesize+4)+10h", alternately one could search "fpos=LocationAfterFrameEndID".

Sentient (FILMS\*.FXA)
This is having neither per-sector STR headers nor Chunk headers, instead it's having raw data with fixed size of 10 sectors per frame.
File Header (sector 0, 800h bytes):
  000h 4    File ID (01h,"XSP") (aka PSX backwards)
  004h 2    Unknown (0001h)
  006h 2    Unknown (0040h) (this is used for something...)
  008h 2    Bitmap Width  (0140h)
  00Ah 2    Bitmap Height (00F0h)
  00Ch 4    Total number of video frames
  010h 4    Number of video sectors per frame (always 8)
  014h 4    Total number of video sectors, excluding audio/dummy (=NumFrames*8)
  018h 1    Zero
  019h 1    Sector List size (28h) (ie. each 4 frames)  ;\or zerofilled when
  01Ah 28h  Sector Types (2=Video, 1=Audio, 0=Dummy)    ;/not present
  042h ..   Zerofilled
  7xxh ..   Unknown, maybe just garbage ...?
  ...  ..   Zerofilled
The frame rate is 15fps with 10 sectors per frame (8xVideo and either 2xAudio or 1xAudio+1xDummy). The Video/Audio/Dummy sector arrangement does repeat each 40 sectors (aka each 4 frames):
  vVvvvvv--vvVvvv--vvvvVv--vvvvvv-Vvvvvvv-  Video
  -------A-------A-------A-------A-------A  Audio
  --------D-------D-------D---------------  Dummy
  V = 1st sector of video frame
  v = 2nd..8th sector of video frame (or fileheader in case of sector 0)
  A = Audio (each 8th sector, ie. sector 07h,0Fh,17h,1Fh,etc.)
  D = Dummy (occurs after some (not all) audio sectors)
 Some files have that sector arrangement stored in header[019h..041h], but
 other files have that header entries zerofilled (despite of using the same
 arrangement).
Video frames are 8 sectors (4000h-byte), first and last 8 bytes are swapped:
  0000h 8     Last 8 bytes of BS v1 bitstream   ;\or garbage padding
  0008h 3FF0h First 3FF0h of BS v1 bitstream    ;/
  3FF8h 8     Footer (64bit, with squeezed BS header and other info)
 The footer bits are:
  0-4    5bit   Quant (00h..1Fh) (only 5bit, not 6bit)
  5-15   11bit  MDEC Size in 20h-word units (80h-byte units)
  16-23  8bit   Unknown (lowbits are often same as bit48 and up?)
  24-31  8bit   BS ID/100h (3800h/100h)
  32-47  16bit  Frame Number (0=First)
  48-63  16bit  Next Sector Number (start of next video frame)
 To decrypt/convert the frame to standard BS v1 format:
  x=[3FF8h]                      ;get footer
  [3FF8h..3FFFh]=[0000h..0007h]  ;last 8 bytes of bitstream
  [0000h]=(x AND FF00FFE0h)      ;size and ID=3800h
  [0004h]=(x AND 1Fh)+10000h     ;quant and version=v1
 The next_sector number is usually current_sector+1 (or +2 if that would be
 audio), in last frame it does point to end of file.
 Bitstreams smaller than 3FF8h are garbage padded (initially some 32bit garbage
 values, and in later frames leftovers from previous bitstream sectors).
Dummy sectors contain 800h bytes:
  000h 4     Always FFFFFFFFh (unfortunately, this isn't a unique ID)
  004h 7FCh  Garbage (zeroes, random, or even leaked ASM source code)
 Dummy sectors have the same Subheader as video sectors, the leading FFFFFFFFh
 could also occur in BS bitstreams or frames with garbage padding, so one must
 use the sector arrangement pattern to identify dummy sectors.
Audio sectors are XA-ADPCM and can be filtered via Subheader, or via sector arrangement pattern.


CDROM File Video Streaming Mis-mastered files

Mis-mastered streaming files
There are several discs that have streaming data stored as partial CDROM images (instead of as real CDROM sectors).
  Format        Content    Where
  raw 920h-byte STR        K9.5 1 - Live in Airedale (ZZBUFFER.STR)  ;\
  raw 920h-byte STR        Need for Speed 3 (MOVIES\ZZZZZZZ*.PAD)    ;
  raw 920h-byte STR        3D Baseball (ZZZZZZZZ.ZZZ)                ; intended
  raw 920h-byte STR        Wing Commander III (DUMMY.DAT)            ; padding
  raw 920h-byte STR        R-Types (DMY\DUMMY.BIN)                   ;
  raw 920h-byte STR        Reel Fishing (MOVIE\STAFF.OLD)            ;
  raw 920h+junk STR+junk   Grand Slam (DUMMY.BIN)                    ;
  raw 920h-byte XA-ADPCM   Spec Ops Airborne Commando (PADDING.NUL)  ;
  raw 920h-byte SW-STR     Cyberia (ENDFILL\*.STR) (software render) ;
  RIFFs/CDXAfmt STRs       Sonic Wings Special (SW00.DMY = two RIFFs);/
  raw 920h-byte XA-ADPCM   Rugrats (MagDemo19: STREAMS\DB02.ISF)     ;\nonsense
  raw 920h-byte Data BABEh Rugrats (MagDemo19: STREAMS\OPEN.BIN)     ; dupes
  raw ???-byte  CDDA       Championship Surfer (MagDemo43: HWX\MUSIC);/
  raw ???-byte  CDDA       Twisted Metal 2 (MagDemo50: TM2\FRWYSUB.DA) ;-?
  raw 920h-byte STR        Sonic Wings Special (MOV\MQ*.STR)         ;-unused?
  raw 920h-byte STR        Apocalypse (MagDemo16: APOC\*.STR)
  raw 920h-byte XA-ADPCM   Apocalypse (MagDemo16: APOC\*.XA)
  raw 920h-byte XA-ADPCM   NFL Xtreme (MagDemo13: NFLX\GAME\SOUND\2PLAYRNO.XA)
  raw 920h-byte XA-ADPCM   Ace Combat 2 (MagDemo01: ACE2.STP)
  raw 920h-byte XA-ADPCM   Colony Wars (MagDemo02: CWARS\DEMO.PAK)
  raw 920h-byte XA-ADPCM   Best Sports demo (AH2\GAMEDATA\COM\MUSIC\MUSIC.IXA)
  raw 920h-byte XA-ADPCM   Tomb Raider: Last Revelation (MagDemo29: TR4\XA1.XA)
  raw 800h-byte XA-ADPCM   Croc 1 demo (MagDemo02: CROC\MAGMUS.STR) (FORM1)
  RIFF/CDXAfmt  XA-ADPCM   Best Sports demo (LOMUDEMO\SFX\COMMENT.STR)
  RIFF/CDXAfmt  ?+XA-ADPCM Ace Combat 3 Electrosphere (MagDemo30: AC3\*.SPB)
  RIFF/CDXAfmt  XA-ADPCM   Colony Wars Venegance (MagDemo14: CWV\SONYDEMO.PAK)
  RIFF/WAVEfmt  CDDA       T'ai Fu (MagDemo16: TAIFU\3_10.WAV, 2x16bit 44100Hz)
  RIFF/WAVEfmt  CDDA       Psalm69 (beta) FRONT\FIRE.TRK
  RIFF/WAVEfmt  CDDA       Harry Potter and the Philosopher's Stone ZZZDUMMY.Z
The 920h-byte sectors exclude the leading Sync mark and MM:SS:FF:Mode2 value.
 Data/movie sectors look as so:
  000h 4    Sub-Header (File, Channel, Submode OR 20h, Codinginfo)
  004h 4    Copy of Sub-Header
  008h 800h Data (2048 bytes)           ;<-- contains STR movie sectors
  808h 4    EDC (zerofilled)
  80Ch 114h ECC (zerofilled)
 And XA-ADPCM sectors look as so:
  000h 4    Sub-Header (File, Channel, Submode OR 64h, Codinginfo)
  004h 4    Copy of Sub-Header
  008h 900h Data (18*128 bytes)         ;\contains XA-ADPCM audio sectors
  908h 14h  Data (zerofilled)           ;/
  91Ch 4    EDC (zerofilled)
The RIFF/CDXAfmt has a standard RIFF header, followed by 930h-byte sectors (same format as when opening CDROM streaming files in Windows). The RIFF/WAVEfmt is just a standard .WAV file.
In case of the ZZ*.* files on retail discs, the developers did intentionally append some non-functional dummy STR files (instead of appending zerofilled 30Mbyte at end of disc).
CDROM File XYZ and Dummy/Null Files
In case of the Demo Discs, the developers did probably have high hopes to release a demo version with working streaming data, just to find out that Sony had screwed up the data format (or maybe they had only accidentally included streaming data, without actually using it in demo version). Confusingly, the corrupted files were released on several discs (magazine demos, and other demo releases).
The Rugrats demo has intact files in RUGRATS\CINEMAT and RUGRATS\XA folders, plus nonsense copies of that files in 920h-byte format in STREAMS folder.

Partially mis-mastered files
Legend of Dragoon (MagDemo34: LOD\XA\LODXA00.XA has FIRST SECTOR mis-mastered (it has TWO sub-headers (01,00,48,00,01,00,48,00,01,01,64,04,01,01,64,04), the remaining sectors are looking okay).

Porsche Challenge (USA) (SRC\MENU\STREAM\*.STR)
The subheader and data of the 1st sector are accidently overwritten by some ASCII string:
  000h 4    Subheader       01 44 2D 52            ".D-R"    ;\distorted
  004h 4    Subheader copy  01 4D 20 47            ".M G"    ;/"CD-ROM G"
  008h 299h Data ASCII      65 6E 65 72 61 ...     "enerator for Windows"...
  2A1h 567h Data BS bitstream (but lacks BS header and start of bitstream)
The 2nd sector and up are containing intact STR headers (for the 2nd-Nth sector of 1st frame, but the whole 1st frame is unusable due to missing 1st sector; however, the following frames are intact).


CDROM File Video BS Compression Versions

STR/BS Version Summary, with popularity in percents (roughly)
  Version         .STR movies   .BS pictures
  BS v2            60%           6%            Most games
  BS v3            20%           4%            Some newer games
  BS v1            15%           0.1%          Old games
  BS ea            2%            - (?)         Electronic Arts titles
  BS iki           0.5%          0.1%          Several games
  BS fraquant      0.2%          0.1%          Rare (X-Files, Eagle One)
  BS v0            0.1%          -             Rare (Serial Experiments Lain)
  BS v2/v3.crypt   0.2%          -             Rare (Star Wars games)
  BS iki.encrypted 0.1%          -             Rare (Panekit)
  Wacwac MDEC      0.1%          -             Rare (Aconcagua)
  Polygon Streams  0.x% (?)      -             Some titles
  Raw MDEC         -             -             Was never used in files?
  MPEG1            -             -             VCD Video CDs
  None             ?%   (?)      90%           No videos or BS pictures
Most games can decrypt v1/v2/v3 videos (no matter which of the three versions they are actually using), newer games do occassionally use v3 for picture compression, but often stick with v2 for video streaming (perhaps because v3 does require slightly more CPU load; unknown if the higher CPU load has been an actual issue, and if it has been solved in the later (more optimized) decompressor versions) (unknown if there are other benefits like v2 having better DC quality or better compression in some cases?).

BS v0 (used by only one known game)
  v0 used by Serial Experiments Lain
This game is apparently using a very old and very unoptimized decoder (although it was released in 1997, when most or all other games did already have decoders with v1/v2/v3 support).
The v0 decoder has different header, lacks End of Frame codes, and uses Huffman codes with different AC values than v1/v2/v3/iki.

BS v1 (used by older games, some of them also having v2 videos)
  v1 used by Wipeout 2097 (MAKE.AV, XTRO*.AV)
  v1 used by Viewpoint (MOVIES\*.STR) (oddly with [08h]=FirstFrame=0 and
        [1Ch]=Unspecified=Nonzero) (the game also has ".str" files in
        VIEW.DIR\streams, but that isn't MDEC/STR stuff)
  v1 used by Ridge Racer Revolution (MOVIE\*.STR)
  v1 used by Policenauts
  v1 used by Final Fantasy VII (FF7)
  v1 used by PSX-SDK: Programmer Tool CDROM (PSX\SAMPLE\PRESS\*\*\*.BS, ascii)
  v1? used by Tekken 2
  v1/v2 used by Final Fantasy Tactics (OPEN*.STR)
  v1/v2 used by Project Horned Owl (*.STR)
  v1/v2 used by Gex (*.FMV)
  (and probably more)
v1 and v2 can be decoded with the same decompressor. The only difference is that v1 was generated with an older compressor (which did accidently store nonsense 22bit escape codes with run=N, level=0 in the bitstream; whereas one could as well use run+N+1 in the next code, or omit it completely if next code is EOB).

BS v2 (most games)
  v2 used by Gex - Enter the Gecko (*.STR)
  v2 used by Tomb Raider (FMV\*.FMV)
  v2 used by Alone (STR*\*.STR)
  v2 used by Kain (*.STR)
  v2 used by Fear Effect (BOOT.SID, LOGO.SID, ABGA\ABGA.FLX)
  v2 used by Parasite Eve 2 (INTERx.STR, and in .CDF's eg. stage1\folder501)
  v2 used by Witch of Salzburg (MOVIE\*.STR)
  v2 used by Breath of Fire III (LOGO\*.STR)
  v2 used by Hear it Now (MOVIE\*.STR)
  v2 used by Legend of Mana (MOVIE\*.STR)
  v2 used by Misadventures of Tron Bonne (STR\*.STR)
  v2 used by Rayman (VIDEO\*.STR)
  v2 used by Resident Evil 1 (PSX\MOVIE\*.STR)                ;\although v3 is
  v2 used by Resident Evil 2 (PL0\ZMOVIE\*.STR, ZMOVIE\*.STR) ;/used in *.BSS
  v2 used by Tokimeki Memorial 2 (VX*.STR)
  v2 used by Spider-Man (CINEMAS\*.STR)
  v2 used by Perfect Assassin (CDV\*.STR)
  v2 used by Pandemonium 2 (*.STR)
  v2 used by Die Hard Trilogy 2 (MOVIE\*.STR)
  v2 used by Need for Speed 3 (MOVIES\*.STR) (oddly with [14h,18h]<>[20h,24h])
  v2 used by Wild Arms (STR\*.STR)
  v2 used by Wild Arms 2 (STR\*.STR)
  v2 used by Frogger (*.STR)
  v2 used by Gundam Battle Assault (XA\*.STR)
  v2 used by Alundra (MOVIE\*.MOV)
  v2 used by Spec Ops (file 95h,96h within BIGFILE.CAT)
  v2 used by Crash Team Racing (file 1E1h..1F8h,1FAh within BIGFILE.BIG)
  (and many more)
Same as v1, but without the compressor bug.

BS v3 (used by some newer games, some of them also having v2 videos)
  v2/v3 used by Lemmings Oh No More Lemmings (ANIMS\*.STR)
  v2/v3 used by Castlevania (*.STR)
  v3 used by Heart of Darkness (CINE\*.STR, SETUP\*.STR)
  v3 used by R-Types (MV\*.STR)
  v3 used by Black Matrix (MOVIE\*.STR)
  v3 used by Nightmare Creatures II (INTRO\*.STR, LEVEL*\*.STR)
  (and many more)
Same as v2, but using Huffman compressed DC values.

BS ea (Electronic Arts)
Used by many EA Sports titles and several other titles from Electronic Arts:
  Castrol Honda Superbike Racing
  EA Sports Supercross 2000, 2001
  Future Cop - L.A.P.D. (retail and MagDemo14: FCOPLAPD\*.WVE and *.FSV)
  Hot Wheels - Turbo Racing
  Jampack Vol. 2
  Knockout Kings 99, 2000, 2001
  Madden NFL 99, 2000, 2001, 2002, 2003, 2004, 2005 (eg. MADN00\FMVIDEO.DAT\*)
  NASCAR 98, 99, 2000, 2001 (and 98 Collector's Edition, and 99 Legacy)
  NASCAR Thunder 2002, 2003, 2004 and NASCAR Rumble
  Nuclear Strike
  Official U.S. PlayStation Magazine Demo Disc 39 (...XXX which game?)
  PlayStation Underground Jampack - Winter 2000
  Road Rash Jailbreak, and Road Rash 3D
  Tiger Woods PGA Tour Golf, and Tiger Woods USA Tour 2001
Uses VLC0 and MDEC chunks (instead of STR headers), the MDEC chunks contain standard BS v2 data, but using custom MDEC values from VLC0 chunk.

BS fraquant
  X-Files (Fox Interactive/Hyperbole Studios, 1999)
  Eagle One: Harrier Attack (Infogrames/Glass Ghost, 2000)
  Blue's Clues: Blue's Big Musical (Mattel/Viacom/TerraGlyph, 2000)
This replaces the 6bit quant value by a 16bit fixed-point quant value (done by manipulating the Quant Table instead of using QuantDC, apart from that extra feature it's internally using normal BS v1/v2/v3 decoding).

BS iki
  iki: Gran Turismo 1 (STREAM.DAT)   ;\with uncommon STR header
  iki: Gran Turismo 2 (STREAM.DAT)   ;/
  iki: Hot Shots Golf 2 / Everybody's Golf 2 (MagDemo31: HSG2\MINGOL2X.BIN)
  iki: Legend of Legaia (MagDemo20: LEGAIA\MOV\MV2.STR)
  iki: Legend of Dragoon (STR\*.IKI)
  iki: Omega Boost (MOVIE\*.IKI)
  iki: Um Jammer Lammy (MagDemo24: UJL\*.IKI) (retail: *\*.IKI and CM\*.IK2)
  iki: plus a dozen of japanese-only titles
This might have been used between v2 and v3, iki is using uncommon BS headers and LZ compressed Quant/DC values (whilst v3 is using Huffman compressed DC values).

Encrypted iki
  Panekit - Infinitive Crafting Toy Case (first 13Mbyte in PANEKIT.STR)
Same as normal iki, with some SWAP/ADD/XOR-encrytion in first 20h-bytes.

Encrypted v2/v3
  v3.xor used by Star Wars Masters of Teras Kasi (MagDemo03: MASTERS\*.STR)
  v2.xor supported (but not actually used) by Star Wars Masters (MagDemo03)
  v3.swap used by Star Wars Rebel Assault II (*.STR, *.SED, Stills)
  v2.swap used by Star Wars Rebel Assault II (*.STR)
  v3.swap used by BallBlazer Champions (*.STR)
Same as normal v2/v3 with simple XOR-encryption or SWAP-encryption.

Wacwac MDEC
  Aconcagua (JP) (2000 Sony/WACWAC!) (STR_01_00.STR and STR_09_01.STR)
Similar to v3, but uses completely different Huffman codes than BS video.

Polygon Streaming (instead of MDEC picture streaming)
  Ape Escape (DEMO\*.STR, STR\*.STR, and KKIIDDZZ.HED\STR\0006h and up)
  Aconcagua (most STRs are Polygon Streams, except two are Wacwac MDEC streams)
  Panekit - Infinitive Crafting Toy Case (last 150Mbyte in PANEKIT.STR)
Polygon streams contain vertices (for textures that are stored elsewhere). Usually needing only one sector per frame. This can be useful for animations that were recorded from real actors. Drawbacks are more edgy graphics and lower color depth (although that may fit in with the game engine).
CDROM File Video Polygon Streaming

MPEG1 (on VCD Video CDs)
MPEG1 uses I/P/B-Frames, the I-Frames may reach similar compression as BS files. However, P-Frames and B-Frames do compress much better than BS files.
CDROM Video CDs (VCD)
MPEG1 isn't used in any PSX games, but VCDs can be viewed on SCPH-5903 consoles (or via software decoder in nocash PSX kernel clone).

Titles without movies
Most PSX titles do include movies, exceptions are some early launch titles and educational titles:
  Ridge Racer 1 (1994)
  Lightspan Online Connection CD


CDROM File Video BS Compression Headers

There are several different BS headers. The File ID/Version entries can be used to detect the correct type. The MDEC Size entry contains the size after Huffman decompression (ie. the half-decompressed size before passing the data to the MDEC decompression hardware) (usually divided by 4 and rounded up to 80h/4 bytes).

BS v1/v2/v3 header
  000h 2    MDEC Size/4 (after huffman decompression) (rounded to 80h/4 bytes)
  002h 2    File ID (3800h)
  004h 2    Quantization step/factor (0000h..003Fh, for MDEC "DCT.bit10-15")
  006h 2    Version (1, 2, or 3) (2 is most common)
  008h ...  Huffman compressed data blocks (Cr,Cb,Y1,Y2,Y3,Y4, Cr,Cb,Y1,Y2..)

Encrypted v2/v3
Encryption is used in Star Wars games, there are two encryption schemes (XOR and SWAP).
XOR-encrypt: Star Wars Masters of Teras Kasi (MagDemo03: MASTERS\*.STR):
  000h 2   MDEC Size/4 (rounded to 80h/4 bytes) (unencrypted) ;\same as normal
  002h 2   File ID (3800h)                      (unencrypted) ; BS v1/v2/v3
  004h 2   Quant (0..3Fh)                       (unencrypted) ;/
  006h 2   Version (in bit15, plus random in LSBs):
             00xxh..7FFFh for v2 (unknown if this could include values 0..3)
             8000h..FFFFh for v3 (bit14-0=random, varies in each frame)
  008h ..  Encrypted bitstream
             (each halfword XORed by BE67h for v2, or XORed by E67Bh for v3)
  ...  (2) Zeropadding to 4-byte boundary (unencrypted)
  ...  ..  Zeropadding to end of sector   (unencrypted)
 The XOR values BE67h/E67Bh are hardcoded in the Star Wars Masters of Teras
 Kasi .EXE (same XOR values for both retail and demo version), unknown if any
 other games are also using that kind of encryption (and if yes, if they are
 using the same XOR values).
SWAP-encrypt: BallBlazer Champions, Star Wars Rebel Assault II (*.STR, *.SED):
  000h 2   MDEC Size/4 (rounded to 80h/4 bytes) ;\same as normal
  002h 2   File ID (3800h)                      ; BS v1/v2/v3
  004h 2   Quant (0..3Fh)                       ;/
  006h 2   Version (random 16bit, 00xxh..FFFFh) ;-no meaningful version info
  008h 2   Bitstream 2nd halfword               ;\to "decrypt" the file,
  00Ah 2   Bitstream 1st halfword               ;/these must be swapped
  00Ch ..  Bitstream 3rd halfword and up        ;-in normal order
Whilst XORing or SWAPping the halfwords is simple, the more difficult part is distinguishing between SWAP-v2/v3 and XOR-v2/v3 encryption. This can be done as so:
  if header[06h]<=0003h then assume unencrypted v0/v1/v2/v3
  if header[06h]>=0004h then strip any trailing 0 bits, and check EndOfFrame..
  if last 10bit = 0111111111 then assume SWAP.v2
  if last 10bit = 1111111111 then assume SWAP.v3
  otherwise assume XOR.v2/v3 (and use header[06h].bit15 to distinguish v2/v3)

BS iki Header
IKI videos have a custom .BS header, including some GT-ZIP compressed data:
  000h 2   MDEC Size/4 (rounded to 80h/4 bytes)         ;\same as normal
  002h 2   File ID (3800h)                              ;/BS v1/v2/v3
  004h 2   Bitmap Width in pixels     ;instead of Quant
  006h 2   Bitmap Height in pixels    ;instead of Version
  008h 2   Size of GT-ZIP compressed data (plus 2-byte alignment padding)
  00Ah ..  GT-ZIP compressed DC/Quant values (plus 2-byte alignment padding)
  ...  ..  Huffman compressed AC data blocks (Cr,Cb,Y1,Y2,Y3,Y4, Cr,Cb,Y1,Y2..)
The number of blocks is NumBlocks=(Width+15)/16*(height+15)/16*6. The size of the decompressed GT-ZIP data is NumBlocks*2.

Encrypted iki
The first 20h byte of the iki header & data are encrypted. Among others, the ID 3800h is inverted (=C7FFh). To decrypt them:
  [buf+00h]=[buf+00h] XOR FFFFFFFFh
  [buf+04h] <--> [buf+08h]          ;exchange 2x32bit
  [buf+0Ch] <--> [buf+0Eh]          ;exchange 2x16bit
  [buf+10h]=[buf+10h]+FFFF6F7Bh
  [buf+14h]=[buf+14h]+69140000h
  [buf+18h]=[buf+18h]+FFFF7761h
  [buf+1Ch]=[buf+1Ch]+6B040000h
Note: The .STR header's StHeadM/StHeadV fields contain a copy of the decrypted values. The PANEKIT.STR file is 170Mbyte tall, but only the first 13Mbyte contain movie data... the rest is unknown stuff... often with zeroes followed by 7B,44,F0,29,E0,28 unknown what for...?

BS fraquant
  X-Files, GRAPHICS\*.STR,*.BIN, LOGOS\*.STR,*.BS, *.BF\*
  Eagle One: Harrier Attack (\*.STR, DATA*\*.STR) (leading zerofilled sectors)
  Blue's Clues: Blue's Big Musical (*.STR) (has one leading zerofilled sector)
This has a normal BS v1/v2/v3 header, with special quant entry:
  004h 2    Quant (0001h..0003h, or fixed-point 8000h..9xxxh)
The decoder is using the default_quant_table (02h,10h,10h,13h,..,53h) multiplied with a fixed point number:
  quant=BsHeader[04h]   ;get fractional quant value
  BsHeader[04h]=0001h   ;force quant=1 (for use in BS v1/v2/v3 decoder)
  if quant<8000h then quant=quant*200h else quant=quant AND 7FFFh
  quant[0]=default_quant_table[0]
  for i=1 to 3Fh,
    x=(default_quant_table[i]*quant)/200h
    if x=00000000h then quant[i]=01h else quant[i]=(x AND FFh)
  next i
  use MDEC(2) command to apply quant[0..3Fh] to both Luma and Chroma tables
  use normal BS v1/v2/v3 decoder to decompress the bitmap
BsHeader[04h] should be 0001h..0003h, or 8000h..862Bh (values outside that range would overflow the 8bit quant table entries). Values 0001h..0003h should should give same results as for normal BS decoding, so only values 8000h and up do need special decoding.
Caution: Despite of the overflows, quant>862Bh is used (eg. X-Files GRAPHICS\GRAPHICS.BIN has quant=88C4h, Blue's Big Musical has quant=93E9h; those images do look okay, so the compressor seems to have recursed the overflows; or the overflow affects only a few pixels), however, very large values with LSBs all zero (eg. 9000h) can cause 8bit table entries to become 00h (due to ANDing the result with FFh).
Note: X-Files LOGOS\POP*.STR have quant=8001h (=near zero), that files are only 60Kbyte and seem to be all black.
Note: The movie engine uses COP2 GPF opcodes to calculate quant values.

v0 Header (in STR files)
  000h 1   Quant for Y1,Y2,Y3,Y4  (00h..3Fh)
  001h 1   Quant for Cr,Cb        (00h..3Fh)
  002h 2   File ID (3800h) (or Frame Number in ENDROLL1.STR on Disc 2)
  004h 2   MDEC Size/2 (!), and without padding (!) (unlike v1/v2/v3/iki)
  006h 2   BS Version (0) (actually MSBs of above Size, but MSBs are always 0)
  008h ..  Huffman Bitstream, first bit in bit7 of first byte

v0 Header (in LAPKS.BIN chunks)
LAPKS.BIN contains several chunks, each chunk contains an animation sequence with picture frame(s), each frame starts with following header:
  000h 2   Bitmap Width in pixels     ;\cropped to non-black screen area,
  002h 2   Bitmap Height in pixels    ;/size can vary within the sequence
  004h 2   Quant for Y1,Y2,Y3,Y4  (0000h..003Fh)
  006h 2   Quant for Cr,Cb        (0000h..003Fh)
  008h 4   Size of compressed BS Bitstream plus 4 ;Transparency at [008h]+0Ch
  00Ch 2   Size/2 of MDEC data (after huffman decompression, without padding)
  00Eh 2   BS Version (0) (actually MSBs of above Size, but it's always 0)
  010h ..  BS Bitstream with DC and AC values (Huffman compressed MDEC data)
  ...  4   Transparency Mask Decompressed Size (Width*Height*2/8) (=2bpp)
  ...  ..  Transparency Mask LZSS-compressed data
For decompressing the transparency mask:
CDROM File Compression LZSS (Serial Experiments Lain)
The Transparency Mask is stored as scanlines (not as macroblocks), the upper/left pixel is in bit7-6 of first byte, the 2bit alpha values are ranging from 0=Transparent to 3=Solid.

BS ea Headers (Electronic Arts)
EA videos are chunk based (instead of using 20h-byte .STR headers).
CDROM File Video Streaming Chunk-based formats
VLC0 Chunk: Custom MDEC values (to be assigned to normal BS v2 Huffman codes).
MDEC Chunks: Width/Height and BS v2 data (using MDEC values from VLC0 chunk).

Raw MDEC
There aren't any known pictures or movies in raw MDEC format. However, the Huffman decompression functions do usually output raw data in this format:
  000h 2   MDEC Size/4 (after huffman decompression) (rounded to 80h/4 bytes)
  002h 2   File ID (3800h)
  004h ..  MDEC data (16bit DC/AC/EOB codes)
  ...  ..  Padding (FE00h-filled to 80h-byte DMA transfer block size boundary)
The first 4 bytes are the MDEC(1) command, the "ID" is always 3800h (equivalent to selecting 16bpp output; for 24bpp this must be changed to 3000h before passing the command to the MDEC hardware). The remaining bytes are MDEC data (padded to 80h-byte boundary).
Macroblock Decoder (MDEC)


CDROM File Video BS Compression DC Values

DC v0
  nnnnnnnnnn        DC Value (signed 10bit, -200h..+1FFh)
This is similar as v1/v2, except there is no End code for End of Frame, and the .BS header contains two separate quant values (for Cr/Cb and Y1-Y4).
  If output_size=NumberOfMdecCodes*2 then EndOfFrame
  If BlockIsCrCb then QuantDC=DC+QuantC*400h else QuantDC=DC+QuantY*400h

DC v1/v2/ea
  nnnnnnnnnn        DC Value (signed 10bit, -200h..+1FEh)
  0111111111        End of Frame (+1FFh, that, in place of Cr)
This is similar as v0, except there is only one Quant value for all blocks, and the header lacks info about the exact decompressed size, instead, compression end is indicated by a newly added end code:
  If DC=+1FFh then EndOfFrame
  QuantDC=DC+Quant*400h

DC v3
Similar as v1/v2, but DC values (and End code) are now Huffman compressed offsets relative to old DC, with different Huffman codes for Cr/Cb and Y1-Y4:
  For Cr/Cb         For Y1..Y4      Offset (added to old DC of Y/Cr/Cb block)
  00                100             +(00h)                      ;\
  01s               00s             -(01h)*4     ,+(01h)*4      ;
  10sn              01sn            -(03h..02h)*4,+(02h..03h)*4 ; required
  110snn            101snn          -(07h..04h)*4,+(04h..07h)*4 ; codes
  1110snnn          110snnn         -(0Fh..08h)*4,+(08h..0Fh)*4 ; for 10bit
  11110snnnn        1110snnnn       -(1Fh..10h)*4,+(10h..1Fh)*4 ; range
  111110snnnnn      11110snnnnn     -(3Fh..20h)*4,+(20h..3Fh)*4 ;
  1111110snnnnnn    111110snnnnnn   -(7Fh..40h)*4,+(40h..7Fh)*4 ;/
  11111110snnnnnnn  1111110snnnnnnn -(FFh..80h)*4,+(80h..FFh)*4 ;-11bit (!)
  -                 11111110        Unused                      ;\
  111111110         111111110       Unused                      ; unused
  1111111110        1111111110      Unused                      ;/
  1111111111        1111111111      End of Frame                ;-end code
  Note: the "snnn" bits are indexing the values in right column,
  with s=0 for negative values, and s=1 for positive values.
The decoding works as so (with oldDcXxx=0 for first macroblock):
  If bits=1111111111 then EndOfFrame
  If BlockIsCr then DC=DecodeHuffman(HuffmanCodesCbCr)+oldDcCr, oldDcCr=DC
  If BlockIsCb then DC=DecodeHuffman(HuffmanCodesCbCr)+oldDcCb, oldDcCb=DC
  If BlockIsY1234 then DC=DecodeHuffman(HuffmanCodesY1234)+oldDcY, oldDcY=DC
  If older_version AND DC>=0 then QuantDC=Quant*400h or (DC)       ;\requires
  If older_version AND DC<0  then QuantDC=Quant*400h or (DC+400h)  ;/11bit
  If newer_version           then QuantDC=Quant*400h+(DC AND 3FFh) ;-wrap 10bit
Note: The offsets do cover signed 11bit range -3FCh..+3FCh. Older v3 decoders did require 11bit offsets (eg. add +3FCh to change DC from -200h to +1FCh). Newer v3 decoders can wrap within 10bit (eg. add -4 to wrap DC from -200h to +1FCh).

DC iki
The DC values (including Quant values for each block) are separately stored as GT-ZIP compressed data in the IKI .BS header.
CDROM File Compression GT-ZIP (Gran Turismo 1 and 2)
Calculate NumBlocks=(Width+15)/16*(height+15)/16*6, decompress the DC values (until DecompressedSize=NumBlocks*2). During Huffman decompression, read the DC values from the decompressed DC buffer (instead of from the Huffman bitstream):
  If BlockNo>=NumBlocks then EndOfFrame
  QuantDC = DCbuf[BlockNo]*100h + DCbuf[BlockNo+NumBlocks]
As shown above, the Hi- and Lo-bytes are stored in separate halves of the DC buffer (which may gain better compression).


CDROM File Video BS Compression AC Values

Below shows the huffman codes and corresponding 16bit MDEC values; the "xx" bits contain an index in the list of 16bit MDEC values, the "s" bit means to negate the AC level (in lower 10bit of the 16bit MDEC value) when s=1.

Huffman codes for AC values BS v1/v2/v3/iki
  10                     FE00h          ;End of Block, EOB
  11s                    0001h
  011s                   0401h
  010xs                  0002h,0801h
  0011xs                 1001h,0C01h
  00101s                 0003h
  00100xxxs              3401h,0006h,3001h,2C01h,0C02h,0403h,0005h,2801h
  0001xxs                1C01h,1801h,0402h,1401h
  00001xxs               0802h,2401h,0004h,2001h
  000001xxxxxxxxxxxxxxxx 0000h..FFFFh   ;Escape code for raw 16bit values
  000001xxxxxx0000000000 0000h..FC00h   ;Escape nonsense level=0 (used in v1)
  0000001xxxs            4001h,1402h,0007h,0803h,0404h,3C01h,3801h,1002h
  00000001xxxxs          000Bh,2002h,1003h,000Ah,0804h,1C02h,5401h,5001h,
                         0009h,4C01h,4801h,0405h,0C03h,0008h,1802h,4401h
  000000001xxxxs         2802h,2402h,1403h,0C04h,0805h,0407h,0406h,000Fh,
                         000Eh,000Dh,000Ch,6801h,6401h,6001h,5C01h,5801h
  0000000001xxxxs        001Fh,001Eh,001Dh,001Ch,001Bh,001Ah,0019h,0018h,
                         0017h,0016h,0015h,0014h,0013h,0012h,0011h,0010h
  00000000001xxxxs       0028h,0027h,0026h,0025h,0024h,0023h,0022h,0021h,
                         0020h,040Eh,040Dh,040Ch,040Bh,040Ah,0409h,0408h
  000000000001xxxxs      0412h,0411h,0410h,040Fh,1803h,4002h,3C02h,3802h,
                         3402h,3002h,2C02h,7C01h,7801h,7401h,7001h,6C01h
  000000000000           Unused

Huffman codes for AC values BS v0 (Serial Experiments Lain)
  10                           FE00h          ;End of Block, EOB
  11s                          0001h
  011s                         0002h
  010xs                        0401h,0003h
  0011xs                       0801h,0005h
  00101s                       0004h
  00100xxxs                    000Ah,000Bh,0403h,1801h,000Ch,000Dh,1C01h,000Eh
  0001xxs                      0006h,0C01h,0402h,0007h
  00001xxs                     0008h,1001h,0009h,1401h
  000001xxxxxx0xxxxxxx         0000h..FC00h+(+001h..+07Fh AND 3FFh) ;\
  000001xxxxxx000000001xxxxxxx 0000h..FC00h+(+080h..+0FFh AND 3FFh) ; Escape
  000001xxxxxx000000000xxxxxxx Unused                               ; codes
  000001xxxxxx1xxxxxxx         0000h..FC00h+(-080h..-001h AND 3FFh) ;
  000001xxxxxx100000000xxxxxxx 0000h..FC00h+(-100h..-081h AND 3FFh) ;
  000001xxxxxx100000001xxxxxxx Unused                               ;/
  0000001xxxs                  000Fh,0802h,2001h,0404h,0010h,0011h,2401h,0012h
  00000001xxxxs                0013h,0405h,0014h,2801h,0015h,0C02h,3001h,0017h,
                               0016h,2C01h,0018h,001Ch,0019h,0406h,0803h,001Bh
  000000001xxxxs               001Ah,3401h,001Dh,0407h,1002h,001Fh,001Eh,3801h,
                               0020h,0021h,0408h,0023h,0022h,1402h,0024h,0025h
  0000000001xxxxs              0804h,0409h,0418h,0026h,3C01h,0027h,0C03h,1C03h,
                               0028h,0029h,002Ah,002Bh,040Ah,002Ch,1802h,002Dh
  00000000001xxxxs             002Fh,002Eh,4001h,0805h,0030h,040Bh,0031h,0033h,
                               0032h,1C02h,0034h,1003h,0035h,4401h,040Ch,0037h
  000000000001xxxxs            0036h,0038h,0039h,5401h,003Ah,0C04h,040Dh,5C01h,
                               2002h,003Bh,0806h,4C01h,003Ch,2402h,6001h,4801h
  000000000000                 Unused
Uses different 16bit MDEC values, and the Escape code is different: 8bit levels are 2bit shorter than v1/v2/v3, but 9bit levels are much longer, and 10bit levels are not supported at all (those v0 Escape codes are described in Sony's File Format documented; albeit accidentally because the doc was actually trying to describe v2/v3).

Huffman codes for AC values BS ea (Electronic Arts)
This is using custom MDEC values from VLC0 chunk, and assigns them to the standard Huffman codes. There are two special MDEC values:
  FE00h End of Block (EOB)
  7C1Fh Escape code (huffman code will be followed by v2-style 16bit value)
VLC0 chunk entries 00h..DFh are mapped to the following Huffman codes:
  10                   00
  11x                  01,02
  011x                 03,04
  010xx                05,06,07,08
  0011xx               0D,0E,0B,0C
  00101x               09,0A
  00100xxxx            2E,2F,22,23,2C,2D,2A,2B,26,27,24,25,20,21,28,29
  0001xxx              15,16,13,14,0F,10,11,12
  00001xxx             1A,1B,1E,1F,18,19,1C,1D
  000001               17h
  0000001xxxx          3E,3F,38,39,30,31,34,35,32,33,3C,3D,3A,3B,36,37
  00000001xxxxx        46,47,54,55,4E,4F,44,45,4A,4B,52,53,5E,5F,5C,5D,
                       42,43,5A,5B,58,59,48,49,4C,4D,40,41,50,51,56,57
  000000001xxxxx       74,75,72,73,70,71,6E,6F,6C,6D,6A,6B,68,69,66,67,
                       64,65,62,63,60,61,7E,7F,7C,7D,7A,7B,78,79,76,77
  0000000001xxxxx      9E,9F,9C,9D,9A,9B,98,99,96,97,94,95,92,93,90,91,
                       8E,8F,8C,8D,8A,8B,88,89,86,87,84,85,82,83,80,81
  00000000001xxxxx     B0,B1,AE,AF,AC,AD,AA,AB,A8,A9,A6,A7,A4,A5,A2,A3,
                       A0,A1,BE,BF,BC,BD,BA,BB,B8,B9,B6,B7,B4,B5,B2,B3
  000000000001xxxxx    C6,C7,C4,C5,C2,C3,C0,C1,C8,C9,D4,D5,D2,D3,D0,D1,
                       CE,CF,CC,CD,CA,CB,DE,DF,DC,DD,DA,DB,D8,D9,D6,D7
  000000000000         Unused
All codes can be freely assigned (Escape and EOB don't need to be at 10 and 000001, and the last huffman bit doesn't have to serve as sign bit).

Notes
All BS versions are using the same Huffman codes (the different BS versions do just assign different 16bit MDEC codes to them).
The huffman codes can be neatly decoded by "counting leading zeroes" (without needing bitwise node-by-node processing; this is done in IKI video decoders via GTE registers LZCS and LZCR). Sony's normal v2/v3 decoders are using a yet faster method: A large table to interprete the next 13bit of the bitstream, the table lookup can decode up to 3 huffman codes at once (if the 13bit contain several small huffman codes).


CDROM File Video BS Picture Files

BS Picture Files
A couple of games are storing single pictures in .BS files:
  Alice in Cyberland (ALICE.PAC\*.BS)
  BallBlazer Champions (BBX_EXTR.DAT\Pics\*) (SWAP-encrypted)
  Bugriders: The Race of Kings (*\*.BS and STILLS\MENUS.BS\*)
  Die Hard Trilogy 2 (DATA\*.DHB, DATA\DH*\L*\*.DHB, MOVIE\*.DHB)
  Dino Crisis 2 (PSX\DATA\ST*.DBS\*)
  Duke Nukem (MagDemo12: DN_TTK\*)
  Final Fantasy VII (FF7) (MOVIE\FSHIP2*.BIN\*) (BS v1)
  Gran Turismo 1 (retail TITLE.DAT\* and MagDemo10/15) (in BS iki format)
  Jet Moto 2 (MagDemo03: JETMOTO2\*)
  Mary-Kate and Ashley Crush Course (MagDemo52: CRUSH\SCRN\*.BS)
  Mat Hoffman's Pro BMX (MagDemo48: MHPB\STILLS.BIN\*) (with width/height info)
  NFL Gameday '99 (MagDemo17: GAMEDAY\FE\GD98DATA.DAT)
  Official U.S. PlayStation Magazine Demo Disc 01-02 (MENU\DATA\*.BSS)
  Official U.S. PlayStation Magazine Demo Disc 03-54 (MENU.FF\*)
  Parasite Eve 2 (INIT.BS, and within .HED/.CDF archives)
  Reel Fishing (*.PAK\*)
  Resident Evil 1 (PSX\STAGE*\*.BSS, headerless archive, 8000h-byte align)
  Resident Evil 2 (COMMON\BSS\*.BSS, headerless archive, 10000h-byte align)
  Rugrats (MagDemo19: RUGRATS\*)
  Rugrats Studio Tour (MagDemo32: RUGRATS\DATA\RAW\*.BS)
  Starwars Demolition (MagDemo39+MagDemo41: STARWARS\SHELL\.BS+.TBL\*)
  Star Wars Rebel Assault 2 (RESOURCE.000\Stills\*) (SWAP-encrypted)
  Ultimate Fighting Championship (MagDemo38: UFC\CU00.RBB\390h..3E2h)
  Vigilante 8 (MagDemo09: EXAMPLE\*)
  Witch of Salzburg (PICT\PIC*\*.BS and DOT1 archives *.BSS, *.DAT, *.BIN)
  X-Files (LOGOS\*.BS and GRAPHICS\GRAPHICS.BIN and GRAPHICS\PACKEDBS.BIN\*)
  You Don't Know Jack 2 (MagDemo41: YDKJV2\RES\UI\*.BS)
Note: Those .BS files are usually hidden in custom file archives.

BS Picture Resolution
Movies have Width/Height entries (in the .STR header). Raw .BS picture files don't have any such information. However, there are ways to guess the correct resolution:
  For BS iki format, use resolution from iki header (eg. Gran Turismo 1)
  For MHPB\STILLS.BIN, there's width/height in chunk headers
  Count the number of blocks (EOB codes) during Huffman decompression
  Divide that number by 6 to get the number of Macroblocks
  Search matches for Height=NumBlocks/Width with Width>=Height and Remainder=0
  If Height=300..400, assume double H-resolution, repeat with Width/2>=Height
  And/or use a list of known common resoltions (see below examples)
  Search arrangements with many similar colors on adjacent macroblocks
Common resolutions are:
  Blocks Pixels   Example
  F0h    256x240  any?
  12Ch   320x240  Resident Evil 2 (COMMON\BSS\*.BSS)
  1E0h   512x240  Demo Disc 03-54 (MENU.FF\*), Duke Nukem (MagDemo12)
  1E0h   640x192  Less common than above (but used by Witch of Salzburg)
  4B0h   640x480  Vigilante 8 (MagDemo09), Jet Moto 2 (MagDemo03)
  var    random   Witch of Salzburg has various random resolutions
  iki    ikihdr   Gran Turismo 1 has A0hxA0h and odd size (!) E8hx28h
  ?      ?        Final Fantasy VII (FF7)
  ?      ?        Ultimate Fighting Championship (UFC\CU00.RBB\3B7h..3E2h)
  118h   320x224  Alice in Cyberland (most files; or two such as panorama)
  230h   ?        Alice in Cyberland (AD_115.BS and AD_123A.BS)
Some other possible, but rather unlikely results would be:
  C8h    320x160  Unlikely for pictures (but used for STR videos, eg. Alone)
  F0h    320x192  Unlikely for pictures (but used for STR videos, eg. Wipeout)
  1E0h   384x320  Very unlikely to see that vertical resolution on PSX
Witch of Salzburg has many small .BS files with various uncommon resolutions (most of them are bundled with 16-byte .TXT files with resolution info).

Extended BS with Width/Height
Starwars Demolition (MagDemo39: STARWARS\SHELL\DEMOLOGO.BS+RESOURCE.TBL\*)
Starwars Demolition (MagDemo41: STARWARS\SHELL\DEMOLOGO.BS+RESOURCE.TBL\*)
  000h 2    Width  (280h)       ;\extra header
  002h 2    Height (1E0h)       ;/
  004h 2    MDEC Size/4 (after huffman decompression) (rounded to 80h/4 bytes)
  006h 2    File ID (3800h)
  008h 2    Quantization step/factor (0000h..003Fh, for MDEC "DCT.bit10-15")
  00Ah 2    Version (1, 2, or 3) (2 is most common)
  00Ch ...  Huffman compressed data blocks (Cr,Cb,Y1,Y2,Y3,Y4, Cr,Cb,Y1,Y2..)


CDROM File Video Wacwac MDEC Streams

Wacwac uses different Huffman codes than BS videos, the decoder has some promising ideas that might yield slightly better compression than BS v3. However, it is used by only one known game:
  Aconcagua (JP) (2000 Sony/WACWAC!)
And even that game is only using it in two movies, and the movies are barely making any use of it: The 20Mbyte intro scene is a picture slide show (where the camera is zooming across twelve black and white images), the 50Mbyte ending scene is providing a more cinematic experience (the camera is scrolling through a text file with developer staff names).

Wacwac MDEC Stream Sectors
  000h 2    STR ID   (0160h)
  002h 2    STR Type WACWAC Tables (0002h=IntroTableSet, 0003h=EndingTableSet)
  004h 2    Sector number within current Frame (0000h..num-1)
  006h 2    Number of Sectors in this Frame
  008h 4    Frame number (6 or 11 and up, because 1st some frames are Polygons)
  00Ch 4    Frame Size in bytes
  010h 2    Bitmap Width  (always 140h)  ;\always 320x208 (in fact, the
  012h 2    Bitmap Height (always 0D0h)  ;/decoder is hardcoded as so)
  014h 4    Quant (0..3Fh) (same for all sectors within the frame)
  018h 8    Zerofilled
  020h 7E0h Raw Bitstream data (without Quant or BS header) (garbage padded)
Aconcagua has dozens of STR files with Polygon Streams. MDEC Streams are found only in two STR files for Intro and Ending scenes:
  Intro=Disc1:\ST01_01\STR_01_00.STR     Ending=Disc2:\ST09_01\STR_09_01.STR
  Leading zeroes (150 sectors)           Leading zeroes (150 sectors)
  Frame 0001h..0005h Polygon Frames      Frame 0001h..000Ah Polygon Frames
  Frame 0006h..0545h MDEC Frames 20MB    Frame 000Bh..0D79h MDEC Frames 50MB
  Frame 0546h..1874h Polygon Frames 48MB
Audio is normal XA-ADPCM, with the first audio sector occuring before 1st frame (after the leading zeropadded 150 sectors).

Wacwac Huffman Bitstreams
Wacwac uses little-endian bitstreams (starting with low bit in bit0 of first byte). To decode the separate blocks in the bitstream:
  Read Huffman code for DC, and output Quant*400h+(DC AND 3FFh)
  Read Huffman code for Size, aka num1,num2,num3 values for below reads
  Repeat num1 times: Read Huffman code for AC1, and output AC
  Repeat num2 times: Read Huffman code for AC2, and output AC
  Repeat num3 times: Read Huffman code for AC3, and output AC
  Output EOB (end of block)
The header/data lacks info about MDEC size after Huffman decompression, the worst case size for 320x208pix would be:
  14h*0Dh*6*41h*2+Align(80h)+Header(4) = 31880h+4 bytes
Note: The bitstream consists of separate 16x208pix slices (set DC for Cr,Cb,Y to zero at begin of each slice, and skip padding to 32bit-boundary at end of each slice).

Wacwac Huffman Table Sets
Aconcagua has two table sets, stored in PROGRAM.BIN (in compressed form, appearing as so: FF,90,16,2E,06,20,03,D6,etc). While watching the intro movie, the uncompressed sets can be found at these RAM locations:
  80112AF8h (1690h bytes)  ;Table Set for Intro Scene
  80114188h (1B68h bytes)  ;Table Set for Ending Scene
Each Table Set has a 38h-byte header, followed by five tables:
  000h 4    Table Set size (1690h or 1B68h)
  004h 4    Table Set exploded size (when allocating 16bit/DC, 32bit/Size/AC)
  008h 2    Size Table max Huffman size in bits  (0Ah or 09h)           ;\Size
  00Ah 2    Size Table number of entries         (40h)                  ;/
  00Ch 2    DC Table max Huffman size in bits    (0Bh)                  ;\
  00Eh 2    DC Table number of entries           (100h)                 ; DC
  010h 2    DC Huffman code Escape 10bit (non-relative 10bit DC value)  ;
  012h 2    DC Huffman size Escape 10bit (3 or 6, escape prefix size)   ;/
  014h 2    AC1 Table max Huffman size in bits   (0Eh or 0Bh)           ;\
  016h 2    AC1 Table number of entries          (0DAh or 100h)         ;
  018h 2    AC1 Huffman code Escape 7bit  (run=0bit, level=signed7bit)  ; AC1
  01Ah 2    AC1 Huffman code Escape 16bit (run=6bit, level=10bit)       ;
  01Ch 2    AC1 Huffman size Escape 7bit  (9 or 7, escape prefix size)  ;
  01Eh 2    AC1 Huffman size Escape 16bit (9 or 7, escape prefix size)  ;/
  020h 2    AC2 Table max Huffman size in bits   (0Eh)                  ;\
  022h 2    AC2 Table number of entries          (AAh or F4h)           ;
  024h 2    AC2 Huffman code Escape 8bit  (run=3bit, level=signed5bit)  ; AC2
  026h 2    AC2 Huffman code Escape 16bit (run=6bit, level=10bit)       ;
  028h 2    AC2 Huffman size Escape 8bit  (10 or 9, escape prefix size) ;
  02Ah 2    AC2 Huffman size Escape 16bit (10 or 9, escape prefix size) ;/
  02Ch 2    AC3 Table max Huffman size in bits   (0Eh)                  ;\
  02Eh 2    AC3 Table number of entries          (87h or B2h)           ;
  030h 2    AC3 Huffman code Escape 8bit  (run=4bit, level=signed4bit)  ; AC3
  032h 2    AC3 Huffman code Escape 16bit (run=6bit, level=10bit)       ;
  034h 2    AC3 Huffman size Escape 8bit  (10 or 9, escape prefix size) ;
  036h 2    AC3 Huffman size Escape 16bit (10 or 9, escape prefix size) ;/
  038h ..   Size Table (64bit per entry)    ;\
  ...  ..   DC Table   (32bit per entry)    ;
  ...  ..   AC1 Table  (64bit per entry)    ; Tables
  ...  ..   AC2 Table  (64bit per entry)    ;
  ...  ..   AC3 Table  (64bit per entry)    ;/
Size Table entries (64bit):
  0-1    Zero
  2-31   Huffman code (10bit max)
  32-39  Number of AC1 codes in this block  ;\implies End of Block (EOB)
  40-47  Number of AC2 codes in this block  ; after those AC codes
  48-55  Number of AC3 codes in this block  ;/
  56-63  Huffman size (1..10 bits)
DC Table entries (32bit):
  0-9    Relative DC Value (relative to old DC from memorized Cr,Cb,Y)
  10-15  Huffman size (1..11 bits)
  16-31  Huffman code (11bit max)
 Notes: For the relative DC's, the decoder does memorize DC for Cr,Cb,Y upon
  decoding Cr,Cb,Y1,Y3 (but does NOT memorize DC when decoding Y2,Y4).
  Initial DC for Cr,Cb,Y is zero at begin of each 16x208pix slice.
 Obscurities: The decoder does accidentally use bit10 to sign-expand the
  DC value in bit0-9 (but does mask-off those bugged sign bits thereafter),
  and the decoder does uselessly memorize Y1 and Y3 separately (but uses only
  the most recently memorized value).
AC1/AC2/AC3 Table entries (64bit):
  0-1    Zero
  2-31   Huffman code (14bit max)
  32-47  MDEC code (6bit run, and 10bit AC level)
  48-63  Huffman size (1..14 bits)
The Escape codes are stored in the 38h-byte Table Set header (instead of in the tables), the init function uses that info for patching escape-related opcodes in the decoder function (that would allow to omit table lookups upon escape codes; the decoder doesn't actually omit such lookups though).
To simplify things, one could store the escape codes in the tables (eg. using special MDEC values like FC00h+35h for run=3bit, level=signed5bit).


CDROM File Video Polygon Streaming

Ape Escape - Polygon Streaming
Used by Ape Escape (Sony 1999) (DEMO\*.STR and some STR\*.STR files and KKIIDDZZ.HED\STR\0006h and up).
The files start with zerofilled sectors (without STR headers), followed by sectors with STR headers with [00h]=0160h, [02h]=8001h (same values as for MDEC), but with [10h..1Fh]=zero (without resolution/header info). And the data at [20h] starts with something like 14h,00h,03h,FFh,2Ah,02h,00h,00h.
That data seems to consist of polygon coordinates/attributes that are rendered as movie frames. The texture seems to be stored elsewhere (maybe in the .ALL files that are bundled with some .STR files).

Panekit - Polygon Streaming
Panekit STR seems to use Polygon Streaming (except 1st some Megabytes are MDEC).

Aconcagua - Polygon Streaming
Aconcagua STR does use Polygon Streaming (except first+last movie are MDEC).

Cyberia (1996) (TF\STR\*.STR)
Cyberia is using Software-rendering for both movies and in-game graphics. That is, PSX hardware features like MDEC, GTE, and GPU-Polygons are left all unused, and the GPU is barely used for transferring data from CPU to VRAM.
The STR header for software-rendered movie frames looks as so:
  000h 2    STR ID   (0160h)
  002h 2    STR Type (0002h=Custom, Software rendering)
  004h 2    Sector number within current Frame (0..num-1)
  006h 2    Number of Sectors in this Frame    (varies)
  008h 4    Frame Number (1=First)
  00Ch 4    Frame Size in Bytes/4 (note: first frame in MAP*.STR is quite big)
  010h 2    Rendering Width  (0140h)
  012h 2    Rendering Height (00C0h)
  014h 0Ch  Unknown (zerofilled or random garbage)
  020h 7E0h Custom data for software rendering
Note: First sector of First frame does usually have byte[22h]=88h (except FINMUS.STR). The Custom data part is often have garbage padding (such like ASCII strings with "c2str" command line tool usage instructions).

Croc 1 (CUTS\*.AN2)
Probably cut-scenes with polygon animations. The files seem to contain 2300h-byte data frames (plus XA-ADPCM sectors inserted here and there).
  000h 4     Number of remaining frames
  ...  22FCh Unknown data (zeropadded if smaller)


 _______________ Unknown Streaming Data (Polygons or whatever) ________________

Custom STR - 3D Baseball (BIGFILE.FOO)
This is used for several files in 3D Baseball (BIGFILE.FOO):
  BIGFILE.FOO\0151h\0005h,0009h,000Fh,0017h,001Bh, 02E5h,02E9h,..,0344h,0348h
  BIGFILE.FOO\0152h\0186h,018Ch,0192h,0198h)
  BIGFILE.FOO\0153h\029Ah,02A0h,02A6h,02ACh)
The files contain some kind of custom streaming data, with custom STR header, and data containing increasing/decreasing bytes... maybe non-audio waveforms?
  000h 2    STR ID   (0160h)
  002h 2    STR Type (0001h=Custom)
  004h 2    Sector number within current Frame (always 0)
  006h 2    Number of Sectors in this Frame    (always 1)
  008h 4    Frame Number (1=First)
  00Ch 4    Frame Size (6FAh or 77Ah, sometimes 17Ah or 1FAh or 20Ah)
  010h 2    Unknown (280h, or sometimes 300h or 340h)
  012h 2    Frame Time (0=First, increases with step [19h], usually +5 or +7)
  014h 2    Unknown (280h, or sometimes 300h or 3C0h, or 0)
  016h 1    Frame Time (same as [012h] AND FFh)
  017h 1    Unknown (0 or 1)
  018h 1    Unknown (40h, or 80h, or C0h)
  019h 1    Duration? (5 or 7, or sometimes less, step for Frame Time)
  01Ah 1    Unknown (3, or less in last some frames)
  01Bh 5    Zerofilled
  020h 7E0h Data (increasing/decreasing bytes... maybe non-audio waveforms?)

Army Men Air Attack 2 (MagDemo40: AMAA2\*.PMB)
  000h 2     STR ID   (0160h)
  002h 2     STR Type (0000h=Custom)
  004h 2     Sector number within current Frame (0..2)
  006h 2     Number of Sectors in this Frame    (always 4) (3xSTR + 1xADPCM)
  008h 4     Frame Number (1=First)
  00Ch 4     Frame Size? (800h, despite of having 3 sectors with 7E0h each?)
  010h 2     Unknown (00h or 01h)
  012h 2     Unknown (A3h or ABh ... 6Ch or 7Bh ... or 43h or 49h)
  014h 2     Sector number within current Frame (0..2) (same as [004h])
  016h 0Ah   Zerofilled
  020h 7E0h  Data (polygon streaming or so?)
Note: The .PMB file is bundled with a .PMH file, which might contain header info?

Bits Laboratory games (Charumera, and True Love Story series)
  Charumera                  ENDING.XA     (with dummy/zero data)
  True Love Story            TLS\MULTI.XA  (with nonzero data)
  True Love Story 2          TLS2\ENDING.STR and TLS2\MULTI.XA
  True Love Story Fan Disc            ;\probably use that format, too
  True Love Story: Remember My Heart  ;/(not verified)
The STR headers have STR ID=0160h and STR Type=0001h, STR header[10h..1Fh] contains nonsense BS video info (with BS ID=3800h, although there isn't any BS data in the actual data part at offset 20h and up).
The files do mainly contain XA-ADPCM sectors, plus some STR sectors in non-MDEC format. Unknown if that STR sectors are separate channels, or if they are used in parallel with the XA-ADPCM channel(s).
Unknown what the STR sectors are used for (perhaps Polygon Streaming, audio subtitles, or simple garbage padding for unused audio sectors). In some files, the STR sectors appear to be just dummy padding (STR header plus zerofilled data area).

Nightmare Project: Yakata
This game has normal MDEC Streams, and Special Streams in non-MDEC format (eg. Disc1, File 0E9h-16Eh and 985h-B58h), perhaps containing Polygon Streams or whatever.
There are two channels (file=1/channel=00h-01h), each channel contains data that consists of 5 sectors per frame (1xHeader plus 4xData). The sectors have STR ID=0160h, and STR Type as follows:
  0000h=Whatever special, channel 0 header (sector 0)
  0400h=Whatever special, channel 1 header (sector 1)
  0001h=Whatever special, channel 0 data   (sector 2,4,6,8)
  0401h=Whatever special, channel 1 data   (sector 3,5,7,9)

Eagle One: Harrier Attack STR files
  \*.STR            MDEC movies  ;\BS fraquant (except, demo version
  \DATA*\*.STR      MDEC movies  ;/            on MagDemo31 uses mormal BS v2)
  \DATA*\M*\L*.STR  Multi-language TXT files with STR header on each sector
  \DATA*\M*\I*.STR  unknown binary data (whatever and SPU-ADPCM)
  \LANGN.STR        unknown binary data (whatever)
All of the above have STR Type=8001h (but only the MDEC movies have BS ID 3800h; the MDEC movies start with 13 zerofilled sectors that are all zeroes without any STR/BS headers).


CDROM File Audio Single Samples VAG (Sony)

VAG audio samples
PSX Lightspan Online Connection CD, cdrom:\CD.TOC:\UI*\*.VAG
PSX Wipeout 2097, cdrom:\WIPEOUT2\SOUND\SAMPLES.WAD:\*.vag (version=02h)
PSX Perfect Assassin, DATA.JFS:\AUDIO\*.VAG and DATA.JFS:\SND\*.VAG
  000h 4    File ID (usually "VAGp")
  004h 4    Version (usually 02h, or 20h)                       (big-endian)
  008h 4    Reserved (0) (except when ID="VAGi")                (big-endian)
  00Ch 4    Channel Size (data size... per channel?)            (big-endian)
  010h 4    Sample Rate (in Hertz) (eg. 5622h=22050Hz)          (big-endian)
  014h 0Ch  Reserved (0) (except when version=2)
  020h 10h  Name (ASCII, zeropadded)
  ... (..)  Optional ID string (eg. "STEREO" in upper/lowercase)
  ... (..)  Optional Padding to Data start
  ...  ..   ADPCM Data for channel(s) (usually at offset 030h)
VAG files are used on PSX, PSP, PS2, PS3, PS4. The overall 1-channel mono format is same for all consoles. But there are numerous different variants for interleaved 2-channel stereo data.

VAG Filename Extensions
  .vag      default (eg. many PSX games)
  .vig      2-channel with interleave=10h (eg. PS2 MX vs ATV Untamed)
  .vas      2-channel with interleave=10h (eg. PS2 Kingdom Hearts II)
  .swag     2-channel with interleave=filesize/2 (eg. PSP Frantix)
  .l and .r 2-channel in l/r files (eg. PS2 Gradius V, PS2 Crash Nitro Kart)
  .str      whatever (eg. P?? Ben10 Galactic Racing)
  .abc      whatever (eg. PSP F1 2009 (v6), according to wiki.xentax.com)

VAG File IDs (header[000h])
  "VAGp"  default (eg. many PSX games)
  "VAG1"  1-channel (eg. PS2 Metal Gear Solid 3)
  "VAG2"  2-channel (eg. PS2 Metal Gear Solid 3)
  "VAGi"  2-channel interleaved (eg. ?)
  "pGAV"  little endian with extended header (eg. PS2 Jak 3, PS2 Jak X)
  "AAAp"  extra header, followed by "VAGp" header (eg. PS2 The Red Star)

VAG Versions (header[004h])
  00000000h   v1.8 PC
  00000002h   v1.3 Mac (eg. PSX Wipeout 2097, in SAMPLES.WAD)
  00000003h   v1.6+ Mac
  00000020h   v2.0 PC (most common, eg. PSX Perfect Assassin)
  00000004h   ? (later games, uh when/which?)
  00000006h   ? (vagconf, uh when/which?)
  00020001h   v2.1 (vagconf2)   ;\with HEVAG coding instead SPU-ADPCM
  00030000h   v3.0 (vagconf2)   ;/(eg. PS4/Vita)
  40000000h   ? (eg. PS2 Killzone) (1-channel, little endian header)

Reserved Header entries for ID="VAGi"
  008h 4  Interleave (little endian) (the other header entries are big endian)

Reserved Header entries for Version=00000002h (eg. PSX Wipeout 2097)
This does reportedly contain some default "base" settings for the PSX SPU:
  014h 2  Volume left                    4Eh,82h  ;-Port 1F801C00h
  016h 2  Volume right                   4Eh,82h  ;-Port 1F801C02h
  018h 2  Pitch (includes fs modulation) A8h,88h  ;-Port 1F801C04h +extra bit?
  01Ah 2  ADSR1                          00h,00h  ;-Port 1F801C08h
  01Ch 2  ADSR2                          00h,E1h  ;-Port 1F801C0Ah
  01Eh 2  ?                              A0h,23h  ;-Port 1F801C0xh maybe?

Reserved Header entries for Version=00000003h (according to wiki.xentax.com)
  01Eh 1  Number of channels (0 or 1=Mono, 2=Stereo)

Reserved Header entries for Version=00020001h and Version=00030000h
  01Ch 2  Zero                                      ;if non-zero: force Mono
  01Eh 1  Number of channels (0 or 1=Mono, 2=Stereo ;if 10h..FFh: force Mono
  01Fh 1  Zero                                      ;if non-zero: force Mono
Unknown if the above "force Mono" stuff is really needed (maybe it was intended to avoid problems with Version=00000002h, and maybe never happens in Version=00000003h and up)?

VAG ADPCM Data
The ADPCM data uses PSX SPU-ADPCM encoding (even on PS2 and up, except PS4 with Version=0002001h or Version=00030000h, which do use HEVAG encoding).
SPU ADPCM Samples
The data does usually start at offset 0030h (except, some files have extra header data or padding at that location).
The first 10h-byte ADPCM block is usually all zero (used to initialize the SPU).
2-channel (stereo) files are usually interleaved in some way.

VAG Endiannes
The file header entries are almost always big-endian (even so when used on little endian consoles). There are a few exceptions:
ID="VAG1" has little endian [008h]=Interleave (remaining header is big-endian).
ID="pVAG" has (some?) header entries in little endian.
Version=40000000h has most or all header entries in little endian (perhaps including the version being meant to be 00000040h).

VAG Channels
VAGs can be 1-channel (mono) or 2-channel (stereo). There is no standarized way to detect the number of channels (it can be implied in the Filename Extension, Header ID, in Reserved Header entries, in the Name string at [020h..02Fh], in optional stuff at [030h], or in a separate VAG Header in the middle of the file).

VAG Interleave
  None       default (for 1-channel mono) (and separate .l .r stereo files)
  800h       when ID="VAG2"
  [008h]     when ID="VAGi" (little-endian 32bit header[008h])
  1000h      when ID="pGAV" and [020h]="Ster" and this or that
  2000h      when ID="pGAV" and [020h]="Ster" and that or this
  10h        when filename extension=".vig"
  10h        when Version=0002001h or Version=00030000h (and channels=2)
  filesize/2 when filename extension=".swag"
  6000h      when [6000h]="VAGp" (eg. PSX The Simpsons Wrestling)
  1000h      when [1000h]="VAGp" (eg. PS2 Sikigami no Shiro)
  ...

AAAp Header
  000h 4     ID "AAAp"
  004h 2     Interleave
  006h 2     Number of Channels (can be 1 or 2?)
  008h 30h*N VAGp header(s) for each channel, with Version=00000020h
  ...  ..    ADPCM Data (interleaved when multiple channels)

See also
http://github.com/vgmstream/vgmstream/blob/master/src/meta/vag.c ;very detailed
http://wiki.xentax.com/index.php/VAG_Audio ;rather incomplete and perhaps wrong


CDROM File Audio Sample Sets VAB and VH/VB (Sony)

VAB vs VH/VB
  .VAB  contains VAB header, and ADPCM binaries   ;-all in one file
  .VH   contains only the VAB header              ;\in two separate files
  .VB   contains only the ADPCM binaries          ;/
PSX Perfect Assassin has some v7 .VH/.VB's (in \DATA.JFS:\SND\*.*)
PSX Resident Evil 2, COMMON\DATA\*.DIE (contains .TIM+.VAB badged together)
PSX Spider-Man, CD.HED\l2a1.vab is VAB v5 (other VABs in that game are v7)
PSX Tenchu 2 (MagDemo35: TENCHU2\VOLUME.DAT\5\* has VAB v20h, maybe a typo)

VAB Header (VH)
  0000h 4       File ID ("pBAV")
  0004h 4       Version (usually 7) (reportedly 6 exists, too) (5, 20h exists)
  0008h 4       VAB ID (usually 0)
  000Ch 4       Total .VAB filesize in bytes (or sum of .VH and .VB filesizes)
  0010h 2       Reserved (EEEEh)
  0012h 2       Number of Programs, minus 1 (0000h..007Fh = 1..128 programs)
  0014h 2       Number of Tones, minus? (max 0800h?) (aka max 10h per program)
  0016h 2       Number of VAGs, minus? (max 00FEh)
  0018h 1       Master Volume (usually 7Fh)
  0019h 1       Master Pan    (usually 40h)
  001Ah 1       Bank Attribute 1 (user defined) (usually 00h)
  001Bh 1       Bank Attribute 2 (user defined) (usually 00h)
  001Ch 4       Reserved (FFFFFFFFh)
  0020h 800h    Program Attributes 10h-byte per Program 00h..7Fh   (fixed size)
  0820h P*200h  Tone Attributes 200h-byte per Program 00h..P-1  (variable size)
  xx20h 200h    16bit VAG Sizes (div8) for VAG 00h..FFh            (fixed size)
  xx20h (...)   ADPCM data (only in .VAB files, otherwise in separate .VB file)
Program Attributes (10h-byte per Program, max 80h programs)
  000h 1      tones        Number of Tones in the Program (Yaroze: 4) (uh?)
  001h 1      mvol         Master Volume   (Yaroze: 0..127)
  002h 1      prior                        (Yaroze: N/A)
  003h 1      mode                         (Yaroze: N/A)
  004h 1      mpan         Master Panning  (Yaroze: 0..127)
  005h 1      reserved0
  006h 2      attr                         (Yaroze: N/A)
  008h 4      reserved1
  00Ch 4      reserved2
Tone Attributes (20h-byte per Tone, max 10h tones per Program)
  000h 1      prior        Tone Priority   (Yaroze: 0..127, 127=highest)
  001h 1      mode         Mode            (Yaroze: 0=Normal, 4=Reverberation)
  002h 1      vol          Tone Volume     (Yaroze: 0..127)
  003h 1      pan          Tone Panning    (Yaroze: 0..127)
  004h 1      center       Centre note (in semitone units) (Yaroze: 0..127)
  005h 1      shift        Centre note fine tuning         (Yaroze: 0..127)
  006h 1      min          Note limit minimum value     (Yaroze: 0..127)
  007h 1      max          Note limit maximum value     (Yaroze: 0..127)
  008h 1      vibW                                      (Yaroze: N/A)
  009h 1      vibT                                      (Yaroze: N/A)
  00Ah 1      porW                                      (Yaroze: N/A)
  00Bh 1      porT                                      (Yaroze: N/A)
  00Ch 1      pbmin        Max? value for downwards pitchbend  (Yaroze: 0..127)
  00Dh 1      pbmax        Max value for upwards pitchbend     (Yaroze: 0..127)
  00Eh 1      reserved1
  00Fh 1      reserved2
  010h 2      ADSR1        Attack,Decay    (Yaroze: 0..127,0..15)
  012h 2      ADSR2        Release,Sustain (Yaroze: 0..127,0..31)
  014h 2      prog         Program number that tone belongs to (Yaroze: 0..127)
  016h 2      vag          VAG number                          (Yaroze: 0..254)
  018h 8      reserved

VAB Binary (VB) (ADPCM data) (to be loaded to SPU RAM)
This can contain max 254 "VAG files" (maybe because having two (?) reserved 8bit numbers?).
Sony wants the total size of the ADPCM data to be max 7E000h bytes (which would occupy most of the 512Kbyte SPU RAM, leaving little space for the echo buffer or additional effects).
Note: The "VAG files" inside of VAB/VB are actually raw SPU-ADPCM data, without any VAG file header. The first 10h-byte ADPCM block is usually zerofilled.


CDROM File Audio Sequences SEQ/SEP (Sony)

SEQ - Single Sequence
.SEQ contains MIDI-style sequences, the samples for the instruments can be stored in a separate .VAB file (or .VH and .VB files).
Used by Perfect Assassin, DATA.JFS:\SND\*.SEQ (bundled with *.VH and *.VB)
Used by Croc (MagDemo02: CROC\CROCFILE.DIR\AMBI*.BIN, MAP*.BIN, JRHYTHM.BIN)
Used by Resident Evil 2 (COMMON\SOUND\*.BGM)
Used by many other games.
  000h 4   File ID "pQES"
  004h 4   Version (1)                                    (big endian)
  008h 2   Resolution (ticks per quarter note) (TPQN)     (01h,80h)
  00Ah 3   Tempo (microseconds per quarter note)          (big endian)
  00Dh 2   Rhythm (NN/NN)                   (04h,02h)
   00Dh 1     Rhythm (Numerator)    ;Numerator of time signature (n)
   00Eh 1     Rhythm (Denominator)  ;Denominator of time signature (2^n)
  00Fh ... Score data, uh?    (with many MIDI KeyOn's: xx,9x,xx,xx)
  ...  3   End of SEQ (2Fh=End of Track)    (FFh,2Fh,00h)
The "Score data" seems to be more or less same as in Standard Midi Format (.smf files), ie. containing timing values and MIDI commands/parameters.

SEP - Multi-Track Sequences
This is a simple "archive" with several SEQ-like sequences.
  000h 4   File ID "pQES"  ;same ID as in .SEQ files (!)
  004h 2   Version (0)     ;value 0, and only 16bit, unlike .SEQ files
  006h ..  1st Sequence
  ...  ..  2nd Sequence
  ...  ..  etc.
Sequences:
  000h 2   Sequence ID (0000h and up)     (big endian)        ;-ID number
  002h 2   Resolution (ticks per quarter note)   (01h,80h)    ;\
  004h 3   Tempo (microseconds per quarter note) (07h,27h,0Eh); as in SEQ files
  007h 2   Rhythm (NN/NN)                        (04h,02h)    ;/
  009h 4   Data size (big endian, from 00Dh up to including End of SEQ)
  00Dh ... Score data, uh?                  (...)             ;\as in SEQ files
  ...  3   End of SEQ (2Fh=End of Track)    (FFh,2Fh,00h)     ;/
Used by Hear It Now (Playstation Developer's Demo) (RCUBE\RCUBE.SEP)
Used by Rayman (SND\BIGFIX.ALL\0002)
Used by Monster Rancher (MagDemo06, MR_DEMO\DATA\MF_DATA.OBJ\025B)
Used by Rugrats (MagDemo19: RUGRATS\DB02\*.SEP and MENU\SOUND\SEPS\*.SEP)
Used by Rugrats Studio Tour (MagDemo32: RUGRATS\DATA\SEPS\*.SEP)
Used by Monkey Hero (MagDemo17: MONKEY\BIGFILE.PSX}*.SEP)
Used by Pitfall 3D
Used by Blue's Clues: Blue's Big Musical (SEPD chunks in *.TXD)

See also
Apart from standard MIDI messages, one can also use custom NRPN messages (Non-Registered Parameter Number). Some PSX-specific messages are described here (including ADSR and Reverb control):
  web.archive.org/web/2/loveemu.hatenablog.com/entry/20060630/PSX_SEQ_Format


CDROM File Audio Other Formats 

 __________________________ .SQ .HD .BD (SSsq/SShd) ___________________________

This is a newer Sony format from 1999 (resembling the older .SEQ .VH .VB format).
  .SQ Sequence Data (with ID "SSsq")
  .HD Voice Header  (with ID "SShd")
  .BD Voice Binary  (raw SPU-ADPCM, same as .VB)
Used by several games:
  Alundra 2
  Ape Escape
  Arc the Lad 3
  i-mode mo Issho - Doko Demo Issho Tsuika Disc
  Koukidou Gensou - Gunparade March
  Omega Boost
  PoPoLoCrois Monogatari II
  The Legend of Dragoon
  Wild Arms 2

Sequence Data (*.SQ) (SSsq)
  000h 2      Master Volume          (usually 64h)
  002h 2      Ticks per quarter note (usually 1E0h)
  004h 2      Tempo                  (varies)
  006h 6      Zerofilled
  00Ch 4      ID "SSsq"
  010h 100h   Sixteen Channels (10h*10h bytes) (see below Data Structures)
  110h ..     MIDI Sequence (terminated by FFh,2Fh,00h)

Voice Header (*.HD) (SShd)
  000h 4      Size of the .HD file itself
  004h 4      Size of the corresponding .BD file
  008h 4      Zero
  00Ch 4      ID "SShd"
  010h 1Ch*4  File List (UNSORTED offsets to File00h..1Bh, or FFFFFFFFh=Unused)
  080h ..     File Data area (all files are 2-byte aligned)
SShd.File00h - Music Instruments:
  000h 2      Number of Instruments, minus 1 (N-1)
  002h N*2    Offsets to Instruments (or FFFFh=unused)
  ...  ..     Instrument entries
SShd.File01h - Velocity Table:
  000h 2      Unused (zero)
  002h 80h    Volumes for velocity 0..7Fh (usually linear/increasing 0..7Fh)
SShd.File02h - Breath controls:
  000h 2      Number of Breath Controls, minus 1 (N-1)
  002h N*2    Offsets to Breath values (or FFFFh=None)
  ...  ..     Breath values (whatever pipe/flute blow volume or so?)
                   maybe with Zeropadding to 2-byte boundary (?)
                   (or actually, each control is always(?) 40h-byte tall,
                   so no padding is needed here?)
SShd.File03h - SFX Sequences:
  000h 2      Number of Sequence packs, minus 1 (N-1)
  002h N*2    Offsets to Sequence packs
  ...  N*var  Sequence pack entries (see below, each can have multiple seq's)
  ...  ..     MIDI Sequences (each terminated by FFh,2Fh,00h)
  ...  ..     Zeropadding to 2-byte boundary
SShd.File04h - SFX Instruments:
  000h 2      Master volume
  002h 0Eh    Zerofilled
  010h 180h   Twentyfour Channels (18h*10h bytes)
  190h 2      Number of Instruments, minus 1 (N-1)
  192h N*2    Offsets to Instruments (relative to base=190h)
  ...  ..     Instrument entries (each may have multiple SFX Tones)
SShd.File05h..File1Bh - Unused:
  These are usually/always unused (with Offset=FFFFFFFFh in File List).

Voice Binary (*.BD) (same as .VB files)
  000h ..     SPU-ADPCM data (usually starting with zerofilled 10h-byte block)

SSsq/SShd Data Structures
Channel entries (in SSsq and SShd.File04h):
  000h 1      Unknown (always 0?)
  001h 1      Index/ID
  002h 1      Program index (from SShd)
  003h 1      SSsq volume
  004h 1      Pan
  005h 4      Unknown (always 0?)
  009h 1      Modulation
  00Ah 1      Pitch Bend
  00Bh 1      Priority
  00Ch 1      Breath
  00Dh 1      Unknown (maybe sixteenths?)
  00Eh 1      Adjusted volume
  00Fh 1      Unknown
Sequence pack entries (in SShd.File03h):
  000h 2      Number of Sequences in this pack, minus 1 (N-1)
  002h N*2    Offsets to MIDI Sequences
Instrument entries (in SShd.File00h and SShd.File04h):
  000h 1      Number of Tones, minus 1 (N-1, plus bit7=type) (or FFh=SFX)
              (when bit7=1, instrument can play multiple tones on a single cmd)
                   "(FFh are SFX instruments,
                   8Xh are instruments, that can play multiple tones on a
                   single command, (uh, what tones, on what command ?)
                   otherwise 0, (uh, maybe 0Xh ?),
                   second nibble is upper bound of notes AKA count - 1)"
  001h 1      Volume
  002h 1      Pan
  003h 1      Unknown/Unused
  004h 1      Pitch Bend Multiplier
  005h 1      Breath Control Index (in SShd.File02h)
                "if there are multiple breath control tables" ;uh, what if not?
  006h 1      SFX Starting note                   ;\only used for SFX,
  007h 1      SFX Number of Tones, minus 1 (N-1)  ;/ie. when [000h]=FFh
  008h N*10h  Tone data (with N as specified in entry [000h] or [007h])
Tone entries (in above Instrument entries):
  000h 1      noteMin    ;\if a KeyOn is called on a specific program,
  001h 1      noteMax    ;/notes are selected if they are in range
  002h 1      keyRoot ;the offset from the note requested is used to pitch bend
  003h 1      sixteenths (flat pitch bend in 1/16 of a semitone)
  004h 2      Offset (div8) to SPU-ADPCM data in .BD file
                   sound bank ptr (*4)  ;uh, this is "div 8", not "mul 4" !!!
  006h 4      ADSR
  00Ah 1      Volume override ("if used", this value "would be << 8" and volume
                   would "be | onto" the lower bits during volume calculation)
  00Bh 1      Volume
  00Ch 1      Pan
  00Dh 1      Pitch Bend Multiplier
  00Eh 1      Breath Control Index
  00Fh 1      Tone Flags
Tone Flags (8bit):
  0    High priority
  1    Noise
  2-3  ?
  4    Pitch Bend "multi" from instrument (=multiplier, multiple?)
  5    Modulation on
  6    Breath Control index from instrument
  7    Reverb on

Thanks to Illeprih for SSsq/SShd details.

 ____________________________ DNSa/PMSa/FNSa/FMSa _____________________________

There are four four file types:
  "DNSa"  (aka SouND backwards)         ;sequence data
  "PMSa"  (aka SaMPles backwards)       ;samples with small header
  "FMSa"  (aka SaMples-F... backwards)  ;samples with bigger header   ;\Legacy
  "FNSa"  (aka SouNd-F... backwards)    ;whatever tiny file           ;/of Kain
Used by several games (usually inside of BIGFILE.DAT):
  Akuji (MagDemo18: AKUJI\BIGFILE.DAT\*) (DNSa,PMSa)
  Gex 2 (MagDemo08: GEX3D\BIGFILE.DAT\*) (DNSa)
  Gex 3: Deep Cover Gecko (MagDemo20: G3\BIGFILE.DAT\*) (DNSa,PMSa)
  Legacy of Kain 2 (MagDemo13: KAIN2\BIGFILE.DAT\*) (DNSa)
  Legacy of Kain 2 (MagDemo26: KAIN2\BIGFILE.DAT\*) (DNSa,PMSa,FNSa,FMSa)
  Walt Disney World Racing Tour (MagDemo35: GK\BIGFILE.DAT\*) (DNSa,PMSa)
Note: The exact file format does reportedly differ in each game.

"PMSa" (aka SaMPles backwaords)
  000h 4     ID "PMSa"
  004h 4     Total Filesize (minus 8)
  008h ..    SPU-ADPCM data (usually starting with zerofilled 10h-byte block)

"DNSa" (aka SouND backwards)
  000h 4      ID "DNSa"   ;aka SND backwards
  004h 2      Offset from DNSa+4 to 8-byte entries (can be odd)
  006h 1      Unknown (3)
  007h 1      Number of 8-byte entries   (N1)
  008h 1?     Number of 10h-byte entries (N2)
  ...  ..     Unknown (..)
  ...  N1*8   Whatever 8-byte entries
  ...  N2*10h Whatever 10h-byte entries
  ...  ..     ... circa 40h 4-byte entries...?
  ...  ..     Unknown (..)
  ...  ..     Several blocks with ID "QESa" or "QSMa"  ;supposedly MIDI-style?

"FNSa" (aka SouNd-F... backwards)
These are whatever tiny files (often with filesize 18h..2Ch).
  000h 4     ID "FNSa"
  004h 2     Always 00h,01h (maybe version)
  006h 1     File ID or so (same as in FMSa)
  007h 1     Usually 0 or 1 (maybe MSB of above)
  008h 2     Zerofilled
  00Ah 1     Number of sample IDs (N)
  00Bh 09h   Zerofilled (may inlcude MSB of above)
  014h N*2   Sample IDs (same as in FMSa)
  ...  ..    Zeropadding to 4-byte boundary

"FMSa" (aka SaMples-F... backwards)
  000h 4     ID "FMSa"
  004h 2     Always 00h,01h (maybe version)
  006h 1     File ID or so (same as in FNSa)
  007h 1     Usually 0 or 1 (maybe MSB of above)
  008h 1     Number of samples (N)
  009h 7     Zerofilled (may inlcude MSB of above)
  010h N*var Sample block(s)
 Sample Block format:
  000h 2     Sample ID (same as in FNSa)
  002h 2     Unknown (varies)
  004h 6     Unknown (usually 64h,FFh,7Fh,40h,54h,00h) (volume/panning/etc?)
  00Ah 2     Unknown (usually 3C3Ch, or similar with LSB=MSB)
  00Ch 1     Unknown (usually 01h or 04h)
  00Dh 1     Unknown (usually 0Ch)
  00Eh 2     Unknown (usually 870Fh)
  010h 2     Unknown (usually 5FC7h or 1FC7h)
  012h 2     Zero
  014h 4     Size of SPU-ADPCM data in bytes
  018h ..    SPU-ADPCM data (usually starting with zerofilled 10h-byte block)


 ____________________________________ AKAO ____________________________________

There a several games that have sound files with ID "AKAO".
  XXX does that include different AKAO formats... for Samples and Midi?
AKAO is also used in several streaming movies:
CDROM File Video Streaming Audio

 ___________________________________ Others ___________________________________

Alone in the Dark IV has MIDB and DSND chunks (which contain sound files).

See also
The page below does mention several PSX sound formats, plus some open source & closed source tools for handling those files.
github.com/loveemu/vgmdocs/blob/master/Conversion_Tools_for_Video_Game_Music.md


CDROM File Audio Streaming XA-ADPCM

Audio Streaming (XA-ADPCM)
Audio streaming is usually done by interleaving the .STR or .BS file's Data sectors with XA-ADPCM audio sectors (the .STR/.BS headers don't contain any audio info; because XA-ADPCM sectors are automatically decoded by the CDROM controller).
Raw XA-ADPCM files (without video) do usually have .XA file extension.


CDROM File Audio CD-DA Tracks

The eleven .SWP files in Wipeout 2097 seem to be CD-DA audio tracks.
The one TRACK01.WAV in Alone in the Dark, too?
Other than that, tracks can be accessed via TOC instead of filenames.


CDROM File Audio MP3/ID3 Tags

Overview
  MPEG-1     FFh,Fxh       Raw        1991/93
  MPEG-2     FFh,Fxh       Raw        1995/96
  MPEG-2.5   FFh,Exh       Raw        2000
  ID3v2.2    "ID3",02h     Header     1998
  ID3v2.3    "ID3",03h     Header     1999
  ID3v2.4    "ID3",04h     Header     2000
  Xing VBR   "Xing"        Bitstream  ?
  Xing CBR   "Info"        Bitstream  ?
  FhG VBRI   "VBRI"        Bitstream  ?
  Lame ver   "LAME"        Bitstream  ?
  Lavc ver   "Lavc"        Bitstream  ?
  Ancillary  "here are"..  Bitstream  ?
  ID3v1.0    "TAG"         Footer     1996
  ID3v1.1    "TAG"         Footer     1997
  ID3v1.2    "EXT"         Footer     ?
  ID3v1+     "TAG+"        Footer     ?
  ID3v2.4    "3DI",04h     Footer     2000
  Lyrics3v1  "LYRICSEND"   Footer     ?
  Lyrics3v2  "LYRICS200"   Footer     1998
  ApeTagv1   "APETAGEX"    Footer     ?
  ApeTagv2   "APETAGEX"    Footer     ?


 ________________________________ Header Tags _________________________________

ID3v2.x
  000h 3    ID "ID3"                                                ;\
  003h 1    Version  (02h..04h) (2=v2.2, 3=v2.3, 4=v2.4)            ;
  004h 1    Revision (always 00h, there aren't any known revisions) ; Header
  005h 1    Flags                                                   ;
  006h 4    Size of below Chunks/Padding (4x7bit = 28bit)           ;/
  00Ah (..) Extended header (usually none such)
  ...  ..   Chunks
  ...  ..   Padding (00h-filled)
  ...  (10) Optional "3DI" Footer (if Ver=4 and FlagsBit4=1, usually none such)
The above header format is same for all ID3v2 versions, so one can simply skip the data by skipping 10+N bytes (plus another 10 bytes in case of the footer ID3v2.4).
However, the chunks are fundamentally different in the three versions:
 ID3v2.2 Chunks:
  000h 3    Chunk Name (3-letter ASCII)
  003h 3    Chunk Size (3x8bit = 24bit)
  006h ..   Chunk Data
 ID3v2.3 Chunks:
  000h 4    Chunk Name (4-letter ASCII)
  004h 4    Chunk Size (4x8bit = 32bit)
  008h 2    Chunk Flags
  00Ah ..   Chunk Data
 ID3v2.4 Chunks:
  000h 4    Chunk Name (4-letter ASCII)
  004h 4    Chunk Size (4x7bit = 28bit)
  008h 2    Chunk Flags
  00Ah ..   Chunk Data
Note: There are extra features like compression, encryption, and unsynchronization, some of them differ per version, but they are rarely (perhaps never) used in practice, so it's difficult to test or implement them.

 _______________________________ Bitstream Tags _______________________________

MP3 frames can contain unused bits at the end of their data area, making it possible to store extra data inside of mp3 frames.
Xing/Info/VBRI is usually found in an empty frame at the begin of the bitstream (empty meaning 0 bits/granule), so the extra data area will usually appear at offset 024h (or elsewhere when using mono, or lower bitrates, or frames with CRC).

Xing Variable Bitrate info (big-endian)
This comes from Xing encoder (and it's also used by Lame encoder):
  000h 4      ID "Xing"
  004h 4      Flags (usually 0000000Fh)
  008h (4)    Number of Frames               ;-when FlagsBit0=1
  ...  (4)    Size of all Frames in bytes    ;-when FlagsBit1=1
  ...  (100)  Table of contents (seekpoints) ;-when FlagsBit2=1
  ...  (4)    VBR Scale (or LAME quality)    ;-when FlagsBit3=1

Info Constant Bitrate info (big-endian)
This is sometimes found in constant bitrate files, the format is same as Xing, but with ID "Info" (instead of "Xing").
The Info does usually contain the whole 120-byte data, including seek points, although that's rather useless in constant bitrate files, though Number of Frames may be useful for computing the duration (without needing to search footers at end of file).

VBRI Variable Bitrate info (big-endian)
This comes from the Fraunhofer encoder (and is rarely used elsewhere):
  000h 4      ID ("VBRI")
  004h 2      Version (0001h)                             example...
  006h 2      Delay as Big-Endian float (16bit float?)    7344
  008h 2      Quality indicator                           75
  00Ah 4      Number of Bytes                             45000
  00Eh 4      Number of Frames                            7344
  012h 2      Number of entries within TOC table     (N)  100
  014h 2      Scale factor of TOC table entries           1
  016h 2      Size per table entry in bytes (max 4)  (B)  2
  018h 2      Frames per table entry                      845
  01Ah N*B    TOC entries for seeking "as Big-Endian integral"
Unknown what "number of frames per scaled integral table entry with floating delay" mean exactly.

LAME and Lavc version strings and other graffitis
Some frames contain encoder version strings that may begin with "LAME" or "Lavc" (often in first and last some frames). The strings may be followed by additional info on encoder settings, or things like excact audio duration (in sample units).
Some test files (eg. l3-sin1k0db.bit) contain the string "here are the ancillary-data !",0Dh,0Ah (divided into smaller 0Eh-byte snippets) at end of each frame.

 ________________________________ Footer Tags _________________________________

ID3v1.0 (NamkraD aka Eric Kemp, 1996-1997)
position: at the end of MP3 file
  000h 3   ID "TAG"
  003h 30  Song name       string
  021h 30  Artist          string
  03Fh 30  Album name      string
  05Dh 4   Year            string
  061h 30  Comment         string
  07Fh 1   Genre           byte        see specification
  080h --> 128 total
Caution: Genre=FFh seems to be used as blank/unknown genre (mp3 decoders must take not to mistake that as a sync mark at end of file).

ID3v1.1 (Michael Mutschler, 1997)
same as TAG, with added track at end of comment field
  000h 3   ID "TAG"                               ;\
  003h 30  Song name                              ;
  021h 30  Artist                                 ; same as v1.0
  03Fh 30  Album name                             ;
  05Dh 4   Year                                   ;/
  061h 28  Comment (max 28 chars)                 ;\
  07Dh 1   Zero (00h=comment end marker)          ; unlike v1.0
  07Eh 1   Track Number (01h..xxh) (or 00h=None)  ;/
  07Fh 1   Genre                                  ;-same as v1.0

ID3v1.2 informal format (BirdCage Software, 2002-2003)
position: in the front of TAG
  000h 3   ID "EXT"
  003h 30  Last 30 chars of trackname  (30+30 = 60 total)
  021h 30  Last 30 chars of artist     (30+30 = 60 total)
  03Fh 30  Last 30 chars of album      (30+30 = 60 total)
  05Dh 15  Last 15 chars of comment    (28+15 = 43 total)
  06Ch 20  Sub genre text              (20 total)
  080h --> 128 total

ID3v1+ Enhanced TAG description:
position: in the front of TAG
  000h 4   ID          ("TAG+")
  004h 60  Song name
  040h 60  Artist name
  07Ch 60  Album name
  0B8h 1   Speed       (01h=slow, 02h=medium, 03h=fast, 04h=hardcore, ?=blank)
  0B9h 30  Genre name
  0D7h 6   Start time  ("mmm:ss")
  0DDh 6   End time    ("mmm:ss")
  0E3h --> 227 total                 227 (E3h)

Lyrics3 Tag v1.0
position: in the front of TAG
  000h 11  ID "LYRICSBEGIN"
  00Bh ..  Lyrics text (max 5100 bytes)
  ...  9   ID "LYRICSEND"
The maximum allowed size appears to be 5Kbytes (11+5100+9=5120). Although other descriptions suggest that the maximum is only 5100 in total, or that the text shouldn't exceed 4096 bytes.

Lyrics3 Tag v2.00 (official specification dated Jun 5, 1998)
position: in the front of TAG
  000h 11     ID "LYRICSBEGIN"
  00Bh SIZ-11 Items (each has 3-byte ID, 5-digit ASCII len, data)
  ...  6      Size of above (SIZ) (6-digit decimal ASCII)
  ...  9      ID "LYRICS200"
This is frequently found in older mp3 files (although it's usually not actually containing any lyrics, more often it's containing strings for track/artist names that exceed the 30-byte TAG limit, or a CRC00008XXXXXXXX entry which contains an uppercase CRC32 on the mp3 audio frames excluding any ID3 headers/footers).
There are two v2.0 versions: One says that IND0000Nxx contains always 2 digits, the other says always 3 digits.

ApeTag v1 and v2
position: in the front of TAG
  000h (32)  Ape Header (if any, v2. only)
  ...  ..    Ape Items
  ...  32    Ape Footer
Ape Header/Footer format:
  000h 8   ID "APETAGEX"
  008h 4   Version (3E8h=1000=v1.000, 7D0h=2000=v2.000)
  00Ch 4   Tag Size in bytes (including footer) (excluding header, if any)
  010h 4   Number of Items
  014h 4   Global Flags (v2 only) (all zero in v1) (indicates header/footer)
  018h 8   Reserved (0)
Ape Item format:
  000h 4   Item Size (LEN)
  004h 4   Item Flags
  008h ..  Item ID (ASCII, terminated by 00h)
  ..   LEN Item Data (can be text or binary, depending on Item Flags)

ID3v2.4 Footer 3DI
Whatever related to ID3v2.4 with store data in the footer (instead header).
Position: After the mp3 audio frames, in front of all other footer tags.
  000h 3     Header ID ("ID3")
  003h 2     Header Version (04h,00h)
  005h 1     Header Flags (with bit4=1=Footer Present)
  006h 4     Header Size Entry (4x7bit=28bit)
  00Ah ..    ID3 chunks/padding (with Size as specified in header/footer)
  ...  3     Footer ID ("3DI") (aka ID3 spelled backwards)
  ...  2     Footer Version (04h,00h)
  ...  1     Footer Flags (with bit4=1=Footer Present)
  ...  4     Footer Size Entry (4x7bit=28bit)

See also
http://fileformats.archiveteam.org/wiki/ID3


CDROM File Archives with Filename 

 _______________________________ Entrysize=08h ________________________________

WWF Smackdown (MagDemo33: TAI\*.PAC)
  000h 4     ID ("DPAC")                                        ;\
  004h 4     Unknown (100h)                                     ;
  008h 4     Number of files (N)                                ;
  00Ch 4     Directory Size (N*8)                               ; Header
  010h 4     File Data area size (SIZE = Totalsize-Headersize)  ;
  014h 4     Unknown (1)                                        ;
  018h 7E8h  Zerofilled (padding to 800h-byte boundary)         ;
  800h N*8   File List                                          ;
  ...  ..    Zerofilled (padding to 800h-byte boundary)         ;/
  ...  SIZE  File Data area                                     ;-Data area
 File List entries:
  000h 8     Filename ("NAME")
  004h 2     File Offset/800h (increasing)
  006h 2     File Size/800h
The DPAC archives can contain generic files (eg .TIM) and child archives (in a separate archive format, with ID "PAC ").

 _______________________________ Entrysize=10h ________________________________

Championship Motocross (MagDemo25: SMX\RESHEAD.BIN and RESBODY.BIN)
RESHEAD.BIN:
  000h N*10h  File List (220h bytes)
 File List entries:
  000h 8      Filename ("FILENAME", if shorter: terminated by 00h plus garbage)
  008h 4      Filesize in bytes
  00Ch 4      Offset/800h in RESBODY.BIN (increasing) (or FFFFFFFFh if Size=0)
RESBODY.BIN:
  000h ..     File Data (referenced from RESHEAD.BIN)

One (DIRFILE.BIN\w*\sect*.bin)
  000h N*10h File List
  ...  ..    File Data area
 File List entries:
  000h 0Ch   Filename (eg. "FILENAME 001")     ;for last entry: "END      000"
  00Ch 4     Offset (increasing, N*10h and up) ;for last entry: zero

True Love Story 1 and 2 (TLS*\MCD.DIR and MCD.IMG)
MCD.DIR:
  000h N*10h  File List
  ...  10h    End marker (FFh-filled)
 File List entries:
  000h 8      Filename (zeropadded if less than 8 chars)
  008h 2      Zero (0000h)
  00Ah 2      Size/800h
  00Ch 4      Offset/800h in MCD.IMG
 Note: Filenames are truncated to 8 chars (eg. "FOREST.T" instead "FOREST.TIM")
MCD.IMG:
  000h ..     File Data area (encrypted in True Love Story 2)
In True Love Story 2, the MCD.IMG data is encrypted as follows:
 init_key_by_filename(name):    ;for MCD.IMG (using filenames from MCD.DIR)
  i=0, key0=0001h, key1=0001h, key2=0001h
  while i<8 and name[i]<>00h
    key0=(key0 XOR name[i])
    key1=(key1 * name[i]) AND FFFFh
    key2=(key2 + name[i]) AND FFFFh
  ret
 init_key_by_numeric_32bit_seed(seed):  ;maybe for LINEAR.IMG and PICT.IMG ?
  key0=(seed) AND FFFFh
  key1=(seed - (seed*77975B9h/400000000h)*89h) AND FFFFh
  key2=(seed - (seed*9A1F7E9h/20000000000h)*3527h) AND FFFFh
  ret
 decrypt_data(addr,len):
  for i=1 to len/2
    key2=key2/2 + (key0 AND 1)*8000h
    key0=key0/2 + (key1 AND 1)*8000h
    key1=key1/2 + ((key1/2 OR key0) AND 1)*8000h
    key0=((((key1+47h) AND FFFFh)/4) XOR key0)+key2+(((key1+47h)/2) AND 1)
    halfword[addr]=halfword[addr] XOR key0, addr=addr+2
  ret
The MCD.* files don't contain any encryption flag. Below are some values that could be used to distinguish between encrypted and unencrypted MCD archives (though that may fail in case of any other games/versions with other values):
  Item                    Unencrypted   Encrypted
  Parent Folder name      "TLS"         "TLS2"
  First name in MCD.DIR   "BACKTILE"    "TEST.RPS"
  First word in MCD.IMG   00000010h     074D4C8Ah

Star Wars Rebel Assault 2 (RESOURCE.*, and nested therein)
BallBlazer Champions (*.DAT, and nested therein)
The Rebel RESOURCE.* files start with name "bigEx" or "fOFS", BallBlazer *.DAT start with "SFXbase" or "tpage", nested files start with whatever other names.
  000h N*10h File List
  ...  (4)   CRC32 on above header (Top-level only, not in Nested archives)
  ...  ..    File Data area
  ...  (..)  Huge optional padding to xx000h-byte boundary (in BallBlazer .DAT)
 File List entries in Top-level archives (with [0Ch].bit31=1):
  000h 8     Filename (zeropadded if less than 8 chars)
  008h 4     Decompressed Size (or 0=File isn't compressed)
  00Ch 4     Offset, self-relative from current List entry (plus bit31=1)
 File List entries in Nested archives (with [0Ch].bit31=0):
  000h 0Ch   Filename (zeropadded if less than 12 chars)
  00Ch 4     Offset, self-relative from current List entry (plus bit31=0)
 Last File List entry has [00h..0Bh]=zerofilled, and Offset to end of file.
Uncompressed Data Format (when List entry [08h]=0 or [0Ch].bit31=0):
  000h ..    Uncompressed Data
  ...  ..    CRC32 on above Data (Top-level only, not in Nested archives)
Compressed Data Format (when List entry [08h]>0 and [0Ch].bit31=1)::
  000h 1     Compression Method (01h=LZ/16bit, 02h=LZ/24bit)
  001h 3     Decompressed Size (big-endian)
  004h ..    Compressed Data
  ...  ..    Zeropadding to 4-byte boundary
  ...  ..    CRC32 on above bytes (method, size, compressed data, padding)
CDROM File Compression RESOURCE (Star Wars Rebel Assault 2)

Vampire Hunter D (MAPFILE\0BEh,..,2C3h,..,853h,86Eh)
  000h  N*10h File List
  ...   ..    Zeropadding to 2000h
  2000h ..    File Data area (includes TIMs, TMDs, and compressed TIMs)
 File List entries:
  000h 0Ch   Filename (zeropadded if less than 12 chars)
  00Ch 4     Offset (absolute offset, increasing, 4-byte aligned)
Caution: This format is very similar to nested archives in Star Wars Rebel Assault 2 (RESOURCE.*) and BallBlazer Champions (*.DAT), the big difference is that those are using Self-relative offsets instead of Absolute offsets. The formats can be distinguished by checking if the directory is zeropadded to 2000h-byte size:
  if [000Ch]=2000h AND [1FFCh]=0 then VampireHunterD_with_AbsoluteOffsets


 _______________________________ Entrysize=14h ________________________________

Fighting Force (MagDemo01: FGHTFRCE\*.WAD)
  000h 4     Number of files                                  (big endian)
  004h N*14h File List
  ...  ..    File Data
File List entries:
  000h 0Ch   Filename ("FILENAME.EXT", zeropadded if shorter than 12 chars)
  00Ch 4     Filesize in bytes (can be odd)                   (big endian)
  010h 4     Fileoffset in bytes (increasing, 4-byte aligned) (big endian)

Parappa (MagDemo01: PARAPPA\*.INT)
Um Jammer Lammy (MagDemo24: UJL\*.INT)
  0000h 2000h Folder 1
  2000h ..    File Data for Folder 1
  ...   2000h Folder 2
  ...   ..    File Data for Folder 2
  ...   2000h Folder End marker (FFFFFFFFh, plus zeropadding)
Folder entries:
  0000h 4      Folder ID (increasing, 1,2,3, or FFFFFFFFh=End)
  0004h 4      Number of files (max 198h) (N)
  0008h 4      File Data Area size/800h   (S)
  000Ch 4      Zero (0)
  0010h N*14h  File List
  ...   ..     Zeropadding to 2000h
  2000h S*800h File Data Area for this folder
File List entries:
  000h 4     Filesize in bytes
  004h 10h   Filename (FILENAME.EXT, zeropadded)
File Offsets are always 4-byte aligned (required for Um Jammer Lammy, which contains Filesizes that aren's multiples of 4).
Note: There can be more than one folder with same ID (ie. when having more than 198h TIM files, which won't fit into a single 2000h-byte folder).

Gran Turismo 1 (MagDemo10: GT\BG.DAT\*, GT\COURSE.DAT\*)
Gran Turismo 1 (MagDemo15: GT\BG.DAT\*, GT\COURSE.DAT\*)
JumpStart Wildlife Safari Field Trip (MagDemo52: DEMO\DATA.DAT\*.DAT)
These are child archives found inside of the main GT-ARC and DATA.DAT archives.
  000h 4     Number of Files (eg. 26h) (usually at least 02h or higher)
  004h N*14h File List
  ...  ..    File Data area
 File List entries:
  000h 10h   Filename ("FILENAME.EXT", zeropadded if shorter)
  010h 4     Offset in bytes (increasing, 4-byte-aligned?)

Alien Resurrection (PACK.BIN)
  000h 4     Number of Files
  004h N*14h File List
  ...  ..    Zeropadding to 800h-byte boundary
  ...  ..    Files (each with appended 800h bytes with checksum/whatever?)
 File List entries:
  000h 0Ch   Filename ("FILENAME.EXT", zeropadded if shorter)
  00Ch 4     Filesize (in bytes, usually a multiple of 800h)
  010h 4     Offset   (in bytes, increasing, usually 800h-byte aligned)
 Files:
  000h ...   Filedata (with size as in File List)
  ...  1     LSB of checksum (all bytes in Filedata added together)
  ...  3     Unknown (more checksum bytes? but isn't a simple sum of bytes)
  ...  7FCh  Zeropadding to 800h-byte boundary

Croc 2 (MagDemo22: CROC2\CROCII.DAT and CROCII.DIR)
Disney's The Emperor's New Groove (MagDemo39: ENG\KINGDOM.DIR+DAT)
Disney's Aladdin in Nasira's Revenge (MagDemo46: ALADDIN\ALADDIN.DIR+DAT)
 DIR:
  000h 4     Number of Entries (0Eh)
  004h N*14h File List
 DAT:
  000h ..    File Data (referenced from CROCII.DIR)
File List entries:
  000h 0Ch   Filename ("FILENAME.EXT", zeropadded if shorter)
  00Ch 4     File Size in bytes
  010h 4     File Offset in .DAT file (800h-byte aligned, increasing)

Alice in Cyberland (ALICE.PAC, and nested .PAC, .FA, .FA2 archives)
  000h N*14h File List
  ...  14h   Zerofilled (File List end marker)
  ...  ..    File Data area
 File List entries:
  000h 0Ch   Filename ("FILENAME.EXT", zeropadded if shorter)
  00Ch 4     Offset (increasing, 4-byte aligned)
  010h 4     Filesize in bytes (can be odd, eg. for .FA2 files)
PAC and FA are uncompressed, FA2 is compressed via some LZ5-variant:
CDROM File Compression LZ5 and LZ5-variants

Interplay Sports Baseball 2000 (MagDemo22:BB2000\DATA\HOG.TOC\UNIFORMS\*.UNI)
  000h N*14h  File List (3Ch*14b bytes, unused entries are zeropadded)
  4B0h ..     Data area (TIM files for player uniforms)
 File List entries:
  000h 10h    Filename ("FILENAME.EXT", zeropadded)
  010h 4      Offset (zerobased, from begin of Data area, increasing)


 _______________________________ Entrysize=18h ________________________________

Invasion from Beyond (MagDemo15: IFB\*.CC)
  000h 0Ch   Fixed ID (always "KotJCo01Dir ") (always that same string)
  00Ch 4     Number of Files
  010h N*18h File List
  ...  ..    File Data area
File List entries:
  000h 10h   Filename ("FILENAME.EXT", zeropadded)
  010h 4     Offset in bytes (increasing, 1-byte or 4-byte aligned)
  014h 4     Filesize in bytes (can be odd)
Note: Alignment is optional: Files in IFB\HANGAR\*.CC and IFB\MAPS\*.CC use 4-byte aligned offsets (but may have odd filesizes). Files in IFB\INCBINS\*.CC don't use any alignment/padding.

Ghost in the Shell (MagDemo03: GITSDEMO\S01\*.FAC)
  000h N*18h File List (18h-bytes each)
  ...  18h   File List end marker (zerofilled)
  ...  ..    File Data
File List entries:
  000h 1     Filename Checksum (sum of bytes at [001h..00Dh])
  001h 1     Filename Length (excluding ending zeroes) (eg. 8, 9, 10, 12)
  002h 0Ch   Filename ("FILENAME.EXT", zeropadded if less than 12 chars)
  00Eh 2     Unknown (2000h) (maybe attr and/or ending zero for filename)
  010h 4     Filesize in bytes (can be odd)
  014h 4     Offset (increasing, 4-byte aligned)

Oddworld: Abe's Exodus (MagDemo17: ABE2\*.LVL)
Oddworld: Abe's Exodus (MagDemo21: ABE2\*.LVL and nested .IDX files)
  000h 4     Header Size in bytes  (2800h) (can be MUCH bigger than needed)
  004h 4     Zero
  008h 4     ID "Indx"
  00Ch 4     Zero
  010h 4     Number of Files (N)   (CEh) (can be zero=empty in .IDX files)
  014h 4     Header Size/800h      (05h)
  018h 4     Zero
  01Ch 4     Zero
  020h N*18h File List
  ...  ..    Zeropadding to end of Headersize
  ...  ..    File Data area
File List entries (in .LVL files):
  000h 0Ch   Filename ("FILENAME.EXT", zeropadded if shorter)
  00Ch 4     Offset/800h
  010h 4     File Size/800h
  014h 4     File Size in bytes
File List entries (in .IDX files):
  IDX files use the same File List entry format as LVL, but the offsets
  seem to refer to an external file with corresponding name, for example:
    cdrom:\ABE2\CR.LVL\CR.IDX     ;directory info
    cdrom:\ABE2\CR.MOV            ;external data (the .MOV being a .STR video)
  XXX: That's not tested/verified, and not implemented in no$psx file viewer.

Monkey Hero (MagDemo17: MONKEY\BIGFILE.PSX and nested .PSX files)
  000h 4     Unknown              (6)
  004h 4     Total Filesize       (1403800h)
  008h 2     Unknown, Alignment?  (800h)
  00Ah 2     Number of Files, excluding zerofilled File List entries (ACh)
  00Ch 4     Header Size          (1800h)
  010h 4     Unknown, Entrysize?  (18h)
  014h 4     Unknown, Entrysize?  (18h)
  018h N*18h File List (can contain unused zerofilled entries here and there!)
  ...  ..    File Data area
File List entries:
  000h 10h   Filename ("FILENAME.EXT", zeropadded)
  010h 4     File Offset in bytes (800h-byte aligned, unusorted/not increasing)
  014h 4     File Size in bytes

NHL Faceoff '99 (MagDemo17: FO99\*.KGB and nested *.PRM *.TMP *.ZAM)
NHL Faceoff 2000 (MagDemo28: FO2000\*.KGB, Z.CAT, and nested *.PRM and *.TMP)
  000h 4     ID "KGB",00h
  004h 4     Number of Files         (N)
  008h (4)   Number of Files negated (-N)   ;<-- optional, not in LITESHOW.KGB
  ...  N*18h File List
  ...  (..)  CBh-padding to alignment boundary (only if align=800h)
  ...  ..    File Data area
File List entries:
  000h 10h   Filename ("FILENAME.EXT", terminated by 00h, padded with CDh)
  010h 4     File Size in bytes
  014h 4     File Offset (800h-byte or 1/4-byte? aligned)

Syphon Filter 1 (MagDemo18: SYPHON\SUBWAY.FOG) (4Mbyte, namelen=10h)
  000h 4     Unknown (80000001h)
  004h 4     Offset/800h to Final Padding area
  008h 8     Zerofilled
  010h N*18h File List
  ...  (..)  CDh-padding to 800h-byte alignment boundary
  ...  ..    File Data area
  ...  800h  Some text string talking about "last-sector bug"
  ...  40BEh Final Padding area (CDh-filled)
File List entries:
  000h 10h   Filename ("FILENAME.EXT", terminated by 00h, padded with CDh)
  010h 4     File Offset/800h (increasing)
  014h 4     File Size/800h
This is almost same as the newer v2 format in Syphon Filter 2 (see there for details).

Centipede (MagDemo23: ARTFILES\*.ART)
  000h 0Fh   ID ("Art", zeropadded)             ;\
  00Fh 1     Type or so ("?")                   ; sorts of File List entry
  010h 4     Number of entries plus 1 (N+1)     ; for root folder
  014h 4     Total Size in bytes (can be odd)   ;/
  018h N*18h File List
  ...  ...   File Data area
 File List entries:
  000h 0Fh   Filename ("FILENAME", zeropadded)
  00Fh 1     Type/extension or so ("X" or "D")
  010h 4     File Offset (unaligned, increasing)
  014h 4     File Size in bytes (can be odd)
Note: C0L7.ART includes zerofilled 18h-bytes as last File List entry, BONU.ART doesn't have any such zerofilled entry.
Unknown if this can have child folders (maybe in similar form as the root folder entry).

Sheep Raider (MagDemo52: SDWDEMO\*.SDW)
Sheep Raider (MagDemo54: SDWDEMO\*.SDW)
  000h 4     Unknown (301h)
  004h 4     Zero (0)
  008h 4     Number of files (N)
  00Ch N*18h File List
  ...  ..    Zeropadding to 800h-byte boundary
  ...  ..    File Data area
 File List entries:
  000h 4     Offset (800h-byte aligned, increasing)
  004h 4     Filesize in bytes
  008h 1     Unknown (01h)
  009h 0Fh   Filename ("FILENAME.EXT",00h, plus garbage padding)
The SDW archive contains malformed 200h*1A4h pixel TIMs.
  Texsize is 6900Eh, but should be 6900Ch = 200h*1A4h*2+0Ch
  Filesize is 6A000h, but should be 69014h = 200h*1A4h*2+14h

Wing Commander III (*.LIB)
  000h 2     Number of Files (C9h)
  002h N*18h File List
  ...  (..)  Padding to 800h-byte boundary (if any, eg. in MOVIES.LIB)
  ...  ..    File data area (800h-byte aligned, or unaligned)
 File List entries:
  000h 4     Filesize in bytes
  004h 4     Offset (increasing, 800h-byte aligned, or unaligned)
  008h 10h   Filename ("filename.ext", zeropadded)

Largo Winch - Commando SAR (LEVELS\*.DCF)
  000h 4     ID "DCAT"
  004h 4     Number of Entries
  008h N*18h File List
  ...  ..    Zerofilled (padding to 800h-byte boundary)
  ...  ..    File Data area
 File List entries:
  000h 10h   Filename ("FILENAME.EXT", terminated by 00h, plus garbage padding)
  010h 4     Filesize in bytes
  014h 4     Offset (increasing, 800h-byte aligned)

Policenauts (NAUTS\*.DPK)
  000h 4     ID "FRID"
  004h 4     Always E0000000h
  008h 4     Always 800h (...maybe alignment)
  00Ch 4     Number of Entries (N)
  010h 4     Header Size (N*18h+20h, plus padding to 800h-byte boundary)
  014h 4     Always 18h (...maybe entry size)
  018h 8     Zerofilled
  020h N*18h File List
  ...  ..    Zerofilled (padding to 800h-byte boundary)
  ...  ..    File Data area
 File List entries:
  000h 0Ch   Filename ("FILENAME.EXT", zeropadded if shorter)
  00Ch 4     Offset (increasing, 800h-byte aligned)
  010h 4     Filesize in bytes
  014h 4     Unknown (checksum? random?)

Actua Ice Hockey 2 (Best Sports Games Ever (demo), AH2\GAMEDATA\*.MAD)
  000h N*18h File List
  ...  ..    File Data area (directly after File List, without end-code)
 Note: There is no file-list end-marker (instead, the Offset in 1st File
       entry does imply the end of File List).
 File List entries:
  000h 10h  Filename ("FILENAME.EXT", zeropadded)
  010h 4    Offset (increasing, 4-byte aligned, or unaligned for TXT files)
  014h 4    Filesize in bytes (or weird nonsense in SFX.MAD)
There are several oddities in demo version (unknown if that's in retail, too):
 SFX.MAD has nonsense Filesize entries (eg. 164h for a 15150h-byte file).
 FACES.MAD contains only one TIM file... but as 3Mbyte junk appended?
 RINKS.MAD and TEAMS.MAD start with 0Dh,0Ah,1Ah followed by 4Mbyte junk.
 MISCFILE.MAD contains several nested .mad files.
 MISCFILE.MAD\panfont.mad\*.txt --> starts with FF,FE --> that's 16bit Unicode?

Muppet Monster Adventure (MagDemo37: MMA\GAMEDATA+WORLDS*\*.INF+WAD)
 INF:
  000h N*18h File List
 WAD:
  000h ..    File Data area
File List entries:
  000h 4     File Offset/800h in .WAD file
  004h 4     File Size in bytes
  008h 10h   Filename ("FILENAME.EXT", zeropadded)

Army Men Air Attack 2 (MagDemo40: AMAA2\*.PCK)
  000h 4     Number of entries (N)
  004h N*18h File List
  ...  ..    Zeropadding to 800h-byte boundary
  ...  ..    File Data area
 File List entries:
  000h 10h   Filename ("FILENAME.EXT", zeropadded)
  010h 4     Fileoffset (800h-byte aligned, increasing)
  014h 4     Filesize in bytes

Mort the Chicken (MagDemo41: MORT\*.PPF and .TPF)
  000h 2     Type (31h=TPF with TIMs, 32=PPF with PMDs)
  002h 2     Number of entries (N) (can be 0=None, eg. STAGE*\MORT.PPF)
  004h 4     File List Size (N*18h)
  008h 4     Header Size (always 14h)
  00Ch 4     Data area Size (Filesize-14h-N*18h)
  010h 4     Data area Offset (14h+N*18h)
  014h N*18h File List
  ...  ..    File Data area
 File List entries:
  000h 10h   Filename ("FILENAME.EXT", zeropadded)
  010h 4     Filesize in bytes
  014h 4     Fileoffset (from begin of Data area, increasing)

Hot Wheels Extreme Racing (MagDemo52: US_01293\VEHICLES\*.CAB)
  000h 4     ID "BACR" (aka RCAB backwards)
  004h 4     Number of entries (N)
  008h N*18h File List
  ...  ..    File Data area
 File List entries:
  000h 10h   Filename ("FILENAME.EXT", zeropadded)
  020h 4     Offset (from begin of Data area, increasing, 4-byte aligned)
  024h 4     Filesize in bytes (can be odd)


 _______________________________ Entrysize=19h ________________________________

WAD Format (Wipeout 2097)
PSX Wipeout 2097, cdrom:\WIPEOUT2\SOUND\SAMPLES.WAD:\*.vag
PSX Wipeout 2097, cdrom:\WIPEOUT2\TRACK*\TRACK.WAD:\*.*
PSX Wipeout 3 (MagDemo25: WIPEOUT3\*)
  000h 2     Number of files
  002h N*19h Directory Entries for all files
  ...  ..    Data for all files (without any alignment, in same order as above)
Directory Entries
  000h 10h Filename (ASCII, can be lowercase), terminated by 00h, plus garbage
  010h 4   Filesize in bytes  ;\maybe compressed/uncompressed, or rounded,
  014h 4   Filesize in bytes  ;/always both same
  018h 1   Unknown (always 00h)
The filesize entry implies offset to next file.

 _______________________________ Entrysize=1Ch ________________________________

Command & Conquer, Red Alert (MagDemo05: RA\*) FAT/MIX/XA
  000h 4     Number of entries with location 0=MIX (M=65h)
  000h 4     Number of entries with location 1=XA  (X=1)
  008h M*1Ch File List for location 0=MIX
  ...  X*1Ch File List for location 1=XA
File List entries:
  000h 10h   Filename (terminated by 00h, padded with garbage)
  010h 4     Offset/800h in DATA.MIX or Offset/930h DATA.XA file (increasing)
  014h 4     Filesize in bytes
  018h 4     File Location (0=DATA.MIX, 1=DATA.XA)

Syphon Filter 2 (MagDemo30: SYPHON\TRAIN.FOG) (2.8Mbyte, namelen=14h)
  000h 4     Unknown (80000001h)
  004h 4     Offset/800h to Final Padding area
  008h 8     Zerofilled
  010h N*1Ch File List
  ...  (..)  CDh-padding to 800h-byte alignment boundary
  ...  ..    File Data area
  ...  3394h Final Padding area (CDh-filled)
File List entries:
  000h 14h   Filename ("FILENAME.EXT", terminated by 00h, padded with CDh)
  014h 4     File Offset/800h (increasing)
  018h 4     File Size/800h
This is almost same as the older v1 format in Syphon Filter 1:
  v1 (Syphon Filter 1) has filename_len=10h (and filelist_entrysize=18h)
  v2 (Syphon Filter 2) has filename_len=14h (and filelist_entrysize=1Ch)
To detect the version: Count the length of the "ASCII chars + 00h byte + CDh padding bytes" at offset 10h.
Note: The FOG archive in Syphon Filter 2 demo version does contain some empty dummy files (with intact filename, but with offset=0 and size=0).

 _______________________________ Entrysize=20h ________________________________

Colony Wars (MagDemo02: CWARS\GAME.RSC)
Colony Wars Venegance (MagDemo14: CWV\GAME.RSC, 8Mbyte)
  000h 4     Number of Files
  004h N*20h File List
  ...  10h   File List End: Name    (zerofilled)
  ...  4     File List End: Offset  (total filesize, aka end of last file)
  ...  0Ch   File List End: Padding (zerofilled)
  ...  ..    File Data area
File List entries:
  000h 10h   Filename ("FILENAME.EXT", terminated by 00h, padded with garbage)
  010h 4     File Offset in bytes (increasing, 4-byte aligned)
  014h 0Ch   Padding (garbage) (usually 800F68A0h,800F68A0h,800F68A0h)
Note: Colony Wars Red Sun does also have a GAME.RSC file (but in different format, with folder structure).

WarGames (MagDemo14: WARGAMES\*.DAT)
  000h 4     Number of Files (1C3h)
  004h N*20h File List
  ...  ..    Zeropadding to 800h-byte boundary
  ...  ..    File Data area
File List entries:
  000h 10h   Filename ("FILENAME.EXT", zeropadded, sorted alphabetically)
  010h 4     File Offset/800h (unsorted, not increasing)
  014h 4     File Size in bytes
  018h 4     File Size/800h
  01Ch 4     Zero

Simple 1500 Series Vol 63 - The Gun Shooting 2 (S*.BIN, and nested therein)
  000h 4      Number of Files (N)
  004h 0Ch    Zerofilled
  010h N*20h  File List
  ...  ..     File Data area
 File List entries:
  000h 14h    Filename ("PATH\FILENAME.EXT", zeropadded)
  014h 4      Filesize in bytes
  018h 4      File Offset (increasing, 10h-byte aligned)
  01Ch 4      Zerofilled
Subdirectories are implemented by simply nesting those archive files within each other, however, the filename's "path\" prefix in the child archives does often give an additional hint on the name of the parent archive (for example, main archive "S02.BIN" may contain a child archive "kei2.bin", which may contain files named "kei\*.seq").

Running Wild (MagDemo15: RUNWILD\*.BIN)
  000h N*20h File List
  ...  4     File List End Offset/800h (end of last file)
  ...  4     File List End Size (zero)
  ...  18h   File List End Name (zerofilled)
  ...  ..    Padding to 800h-byte boundary (each 20h-byte: 01h, and 1Fh zeroes)
  ...  ..    File Data
File List entries:
  000h 4     Offset/800h (increasing)
  004h 4     Filesize in bytes
  008h 18h   Filename ("FILENAME.EXT" or ":NAME" or ":NAME:NAME", zeropadded)
Files with extension .z or .Z are compressed:
CDROM File Compression Z (Running Wild)

Test Drive Off-Road 3 (MagDemo27: TDOR3\TDOR3.DAT)
About same as the other Test Drive games, but with shorter filenames.
  000h N*20h  File List (1920h bytes used; with padding: 5800h bytes in total)
  ...  ..     Zeropadding to Headersize (5800h)
  ...  ..     File Data area
 File List entries:
  000h 18h    Filename ("FILENAME.EXT" or "PATH\FILENAME.EXT", zeropadded)
  018h 4      Filesize in bytes
  01Ch 4      File (Offset-Headersize)/800h
TDOR3.DAT contains DOT1 child archives and many RNC compressed files:
CDROM File Compression RNC (Rob Northen Compression)

Tiny Tank (MagDemo23: TINYTANK\*.DSK)
  000h 4     ID ("TDSK")                                      ;\
  004h 4     Number of Files (1Bh)                            ; Directory
  008h N*20h File List                                        ;/
  ...  4     1st File Size (same as Size entry in File List)  ;\File Data area
  ...  ..    1st File Data                                    ; (each file os
  ...  4     2nd File Size (same as Size entry in File List)  ; preceeded by
  ...  ..    2nd File Data                                    ; a size entry)
  ...  ..    etc.                                             ;/
 File List entries:
  000h 10h   Filename ("FILENAME.EXT", zeropadded)
  010h 4     File Size in bytes
  014h 4     Unknown (35xxxxxxh..372xxxxxh)
  018h 4     Unknown (3724xxxxh) (Timestamp maybe?)
  01Ch 4     File Offset in bytes (increasing, 4-byte aligned)
Note: The File Offset points to a 32bit value containing a copy of the Filesize, and the actual file starts at Offset+4.

MAG 3 (MagDemo26: MAG3\MAG3.DAT, 7Mbyte)
  000h N*20h  File List (B60h bytes)
  ...  ..     Zeropadding to 800h-byte boundary
  ...  ..     File Data area (files are AAh-padded to 800h-byte boundary)
 File List entries:
  000h 4      Filesize in bytes
  004h 2      File Offset/800h (16bit) (increasing)
  006h 1Ah    Filename ("FILENAME.EXT" or "PATH\FILENAME.EXT", zeropadded)

Play with the Teletubbies (MagDemo35: TTUBBIES\*.RES)
  000h 2     Zero (0000h)
  002h 2     Number of Files (N)
  004h 4     Data Base (N*20h+10h)
  008h 4     Unknown (20h)  ;-maybe File List entry size?
  00Ch 2     Unknown (10h)  ;\maybe filename length and/or header size?
  00Eh 2     Unknown (10h)  ;/
  010h N*20h File List
  ...  ..    File Data area
File List entries:
  000h 4     Zero
  004h 4     File Offset (increasing, 4-byte aligned, relative to Data Base)
  008h 4     File Size in bytes (can be odd)
  00Ch 4     Zero
  010h 10h   Filename ("FILENAME.EXT", zeropadded)

Mat Hoffman's Pro BMX (old demo) (MagDemo39: BMX\FE.WAD+STR) (uncompressed)
Mat Hoffman's Pro BMX (new demo) (MagDemo48: MHPB\FE.WAD+STR) (compressed)
 WAD:
  000h N*20h File List
 STR:
  000h ..    File Data (MagDemo39: 4.5Mbyte, MagDemo48: compressed/2.8Mbyte)
 File List entries:
  000h 14h   Filename ("FILENAME.EXT", zeropadded)
  014h 4     Offset in bytes, 4-byte aligned, in STR file
  018h 4     Filesize, compressed (always rounded to multiple of 4 bytes)
  01Ch 4     Filesize, decompressed (zero when not compressed)
The decompressor is using an Inflate variant with slightly customized block headers:
  - end flag is processed immediately (instead of after the block)
  - blocktype is only 1bit wide (instead of 2bit)
  - stored blocks have plain 16bit len (without additional 16bit inverse len)
Everything else is same as described here:
CDROM File Compression ZIP/GZIP/ZLIB (Inflate/Deflate)
Instead of "tinf_uncompress", use the function below:
 bmx_tinf_style_uncompress(dst,src)
  tinf_init()                   ;init constants (needed to be done only once)
 @@lop:
  if tinf_getbit()=0 then goto @@done   ;end flag, 1bit
  if tinf_getbit()=0 then               ;blocktype, 1bit
    tinf_align_src_to_byte_boundary()
    len=LittleEndian16bit[src], src=src+2   ;get len (without inverse len)
    for i=0 to len-1, [dst]=[src], dst=dst+1, src=src+1, next i   ;uncompressed
  else
    tinf_decode_dynamic_trees(), tinf_inflate_compressed_block()  ;compressed
  gpto @@lop
 @@done:
  ret
Note: Apart from the MHPB\FE.WAD archive, many MHPB\*.BIN files seem to be also compressed (unknown if that's the same compression method; and, if so, they would lack decompressed size info).

 _______________________________ Entrysize=28h ________________________________

Demo Menu, PlayStation Magazine Demo Disc 03-54, MENU.FF
Used on most PlayStation Magazine Demo Discs (Disc 03-54, except Disc 01-02)
Used on PlayStation Underground 3.1 (and maybe other issues)
Used on Interactive CD Sampler Disc Volume 10 (maybe others, but not Vol 4,5)
  000h 4     Number of entries (eg. 20h or 28h)
  004h N*28h File List
  ...  ..    Garbage padding to 800h-byte boundary
  ...  ..    File Data
  ...  ..    Huge zeropadding to 200000h or 2EE000h (2048Kbyte or 3000Kbyte)
File List entries:
  000h 20h   Filename (terminated by 00h, padded with... looks like garbage)
  020h 4     Size/800h
  024h 4     Offset/800h (increasing)
Contains .BS, .TIM, .TXT, .VH, .VB files. The size seems to be always(?) 2048Kbytes, 2992Kbytes, 2000Kbytes, or 3000Kbytes (often using only the first quarter, and having the remaining bytes zeropadded).

Test Drive 4 (MagDemo03: TD4.DAT) (headersize=2000h, used=0...h)
Test Drive 5 (MagDemo13: TD5.DAT) (headersize=3000h, used=1EF8h)
Demolition Racer (MagDemo27: DR\DD.DAT) (headersize=5000h, used=2328h)
This is used by several games, with different Headersizes (2000h or 3000h or 5000h), with Offsets relative to the Headersize. To detect the Headersize, skip used entries, skip following zeropadding, then round-down to 800h-byte boundary (in case the 1st file contains some leading zeroes).
  000h N*28h File List (less than 0C00h bytes used in TD4 demo)
  ...   ..   Zeropadding to Headersize (2000h or 3000h or 5000h)
  ...   ..   File Data
File List entries:
  000h 20h   Filename ("PATH\FILENAME.EXT", zeropadded)
  020h 4     Size in bytes
  024h 4     (Offset-Headersize)/800h (increasing)
TD5.DAT and DD.DAT contain DOT1 child archives and many RNC compressed files:
CDROM File Compression RNC (Rob Northen Compression)

Gekido (MagDemo31: GEKIDO\GLOBAL.CD)
  0000h N*28h File List
  21C0h ...   Unknown random gibberish? (23h,E8h,0Ch,1Dh,79h,C5h,24h,...)
  4000h ...   File Data area
File List entries:
  000h 1Ch   Filename ("\PATH\FILENAME.EXT;0", zeropadded)
  01Ch 4     Filesize in bytes
  020h 4     Fileoffset in bytes (4000h and up, increasing)
  024h 4     Filechecksum (32bit sum of all bytes in the file)
There is no "number of files" entry, and no "file list end marker" (though the "random gibberish" might serve as end marker, as long it doesn't start with "\" backslash).

Team Buddies (MagDemo37: BUDDIES\BUDDIES.DAT\* and nested *.BND files)
  000h 4     ID "BIND"
  004h 4     Number of files (N)
  008h N*28h File List
  ...  ..    File Data area
File List entries:
  000h 20h   Filename ("\FILENAME.EXT", zeropadded)
  020h 4     File Offset (increasing, 4-byte aligned)     ;\see note
  024h 4     File Size in bytes (always a multiple of 4)  ;/
Note: There is a 4-byte gap between most files, that appears to be caused by weird/bugged alignment handling done as so:
  size=((filesize+3) AND not 3)       ;size entry for curr file (plus 3)
  offs=((filesize+4) AND not 3)+offs  ;offs entry for next file (plus 4 !!!)
Namely, odd filesizes (eg. for TXT files in BUDDIES.DAT\00D2h..00D7h) are forcefully rounded-up to 4 bytes boundary. If that rounding has occurred then there is no additional 4-byte gap (but the 4-byte gap will appear if the original filesize was already 4-byte aligned).

JumpStart Wildlife Safari Field Trip (MagDemo52: DEMO\DATA.DAT)
  000h 4     Number of entries (N)
  004h 4     Number of entries (same as above)
  008h 4     Number of entries (same as above)
  00Ch 4     Number of entries (same as above)
  010h N*28  File List
  ...  ..    Zeropadding to 800h-byte boundary
  ...  ..    File Data area
 File List entries:
  000h 20h   Filename ("\PATH\FILENAME.EXT", zeropadded)
  020h 4     Offset/800h, from begin of Data area (increasing)
  024h 4     Filesize in bytes


 _______________________________ Entrysize=34h ________________________________

Army Men: Air Attack (MagDemo28: AMAA\PAK\*.PAK)
  000h 4      Number of Files
  004h N*34h  File List
  ...  ..     Zeropadding to 4000h
  4000h ..    File Data area
 File List entries:
  000h 10h    Filename ("FILENAME.EXT", zeropadded)
  010h 4      Filesize in bytes  ;\always both same, always
  014h 4      Filesize in bytes  ;/both multiple of 800h
  018h 4      Zero
  01Ch 4      Type    (07h..1Ah)
  020h 4      Subtype (00h..01h)
  024h 10h    Zero
The used Type.Subtype values are:
  07h.0   .TIM (*.TIM)
  07h.01h .TIM (HUD_*.TIM)
  08h.0   .TIM (PSTART.TIM)
  09h.0   .TIM (FONT.TIM)
  0Ah.0   .SFX
  0Eh.0   .MBL
  10h.0   .ATR
  11h.0   .RLC
  13h.0   .AST
  15h.0   .SCD
  16h.0   .TXT (PAUSED.TXT)
  17h.0   .TXT (OBJECT*.TXT)
  18h.0   .BIN
  1Ah.0   Misc (.3DO=TIM, .V=TXT, and TERRAIN.CLP .HI .LIT .MAP .PAT .POB .TER)


 _______________________________ Entrysize=40h ________________________________

Net Yaroze Demo Disc (*.FPC)
  000h 4     Number of Files (N)
  004h N*40h File List
  ...  ..    File Data area
  ...  ..    Padding to 4-byte boundary
 File List entries:
  000h 4     Fileoffset (increasing, 4-byte aligned)
  004h 4     Filesize   (in bytes, can be odd)
  008h 38h   Filename   ("FILENAME.EXT", zeropadded) (usually max 12 chars)
FPC is used on the Yaroze Demo disc (and several other homebrew Yaroze compilations), it does usually contain a set of data files, a PSX executable in ECOFF format, and an AUTO file with information on how to load the separate files to which memory addresses.

Ninja (MagDemo13: NINJA\CUTSEQ\*.WAD and NINJA\WADS\*.WAD)
  000h 4     Number of Files (N)
  004h 4     Size of File Data area (SIZ) (total filesize-8-N*40h)
  008h N*40h File List
  ...  SIZ   File Data area
 File List entries:
  000h 4     Filesize in bytes
  004h 4     Fileoffset in bytes (zerobased, from begin of File Data area)
  008h 38h   Filename, zeropadded

You Don't Know Jack (MagDemo23: YDKJ\RES\*.GLU)
You Don't Know Jack 2 (MagDemo41: YDKJV2\*\*.GLU)
  000h 4     ID ("GLUE")
  004h 4     Unknown (always 400h)
  008h 4     Number of Files (N)
  00Ch 4     Header Size (40h+N*40h)
  010h 30h   Zerofilled
  040h N*40h File List
  ...  ..    Garbage padding to alignment boundary
  ...  ..    File Data area
 File List entries:
  000h 20h   Filename ("FILENAME.EXT", zeropadded)
  020h 4     File Offset in bytes (increasing, 800h-byte aligned)
  024h 4     File Size in bytes
  028h 2     File ID Number 1 (eg. 1-71 for C01.GLU-C71.GLU)
  02Ah 2     Unknown (random, checksum, ?)
  02Ch 4     File ID Number 2 (eg. increasing: 1, 2, 3)
  030h 10h   Zerofilled
Most .GLU files are 800h-byte aligned (except SHORTY\*.GLU and THREEWAY\*GLU which use 4-byte alignment).
The files do start on alignment boundaries, but there is no alignment padding after end of last file.

i-mode mo Issho - Doko Demo Issho Tsuika Disc (IMODE.417\*)
  000h 4     ID ("NAR",00h)
  004h 4     Unknown (40h) ;maybe File List entry size?
  008h 4     Header Size (10h+N*40h)
  00Ch 4     Number of Files (N) (min=1)
  010h N*40h File List
  ...  ..    File Data area
 File List entries:
  000h 4     File ID  (increasing)
  004h 4     Offset   (increasing, 4-byte aligned)
  008h 4     Filesize in bytes (can be odd)
  00Ch 4     Filetype (ASCII, usually same as file extension, in lowercase)
  010h 4     Unknown  (looks like timestamp?)
  014h 2Ch   Filename ("FILENAME.EXT", zeropadded)

UNIROM (homebrew expansion ROM installer) (*_ROMS.DAT)
  000h N*40h File List
  ...  ..    Zeropadding (usually to offset 2000h)
  ...  ..    Data
  ...  ..    Zeropadding (to 800h-byte boundary)
 File List entries:
  000h 4    Size in bytes
  004h 4    Offset in bytes (increasing, 800h-byte aligned)
  008h 4    Checksum (sum of all data bytes)
  00Ch 4    Zero
  010h 30h  Filename (ASCII, without extension, zeropadded)


 _______________________________ Entrysize=60h ________________________________

Army Men Air Attack 2 (MagDemo40: AMAA2\*.PCK\*.PAK)
  000h 4     Number of entries (N)
  010h N*60h File List
  ...  ..    Zeropadding to 2000h
  2000h ..   File Data area
 File List entries:
  000h 4     Timestamp? (BFxxxxh..C0xxxxh) (or zero, in first file)
  004h 4     Unknown (always 421C91h)
  008h 4     Unknown (200h or 60200h)
  00Ch 4     Filesize (uncompressed)
  010h 4     Filesize (compressed, or 0 when not compressed)
  014h 4     File Checksum (sum of all bytes in uncompressed file data)
  018h 4     Unknown (random 32bit value?)
  01Ch 10h   Filename ("FILENAME.EXT", zeropadded)
  02Ch 4     Zerofilled
  030h 4     Unknown (0 or 1 or 8)
  034h 4     File Type (see below)
  038h 8     Zerofilled
  040h 4     Offset MSBs (Fileoffset-2000h)/800h  ;\increasing, 4-byte aligned
  044h 4     Offset LSBs (Fileoffset AND 7FFh)    ;/(or zero when filesize=0)
  048h 18h   Zerofilled
File Type values are 07h=TIM, 0Ah=SFX, 0Eh=MBL, 10h=ATR, 13h=AST, 15h=SCD, 19h=VTB, 1Bh=DCS, 1Dh=DSS, 1Eh=STR, 1Fh=DSM, 20h=FNT, 21h=TER, 25h=PMH, 26h=Misc.
Most of the files are SCRATCH compressed:
CDROM File Compression LZ5 and LZ5-variants
There are also several uncompressed files (eg. VERSION.V, *.SFX, and many of the TERRAIN.* files).

 _______________________________ Entrysize=90h ________________________________

Grind Session (MagDemo33: GRIND\SLIP.GRV)
Grind Session (MagDemo36: GRIND\SLIP.GRV)
Grind Session (MagDemo42: GRIND\SLIP.GRV)
Grind Session (MagDemo45: GRIND\SLIP.GRV)
  000h 4     ID (A69AA69Ah)
  004h 4     Number of files (N)
  008h N*90h File List
  ...  ..    File Data area
 File List entries:
  000h 80h   Filename ("DATA\FILENAME.EXT",00h, plus CDh-padding)
  080h 4     File Offset in bytes (increasing, 4-byte aligned)
  084h 4     File Size in bytes
  088h 8     Unknown (random/checksum?)


 _____________________________ Variable Entrysize _____________________________

HED/WAD
  Used by Spider-Man (MagDemo31,40: SPIDEY\CD.HED and CD.WAD)
  Used by Spider-Man 2 (MagDemo52: SPIDEY\CD.HED and CD.WAD)
  Used by Tony Hawk's Pro Skater (MagDemo22: PROSKATE\CD.HED and CD.WAD)
  Used by Apocalypse (MagDemo16: APOC\CD.HED and CD.WAD)       ;with PADBUG
  Used by MDK (Jampack Vol. 1: MDK\CD.HED and CD.WAD)          ;without ENDCODE
  Used by Mat Hoffman's Pro BMX (old demo) (MagDemo39: BMX\BMXCD.HED+WAD)
Format of the CD.HED file:
  000h ..  File Entries (see below)
  ...  (1) End code (FFh) (if any, not present in MDK)
File Entry format:
  000h ..  Filename (ASCII, terminated by 00h, zeropadded to 4-byte boundary)
  ...  4   Offset in CD.WAD (in bytes, usually 800h-byte aligned)
  ...  4   Filesize (in bytes)
PADBUG: Apocalypse does append 1..800h bytes alignment padding (instead of 1..7FFh or 0 bytes).

Dance UK (DATA.PAK)
  000h 4      Number of Files (N) (1ADh)
  004h 4      Unknown (7) (maybe HeaderSize/800h, same as first Offset/800h ?)
  008h 4      Unknown (1430h = 14h+N*0Ch, same as first Name pointer)
  00Ch 4      Unknown (1430h = 14h+N*0Ch, same as first Name pointer)
  010h 4      Unknown (1430h = 14h+N*0Ch, same as first Name pointer)
  014h N*4    Name List (pointers to name strings, 1430h and up)  6B4h bytes
  ...  N*4    Size List (filesize in bytes)                       6B4h bytes
  ...  N*4    Offset List (Offset/800h)                           6B4h bytes
  ...  N*var  Name Strings (ASCII strings, "folder\filename.ext",00h)
  ...  ..     Zerofilled (padding to 800h-byte boundary)
  ...  ..     File Data area

Kula Quest / Kula World / Roll Away (*.PAK)
  000h 4     Number of Files (N)
  004h N*8   File List (2x32bit entries: Offset, Size) (unaligned, can be odd)
  ...  N*4   File Name Offsets
  ...  N*var File Name Strings ("FILE NN",0Ah,00h)
  ...  ..    Garbage-padding to 4-byte boundary
  ...  (4)   Optional extra garbage? ("MON " in ATLANTFI.PAK, MARSFI.PAK, etc.)
  ...  ..    File Data area (ZLIB compressed, starting with big-endian 789Ch)
CDROM File Compression ZIP/GZIP/ZLIB (Inflate/Deflate)

Largo Winch - Commando SAR (NTEXTURE\*.GRP and LEVELS\*.DCF\*.CAT and *.GRP)
  000h 4     ID (12h,34h,56h,78h) (aka 12345678h in big endian)
  004h 4     Header Size (offset to File Data area)
  008h 4     Number of Entries (can be 0=None, eg. LEVELS\LARGO07.DCF\Z16.CAT)
  00Ch N*var Name List (Filenames in form "FILENAME.EXT",00h)
  ...  ..    Zeropadding to 4-byte boundary
  ...  N*4   Size List (Filesizes in bytes)
  ...  ..    File Data area

Jackie Chan Stuntmaster (RTARGET\GAME.GCF and LEV*.LCF)
  000h 4     Number of files (N) (3..EBh)                 (big-endian)
  004h N*Var File List (list size is implied in first file offset)
  ...  ..    Zeropadding to 800h-byte boundary
  ...  ..    File Data area
 File List entries:
  000h 4     File Type (ascii, .LLN .TXI .TPG .RCI .RCP .WDB .PCI .PCP .BLK)
  004h 4     File Size (can be odd)                       (big-endian)
  008h 4     File Offset (increasing, 800h-byte aligned)  (big-endian)
  00Ch 4     Extra Size (0 or 4 or 8)                     (big-endian)
  010h ..    Extra Data (if any) (32bit number, or "TEXTURES")

Syphon Filter 1 (MagDemo18: SYPHON\*.HOG, SYPHON\SUBWAY.FOG\*.HOG,SLF.RFF)
Syphon Filter 2 (MagDemo30: SYPHON\*.HOG, SYPHON\TRAIN.FOG\*.HOG,SLF.RFF)
  000h 4     Timestamp? (36xxxxxxh=v1?, 38xxxxxxh=v2?, other=SLF.RFF)
  004h 4     Number of Files          (N)
  008h 4     Base for Offset List  (always 14h)
  00Ch 4     Base for String Table (v1=N*4+14h, or v2=N*4+18h)
  010h 4     Base for File Data (end of String Table plus align 4/800h/920h)
  014h N*4   Offsets to File(s) (increasing, first=0, relative to above [010h])
  ... (4)    v2 only: End Offset for Last File (HOG filesize minus [010h])
  ...  ..    String Table (filename list in form of "FILENAME.EXT",00h)
  ...  ..    Zeropadding to 4-byte or 800h-byte boundary
  ...  ..    File Data area
There are two versions: Syphon Filter 1 (v1) and Syphon Filter 2 (v2):
  v1 has [0Ch]=N*4+14h (without end-of-last-file entry; use end=total_size)
  v2 has [0Ch]=N*4+18h (and does have end-of-last-file entry)
  v1 has STR files in ISO filesystem (not in HOG archives)
  v2 has STR files in MOVIES.HOG (with [10h]=920h and [14h and up]=sectors)
Normally, the following is common for v1/v2:
  v1/v2 has [10h]=data base, aligned to 4 or 800h
  v1/v2 has [14h and up] in BYTE-offsets, relative to base=[10h]
  v1/v2 uses HOG format in .HOG files also in SLF.RFF
  v1/v2 has further .RFF files (but that aren't in HOG format)
There are several inconsistent special cases for some v2 files:
  v2 MOVIE.HOG has [10h]=920h (which is meant to mean base="after 1st sector")
  v2 MOVIE.HOG has [14h and up] in SECTOR-units, with base="after 1st sector"
  v2 SLF.RFF does contain two HOG archives badged together (plus final padding)
  v2 has some empty 0-byte .HOG files (at least so in demo version)
Danger: The special value 920h means that headersize is one 800h-byte sector (whereas 920h is dangerously close to REAL headersize, eg. v1 PCHAN.HOG has headersize=908h which means one 800h-byte sector plus 108h bytes) (the 920h thing should occur only in v2 though, since v1 has STR files stored in ISO filesystem instead of in HOG archives).

Electronic Arts 32bit BIGF archives
  000h 4   ID "BIGF" (normal case, all big-endian, 4-byte aligned)     ;\
           ID "BIGH" (with [04h]=little-endian instead big-endian)     ;
           ID "BIG4" (with 40h-byte alignment padding instead 4-byte)  ;
  004h 4   Sum of Header+Filesizes (excluding Padding's!) (big-endian) ; Header
  008h 4   Number of entries (N)                  ;11h    (big-endian) ;
  00Ch 4   Size of Header (including File List)   ;11Fh   (big-endian) ;
  010h ..  File List                                                   ;/
  ...  ..  Padding to 1/4/8-byte boundary (optional, before each file) ;\Data   ...  ..  File Data                                                   ;/
File List entries (with variable length names, entries aren't 4-byte aligned):
  000h 4   Offset in bytes (increasing, often 4/8-byte aligned)    (big-endian)
  004h 4   Size in bytes (can be odd, but often rounded to 4-byte) (big-endian)
  008h ..  Filename (ASCII, terminated by 00h) ;variable length
  Note: Filenames can be empty ("",00h) (eg. in WCWDEMO\ZSOUND.BIG)
Used by PGA Tour 96, 97, 98 (*.VIV)
Used by FIFA - Road to World Cup 98 (MOP*.BK*, Z4TBLS.BIG\*.t, ZMO*.BIG\*.viv)
Used by Fifa 2000 (Best Sports demo: FIFADEMO\*.BIG, *.SBK, and nested .viv)
Used by Need for Speed 3 Hot Pursuit (*.VIV)
Used by WCW Mayhem (MagDemo28: WCWDEMO\*.BIG) (odd filesizes & nameless files)
This is reportedly also used for various other Electronic Arts games for PC, PSX, and PS2 (often with extension *.BIG, *.VIV).
Reportedly also "BIGH" and "BIG4" exist:
  http://wiki.xentax.com/index.php/EA_BIG_BIGF_Archive
Other Electronic Arts file formats (used inside or alongside big archives):
  https://wiki.multimedia.cx/index.php/Electronic_Arts_Formats_(2) - BNK etc

Electronic Arts 24bit C0FB archives
  000h 2   ID C0FBh                (C0h,FBh)  (big-endian)      ;\
  002h 2   Size of Header-4        (00h,15h)  (big-endian)      ; Header
  004h 2   Number of Files         (00h,01h)  (big-endian)      ;
  006h ..  File List                                            ;/
  019h ..  Padding to 4-byte boundary?                          ;-Padding
  01Ch ..  File Data                                            ;-Data
  ...  4   "CRCF"                                               ;\
  ...  4   Unknown (0C,00,00,00) (chunk-size little-endian?)    ; Footer
  ...  4   Unknown (3B,2E,00,00) (checksum maybe?)              ;/
File List entries (with variable length names, and unaligned 24bit values):
  000h 3   Offset in bytes (increasing)        ;(big-endian, 24bit)
  004h 3   Size in bytes                       ;(big-endian, 24bit)
  008h ..  Filename (ASCII, terminated by 00h) ;variable length
Used by FIFA - Road to World Cup 98 (*.BIG)
Used by Sled Storm (MagDemo24: ART\ZZRIDER.UNI, with 8 files insides)

Destruction Derby Raw (MagDemo35: DDRAW\*.PTH+.DAT, and nested therein)
 PTH File:
  000h N*var File List
 DAT File:
  000h ..    File Data area
File List entries:
  000h ..    Filename ("FILENAME.EXT",00h) (variable length)
  ...  4     File Size in bytes (can be odd)
  ...  4     File Offset in bytes in DAT file (increasing, unaligned)
Caution: Filenames in PTH archives aren't sorted alphabetically (so DAT isn't always guaranteed to be the previous entry from PTH, namely, that issue occurs in MagDemo35: DDRAW\INGAME\NCKCARS.PTH\*.PTH+DAT).
Caution: The whole .DAT file can be compressed: If the sum of the filesizes in PTH file does exceed the size of the DAT file then assume compression to be used (normally, the top-level DATs are uncompressed, and nested DATs are compressed).
CDROM File Compression PCK (Destruction Derby Raw)

SnoCross Championship Racing (MagDemo37: SNOCROSS\SNOW.TOC+.IMG)
 TOC:
  000h N*var File List
 IMG:
  000h ..    File Data area
File List entries:
  000h ..    Filename ("DATA\FILENAME.EXT",00h) (variable length)
  ...  4     File Offset (increasing, 800h-byte aligned, in .IMG file)
  ...  4     File Size in bytes
Resembles DDRAW\*.PTH+.DAT (but Offset/Size are swapped, and uses 800h-align).
Note: The archive contains somewhat corrupted TGA's:
  TGA[10h..11h] = 08h,08h  ;bpp=8 (okay) and attr=8 (nonsense)
  TGA[10h..11h] = 10h,01h  ;bpp=16 (okay) and attr=1 (okay) but it's yflipped


CDROM File Archives with Offset and Size

Crash Team Racing (retail: BIGFILE.BIG, and MagDemo30/42: KART\SAMPLER.BIG)
  000h 4     Zero
  004h 4     Number of Files (260h)
  010h N*8   File entries
  ...  ..    Zeropadding to 800h byte boundary
  ...  ..    File Data
File Entries:
  000h 4   Fileoffset/800h (increasing)
  004h 4   Filesize in bytes
Filetypes in the archive include...
  MDEC v2 STR's  (file 1E1h..1F8h,1FAh)
  TIM textures  (file 01FBh..0200h and others)
  empty files   (file 01F9h and others)
  small archives with named entries (file B5h,124h,125h,126h and others)
  stuff with date string and names (file 253h,256h)
  there seem to be no nested BIG files inside of the main BIG file

Black Matrix (*.DAT)
  000h 4    Number of files (N) (eg. 196h)
  004h 4    Unknown (always 0Bh) (maybe sector size shift?)
  008h N*4  File List
  ...  ..   Zeropadding to 800h-byte boudary
  ...  ..   File Data
File List entries:
  000h 2    Offset/800h (increasing)
  002h 2    Size/800h (can be zero)
The "files" might actually contain small child folders? Or the whole stuff is just some kind of data structure, not an actual file system archive.

Charumera (*.CVF)
  000h N*4  File List
  ...  ..   Zeropadding to 800h-byte boundary
  ...  ..   File Data area
 File List entries:
  000h 1    Size/800h   (8bit)
  001h 3    Offset/800h (24bit, increasing)

Vs (MagDemo03: THQ\*) has .CDB archives
  000h  N*8   File List
  ...   ..    Zeropadding to 800h-byte boundary
  ...   ..    File Data
  ...   ..    Garbage padding (can be several megabytes tall)
File List entries:
  000h 2     Offset/800h (increasing)
  002h 2     Size/800h (same as below, rounded up to sector units)
  004h 4     Size in bytes
Note: The files may consist of multiple smaller files badged together (eg. DISPLAY.CDB contains several TIMs per file).
Some CDB archives have garbage padding at end of file: BIN.CDB (2Kbyte), CSEL.CDB (80K), DISPLAY.CDB (70K), MOT.CDB (10648Kbyte). Maybe that's related to deleted files in the Vs demo version and/or to updating the CDB archives with newer/smaller content, but without truncating the CDB filesize accordingly.

Monster Rancher (MagDemo06: MR_DEMO\*.OBJ)
Deception III Dark Delusion (MagDemo33: DECEPT3\K3_DAT.BIN)
Star Trek Invasion (MagDemo34: STARTREK\STARTREK.RES)
Similar as .CDB archives (but with 32bit offset, and without duplicated size).
  000h  N*8   File List
  ...   4     File List end marker (00000000h)
  ...   ..    Garbage padding to 800h-byte boundary
  ...   ..    File Data
File List entries:
  000h 4     Offset/800h (increasing)
  004h 4     Size in bytes (often zero; for unused file numbers)
Note: Files are usually padded with 0..7FFh bytes to 800h-byte boundary, but STARTREK.RES does append additional 800h-byte padding after each file (ie. 800h..FFFh padding bytes in total).

Einhander (MagDemo08: BININDEX.BIN/BINPACK0.BIN/BINPACK1.BIN)
  000h X*4  File List for BINPACK0.BIN                   ;\
  ...  ..   Zeropadding                                  ; BINPACK0
  410h ..   Unknown (some/all of it looks like garbage)  ;/
  800h Y*4  File List for BINPACK1.BIN                   ;\
  ...  ..   Zeropadding                                  ; BINPACK1
  C10h ..   Unknown (some/all of it looks like garbage)  ;/
File List entries:
  000h 2    Offset/800h in BINPACK0.BIN or BINPACK1.BIN
  002h 2    Size/800h

SO98 Archives (NBA Shootout '98, MagDemo10: SO98\..*.MDL *.TEX *.ANI *.DAT)
Resembles .BZE (in terms of duplicated size entry).
  000h 4     Number of Files
  004h 4     Size of File Data area (total filesize-N*0Ch-8)
  008h N*0Ch File List
  ...  ..    File Data area
File List entries:
  000h 4   Offset (zerobased, from begin of File Data area)
  004h 4   Size in bytes
  008h 4   Size rounded to mutiple of 4-bytes
.DAT contains .TIM .SEQ .VB .VH and nested SO98 archives
.MDL contains whatever (and empty 0-byte files)
.TEX contains .TIM
.ANI contains whatever

Gran Turismo 1 (MagDemo10: GT\*.DAT) GT-ARC
Gran Turismo 1 (MagDemo15: GT\*.DAT) GT-ARC
Gran Turismo 2 (GT2.VOL\arcade\arc_fontinfo) GT-ARC
  000h 0Ch   ID "@(#)GT-ARC",00h,00h
  00Ch 2     Content Type (8001h=Compressed, 0001h=Uncompressed)
  00Eh 2     Number of Files (eg. 0Fh)
  010h N*0Ch File List
  ...  ..    File Data area
 File List entries:
  000h 4     Offset in bytes (increasing, unaligned)
  004h 4     Compressed File Size (can be odd)  ;\both same when uncompressed
  008h 4     Decompressed File Size             ;/(ie. when [00Ch]=0001h)
MESSAGES.DAT, SOUND.DAT, TITLE.DAT which are completely uncompressed GT-ARC's. Most other GT-ARC's contain LZ compressed files. In case of CARINF.DAT it's vice-versa, the files are uncompressed, but the GT-ARC itself is LZ compressed (the fileheader contains 00h,"@(#)GT-A",00h,"RC",00h,00h; it can be detected via those bytes, but lacks info about decompressed size).
CDROM File Compression GT-ZIP (Gran Turismo 1 and 2)

O.D.T. (MagDemo17: ODT\*.LNK and ODT\RSC\NTSC\ALLSOUND.SND and nested LNK's)
Barbie Explorer (MagDemo50: BARBIEX\*.STR and nested therein)
  000h 4     Number of Files (N)
  004h N*8   File List
  ...  ..    File Data area
File List entries:
  000h 4     Offset in bytes (increasing, 1/4-byte? aligned)
  004h 4     File Size in bytes (usually N*4, TXT's in ODT are padded as so)
Quirk: Instead of rounding only Offsets to N*4 byte boundary, all Sizes are rounded to N*4 bytes (eg. TXT files in ODT\RSC\NTSC\GFILES.LNK\01 with odd number of characters are are zeropadded to N*4 bytes).
Note: The PADBUG archives in Final Fantasy VIII (FF8) are very similar (but have a different alignment quirk).

Bust A Groove (MagDemo18: BUSTGR_A\*.DFS and BUSTGR_B\*.DFS) (DFS)
Bust-A-Groove 2 (MagDemo37: BUSTAGR2\BUST2.BIN\*) (main=DF2 and child=DFS)
Same as in O.D.T. with extra "DFS_" ID at start of file.
  000h 4     ID "DFS_" (with align 4) or "DF2_" (with align 800h)
  004h 4     Number of Files (N)
  008h N*8   File List
  ...  ..    File Data area
 File List entries:
  000h 4     Fileoffset in bytes (4-byte or 800h-byte aligned, increasing)
  004h 4     Filesize in bytes (can be odd, eg. in BUSTGR_A\SELECT.BPE\*)
The game does use uncompressed DFS archives (in .DFS files) and compressed DFS archives (in .BPE files):
CDROM File Compression BPE (Byte Pair Encoding)
The game does also use .DBI files (which contain filenames and other strings, whatever what for).

Monaco Grand Prix Racing Simulation 2 (MagDemo24: EXE\*\*.SUN)
Same as DFS, but with Total Filesize instead of "DFS_".
  000h 4     Total used filesize (excluding zeropadding to 2EE000h)
  004h 4     Number of Files (N)
  008h N*8   File List
  ...  ..    File Data area
  ...  (..)  In some files: Zeropadding to 2EE000h (3072Kbytes)
File Entries:
  000h 4     Offset (increasing, 4-byte aligned, see note)
  004h 4     Filesize in bytes (can be odd in Monaco)
Note: The alignment in Monaco is a bit glitchy:
  If (Size AND 3)=0 then NextOffset=Offset+Size             ;Align4
  If (Size AND 3)>0 then NextOffset=Offset+Size+Align800h   ;Align800h
  Namely, Monaco has files with Size=3BC5h.
The first file starts with unknown 32bit value, followed by "pBAV".

Rollcage (MagDemo19: ROLLCAGE\SPEED.IMG) (2Mbyte)
Rollcage Stage II (MagDemo31: ROLLCAGE\SPEED.IDX+SPEED.IMG) (3Kbyte+9Mbyte)
Sydney 2000 (MagDemo37: OLY2000\DEMO.IDX+DEMO.IMG) (1Kbyte+2Mbyte)
 Rollcage 1 uses a single IMG file that contains both directory and data:
  000h 4     Header offset (0)          ;\
  004h 4     Header size (10h+N*10h)    ; this seems to be a File List entry
  008h 4     Header size (10h+N*10h)    ; for the header itself
  00Ch 4     Zero                       ;/
  010h N*10h File List                  ;-File List for actual files
  ...  ..    Zeropadding to 800h-byte boundary
  ...  ..    File Data area
  Number of files is "IMG[04h]/10h" (minus 1 for excluding the header itself)
 The other titles have seaparate IDX and IMG files for directory and data:
  SPEED.IDX = Directory (N*10h bytes File List with offsets into SPEED.IMG)
  SPEED.IMG = File data
  Number of files is "Filesize(SPEED.IDX)/10h"
File List entries:
  000h 4     Fileoffset in bytes (800h-byte aligned, increasing)
  004h 4     Filesize in bytes
  008h 4     When compressed:   GT20 Header [004h] (decompressed size)
             When uncompressed: Same as filesize
  00Ch 4     When compressed:   GT20 Header [008h] (overlap, usuallly 3, or 7)
             When uncompressed: Zero
The compression related entries allow to pre-allocated the decompression buffer (without needing to load the actual GT20 file header), and then load the comprssed file to the top of the decompression buffer.
CDROM File Compression GT20 and PreGT20

Ultimate 8 Ball (MagDemo23: POOL.DAT) (5.5Mbyte)
  000h 4      Number of Entries
  004h N*0Ch  File List
  ...  ..     Zeropadding to 800h-byte boundary
  ...  ..     File Data area
 File List entries:
  000h 4      Unknown (random/checksum?)
  004h 4      File Offset (800h-byte aligned, increasing)
  008h 4      File Size in bytes
Notes: The LAST file isn't zeropadded to 800h-byte boundary. The File List includes some unused entries (all 0Ch-bytes zerofilled).

BIGFOOL - 3D Baseball (BIGFILE.FOO)
  000h N*0Ch  File List                                   (154h entries)
  ...  N*4    Filename Checksums (?)                      (154h entries)
  ...  ..     Zerofilled (padding to 800h-byte boundary)
  ...  ..     File Data area
The 1st list entry describes the current directory itself, as so:
  000h 4      Number of entries (including the 1st entry itself)
  004h 4      Offset/800h (always 0, relative from begin of directory)
  008h 4      Type        (always 3=Directory)
Further list entries are Files or Subdirectories, as so:
  000h 4      For Files: Size in bytes, for Directories: Number of entries
  004h 4      Offset/800h (from begin of current directory, increasing)
  008h 4      Type        (0=File, 3=Directory)

Spec Ops - Airborne Commando (BIGFILE.CAT and nested CAT files therein)
  000h 4     File ID                                 (always 01h,02h,04h,08h)
  004h 4     Maybe Version?                          (always 01h,00h,01h,00h)
  008h 4     Header Size (18h+N*8+ArchiveNameLength)    ;eg. 4ECh
  00Ch 4     Sector Alignment (can be 4 or 800h)
  010h 4     Number of Files (N)                        ;eg. 99h
  014h 4     Length of Archive Name (including ending 00h)
  018h N*8   File entries (see below)
  ...  ..    Archive Name, ASCII, terminated by 00h     ;eg. "bigfile.dir",00h
  ...  ..    Zeropadding to Sector Alignment boundary
  ...  ..    File Data
File Entries:
  000h 4   Fileoffset (with above Sector Alignment) (increasing)
  004h 4   Filesize in bytes
Filetypes in the archive include...
  nested CAT archives (file 07h,0Ch,11h,16h,1Bh,20h,25h,etc)
  empty files         (file 3Eh,5Ah-5Fh,62h-67h,etc)
  MDEC v2 STR's       (file 95h-96h)
  XA-ADPCM's          (inside of nested CAT, in file94h\file*)
There are "strings" in some files, are those filenames, eg. Icon_xxx etc?

Hot Shots Golf 2 (retail: DATA\F0000.BIN, MagDemo31/42: HSG2\MINGOL2.BIN)
The DATA directory is 13800h bytes tall. But, the PSX kernel supports max 800h bytes per ISO directory (so the kernel can only see the first 33 files in that directory). The game isn't actually trying to parse the ISO directory entries, instead, it's using the 2800h-byte offset/size list in F0000.BIN to access the directory content:
  0000h+N*4 1     Sector MM in BCD      ;\based at 00:06:00 for file 0
  0001h+N*4 1     Sector SS in BCD      ; (unused files are set to 00:00:00)
  0002h+N*4 1     Sector FF in BCD      ;/
  0003h+N*4 1     Size MSB in hex (Size/800h/100h)
  2000h+N   1     Size LSB in hex (Size/800h AND FFh)
  2800h     (..)  Data area for file 001h..590h (demo version only)
Retail Version disc layout:
  Sector 000ADh  SCUS_944.76       ;exefile     ;\
  Sector 00130h  SYSTEM.CNF                     ; iso root folder
  Sector 00131h  DATA (sub-folder, 27h sectors) ;/
  Sector 00158h  (padding)                      ;-padding to 00:06:00
  Sector 001C2h  DATA\F0000.BIN    ;file 000h   ;\
  Sector 001C7h  DATA\F0001.BIN    ;file 001h   ;
  ...                                           ; iso data folder
  Sector 00B54h  DATA\F0032.BIN    ;file 020h   ;
  Sector 00B9Bh  DATA\F0033.BIN    ;file 021h   ;  ;\files exceeding the 800h
  ...            ...                            ;  ; directory size limit, not
  Sector 1A0C9h  DATA\F1907.BIN    ;file 773h   ;/ ;/accessible via PSX kernel
  Sector 1AAF1h  DUMMY.BIN                      ;-iso root folder (padding)
Demo version in Playstation Magazine is a bit different: It has only two large .BIN files (instead of hundreds of smaller .BIN files). The directory is stored in first 2800h bytes of MINGOL2.BIN. The MM:SS:FF offsets are numbered as if they were located on sector 00:06:00 and up (to get the actual location: subtract 00:06:00 and then add the starting sector number of MINGOL2.BIN).
  Sector 07148h  HSG2\MINGOL2.BIN  ;file 000h..590h  ;demo binary files
  Sector 0AC1Dh  HSG2\MINGOL2X.BIN ;file 76Ch        ;demo streaming file(s)
  Sector 0B032h  HSG2\SCUS_944.95  ;exefile          ;demo exe file
Note: File 000h is a dummy entry referring to the 2800h-byte list itself (retail file 000h has offset=00:06:00 but size=0, demo file 000h has offset and size set to zero). File 001h is the first actual file (at offset=00:06:05, ie. after the 2800h-byte list)

Threads of Fate (MagDemo33: TOF\DEWPRISM.HED+.EXE+.IMG)
The demo version uses "Virtual Sectors" in HED+EXE+IMG files. Apart from that, the format is same as for the "Hidden Sectors" in retail version:
CDROM File Archives in Hidden Sectors

Vampire Hunter D (MAPFILE.BIN and MAPFILE.DAT)
 MAPFILE.DAT:
  000h N*8   File List entries
 MAPFILE.BIN:
  000h ..    Data (67Mbytes)
 File List entries:
  000h 4     Size in bytes (can be 0=empty)
  004h 4     Offset/800h in MAPFILE.BIN (increasing, 0 and up)

Vampire Hunter D (CHRHEAD.BIN and CHRFILE.BIN)
 CHRHEAD.BIN:
  000h 4     Total Size of CHRHEAD.BIN (10h+N*0Ch)
  004h 4     Number of entries (N)
  008h 8     Zerofilled
  010h N*0Ch File List
 CHRFILE.BIN:
  000h ..    Data
 File List entries:
  000h       Compressed size in bytes
  004h       Offset/800h in CHRFILE.BIN
  008h       Decompressed size in bytes (or 0=Uncompressed)

WWF Smackdown (MagDemo33: TAI\*.PAC\*, and nested therein)
These "PAC " files are found in the main archives (which use a separate archive format, with ID "DPAC").
  000h 4     ID ("PAC ")                                        ;\
  004h 4     Number of files (N)                                ; Header
  008h N*8   File List                                          ;/
  ...  ..    File Data area                                     ;-Data area
File List entries:
  000h 2     File ID (inreasing, but may skip numbers, ie. non-linear)
  002h 3     File Offset (increasing, relative to begin of Data area)
  005h 3     File Size
Bug: TAI\C.PAC\EFFC\0001h has TWO entries with File ID=0002h.

Tyco R/C Racing (MagDemo36: TYCO\MAINRSRC.BFF)
  000h 4     Unknown (1)
  004h 4     Filelist Offset          (800h)
  008h 4     Filelist Size (N*8+4)    (7ACh)
  ...  ..    Padding to 800h-byte boundary (see note)
  800h 4     Number of files (N)      (F5h)
  804h N*8   File List
  ...  ..    Padding to 800h-byte boundary (see note)
  ...  ..    File Data area
File List entries:
  000h 4     File Offset in bytes (increasing, 800h-byte aligned)
  004h 4     File Size in bytes
Padding Note: Padding after headers & files is weirdly done in two steps:
  Step 1: Zeropadding to 200h-byte boundary    (first 0..1FFh bytes)
  Step 2: Garbagepadding to 800h-byte boundary (last 0..600h bytes)

Team Buddies (MagDemo37: BUDDIES\BUDDIES.DAT)
  000h 2     ID ("BD")
  002h 2     Number of files (N)
  004h N*8   File List
  ...  ..    Zeropadding to 3000h
  3000h ..   File Data area
File List entries:
  000h 4     File Offset/800h (increasing)
  004h 4     File Size in bytes

Gundam Battle Assault 2 (DATA\*.PAC, and nested therein)
  000h 4     ID ("add",00h)
  004h 4     Fixed (4)
  008h 4     Offset to File List (usually/always 20h)
  00Ch 4     Number of Files (N)
  010h 4     Fixed (10h)
  014h 0Ch   Zerofilled
  020h N*10h File List
  ...  ..    File Data area
File List entries:
  000h 4     Offset (increasing, 4-byte aligned)  ;\or both zero
  004h 4     Size (can be odd)                    ;/
  008h 4     Unknown (0) (or 00h,10h,11h,20h,30h,40h when Offset/Size=0)
  00Ch 4     Zero (0)

Doko Demo Issho (DOKODEMO.417)
i-mode mo Issho - Doko Demo Issho Tsuika Disc (IMODE.417)
  000h 4     ID ("CNA",00h)
  004h 4     Unknown (1)
  008h 4     Number of Files (N) (5A4h)
  00Ch 4     Size of File Data area (total_size-N*10h-40h-padding)
  010h 0Ch   Zerofilled
  01Ch 0Ch   Name "IMODE.417", zeropadded (same as filename in ISO filesystem)
  028h 18h   Zerofilled
  040h N*10h File List
  ...  ..    Zeropadding to 800h-byte boundary
  ...  ..    File Data area
 File List entries:
  000h 4     File ID (increasing, with gaps)
  004h 4     Offset/800h (increasing)
  008h 4     Filesize in bytes
  00Ch 4     Zero

Incredible Crisis (MagDemo38: IC\*.CDB)
  000h 4     Number of files (N)
  004h N*4   File List
  ...  ..    Zeropadding to 800h-byte boundary
File List entries:
  000h 2     File Offset/800h (increasing)
  002h 2     File Size/800h

Ape Escape Sound Archive (MagDemo22:KIDZ\KKIIDDZZ.HED\DAT\1Bh-1Dh,49h-53h,..)
Ape Escape Sound Archive (MagDemo44:KIDZ\KKIIDDZZ.HED\DAT\1Bh-1Dh,4Fh-59h,..)
  000h 5*4   File Sizes   (can be odd) (can be 0 for 2nd and 5th file)
  014h 5*4   File Offsets (28h and up, increasing by sizes rounded to N*10h)
  028h ..    File Data area (first file usually/always contains "SShd")

Ultimate Fighting Championship (MagDemo38: UFC\CU00.RBB)
  0000h 4    ID "siff"                                  ;\Header
  0004h 4    Total Filesize (DADB1Ch)                   ;/
  0008h 4    ID "RSRC"                                  ;\
  000Ch 4    String Size (70h)                          ; ASCII string
  0010h 70h  String "RC ver1.0 Copyright",...,00h       ;/
  0080h 4    ID "RIDX"                                  ;\
  0084h 4    File List Size     (1F78h) (3EFh*8)        ; Directory
  0088h N*8  File List (Offset, Size1)                  ;/
  2000h 4    ID "EXIX"                                  ;\
  2004h 4    Extended List Size (FBCh)  (3EFh*4)        ; Extended
  2008h N*4  Extended List (Size2)                      ;/
  2FC4h 4    ID "GAP0"                                  ;\Alignment Padding
  2FC8h 4    Padding Size (2Ch)                         ; (so that next chunk
  2FCCh 2Ch  Padding (1Ah-filled)                       ;/starts at boundary-8)
  2FF8h 4    ID "RBB0"                                  ;\
  2FFCh 4    File Data area Size (DAAB1Ch)              ; Data area
  3000h ..   File Data area                             ;/
File List entries (RIDX):
  000h 4     File Offset (increasing, 4-byte aligned, from ID "RBB0" plus 8)
  004h 4     File Size in bytes (can be odd)
Extended List entries (EXIX):
  000h 4     File Size in bytes (always the same size as in RIDX chunk)

Ultimate Fighting Championship (MagDemo38: UFC\CU00.RBB\183h,37Bh..3EBh)
  000h 4     ID "OIFF"                                  ;\Header
  004h 4     Total Filesize                             ;/
  008h 4     ID "TIMT" or "ANMT"                        ;\
  00Ch 4     Size (N*4)                                 ; Directory Table
  010h N*4   File List (offsets from begin of Data ID+8);/
  ...  4     ID "TIMD" or "ANMD"                        ;\
  ...  4     Data Area size (SIZ) (Filesize-18h-N*4)    ; Data area
  ...  SIZ   Data Area                                  ;/

E.T. Interplanetary Mission (MagDemo54: MEGA\MEGA.CSH+.BIN)
 MEGA.CSH:
  000h N*0Ch File List
 MEGA.BIN:
  000h ..    File Data area
File List entries:
  000h 4     Offset (in MEGA.BIN file, 800h-byte aligned, increasing)
  004h 4     Unknown (32bit id/random/checksum/whatever)
  008h 4     Filesize in bytes

Driver 2 The Wheelman is Back (MagDemo40: DRIVER2\SOUND\*\*)
  000h 4     Number of entries (1 or more) (N)
  004h N*10h File List
  ...  ..    File Data area (.VB aka SPU-ADPCM)
 File List entries:
  000h 4     Offset from begin of Data area, increasing
  004h 4     Filesize in bytes
  008h 4     Unknown (0 or 1)
  00Ch 4     Unknown (AC44h, 0FA0h, 2EE0h, 2710h, 2B11h, 3E80h, 1F40h, etc.)
 Note: Above AC44h might be 44100Hz, or just file number 44100 decimal?

Thrasher: Skate and Destroy (MagDemo27: SKATE\ASSETS\*.ZAL) (Z-Axis)
Dave Mirra Freestyle BMX (MagDemo36: BMX\ASSETS\*.ZAL) (Z-Axis)
Dave Mirra Freestyle BMX (MagDemo46: BMX\ASSETS\*.ZAL) (Z-Axis)
  000h 4     ID (always 2A81511Ch)
  004h 0Ch   Zerofilled
  010h 1     Unknown (1)
  011h 1     Compression Flag for all files (00h=Uncompressed, 80h=Compressed)
  012h 2     Number of files (bit0-13?=N, bit14=Unknown, can be set)
  014h N*0Ch File List, 12 bytes/entry      ;<-- when [11h]=00h=uncompressed
  014h N*10h File List, 16 bytes/entry      ;<-- when [11h]=80h=compressed
  ...  ..    File Data area
File List entries (0Ch or 10h bytes per entry, depending on compression):
  000h 4     File ID (usually 0=first, increasing) (or 0001h,7531h,7532h,...)
  004h 4     Offset-10h in bytes (increasing, 4h-byte aligned)
  008h 4     Filesize, uncompressed (can be odd)
  00Ch (4)   Filesize, compressed (can be odd)   ;<-- exists only if compressed
For decompression, see:
CDROM File Compression ZAL (Z-Axis)

Speed Punks (MagDemo32: SPUNKS\*.GDF)
  000h 4     ID "0FDG XSP" (aka PSX GDF0 backwards)
  008h 4     Header Size (N*10h+10h)
  00Ch 4     Number of files (N)
  010h N*10h File List
  ...  ..    Zeropadding to 800h-byte boundary
  ...  ..    File Data area
 File List entries:
  000h 4     ID/Type ("MARV", "MARS", "MARD", "PMET", "COLR", "MROF")
  004h 4     ID/Num  (usually 1 SHL N, or all zero)
  008h 4     Offset (800h-byte aligned, increasing)
  00Ch 4     Size in bytes

Legend of Dragoon (MagDemo34: LOD\SECT\*.BIN, and nested therein)
  000h 4     ID "MRG",1Ah
  004h 4     Number of Files (eg. 0, 1, 2, 193h, 2E7h, or 1DBBh)
  008h N*8   File List
  ...  ..    Padding to 800h-byte boundary (8Ch-filled) (not in nested MRG's)
  ...  ..    File Data area
 File List entries:
  000h 4     Offset/800h, or 4-byte aligned Offset/1 (increasing)
  004h 4     Size (can be odd, and can be zero)
 Size oddities:
  Empty files in demo version have Size=0 and Offset=0.
  Empty files in retail version have Size=0 and Offset=OffsetOfNextFile.
  MRG archives can start or end with Empty files.
  All files can be empty (eg. retail DRAGN0.BIN\1190h).
  NumFiles can be zero (eg. retail DRAGN0.BIN\1111h, demo DRAGN0.BIN\10E2h).
 Offset oddities:
  SECT\*.BIN have Offset/800h
  Nested MRGs have 4-byte aligned Offset/1
  The two variants can be detected as:
   if FirstOffset=(NumFiles*8+8) then NestedVariant
   if FirstOffset=(NumFiles*8+8+7FFh) AND NOT 7FFh then RootVariant
  Whereas, FirstOffset is the first NONZERO offset in file list (important
  for demo version, which has archives that start with ZERO offsets).

RC Revenge (MagDemo37: RV2\BB\3.BBK and Retail: BB\*\*.BBK)
This does basically contain four large files (and four info blocks with info on the content of those files).
  000h 4     Random/Checksum?
  004h 4     Faded ID (FADED007h)
  008h 4     Part 1 Offset (Sound)     (always E5Ch)
  00Ch 4     Part 2 Offset (Texture)   (when Type=01h: Offset-E5Ch)
  010h 4     Part 3 Offset (?)         (when Type=01h: Offset-E5Ch)
  014h 4     Part 4 Offset (?)         (when Type=01h: Offset-E5Ch)
  018h 4     Type (10h or 20h=Normal)  (or 01h=Special in BB\8\*.BBK)
  01Ch B0Ch  Part 1 Info (Sound)       (when Type=01h: garbage-filled)
  B28h 314h  Part 2 Info (Texture)
  E3Ch 14h   Part 3 Info (?)
  E50h 0Ch   Part 4 Info (?)
  E5Ch ..    Part 1 Data (Sound, SPU-ADPCM data, if any)
  ...  ..    Part 2 Data (Texture data) (starts with BDEF1222h or BDEF1111h)
  ...  ..    Part 3 Data (?)   ;\maybe map, models, and/or whatever
  ...  ..    Part 4 Data (?)   ;/
Part 1 Info (Sound info) (if any):
  01Ch 4     Random/Checksum?
  020h 4     Faded ID (FADED007h)
  024h 4     Part 1 Size              (eg.7C7F0h)
  028h 4     SPU Start Addr           (1010h) (for data from file offset E5Ch)
  02Ch 4     SPU Middle Addr          (eg. 58F70h)
  030h 4     SPU End Addr             (eg. 7D800h) (start+size)
  034h 2     Middle entry number      (often 3Ch)
  036h 2     Number of used entries-1 (eg. 50h means that 51h entries are used)
  038h AF0h  Sample List (100 entries, unused ones are zerofilled)
  914h 214h  Zerofilled (unused 1Ch-byte entries) (total is 1Ch*64h)
 Sample List entries:
  000h 4     SPU Offset (1010h and up) (SpuOffset=1010h is FileOffset=E5Ch)
  004h 4     Sample Size in bytes
  008h 4     Unknown (0)
  00Ch 4     Unknown (0)
  010h 4     Pitch   (400h=11025Hz, 800h=22050Hz, 2E7h=8000Hz, 8B5h=24000Hz)
  014h 4     Unknown (0 or 1)
  018h 4     File ID (00001F08h and up)
Part 2 Info (Texture info):
  B28h 4     Random/Checksum?
  B2Ch 4     Faded ID (FADED007h)
  B30h 4     Part 2 Size      (N*16000h)  ;Width=2C0h halfwords, Height=N*64
  B34h 4     Zero             (0h)
  B38h 4     Some RAM Address (8010xxxxh)
  B3Ch 4     Unknown          (eg. 195h or E3h) ;same as at [DA4h]
  B40h 4+4   VRAM Address X,Y (140h,0)          ;maybe load target
  B48h 4+4   VRAM Address X,Y (140h,0)          ;maybe palette base?
  B50h 4+4   VRAM Address X,Y (xx0h,Height-40h) ;often at/near end of used area
  B58h 4     Unknown          (eg. 1D0h or 1E0h)
  B5Ch 4     Unknown          (eg. 1Ah or 0Dh)
  B60h 200h  Some halfwords?  (most are FFFFh, some are 0000h)
  D60h 40h   Zerofilled       (0)
  DA0h 4     Unknown          (eg. 185h or E2h)
  DA4h 4     Unknown          (eg. 195h or E3h) ;same as at [B3Ch]
  DA8h 9x10h Special Texpages (VramX,Y, SizeX,Y, StepX,Y, Flag/Type/Num or so?)
  E38h 4     Some RAM Address (800Axxxxh)
Part 3 Info:
  E3Ch 4     Random/Checksum?
  E40h 4     Faded ID (FADED007h)
  E44h 4     Part 3 Size                  (eg. A9728h or 51264h)
  E48h 4     RAM End Address (start+size) (eg. 801Fxxxxh) (near memtop)
  E4Ch 4     RAM Start Address (end-size) (eg. 801xxxxxh)
Part 4 Info:
  E50h 4     Random/Checksum?
  E54h 4     Faded ID (FADED007h)
  E58h 4     Part 4 Size (usually 10CCCh) (or 105E0h in demo version)
Note: File CAT\RDS.CAT does also start with ID=FADED007h (but contains whatever different stuff).


CDROM File Archives with Offset

Below are archives that start with a simple Offset list. The DOT1 and DOTLESS types are "standard" archives used by many PSX games (although the "standard" was probably independently created by different developers).

DOT1 Archives (named after the ".1" extension in R-Types)
Used by various titles:
  R-Types (CG.1, PR\PR.1, and nested inside CG.1)
  Final Fantasy IX (nested inside FF9.IMG, FF9.IMG\DB, FF9.IMG\DB\DOT1)
  Legend of Mana (*.EFF,*.SET,*.BTP(?) in folders SND*,SOUND,WM(?))
  Witch of Salzburg (*.ANM/BIN/BSS/DAT/MDL/SCE)
  Rayman (RAY\*.XXX, RAY\SND\*.ALL, and nested inside *.XXX)
  Pandemonium II (JESTERS.PKG\0101\0008 and JESTERS.PKG\0101\000D)
  Incredible Crisis (MagDemo38: IC\TAN_DAT.CDB\<DOTLESS>\<DOT1>\<SHIFTJIS>)
  Various games on PlayStation Magazine Demo Discs (Disc 03-54)
DOT1 (in lack of a better name) is a simple archive format that contains Number of Entries and List with Increasing Offsets to File data.
  000h 4    Number of Files (N)                 (eg. 2..18)
  004h N*4  File List (offsets to each file, increasing, aligned)
  ...  (4)  Optional: Total filesize (aka end-offset for last list entry)
  ...  ..   Optional: Zeropadding to alignment boundary (when alignment>4)
  ...  ..   File Data
There are four variants with different alignment (and in some cases, with an extra entry with end-offset for last file):
  Align800h, no extra entry    R-Types (CG.1 and PR\PR.1)
  Align4,    no extra entry    R-Types (nested in CG.1), FF9 (in IMG, IMG\DB)
  Align2,    no extra entry    Incredible Crisis (IC\TAN_DAT.CDB\*\*)
  Align800h, with extra entry  MLB 2000 (DATA.WAD)
  Align10h,  with extra entry  Witch of Salzburg (*.ANM/BIN/BSS/DAT/MDL/SCE)
  Align4,    with extra entry  Rayman (*.XXX, *.ALL)
The files can be detected by checking [004h]=4+(N*4), 4+(N*4)+Align800h, 4+(N*4)+4, or 4+(N*4)+4+Align10h, and checking that the offsets are increasing with correct alignment (Rayman has some empty files with same offset), and don't exceed the total filesize. And that the alignment space is zeropadded (in case of R-Types, only the header is 00h-padded, but files are FFh-padded).
The detection could go wrong, especially if the archive contains very few files, some of the nested DOT1's contain only one file (header "00000001h, 00000008h", without any further increasing offsets or padding). As workaround, accept such files only if they have a ".1" filename extension, or if they were found inside of a bigger DOT1, IMG, or DB archive.
Final Fantasy IX contains some DOT1's with fewer than few entries (the file being only 4-bytes tall, containing value NumEntries=00000000h).

NFL Gameday '98 (MagDemo04: GAMEDAY\*.FIL) (32bit) (with nested FIL's)
NFL Gameday '99 (MagDemo17: GAMEDAY\*.FIL) (32bit)
NFL Gameday 2000 (MagDemo27: GAMEDAY\*.FIL) (16bit and 32bit)
NCAA Gamebreaker '98 (MagDemo05: GBREAKER\*.FIL,*.BIN) (16bit and 32bit)
NCAA Gamebreaker 2000 (MagDemo27: GBREAKER\*.FIL) (16bit and 32bit)
FIL/32bit (with [02h]=FFFFh):
  000h 2    Number of Files (N)
  002h 2    ID for 32bit version (FFFFh=32bit entries)
  004h N*4  File List (offsets to each file, increasing, 4-byte aligned)
  ...  ..   File Data
FIL/16bit (with [02h]<>FFFFh, eg. FLAG*.FIL and VARS\STARTUP2.FIL\0\*):
  000h 2    Number of Files (N)
  002h N*2  File List (offsets to each file, increasing, 4-byte aligned)
  ...  ..   Zeropadding to 4-byte boundary
  ...  ..   File Data

Reel Fishing (*.MB, *.PAK, and nested therein)
  000h 2    Unknown/Fixed (always 0001h)
  002h 2    Number of Files (N)
  004h N*4  File List (offsets to each file, increasing) (4-byte aligned?)
  ...  ..   File Data
Roughly resembles FIL/32bit ... and Muppet Monster Adventure.

PreSizeDOT1 (Ace Combat 2) (retail and MagDemo01: ACE2.DAT\*)
Like DOT1, but with Total Filesize being oddly stored at begin of file.
  000h 4    Total Filesize (aka end-offset for last list entry)
  004h 4    Number of Files (N)
  008h N*4  File List (offsets to each file, increasing, 4-byte aligned)
  ...  ..   File Data
Note: Ace Combat 2 contains PreSizeDOT1 (ACE2.DAT\02h..1Dh,36h..B2h) and normal DOT1 archives (nested in PreSizeDOT1's and in ACE2.DAT\B3h..E1h).

Vampire Hunter D (EFFECT\*.TPK and MAPFILE\880h and MENU\*.PTI)
This is a DOT1 archive with two extra Zeroes at [000h] and [004h].
  000h 4     Zero
  004h 4     Zero
  008h 4     Number of entries
  008h N*4   File List (Offsets)
  ...  ..    Data (for TPK: TIM with 4-byte extra header) (for PTI: raw TIM)
Data File format (in TPK files with extra header):
  000h 4     Unknown (can be 00h,01h,10h,11h,20h,30h)
  004h ...   TIM file
Note: Most *.TPK files are compressed (except S071_2.TPK and *.PTI).

Vampire Hunter D (EFFECT\*.MPK and MAPFILE\07Bh,0BFh,..,88Eh)
This is a DOT1 archive with one extra Zero at [004h].
  000h 4     Number of entries
  004h 4     Zero
  008h N*4   File List (32bit Offsets)
  ...  ..    Data (usually TMD model files) (or Non-ASCII text strings?)
The archive format is used for models and other stuff:
  EFFECT\*.MPK              --> contains TMD models
  MAPFILE\87Fh,883h,..,87Fh --> contains TMD models
  MAPFILE\07Bh,0BFh,..,88Eh --> contains Non-ASCII text strings (?)

DOT-T (somewhat same as DOT1, but with 16bit entries)
Armored Core (MagDemo02, AC10DEMP\*.T)
  000h 2    Number of Files
  002h N*2  File List (Offset/800h to file data, increasing)
  ...  2    Total Size/800h (end-offset for last file)
  ...  ..   Zeropadding to 800h-byte boundary
  ...  ..   File Data
This can contain many empty 0-byte files (aka unused file numbers; though maybe those files exist in the retail version, but not in the demo version).

DOTLESS Archive
Hot Shots Golf (MagDemo07: HSG\*.DAT)
Hot Shots Golf 2 (retail: DATA\F0000.BIN\*, MagDemo31/42: HSG2\MINGOL2.BIN\*)
Starblade Alpha (FLT\*.DAT, TEX\*.DAT)
Incredible Crisis (MagDemo38: IC\TAN_DAT.CDB\<DOTLESS>)
  000h N*4  Offsets to File data (increasing, usually 4-byte aligned)
  ...  (4)  Filesize (end-offset for last file) (only in Ape Escape)
  ...  ...  File Data
Like DOT1, but without Number of Files entry (instead, the first offset does imply the end of file list). There's no extra entry for end of last file (instead, that's implied in the total filesize). Most files have at least 5 entries, but HSG\TITLE0.DAT seems to contain only one entry (ie. the whole header contains only one value, 00000004h, followed by something that looks like raw bitmap data).
Also used by Ape Escape (MINIGAME\* included nested ones), the Ape Escape files do have an end-marker with last-offset (that will appear as an empty 0-byte file at end of list when not specifically handling it). MINIGAME\MINI2\BXTIM.BIN does also have several 0-byte files inside of the file list.

Twisted Metal: Small Brawl (MagDemo54: TMSB\SHL\*.TMS)
  000h 4     Size of Data Area (total filesize minus 0D0h)
  004h 4     Number of files
  008h N*4   File List (zerobased offsets from begin of Data Area)
  ...  ..    Zeropadding to 0D0h
  0D0h ..    File Data Area
This resembles DOT1, with an extra size entry and padding to 0D0h.

Ridge Racer Type 4 (MagDemo19: R4DEMO\R4.BIN, 39Mbyte)
Ridge Racer Type 4 (MagDemo21: R4DEMO\R4.BIN, 39Mbyte)
Basically, this is alike DOT1, but SECTOR numbers, and with extra entries...
  000h 4     Number of Files (N) (3C9h)
  004h N*4   File List (Offset/800h)
  ...  4     Total Size/800h                  ;<-- last offset
  ...  4     Unknown (00,E8,82,2E)            ;<-- ??? maybe chksum*800h or so?
  ...  ..    Zeropadding to 800h-byte boundary
  ...  ..    File Data area

Legend of Legaia (MagDemo20: LEGAIA\PROT.DAT)
  000h 4     Zero
  004h 4     Number of Entries (4D3h)
  008h N*4   File List (Offset/800h)
  ...  4     Total Size/800h (aka end Offset/800h of last file)
  ...  ..    Zeropadding to 800h-byte boundary
  ...  ..    File Data area
The PROT.DAT does not contain filenames, however, it's bundled with CDNAME.TXT, which appears to contain symbolic names for (some) indices:
  #define init_data 0           ;for file 0000h
  #define gameover_data 1       ;for file 0001h
  #define town01 3              ;for file 0003h
  #define town0b 12             ;for file 000Ch
  ...                           ;...
  #define other6 1222           ;for file 04C6h
  #define other7 1228           ;for file 04CCh
The DAT file contains many zerofilled "dummy" files with 800h-byte size.

Bloody Roar 1 (MagDemo06: BL\*.DAT)
Bloody Roar 2 (MagDemo22: ASC,CMN,EFT,LON,SND,ST5,STU\*.DAT)
  000h 4     Number of Entries (N)
  004h N*4   File List (Offset-(4+N*4), increasing) (or FFFFFFFFh=Unused entry)
  ...  ..    File Data area
Most or all files in DAT archives are PreGT20 compressed.
CDROM File Compression GT20 and PreGT20
Note: Unused entries can occur anywhere, eg. Bloody Roar 2 CMN\SEL01.DAT does have both first and LAST entry marked as unused (FFFFFFFFh). Also, there may be a lot of unused entries, eg. Bloady Roar 1 CMN\TITLE00.DAT uses only 5 of 41h entries).

Klonoa (MagDemo08: KLONOA\FILE.IDX\*)
  000h 4     ID "OA05"
  004h N*4   Offset List (usually/always 5 used entries, plus zeropadding)
  030h ..    File Data area (usually/always starting at offset 30h)

C - The Contra Adventure (DATA\SND\*.SGG)
  000h 4    ID "SEGG"
  004h 4    Offset to .VH file
  008h 4    Offset to .VB file
  00Ch 4    Number of .SEQ files (N) (usually 6Eh, or 08h in MENU.SGG)
  010h N*4  Offsets to .SEQ files (increasing, unaligned)
  ...  ..   SEQ files
  ...  ..   Padding to 4-byte boundary
  ...  ..   VH file
  ...  ..   VB file

Ninja (MagDemo13: NINJA\VRW\*.VRW)
  000h 8     ID "VRAM-WAD" (here as archive ID, although same as compress ID)
  004h N*4   File List (offsets to Data)  ;NumFiles=(FirstOffset-8)/4
  ...  ..    Data (compressed .PAK files, which do ALSO have ID="VRAM-WAD")
The compressed .PAK files are using a LZ5-variant:
CDROM File Compression LZ5 and LZ5-variants

The Next Tetris (MagDemo22: TETRIS\*) has PSX.BSE (and nested therein)
  000h 4     Unknown (3)
  004h 4     Total Size
  008h 4     Number of Files (N) (max 40h, for max 40h*4 bytes in file list)
  00Ch N*4   File List (increasing offsets, 800h-byte aligned)
  ...  ..    Unknown (looks like garbage padding for unused File List entries)
  10Ch 6F4h  42h-filled padding to 800h-byte boundary
  800h ..    File Data area

Tactics Ogre (UBF*.BIN)
  000h 8     Fixed (88h,0,0,0,0,0,0,0)
  008h 4     Number of Files (eg. 1Dh or 585h, including last/end file)
  00Ch N*4   File List (increasing offsets, 800h-byte aligned)
  ...  ..    Zeropadding to 800h-byte boundary
  ...  ..    File Data area
Note: The last file is a TXT file containing "LINK-FILE END....",0Dh,0Ah,1Ah, plus zeropadding to 800h-byte boundary.

Spyro the Dragon (MagDemo12: SPYRO\PETE.WAD)
  000h 4     Total Filesize (3E800h in Spyro)
  004h N*8   File List      (1B0h bytes in Spyro)
  ...  ..    Zeropadding to 800h-byte boundary
  ...  ..    File Data (4-byte aligned, despite of above 800h-byte hdr padding)
File List entries:
  000h 4     Fileoffset (increasing, 4-byte aligned)
  004h 4     File ID? (unsorted, not increasing, used range is 000h..1FAh)

X-Files - Bitmap/Animation Sequence (*.BF)
  000h 4    Fixed ID ("bf00")
  004h 2    Number of Files (N)
  006h 2    Unknown       (always 42h, maybe frame rate or so?)
  008h 2    Bitmap Width  (always 28h aka 40 decimal)
  00Ah 2    Bitmap Height (always 1Eh aka 30 decimal)
  00Ch N*4  File List (increasing 32bit offsets, 4-byte aligned)
  ...  ..   File Data area (contains .BS fraquant files, played in sequence)


CDROM File Archives with Size

DOTCAT - Porsche Challenge (*.CAT, after decompressing them)
  000h 4     Number of files (N) (existing ranges are 01h..3Fh)
  00Ch N*4   File List (filesizes in bytes, always multiple of 4)
  ...  ..    File Data area (usually starts with 0002ABBAh in 1st file)

Disney-Pixar's Monsters, Inc. (MagDemo54: MINC\*.BZE)
  000h 4     Zero (0)
  004h 4     Type/ID (27100h=160000, 2BF20h=180000, 30D40h=200000 decimal)
  008h 4     Number of files (N)
  00Ch N*0Ch File List
  ...  ..    Zeropadding to 7FCh
  7FCh 4     Checksum (32bit sum of SIGN-EXPANDED bytes at [000h..7FBh])
  ...  ..    File Data
File List entries:
  000h 4     File Type/ID or so (roughly increasing, eg. 1,3,6,5,7,8,9,A,B)
  004h 4     Filesize in bytes
  008h 4     Filesize rounded up to multiple of 800h bytes

Bugs Bunny: Lost in Time (MagDemo25: BBLIT\*.BZZ) (without extra entry)
The Grinch (MagDemo40: GRINCH\*.BZZ) (with extra entry)
Resembles .BZE, but without the Type entry in Header.
  000h 4     Fixed 1 (maybe version, or compression flag)
  004h (4)   Unknown (000xxxx0h)   ;<-- Extra in The Grinch only (not Bunny)
  ...  4     Number of files
  ...  N*0Ch File List
  ...  ..    Zeropadding to 7FCh
  7FCh 4     Checksum (32bit sum of SIGN-EXPANDED bytes at [000h..7FBh])
  ...  ..    File Data
File List entries:
  000h 4     File Type/ID or so (roughly increasing, eg. 1,2,3,6,5,7,8,9,A)
  004h 4     Filesize in bytes (rounded to N*4 even if compressed data is less)
  008h 4     Filesize rounded up to multiple of 800h bytes
Files are compressed, starting with 0Bh, same as in Jersey Devil...
CDROM File Compression BZZ
Note: The TIM files in Bugs Bunny and The Grinch BZZ archives consists of two TIMs badged together: A 4x4 pix dummy TIM, followed by the actual 512x125 pix TIM (in some cases followed some extra bytes at end of file?).

Jersey Devil .BZZ (MagDemo10: JD\*.BZZ)
Resembles .BZE, but without the Type entries in Header and File List, and without Header checksum.
  000h 4     Fixed 1 (maybe version, or compression flag)
  004h 4     Number of files (4)
  008h N*8   File List
  ...  ..    Zeropadding to 800h-byte boundary (without checksum, unlike .BZE)
  ...  ..    File Data
File List entries:
  000h 4     Size in bytes
  004h 4     Size rounded to multiple of 800h
Files are compressed, starting with 0Bh, same as in Bugs Bunny...
CDROM File Compression BZZ

Jackie Chan Stuntmaster (RCHARS\*.RR)
NBA Basketball 2000 (MagDemo28: FOXBB\*.RR)
  000h 2     ID ("PX")
  002h 2     Unknown (1 or 3)
  004h 4     Header Size (eg. 80h, 7C0h, or 1730h) (N*8+8)
  008h N*8   File List
  ...  ..    Zeropadding to 800h-byte boundary
  ...  ..    File Data area
 File List entries:
  000h 4     Offset (increasing, 800h-byte aligned)
  004h 1     Zero
  005h 3     Filesize in bytes (24bit) (can be odd)
Jackie Chan Stuntmaster does always have headersize=1730h (with many unused entries with size=0, both in the middle & at the end of File List).

Bomberman World (MagDemo15: BOMBER\*.RC)
                XXX detect this WITH extension=".RC" check before OBJ
                    (else type=1 could be mistaken as offs=1) (eg RC1\BP0*.RC)
Resembles .OBJ but contains Filetype? instead of Offset.
  000h N*8   File List
  ...  8     File List end (zerofilled)
  ...  ..    Garbage padding to 800h-byte boundary
File List entries:
  000h 4     Filetype (see below)
  004h 4     Filesize in bytes
There can be several files with same type in one .RC archive. Type values are:
  00h = End of File List (at least so when Type and Size are both zero)
  01h = .TIM
  02h = Unknown
  03h = Unknown
  05h = .VH
  06h = .VB
  09h = Unknown
  0Ah = .TIM (left half of a larger image) (right half has type 01h)
  0Bh = Unknown
  0Ch = Unknown

Mat Hoffman's Pro BMX (new demo) (MagDemo48: MHPB\BMXCD.HED+WAD)
This format is used by the NEW demo version on MagDemp48 (the OLD demo version on MagDemo39 did use Spider-Man-style HED/WAD format with filenames).
 HED:
  000h 2     Number of entries (N)
  002h N*6   File List
 WAD:
  000h ...   File data (at 800h-byte aligned locations)
File List entries:
  000h 3     File ID (24bit)
  003h 3     File Size in bytes (21bit, max 2Mbyte) (upper 3bit=unused?)
Note: HED is processed at 80052AC0h in MagDemo48.

Madden NFL 2000 (MagDemo27: MADN00\*.DAT and nested therein)
Madden NFL 2001 (MagDemo39: MADN01\*.DAT and nested therein)
  000h 4     Header Size (N*SectorSize) (xxh, 800h, 1000h, 4800h, or 920h)
  004h 4     Sector Size (4=ChildArchive, 800h=MainArchive, 920h=FMV/MADN00)
  008h 4     File List entrysize (0=32bit, 1=16bit/MADN00, 4=16bit/MADN01)
  00Ch N*2/4 File List (16bit or 32bit filesizes in bytes)
  ...  ..    Zeropadding to SectorSize boundary
  ...  ..    Files (with above sizes, each zeropadded to SectorSize boundary)
Dummy files have filesize=1 (but they do nethertheless occupy a whole data sector).
Unknown why the FMV file in MADN00 is using SectorSize=920h (it appears to be FORM2 related, although the file seems to be stored in FORM1 sectors, but the STR movie appears to work okay despite of the odd size).

Croc 2 (MagDemo22: CROC2\CROCII.DIR\FESOUND.WAD)
Disney's The Emperor's New Groove (MagDemo39:ENG\KINGDOM.DIR\FESOUND.WAD)
Disney's Aladdin in Nasira's Rev. (MagDemo46:ALADDIN\ALADDIN.DIR\FESOUND.WAD)
Harry Potter: Philosopher's Stone (POTTER.DIR\FESOUND.WAD, FETHUND.WAD)
Harry Potter: Chamber of Secrets (POTTER.DIR\FE3_SOND.WAD, FE5_THND.WAD)
  000h 4     Total Filesize-4  (or, in Potter games: Filesize-0)
  004h N*14h File List (2 entries in Croc2, 3 entries in Aladdin/Emperor/Pott)
  ...  ..    File Data area (SPU-ADPCM) (.VB files with leading zeroes)
 File List entries:               (Aladdin/Emperor) (Croc2)         (Potter)
  000h 4     Sample Rate in Hertz (AC44h=44100Hz)   (5622h=22050Hz) (7D00h)
  004h 2     Sample Rate Pitch    (1000h=44100Hz)   (0800h=22050Hz) (B9Ch)
  006h 2     Unknown              (7Fh)             (32h)           (7Fh)
  008h 4     Unknown              (1)               (8)             (8)
  00Ch 4     Unknown              (1FC0001Fh)       (40008Fh)       (1FC0001Fh)
  010h 4     Filesize             (xxx0h)           (xxx0h)         (xxx0h)
The number of files is implied in sum of filesizes versus total size.
The two Sample Rate values are related as so: Pitch=Hertz*1000h/44100.

Harry Potter: Chamber of Secrets (POTTER.DIR\FE3_WIZC.WAD)
  000h 4     ID ("CPRS")
  004h 4     Maybe Header Size (N*10h+8)
  008h 4     Number of Files (N)
  00Ch 4     Zero
  010h N*10h File List
  ...  ..    Zeropadding to 1000h
  1000h ..   File Data (SPU-ADPCM data)
 File List entries:
  000h 4     Offset-1000h       (0 and up, increasing, 800h-byte aligned)
  004h 2     Sample Rate Pitch  (5CEh=16000Hz or 800h=22050Hz)
  006h 2     Whatever           (always 2)
  008h 4     Whatever           (always 0)
  00Ch 4     Filesize in bytes  (always multiple of 800h)

Dino Crisis 1 and 2 (PSX\DATA\*.DAT and *.DBS and *.TEX) ("dummy header")
  000h 800h  File List (with 10h or 20h bytes per entry)
  800h ..    File Data (each file is zeropadded to 800h-byte boundary)
File List entrysize can be 10h or 20h bytes:
  Dino Crisis 1 --> always size 10h
  Dino Crisis 2 --> usually size 20h
  Dino Crisis 2 --> sometimes size 10h (eg. SC24.DAT, SC48.DAT, WEP_*.DAT)
File List entries:
 File List entries, type 0 and 7:
  000h 4     Type (0=Data (or .BS pictures), 7=CompressedData)
  004h 4     Size
  008h 4     RAM Addresss (80000000h..801FFFFFh)
  00Ch 4     Zero
  010h (10h) Zerofilled
 File List entries, type 1 and 2 and 8:
  000h 4     Type (1=Bitmap, 2=Palette, 8=CompressedBitmap)
  004h 4     Size (see below Size Notes)
  008h 2     VRAM Address X     (0..3FFh)
  00Ah 2     VRAM Address Y     (0..1FFh) (or 280h in Dino 2 ST703.DAT)
  00Ch 2     Width in halfwords (1..400h)
  00Eh 2     Height             (1..200h)
  010h (10h) Zerofilled
 File List entries, type 3 and 4:
  000h 4     Type (3=VoiceHeader("Gian"), 4=VoiceData(SPU-ADPCM))
  004h 4     Size
  008h 4     SPU Address (0..7FFF0h)
  00Ch 2     Unknown (0..7)  ;\usually both same (or val1=0, val2>0)
  00Eh 2     Unknown (0..7)  ;/
  010h (10h) Zerofilled
 File List entries, type 5 (eg. ME*.DAT):
  000h 4     Type (5=Unknown... maybe Midi-style or so)
  004h 4     Size
  008h 4     Load Address (0, or on next 4-byte boundary after previous file)
  00Ch 2     Unknown (0..2)  ;\always both same
  00Eh 2     Unknown (0..2)  ;/
  010h (10h) Zerofilled
 File List entries, type 6 and 9:
  The EXE code does also accept type 6 and 9 (type 6 is handled same as
  type 0, and type 9 is ignored), but the actual archives don't seem to
  contain any files with those types.
 File List entries, padding for unused entries:
  000h 10h   Type ("dummy header    ")
  010h (10h) Zerofilled
Size Notes:
 Bitmaps and Palettes can have following sizes:
  Width*Height*2                       ;normal case
  Width*Height*2 + Align(1000h)        ;eg. Dino Crisis 1 DOOR*.DAT
  Width*Height*2 + Align(800h)         ;eg. Dino Crisis 2 DOOR27.DAT
 CompressedBitmaps can have following sizes in compressed form:
  Less than Width*Height*2             ;normal case
  Less than Width*Height*2 + 1000h     ;eg. Dino Crisis 2 M_RESULT,ST002.DAT
 CompressedBitmaps can have following sizes after decompression:
  Width*Height*2 + 8                   ;normal case
  Width*Height*2 + Align(1000h?) + 8   ;eg. Dino Crisis 2 M_RESULT,ST002.DAT
Note: Dino Crisis DEMO version (MagDemo28: DINO\TRIAL.DAT) does also contain "dummy header" DAT archives (but, unlike as in retail version, they are hidden somewhere inside of the headerless 14Mbyte TRIAL.DAT archive).
Type 7 and 8 are using LZSS compression:
CDROM File Compression LZSS (Dino Crisis 1 and 2)
Apart from LZSS, Type 4 is using SPU-ADPCM compression, and some Type 0 files contain .BS compressed pictures (eg. Dino Crisis 2 PSX\DATA\ST*.DBS\*).


CDROM File Archives with Chunks

Chunk-based archives have chunk headers for each file, but don't have a central directory. That's mainly useful when loading the whole archive to memory.

Interchange File Format (IFF)
IFF has been invented by Electronic Arts in 1985 on Amiga (hence using 2-byte alignment and big-endian size values).
IFF does mainly define a standarized file structure for use with custom group/chunk types (it does also define some Amiga-specific standard audio/video types, but that stuff is barely useful outside of the Amiga world).
The files are starting with a Group Header, followed by data Chunks (or nested Groups):
 Group Header:
  000h 4     Group ID ("FORM") (or "LIST" or "CAT " or "PROP")
  004h 4     Group Size-08h (SIZ) (filesize-8) (big-endian)
  008h 4     Group Type (4-character ASCII) (should be a unique identifier)
  00Ch SIZ-4 Chunk(s), and/or nested Group(s)
 Chunk Format:
  000h 4     Chunk Type (4-character ASCII) (meaning depends on Group Type)
  004h 4     Chunk Size (SIZ) (big-endian)
  00Ch SIZ   Data (eg. .TIM, .VB, .VH or custom data)
  ...  ..    Zeropadding to 2-byte boundary
Used by Forsaken (MagDemo09: FORSAKEN\*\*.BND,MP,PCO)
Used by Perfect Assassin (DATA.JFS\DATA\SCREEN1.LBM)
Used by Star Wars Demolition (MagDemo39,41: STARWARS\*.EXP)
Used by Turbo Prop Racing (MagDemo11: RRACER\*.IFF, except COURSE.IFF)
Used by Viewpoint (VIEW.DIR\*.VCF,*.VCS,*.ST*) (see below Viewpoint IFF notes)
Used by Vigilante 8 (MagDemo09: EXAMPLE\*.EXP)
Used by Wing Commander III (*.LIB\*.IFF)

Viewpoint IFF variant
Viewpoint VIEW.DIR\streams contains custom FORM.VCST groups, all child chunks in such groups are having 0Ch-byte chunk headers:
  000h 4      Chunk ID    (4-letter ASCII)  (VCSP/VCOV or VCBG/VCML/VCMR/FREE)
  004h 4      Chunk Size  (SIZ)             (big-endian)
  008h 4      Extra Value (usually 0..100h) (little-endian)
  00Ch SIZ-4  Body
The VCSP/VCOV chunks are child groups (like nested FORMs), but with the binary Extra Value instead of 4-letter type). The VCBG/VCML/VCMR/FREE are data chunks, but with the Extra value best being treated as part of the chunk header (so the body will contain raw data, like raw .VB data in case of VCBG/VCML).
Bugs in Viewpoint FORMs: fonts\*.vcf have correct Groupsize=Filesize-8, but screens\*.vcf have incorrect Groupsize=Filesize-4, and streams\*.vcf have weirdest random Groupsize=Filesize+(-04h,+08h,+14h,+5A0h,etc.).

Z-Axis little-endian IFF variant
Unlike real IFF, these are using little-endian, and don't have a Group Type entry. There seem to be no nested FORMs. Alignment is kept as 2-byte.
 Group Header:
  000h 4     Group ID ("FORM" or "BODY")
  004h 4     Group Size-08h (SIZ) (little-endian)
  008h SIZ   Chunk(s)
 Chunk Format:
  000h 4     Chunk Type (4-character ASCII)
  004h 4     Chunk Size (SIZ) (little-endian)
  00Ch SIZ   Data
  ...  ..    Zeropadding to 2-byte boundary
ID "FORM" used by Thrasher: Skate and Destroy (MagDemo27: SKATE\ASSETS\*.ZAL\*)
ID "FORM" used by Dave Mirra Freestyle BMX (MagDemo36,46: BMX\ASSETS\*.ZAL\*)
ID "BODY" used by Colony Wars (MagDemo02: CWARS\GAME.RSC\*.BND)
ID "BODY" used by Colony Wars Venegance (MagDemo14: CWV\GAME.RSC\*.BND)

Alice in Cyberland little-endian IFF variant (.TPK)
Same as Z-Axis IFF variant, except Group IDs are different, and the Header sizes are included in the Group/Chunk sizes.
 Group Header:
  000h 4     Group ID ("hTIX","hFNT","hMBD","hHBS")
  004h 4     Group Size (total filesize) (little-endian)
  ...  (8)   Unknown extra (0,0,0,0,0Ch,0,0,0)   ;<-- only in "hHBS" files
  ...  ..    Chunk(s)
 Chunk Format:
  000h 4     Chunk Type ("cCLT","cBIT","cSTR","cMAP","cIDX","cVAB","cSEQ")
  004h 4     Chunk Size (SIZ) (little-endian)
  00Ch SIZ-8 Data
  ...  ..    Maybe Zeropadding to boundary? (Chunk Size is always N*4 anyways)
ID "hTIX" used by Alice in Cyberland (ALICE.PAC\alice.tpk, csel.tpk, etc.)
ID "hFNT" used by Alice in Cyberland (ALICE.PAC\alice.tpk, juri.tpk, etc.)
ID "hMBD" used by Alice in Cyberland (ALICE.PAC\*.FA2\*.MBD)
ID "hHBS" used by Alice in Cyberland (ALICE.PAC\0x_xx.HBS)

Touring Car Championship (MagDemo09: TCAR\GAME\*\*.BFX)
Jarret & LaBonte Stock Car Racing (MagDemo38: WTC\*\*.BFX)
Contains several simple chunks:
  000h 4     Chunksize in bytes (SIZ) (usually a multiple of 4)
  004h SIZ   Chunkdata (eg. .TIM file or other stuff)
There is no end-marker in last chunk (it simply ends at total filesize).

Colony Wars Venegance (MagDemo14: CWV\GAME.RSC\VAG.WAD)
Colony Wars Red Sun (MagDemo31: CWREDSUN\GAME.RSC\0002\VAG_WAD)
Contains several simple chunks with filenames:
  000h 0Ch   Chunk Filename ("filename.ext", zeropadded if shorter)
  00Ch 4     Chunk Data Size in bytes (SIZ)
  010h SIZ   Chunk Data (usually VAGp files, in VAG.WAD)
There is no end-marker in last chunk (it simply ends at total filesize).
Red Sun VAG_WAD is a bit odd: The "extension" is _WAD instead .WAD, the chunk names include prefix "RedSun\", which leaves only 5 chars for the actual name, causig duplicated names like "RedSun\laser" (which were supposedly meant to be named laser1, laser2, laser3 or the like), and many of the Red Dun VAG files contain damaged 30h-byte VAG header entries, eg. zero instead of ID "VAGp").

Mat Hoffman's Pro BMX (new demo) (MagDemo48: MHPB\STILLS.BIN)
Contains .BS files in several chunks:
  000h ..    Chunk(s) (.BS files with extra header info)
  ...  4     End Marker (00000000h)
 Chunk format:
  000h 4     Chunk size (including whole chunk header)
  004h 2     Bitmap Width  (eg. F0h)
  006h 2     Bitmap Height (eg. 80h)
  008h 2     Data Size/4 (same as (Chunksize-0Ch-filenamelen)/4)
  00Ah 2     MDEC Size/4 (same as at Data[0])
  00Ch ..    Filename (eg. "lsFact",00h or "bsRooftop1",00h)  ;\filename field
  ...  ..    Filename Zeropadding to 4-byte boundary          ;/
  ...  ..    Data (in BS v2 format) (MDEC Size/4, BS ID 3800h, etc.)
Note: STILLS.BIN exists in newer BMX demo in MagDemo48 only (not in MagDemo39).

Doom PSXDOOM\*\*.IMG (bitmap chunks)
The IMG files consist of several chunks in following format:
  000h 4    Chunk Size (18h plus size of Data and Padding)
  004h 4    Unknown    (80xxxxxxh) (RAM address?)
  008h 4    Unknown    (1D4A00xxh) (LSB usually 08h, or sometimes 01h or 20h)
  00Ch 2    File ID    (0xxxh)
  00Eh 2    Method     (0000h=LZSS Compressed, 0001h=Uncompressed)
  010h 4    Unknown    (80xxxxxxh) (RAM address?)
  014h 4    Unknown    (80xxxxxxh) (RAM address?)
  018h ..   Data       (plus garbage-padding to 4-byte boundary)
The data part does usually contain compressed bitmaps (using the same LZSS compression as in Doom WAD files) (but there are also some small uncompressed bitmaps, eg. MAPSPR01\01C7).

Ridge Racer (TEX*.TMS)
Ridge Racer Revolution (BIG*.TMS)
Ridge Racer Type 4 (MagDemo19+21: R4DEMO\R4.BIN\*\*)
  000h 4     ID (100h)
  004h ..    Chunk(s)
  ...  4     Zero (Chunk Size=0=End)
  ...  ..    Optional zeropadding to 800h-byte boundary (in R4.BIN\*)
Chunk Format:
  000h 4     Chunk Size (SIZ)
  004h SIZ   Chunk Data (TIM file) (note: includes 0x0pix TIMs with palette)

Jet Moto 2 (MagDemo03: JETMOTO2\*.TMS)
Twisted Metal 2 (MagDemo50: TM2\*.TMS)
Contains a fileheader and .TIM files in several chunks:
  000h 8     ID "TXSPC",0,0,0 (aka CPSXT backwards)
  008h 4     Timestamp? (32A5C8xxh)
  00Ch 4     Number of Chunks (N) (can be 0=None, eg. TM2\SCREEN\ARROWS.TMS)
  010h N*4   Unknown
  ...  N*var Chunks
 Chunk format:
  000h 4     Chunk Size-4 (SIZ)
  004h SIZ   Chunk Data (TIM file)

Princess Maker - Yumemiru Yousei (BDY\*.BD and PM.*)
The BDY\*.BD files do simply contain several chunks:
  000h ..   Chunk(s)
The PM.* files do contain several "folders" with fixed size:
  000h ..   Chunk(s) for 1st folder              ;\Foldersizes are:
  ...  ..   Zeropadding to Foldersize-boundary   ;  20000h (PM.DT0 and PM.PCC)
  ...  ..   Chunk(s) for 2nd folder              ;  28000h (PM.MAP)
  ...  ..   Zeropadding to Foldersize-boundary   ;  42000h (PM.SD0)
  ...  ..   etc.                                 ;/
Chunk Format:
  000h 4    Chunk ID   (800000xxh)
  004h 4    Chunk Size (size of Data part, excluding ID+Size)
  008h ..   Data
The Data for different Chunk IDs does usually have a small header (often with w,h,x,y entries, aka width/height, vram.x/y) followed by the actual data body:
  80000004h  x(2),y(2),width(2),height(2)    Bitmap 8bpp          ;PM.PCC,MAP
  80000005h  w(2),h(2),zero(4)               Array32bit(w,h)      ;PM.MAP
  80000006h  x(2),width(2)                   Bitmap Palette       ;PM.*
  80000007h  x(2),y(2),w(1),h(1),zero(2)     Array8bit(w,h)       ;PM.MAP
  80000010h  width(2),height(2),x(2),y(2)    Bitmap 16bpp         ;*.BD
  80000012h  zero(0)                         ?                    ;*.BD
  80000014h  x(2),y(2),width(2),height(2)    Bitmap 4bpp          ;PM.DT0
  80000016h  x(2),y(2),w(1),h(1),n(1),3Fh(1) BitmapArray4bpp(n*2) ;PM.DT0
  80000018h  ...                             ?                    ;PM.PCC
  8000001Ah  zero(8)                         ?                    ;PM.PCC
  8000001Ch  x(2),y(2),width(2),height(2)    Bitmap 1bpp flags?   ;*.BD
  80000020h  zero(8)                         Sound .SEQ file      ;PM.SD0
  80000021h  zero(8)                         Sound .VH file       ;PM.SD0
  80000022h  zero(8)                         Sound .VB file       ;PM.SD0
  80000024h  x(2),zero(6)                    ?                    ;PM.DT0\4\0
  00000000h  Zeropadding to next folder      Zeropadding          ;PM.*

Project Horned Owl (COMDATA.BIN, DEMODATA.BIN, ROLL.BIN, ST*DATA.BIN)
  000h ..    Chunks
Chunk Format:
  000h 1     Chunk Type (see below)
  001h 3     Unknown (some flags or file ID, or zero in many files)
  004h 4     Chunk Size (SIZ)
  008h SIZ   Chunk Data (eg. SEQ file)
Chunk Type values:
  02h  unknown                      ST*.BIN
  05h  .TXT                         ROLL.BIN
  05h  LZ-compressed TIM            DEMODATA.BIN, ST*.BIN (except ST1*.BIN)
  06h  DOT1 with stuff and TSQ??    ST*.BIN
  07h  .TMD                         DEMODATA.BIN, ST*.BIN (except ST1*.BIN)
  08h  unknown                      ST*.BIN
  09h  "PRM:"                       ST*.BIN
  0Ah  unknown                      ST*.BIN
  0Bh  DOT1 with stuff              ST*.BIN (except ST1*.BIN) (odd: ST3*.BIN)
  0Ch  .SEQ                         ROLL.BIN, ST*.BIN
  0Dh  unknown                      COMDATA.BIN
  0Eh  unknown                      ST*.BIN
  0Fh  DOT1 with LZ-compressed TIMs ST*.BIN
  10h  DEFLATE-compressed TIM       COMDATA.BIN, ROLL.BIN, ST*.BIN
  11h  DOT1 with stuff              ST*.BIN
  Note: Type=05h can be uncompressed TXT or compressed TIM.
For detection, the existing .BIN files start with following values:
  07 00 00 00 xx xx 00 00 41 00 00 00 ..   TMD Model ("A")
  0C 00 00 00 xx xx 00 00 70 51 45 53 ..   SEQ Midi  ("pQES")
  0E xx 00 00 08 00 00 00 xx xx xx xx ..   Whatever in ST7DATA.BIN (see note)
  10 01 00 00 24 28 00 00 EC 9B 7F 70 ..   Deflated TIM in COMDATA.BIN
  10 08 1A 00 30 0C 00 00 ED 58 4F 88 ..   Deflated TIM in ROLL.BIN
  ST7DATA.BIN has 2 chunks with Type=0Eh, followed by SEQ chunk at offset=20h.
TIMs are compressed via HornedLZ (Type=05h,0Fh) or Deflate (Type=10h).
CDROM File Compression HornedLZ
CDROM File Compression ZIP/GZIP/ZLIB (Inflate/Deflate)
The game's Inflate function does ignore the 2bit blocktype: All blocks must have dynamic trees (fixed trees and uncompressed blocks aren't supported).

Blaster Master (DATA\*.IDX, DATA\*.DAT)
DATA\GRP.IDX, DATA\MAP.IDX, DATA\SEQ.IDX DATA\VAB.IDX:
  000h N*2  Chunk List (16bit Offset/800h to Part-1-Chunks in .DAT files)
  ...  ..   Zeropadding to 800h-byte boundary
  Notes:
  The Chunk List can contain zeroes (as first entry at offset 0, and as
  unused entries; in VAB.IDX those can be followed by further USED entries).
  For 2-part DAT files, the Chunk List contains offsets for Part 1 only.
DATA\SEQ.DAT:
  000h 4    Chunksize/800h                                           ;\
  004h 4    Datasize in bytes                                        ; Single
  008h 4    Always 015A5A01h or 015A5A00h                            ; Part
  00Ch 4    Always 2803h                                             ; with
  010h ..   Midi data .SEQ file                                      ; 1 file
  ...  ..   Zeropadding to 800h-byte boundary                        ;/
DATA\VAB.DAT:
  000h 4    Chunksize/800h                                           ;\
  004h 4    Size of .VH Voice Header in bytes                        ; Single
  008h 4    Size of .VB Voice Binary in bytes                        ; Part
  00Ch ..   Voice Header .VH file                                    ; with
  ...  ..   Zeropadding to 800h-byte boundary                        ; 2 files
  ...  ..   Voice Binary .VB file                                    ;
  ...  ..   Zeropadding to 800h-byte boundary                        ;/
DATA\GRP.DAT and DATA\MAP.DAT:
  000h 4    Part 1 Chunksize/800h                                    ;\
  004h 4    Size of all TIM files in bytes (can be 0=None)           ; Part 1
  008h ..   Texture data (several TIMs appended after each other)    ;
  ...  ..   Zeropadding to 800h-byte boundary                        ;/
  ...  4    Number of Files (N)                                      ;\
  ...  4    Part 2 Chunksize/800h                                    ;
  ...  N*8  File List                                                ; Part 2
  ...  ..   Garbage-padding to 800h-byte boundary?                   ;
  ...  ..   File Data area (each file Garbage-padded to 800h-byte)   ;
 File List entries:                                                  ;
  000h 4    File Type/ID                                             ;
  004h 4    Size in bytes                                            ;/
The DAT files are chunk-based (unfortunately, each DAT file is using its own chunk format, some of them are using 2-part chunks).
The DAT chunks can be parsed without using the IDX file (the IDX can be helpful for quick lookup, but even then, one will still need to parse the DAT chunk headers to find the actual contents like TIM, SEQ, VB, VH files).

Misadventures of Tron Bonne chunks (DAT\*.BIN)
The BIN files do start with chunk type 0, 1 or 5 (type 8 occurs only later on, after type 5). Computing the sectors per chunk requires messy chunk-dependent calculations:
  type 0 --> sectors=([04h]+7FFh+40h)/800h                  ;misc
  type 1 --> sectors=([04h]+7FFh)/800h                      ;vram
  type 5 --> sectors=([24h]+7FFh)/800h+([2Ch]+7FFh)/800h+1  ;adpcm
  type 8 --> sectors=([04h]+7FFh+800h)/800h                 ;midi
Type 00h, Misc data:
  000h 4     Chunk Type (00h)
  004h 4     Chunk Size in Bytes     (SB)                ;-excluding hdrsiz
  008h 4     Chunk Size in Sectors   (SB+40h+7FFh)/800h  ;-including hdrsiz
  00Ch 08h   Zerofilled
  014h 4     Unknown                 (xxh)
  018h 4     Main RAM Address ?      (80xxxx00h)
  01Ch 24h   Zerofilled
  040h SB    Data
  ...  ..    Zeropadding to 800h-byte boundary
Type 01h, VRAM Data:
  000h 4     Chunk Type (01h)
  004h 4     Chunk Size in Bytes     (SB+800h)           ;\including hdrsiz
  008h 4     Chunk Size in Sectors   (SB+800h+7FFh)/800h ;/
  00Ch 04h   Zerofilled
  010h 4     Unknown                 (0 or 1000h)
  014h 4     Unknown                 (0 or 1)
  018h N*20h Bitmap List             (see below)
  ...  20h   Bitmap List End Code    (0,0,0,0,FFFFFFFFh,0,0,0)
  ...  ..    Zeropadding to 800h-byte boundary
  800h SB    Data   ;for Width*2*Height bytes of all bitmap(s)
  ...  ..    Zeropadding to 800h-byte boundary
 Bitmap List entry format:
  000h 4     VRAM Address X (140h or 380h or 3C0h etc)
  004h 4     VRAM Address Y (0 or 100h or 0Fxh or 1Fxh)
  008h 4     Bitmap Width  (in halfwords)
  00Ch 4     Bitmap Height
  010h 4     Bitmap Size   (Width*Height*2)+0,E0h,100h,1E0h (buggy)
  014h 4     Bitmap Type   (0=Bitmap, 1=Palette)
  018h 08h   Zerofilled
Type 05h, Audio SPU-ADPCM Data:
  000h 4     Chunk Type (05h)
  004h 4     Chunk Size in Bytes     (SH+SB)             ;\weirdly, excluding
  008h 4     Chunk Size in Sectors   (SH+SB+7FFh)/800h   ;/hdrsiz and paddings
  00Ch 08h   Zerofilled
  014h 4     Unknown                 (000000xxh)
  018h 4     Unknown                 (000000xxh)
  01Ch 4     Unknown                 (000000xxh)
  020h 4     SPU RAM Address ?       (000xxxx0h)
  024h 4     Size of .VH file (SH)   (0000xx20h)
  028h 04h   Zerofilled
  02Ch 4     Size of .VB file (SB)   (000xxxx0h)
  030h 7D0h  Zerofilled
  800h SH    Data for .VH file
  ...  ..    Zeropadding to 800h-byte boundary
  ...  SB    Data for .VB file
  ...  ..    Zeropadding to 800h-byte boundary
Type 08h, Audio MIDI data:
  000h 4     Chunk Type (08h)
  004h 4     Chunk Size in Bytes     (SB)                ;\excluding hdrsiz
  008h 4     Chunk Size in Sectors   (SB+7FFh)/800h      ;/
  00Ch 0Ch   Zerofilled
  018h 4     Unknown                  (usaully 1)
  01Ch 4     Unknown                  (usually 0..2Bh)
  020h 4     Number of MIDI sequences (usually 1..3)
  024h 7DCh  Zerofilled
  800h SB    MIDI Sequence(s)
  ...  ..    Zeropadding to 800h-byte boundary
 MIDI Sequence format:
  000h 4     Size in bytes (including sequence header and padding)
  004h 3     Unknown    ;\maybe resolution    (xxh,xxh,0xh)
  007h 3     Unknown    ;/and/or tempo?       (00h,E0h,01h)
  00Ah 2     Rhythm (NN/NN) ?                 (04h,02h)
  00Ch ...   Score data (with many MIDI KeyOn's: 9x,xx,xx,tt)
  ...  3     End of SEQ (2Fh=End of Track)    (FFh,2Fh,00h)
  ...  ..    Zeropadding to 4-byte boundary

See also
CDROM File Archive Darkworks Chunks (Alone in the Dark)
CDROM File Archive Blue Chunks (Blue's Clues)
CDROM File Archive HED/CDF (Parasite Eve 2)
CDROM File Compression LZSS (Serial Experiments Lain)
CDROM File Compression SLZ/01Z (chunk-based compressed archive)


CDROM File Archives with Folders

There are several ways to implement folder-like directory trees:
  - Using multiple archive files nested within each other
  - Using filenames with path string (eg. "path\filename.ext")
Other than that, below are special formats with dedicated folder structures.

Archives with Folders
CDROM File Archive HUG/IDX/BIZ (Power Spike)
CDROM File Archive TOC/DAT/LAY
CDROM File Archive WAD (Doom)
CDROM File Archive WAD (Cardinal Syn/Fear Effect)
CDROM File Archive DIR/DAT (One/Viewpoint)
CDROM File Archive HED/CDF (Parasite Eve 2)
CDROM File Archive IND/WAD (MTV Music Generator)
CDROM File Archive GAME.RSC (Colonly Wars Red Sun)
CDROM File Archive BIGFILE.DAT (Soul Reaver)
CDROM File Archive FF8 IMG (Final Fantasy VIII)
CDROM File Archive FF9 IMG (Final Fantasy IX)
CDROM File Archive GTFS (Gran Turismo 2)
CDROM File Archive Nightmare Project: Yakata
CDROM File Archive FAdj0500 (Klonoa)
See also: PKG (a WAD.WAD variant with folders)

Perfect Assassin (*.JFS)
 Overall File Structure
  JFS for root                                   ;\
  JFS for 1st folder   ;\these are dupicated,    ; header with complete list
  JFS for 2nd folder   ; also stored in below    ; of all file/folder names
  JFS for 3rd folder   ; data area               ;
  etc.                 ;/                        ;/
  JFS for 1st folder, plus data for files in that folder  ;\
  JFS for 2nd folder, plus data for files in that folder  ; data area
  JFS for 3rd folder, plus data for files in that folder  ;
  etc.                                                    ;/
JFS Headers (0Ch+N*14h bytes)
  00h 4     ID "JFS",00h
  04h 4     Size in bytes (for root: including nearby child JFS's)
  08h 4     Number of file/folder entries in this folder (N)
  0Ch N*14h File/Folder entries
File Entries (with [10h].bit31=0):
  00h 12  "FILENAME.EXT" (or zeropadded if shorter)
  0Ch 4   Offset from begin of JFS in data area (without any alignment)
  10h 4   Size in bytes, plus 00000000h=File
Folder Entries (with [10h].bit31=1):
  00h 12  "DIRNAME.EXT" (or zeropadded if shorter)
  0Ch 4   Offset to child JFS in data area
  10h 4   Offset to child JFS in header area, plus 80000000h=ChildFolder
The JFS format is almost certainly unrelated to IBM's "Journaled File System".

Alone in the Dark The New Nightmare (FAT.BIN=Directory, and DATA.BIN=Data)
 FAT.BIN:
  00h 2     Number of folders (X) (43h)
  02h 2     Number of files   (Y) (8F0h)
  04h 4     Unknown               (1000h)
  08h X*10h Directory Entry 0000h..X-1 (entry 0000h is named "ROOT")
  ..  Y*10h File Entry 0000h..Y-1
 DATA.BIN:
  00h ..    File Data area
Directory Entries (10h bytes):
  00h 8    Name (terminated by 00h if less than 8 chars)
  08h 2    First Subdirectory number (0001h and up, 0000h would be root)
  0Ah 2    Number of Subdirectories  (0000h=None, if so above is usually 00FFh)
  0Ch 2    First File number         (0000h and up)
  0Eh 2    Number of files           (0000h=None, if so above is usually 00FFh)
File Entries (10h bytes):
  00h 8    Name (terminated by 00h if less than 8 chars)
  08h 4    Offset/800h to DATA.BIN
  0Ch 4    Size in bytes (when compressed: decompressed size+02000000h)
Compressed files (in LEVELS\*\* with Size.bit25=1) can be decompressed as so:
CDROM File Compression Darkworks
The files include some TIM images, WxH images, binary files, and chunks:
CDROM File Archive Darkworks Chunks (Alone in the Dark)

Interplay Sports Baseball 2000 (MagDemo22: BB2000\* HOG.DAT and HOG.TOC)
 HOG.TOC:
  000h N*14h Folder/File List (starting with root folder)
 HOG.DAT:
  000h ..    File Data (referenced from HOG.TOC)
Folder entries:
  000h 1     Type      ("D"=Directory)
  001h 8     Name      ("FILENAME", zeropadded if shorter) (or "\" for root)
  009h 3     Extension (usually zero for directories)
  00Ch 4     Folder Offset/14h in .TOC file (aka 1st child file/folder index)
  010h 4     Folder Size/14h                (aka number of child files/folders)
File entries:
  000h 1     Type      ("F"=File)
  001h 8     Name      ("FILENAME", zeropadded if shorter)
  009h 3     Extension ("EXT", zeropadded if shorter)
  00Ch 4     File Offset/800h in .DAT file (increasing)
  010h 4     File Size in bytes

Tenchu 2 (MagDemo35: TENCHU2\VOLUME.DAT)
  000h 4     Unknown (demo=A0409901h, us/retail=A0617023h)
  004h 4     Unknown (0h)
  008h 4     Number of files   (F) (demo=B7h, us/retail=1294h)
  00Ch 4     Number of folders (D) (demo=0Fh, us/retail=3Eh)
  010h D*8   Folder List
  ...  ..    Zerofilled (padding to 800h-byte boundary)
  800h F*10h File List
  ...  ..    Zerofilled (padding to 800h-byte boundary)
  ...  ..    File Data area
Folder List entries:
  000h 4     Folder ID (Random, maybe folder name checksum?)
  004h 4     First file number in this folder (0=first, increasing)
File List entries:
  000h 4     File Offset/800h
  004h 4     File Size in bytes
  008h 4     Folder ID (same as Parent Folder ID in Folder List)
  00Ch 4     File ID (Random, maybe file name checksum?)

Blasto (MagDemo10: BLASTO\BLASTO.DAT and BLASTO\BLASTO.LFS)
 LFS:
  000h N*18h File/Folder List
 DAT:
  000h ..    File data
File entries (with [10h]=Positive):
  000h 10h   Filename ("FILENAME.EXT", zeropadded)
  010h 4     Offset in bytes, in BLASTO.DAT
  014h 4     Size in bytes
Folder entries (with [10h]=Negative):
  000h 10h   Foldername ("DIRNAME", zeropadded)
  010h 4     Index to first child (at Offset=(-Index)*18h in BLASTO.LFS)
  014h 4     Zero
Folder end marker (with [00h]=00h or 80h):
  000h 1     End marker, at end of root & child directories (00h or 80h)
  001h 17h   Unknown

Hamster Club-i (DATA00.LD)
Root Folder (contains child folders):
  000h 4     Root ID (20001107h)
  004h 4     Number of Folders (N)
  008h N*0Ch Folder List
  ...  ..    Zeropadding to 800h-byte boundary
  ...  ..    Child Folder area
 Folder List entries:
  000h 4   Offset/800h (from begin of Child Folder area) (increasing)
  004h 4   Size in bytes
  008h 4   Number of files in child directory
Child Folders (contain files):
  000h 4     Child ID (20001108h)
  004h 4     Number of Files (N) (same as in Folder List entry)
  008h N*08h File List
  ...  ..    Zeropadding to 800h-byte boundary
  ...  ..    1st File Data
  ...  ..    Zeropadding to 800h-byte boundary
  ...  ..    2nd File Data
  ...  ..    Zeropadding to 800h-byte boundary
  ...  ..    etc.
 File List entries:
  000h 4   Unknown (0 or 1 or 2)
  004h 4   Size in bytes

Twisted Metal 4 (MagDemo30: TM4DATA\*.MR and *.IMG)
These are relative small archives with hundreds of tiny chunks (with registry style Symbol=Value assignments), and a few bigger chunks (with .mod .vab .bit .clt files).
  000h 4     Fixed ID (CCCC0067h)
  004h ..    Root Folder (with Name="Root",00h,FDh,FDh,FDh)
 Folder Chunk format:
  000h 1     Length of Name (including 4-byte padding)
  001h 1     Number of Child Folders
  002h 2     Number of Child Files
  004h ..    Name ("name",00h, CDh-padded to 4-byte boundary; Root=FDh-padded)
  ...  ..    Child File(s)
  ...  ..    Child Folder(s)
 File Chunk format:
  000h 1     Length of filename (including 4-byte padding)
  001h 1     Filetype           (see below)
  002h 2     Array Size         (or FFFFh for non-array filetypes)
  004h 4     Filesize (SIZ)     (including 4-byte padding)
  008h 4     Decompressed Size  (or 0=Uncompressed)
  00Ch ..    Filename/Symbol    ("name.ext",00h, CDh-padded to 4-byte boundary)
  ...  SIZ   Data/Value         (CDh-padded to 4-byte boundary)
Some filenames have trailing non-ascii characters, for example:
  "AXEL.MR\display\resolution\r3\Groups\Combined_Polyset",1Ah,01h,04h,00h
  "CALYPSO.MR\display\resolution\r3\Groups\Combined_Polyset",A8h,00h, CDh,CDh
Filetypes:
  Typ Size  Expl.
  02h var   Text String (terminated by 00h, garbage-or-00h-padded to 4-byte)
  03h 8     Misc (*.IMG\textures\*)                          ;\
  03h 20h   Misc (*.MR\display\resolution\r*\Groups\*)       ; these are all
  03h var   Misc (*.MR\display\resolution\*List)             ; filetype=03h
  03h file  Misc (*.MR\display\*.bit) (same as type=0Ch)     ;/
  04h 4     Numeric 32bit
  05h 8     Numeric 4x16bit point (X,Y,Z,CDCDh)
  06h file  Model (*.mod) (DOTLESS archive with model data)
  0Bh 4     Numeric 32bit repeat,light
  0Ch file  XYWH Bitmap/Palette (*.bit, *.clt) (in GAME.IMG, MENU\menu)
  0Dh 4     Numeric 32bit delay
  0Eh 4     Numeric 32bit color (maybe 24bit RGB plus 00h-padding?)
  0Fh 10h   Whatever 10h-byte "pos"
  10h file  Sony .VAB file (*.vab)
  12h N*1   Array? (with Arraysize=0014h)
  16h N*??  Array Text Strings (with Arraysize=0001h) (in MAIN.MR\worlds)
  1Ah N*10h Array Guns,startpoints (RCCAR.MR\*, NEON.MR\world)
  1Bh 4     Numeric 2x16bit (X,Y) (in MENU.MR)
  1Ch N*4   Array lloc (in MENU.MR\menu\screens) (with Arraysize=04h or 1Fh)
  25h 8     Whatever 8-byte (in GAME.MR\dualShock)
  26h N*8   Array CollideArray (in GAME.MR\dualShock) (with Arraysize=4 or 6)
Compressed Data (when [008h]<>0):
  000h ..    ZLIB compressed data (usually starting with big-endian 789Ch)
  (compression is used for almost all files, except VERY small ones)
CDROM File Compression ZIP/GZIP/ZLIB (Inflate/Deflate)


CDROM File Archive HUG/IDX/BIZ (Power Spike)

Power Spike (MagDemo43: POWER\GAME.IDX and .HUG)
POWER\GAME.HUG
  000h ..    File Data
POWER\GAME.IDX
  000h 4     ID "HUGE"
  004h 4     Checksum (sum of all bytes at [010h and up])
  008h 4     Number of Folders (D) (87h)
  00Ch 4     Number of Files   (F) (F9h)
  010h D*1Ch Folder List (Folder 0..D-1)
  ...  F*18h File List   (File 0..F-1)
Folder List entries:
  000h 0Ch   Folder Name ("DIRNAME", zeropadded)
  00Ch 4     First Child File      (or FFFFFFFFh=None)
  010h 4     Number of Child Files (or 00000000h=None)
  014h 4     First Child Folder    (or FFFFFFFFh=None)
  018h 4     Next Sibling Folder   (or FFFFFFFFh=None)
File List entries:
  000h 0Ch   File Name ("FILENAME.EXT", zeropadded if shorter than 12)
  00Ch 4     File Checksum (sum of all bytes in file added together)
  010h 4     File Offset/800h in GAME.HUG
  014h 4     File Size in bytes
The root entries are Folder 0 (and its siblings). That is, the root can contain only folders (not files).
The IDX/HUG archive contains many BIZ archives (and some TXT files).

Power Spike (MagDemo43: POWER\GAME.IDX\*.BIZ) (BIZ nested in IDX/HUG)
  000h 4     ID "BIG!"
  004h 4     Number of entries (N)
  008h N*1Ch File List
  ...  ..    BIZ compressed File Data
File List entries
  000h 10h   Filename (zeropadded)
  010h 4     File Offset (increasing, unaligned, can be odd)
  014h 4     File Size decompressed
  018h 4     File Size compressed
All files in the BIZ archive are BIZ compressed (unknown if it does also support uncompressed files).
CDROM File Compression LZ5 and LZ5-variants
The BIZ archive seems to be solely containing PSI bitmaps (even files in GAME.IDX\SOUND\MUSIC\*.BIZ do merely contain PSI bitmaps, not audio files).


CDROM File Archive TOC/DAT/LAY

Used in PSX Lightspan Online Connection CD (CD.TOC, CD.DAT, CD.LAY).
  CD.TOC contains File/Folder entries
  CD.DAT contains the actual File bodies
  CD.LAY devkit leftover (list of filenames to be imported from PC to TOC/DAT)
The .TOC file doesn't have any file header, it does just start with the first File/Folder folder entry in root directory. The directory chains with file/folder entries are sorted alphabetically, each chain is terminated by a final entry which does point to parent directory.

File Entries
  00h 4   Offset to next Sibling File/Folder/Final entry
  04h 4   Filesize in bytes
  08h 4   Filedata Offset/800h in CD.DAT
  0Ch ..  Filename (ASCII, terminated by 00h)
  ... ..  Padding to 4-byte boundary (garbage)

Folder Entries (with Filesize=FFFFFFFFh)
  00h 4   Offset to next Sibling File/Folder/Final entry
  04h 4   Filesize (always FFFFFFFFh in Folder entries)
  08h 4   Offset to first File/Folder in Child directory
  0Ch ..  Name of Child directory (ASCII, terminated by 00h)
  ... ..  Padding to 4-byte boundary (garbage)

Final Entries (with Name="",00h and Filesize=FFFFFFFxh)
  00h 4   Offset to next Sibling entry (00000000h=None)
  04h 4   Filesize (FFFFFFFFh in child folders, FFFFFFFEh in root folder)
  08h 4   Offset to first File/Folder in Parent directory (or to self for root)
  0Ch 1   Empty Name ("",00h)
  0Dh 3   Padding to 4-byte boundary (garbage)


CDROM File Archive WAD (Doom)

Doom, PSXDOOM\ABIN\*.WAD and PSXDOOM\MAPDIR*\*.WAD)
The .WAD format is used by Doom (for DOS, Jaguar, PSX, etc), various homebrew Doom hacks, and some other developers have adopted the format and used .WAD in other game engines.
  000h 4     ID "IWAD" (or "PWAD" for homebrew patches, or "PACK" in A.D. Cop)
  004h 4     Number of File List entries (N) (including final ENDOFWAD entry)
  008h 4     Offset to Directory Area (filesize-N*10h)
  00Ch ..    File Data area
  ...  N*10h File List
File List entries:
  000h 4   Offset to file data (increasing by compressed size, 4-byte aligned)
  004h 4   Filesize in bytes   (uncompressed size) (zero in ENDOFWAD file)
  008h 8   Filename (uppercase ASCII, zeropadded if less than 8 chars)

Folders
The directory can contain names like F_START, F_END, P1_START, P1_END with filesize=0 to mark begin/end of something; that stuff can be considered as subdirectories with 1- or 2-character names.
Notes: There are also regular files with underscores which are unrelated to folders (eg. F_SKY01). There are also 0-byte dummy files (eg. MAP17 in first entry MAP17.WAD). And there's a 0-byte dummy file with name ENDOFWAD in last file list entry (at least, it's present versions with compression support).

LZSS Decompression (used in PSXDOOM\*\*.WAD and PSXDOOM\*\*.IMG)
In .WAD files, compression is indicated by Filename[0].bit7=1. The compressed size is NextFileOffset-FileOffset (that requires increasing offsets in File List, including valid offsets for 0-byte files like F_START, F_END, ENDOFWAD).
In .IMG files, compression is indicated by ChunkHdr[0Eh].bit0=0. Compressed size is chunksize-18h, uncompressed size can be only determined after decompressing the file.
  @@collect_more:
   flagbits=[src]+100h, src=src+1    ;8bit flags
  @@decompress_lop:
   flagbits=flagbits SHR 1
   if zero then goto @@collect_more
   if carry=0 then
     [dst]=[src], dst=dst+1, src=src+1
   else
     disp=([src]*10h)+([src+1]/10h)+1, len=([src+1] AND 0Fh)+1, src=src+2
     if len=1 then goto @@decompress_done
     for i=1 to len, [dst]=[dst-disp], dst=dst+1, next i
   endif
   goto @@decompress_lop
  @@decompress_done:
   ret
The game engine may insist on some files to be compressed or uncompressed (so compression may be required even if the uncompressed data would be smaller).

More info: http://doomwiki.org/wiki/WAD

Apart from WAD, another Doom file format is...

Doom PSXDOOM\*\*.LCD files (sound samples)
  000h 2    Number of Files (N) (usually 01h..3Eh)
  002h 2*N  File IDs
  ...  ..   Zeropadding to 800h-byte boundary
  800h ..   SPU-ADPCM Data (aka .VB files)
There is no offset/size information for the VB files (however, each VB file does consist of 16-byte ADPCM blocks; the 1st block is usually zerofilled, and the last block contains an end-flag in byte[01h].bit0) (for whatever reason, some files have extra blocks appended after the last file, eg. MUSIC\MUSLEV10.LCD).


CDROM File Archive WAD (Cardinal Syn/Fear Effect)

.WAD files (Cardinal Syn/Fear Effect)
This format exists in two version:
  Old format: Without leading Header Size entry (Cardinal Syn MagDemo03: SYN\*)
  New format: With leading Header Size entry    (eg. Fear Effect)
Version detection could be done somewhat as so:
  if [04h]*1Ch+8 >= [00h] then OLD version
For loading the Old Header, one must guess the max header size (4000h should work, in fact, most or all Old Headers seem to be max 800h), or load more data on the fly as needed.
  000h (4) Header Size (including folder/type/file directories) (new version)
  ...  4   Number of Folders
  ...  ..  Folder List (root)
  ...  ..  Type Lists  (for each folder)
  ...  ..  File Lists  (for each folder\type)
  ...  ..  File Data   (for each folder\type\file)
 Folder List Entries:
  000h 14h Folder name (ASCII, zeropadded)
  014h 4   Offset to Type List
  018h 4   Number of different Types in this folder
 Type List Entries:
  000h 4   Offset to file entries (of same type, eg. .TIM files)
  004h 4   Number of file entries (of same type, eg. .TIM files)
  008h 4   Sum of all Filesizes with that type
  00Ch 4   Group Type (0000000xh)
 File List entries (Files within Type list):
  000h 14h Name (ASCII, terminated by 00h, plus garbage padding)
  014h 4   Offset to File Data  (seems 4-byte aligned... always?)
  018h 4   File Type (000x00xxh)
  01Ch 4   Filesize in bytes  ;\maybe compressed/uncompressed, or rounded,
  020h 4   Filesize in bytes  ;/always both same
Note: The Type List for one folder can contain several entries with same Group Type, eg. Fear Effect GSHELLE.WAD\CREDIT has 5 type list entries (with 2xGroup0, 2xGroup1, 1xGroup2).

The Type List, Group Type and File Type stuff seems to have no function, apart from faster look up (the types are also implied in the filename extension). Except, Fear Effect .RMD .VB .VH have some unknown stuff encoded in File Type bit16-19.
Group Type is usually 0 (except for .TIM .VB .VH .MSG .SPU .OFF).
The .TIM .VB .VH .SEQ files are using standard Sony file formats. The .PMD file seems to be also Sony standard (except that it contains a 00000000h prefix, then followed by the 00000042h PMD format ID).

Cardinal Syn Types
  .BGD FileType=00000001h
  .ANM FileType=00000003h
  .TIM FileType=00000004h (GroupType=1)
  .SP2 FileType=00000005h
  .PMD FileType=00000007h
  .MOV FileType=00000008h
  .SPR FileType=0000000Ch
  .PVT FileType=0000000Dh
  .DB  FileType=0000000Eh
  .VH  FileType=00000010h (GroupType=1) ;only in OLDER demo version MagDemo03
  .VB  FileType=00000011h (GroupType=1)
  .MSG FileType=00000012h (GroupType=1) (actually, this is .TIM, too)
  .KMD FileType=00000013h
  .OC  FileType=00000018h
  .EMD FileType=00000019h
  .COL FileType=0000001Bh
  .CF  FileType=0000001Ch
  .CFB FileType=0000001Dh
  .CL  FileType=0000001Eh
  .SPU FileType=0000001Fh (GroupType=1) ;added in newer demo version MagDemo09
  .OFF FileType=00000020h (GroupType=1) ;added in newer demo version MagDemo09
  .RCT FileType=00000021h               ;added in newer demo version MagDemo09

Fear Effect Types
  .TIM FileType=00000000h (GroupType=1)
  .RMD FileType=000x0001h
  .DB  FileType=00000002h
  .ANM FileType=00000003h
  .SYM FileType=00000004h
  .VB  FileType=000x0008h (GroupType=1)
  .SEQ FileType=00000010h
  .BIN FileType=00000012h
  .SFX FileType=00000013h
  .VH  FileType=000x0014h (GroupType=2)
  .TM  FileType=00000015h
  .NRM FileType=00000017h
  .WPD FileType=00000018h


CDROM File Archive DIR/DAT (One/Viewpoint)

DIR/DAT (One/Viewpoint)
  Used by One (DATAFILE.BIN and DIRFILE.BIN)
  Used by Viewpoint (VIEW.DAT and VIEW.DIR)
Format of the DIR file:
  000h 60h Extension List (20h x 3-char ASCII, zeropadded if shorter than 3)
  060h ..  Root Directory    (can contain folders and files)
  ...  ..  Child Directories (can contain files) (maybe also sub-folders?)
Extension List contains several uppercase 3-character ASCII extensions, in a hex editor this will appear as a continous string of gibberish (dots=00h):
  In Viewpoint: "...VCSVCFBINTXTVH.VB.STRST1ST2ST3......//..."
  In One:       "...VCTVCKSNDBINCPEINI..................//..."
Directory Entries contain bitstreams with ASCII characters squeezed into 6bit values:
  000h 1   Length of Filename and Extension index
             bit7-3  File Extension Index (0..1Fh = Offset I*3 in DIR file)
             bit2-0  Filename Length-1    (0..7 = 1..8 chars)
  001h ..  Filename in 6bit chars (N*6+7/8 bytes = 1..6 bytes for 1..8 chars)
             bit7-2  1st character, whole 6bit            ;\1st byte
             bit1-0  2nd character, upper 2bit (if any)   ;/
             bit7-4  2nd character, lower 4bit (if any)   ;\2nd byte (if any)
             bit3-0  3rd character, upper 4bit (if any)   ;/
             bit7-6  3rd character, lower 2bit (if any)   ;\3rd byte (if any)
             bit5-0  4th character, whole 6bit (if any)   ;/
             bit7-2  5th character, whole 6bit (if any)   ;\4th byte (if any)
             bit1-0  6th character, upper 2bit (if any)   ;/
             bit7-4  6th character, lower 4bit (if any)   ;\5th byte (if any)
             bit3-0  7th character, upper 4bit (if any)   ;/
             bit7-6  7th character, lower 2bit (if any)   ;\6th byte (if any)
             bit5-0  8th character, whole 6bit (if any)   ;/
             bitN-0  Zeropadding in LSBs of last byte     ;-zeropadding
           The 6bit characters codes are:
             00h..09h="0..9", 0Ah..23h="a..z", 24h="_", 25h..3Fh=Unused
  ...  4   Filesize and End Flag
             bit31   End of Directory Flag   (0=Not last entry, 1=Last entry)
             bit30-0 Filesize 31bit          (or 0=Child Folder)
  ...  4   Offset and fixed bit
             bit31   Unknown (always 1)
             bit30-0 File Offset in DAT file (or Folder offset in DIR file)


CDROM File Archive Darkworks Chunks (Alone in the Dark)

Alone in the Dark The New Nightmare (FAT.BIN\*)
The files in FAT.BIN are using a messy chunk format: There's no clear ID+Size structure. There are 7 different chunk types (DRAM, DSND, MIDB, G3DB, VRAM, WEAP, HAND), each type requires different efforts to compute the chunk size.

VRAM Chunks (Texture/Palette) (in various files)
  000h 4     ID "VRAM"
  004h 4     With Tags (0=No, 1=Yes) (or "DRAM" when empty 4-byte chunk)
  008h (4)   Number of Tagged items (N) (0=None)  ;\only when [4]=1
  00Ch N*10h Tagged Item(s)                       ;/(not so in LEVELS\*\VIEW*)
  ...  ..    Scanline Rows(s)
  ...  4     End code (00000000h) (aka final Scanline Row with width=0)
 Tagged Item(s) (IMG, LINE, GLOW, FLARE, BALLE, BLINK, COURIER7, BMP_xxx):
  000h 8     Tag (ASCII, if less than 8 chars: terminate by 00h, pad by FDh)
  008h 8     Data
 Scanline Row(s) (bitmap scanlines and palette data):
  000h 4     Header (bit0-8=Width, bit10-18=Y, bit20-29=X, bit9,19,30,31=?)
  004h W*2   Data (Width*2 bytes, to be stored at VRAM(X,Y))
Empty VRAM chunks can be either 4 or 10h bytes tall. The 4-byte variant is directly followed by another chunk name (eg. "VRAMDRAM"), the 10h-byte variant contains four words ("VRAM",WithTags=1,NumTags=0,EndCode=0).
Note: Some files contain two VRAM chunks (eg. LEVELS\*\VIEW*).

G3DB Chunks (Models) (in various files)
  000h 4   ID "G3DB"
  004h 4   Unknown (0, 1, or 2)
  008h 4   Size of Data part (SIZ)
  00Ch 4   Number of List entries (eg. 6 or 0Ah or 117Ch) (N)
  010h SIZ Data (supposedly LibGDX models in G3DB format)
  ...  N*4 List

DRAM Chunks (Text and Binary data) (in various files)
  000h 4   ID "DRAM"
  004h 4   Size of Data part (SIZ) (can be odd)
  008h 4   Number of List entries (N)
  00Ch SIZ Data (raw data, and/or tags TEXT, SPC, COURIER7)
  ...  N*4 List

WEAP Chunks (Weapons) (in WEAPON\*\*)
  000h 4   ID "WEAP"
  004h 4   Size-10h?
  008h ..  Data
Followed by VRAM and DSND chunks.

HAND Chunks (Hands) (in LEFTHAND\*\HAND*)
  000h 4   ID "HAND"
  004h 4   Size-0Ch?  (18h)
  008h 8   Zerofilled
  010h 4x4 Unknown (FFh,FF00h,xF0000h,FF3232h,FF6464h,FFDCDCh,FFFFFFh,..)
  020h 4   Unknown (0, 1, 101h, or 201h)
Followed by VRAM and G3DB chunks.

MIDB Chunks (Music) (in MIDI\*\*)
  000h 4      ID "MIDB"
  004h 1      Unknown (0 or 1)
  005h 1      Number of SEQ blocks              (1..4) (S)
  006h 1      Number of Unknown 80h-byte blocks (1..2) (U)
  007h U*80h  Unknown Blocks (mostly FFh-filled)
  ...  S*Var  SEQ Block(s)
  ...  ..     VAB Block
 SEQ Blocks:
  Probably some MIDI sequence data, similar to Sony's .SEQ format.
  000h 4      Size-0Ch (can be odd)
  004h 8      Name (zeropadded if less than 8 chars)
  00Ch 4      ID "DSEQ"    ;\Size
  010h ..     Data         ;/
 VAB Blocks:
  Apparently inspired on Sony's .VAB format (but the ID is spelled other way
  around, Lists have variable size, and entries have different format).
  000h 4      ID "VABp"  (this is: not pBAV, unlike normal .VAB files)
  004h 4      Unknown (0)
  008h 4      Unknown (0)
  00Ch 4      Size of all SPU-ADPCM samples (SIZ)
  010h 2      Number of List 1 entries (N1)
  012h 2      Number of List 2 entries (N2)
  014h 2      Number of Samples        (N3)
  016h 6      Unused? (CCh-filled)
  01Ch N1*10h List 1
  ...  N2*10h List 2
  ...  N3*2   Sample Size List (size of each SPU-ADPCM sample)
  ...  SIZ    SPU-APDCM Sample(s)

DSND Chunks (Sounds) (in various files)
  000h 4   ID "DSND"
  004h 4   Unknown (0 or 2)
  008h ..  VAB Block (same as in MIDB chunks, see there)

Note
DRAM and MIDB chunks can have odd size; there isn't any alignment padding, so all following chunks can start at unaligned locations.


CDROM File Archive Blue Chunks (Blue's Clues)

Blue's Clues: Blue's Big Musical (*.TXD)
  000h 4    Size of AUDD+SEPD+VABB chunks ;\for quick look-up only
  004h 4    Size of all VRAM chunks       ; (can be ignored by chunk crawlers)
  008h 4    Size of STGE+ANIM+FRAM chunks ;/(note: sum is total filesize-0Ch)
  ...  ..   AUDD Chunk    (contains .VH)                  ;\
  ...  ..   SEPD Chunk(s) (contains .SEP)                 ; sound
  ...  ..   VABB Chunk    (contains .VB)                  ;/
  ...  (..) VRAM Chunk(s) (not in IN\FE2.TXD)             ;-textures/palettes
  ...  (..) STGE Chunk    (if any, not in IN\FE*.TXD)     ;-stage data?
  ...  (..) ANIM Chunk    (if any, not in IN\FE*.TXD)     ;\animation
  ...  (..) FRAM Chunk(s) (if any, not in IN\FE*.TXD)     ;/
  ...  (..) Further groups with ANIM+FRAM Chunks (if any) ;-more animation(s)
 AUDD Chunks:
  000h 4    Chunk ID ("AUDD")
  004h 4    Chunk Size (of whole chunk from Chunk ID and up)
  008h 4    Compression Flag (0=Uncompressed)
  00Ch 4    Zero
  010h ..   VH File (Sony Voice Header, starting with ID "pBAV")
 SEPD Chunks:
  000h 4    Chunk ID ("SEPD")
  004h 4    Chunk Size (of whole chunk from Chunk ID and up)
  008h 4    Compression Flag (0=Uncompressed)
  00Ch 2    Zero
  00Eh 2    Number of sequences (in the SEP sequence archive)
  010h 4    Zero
  014h ..   SEP File (Sony Sequence archive, starting with ID "pQES")
  ...  ..   Zeropadding to 4-byte boundary
 VABB Chunks:
  000h 4    Chunk ID ("VABB")
  004h 4    Chunk Size (of whole chunk from Chunk ID and up)
  008h 4    Compression Flag (0=Uncompressed)
  00Ch ..   VB File (Sony Voice Binary, with raw SPU-ADPCM samples)
 VRAM Chunks:
  000h 4    Chunk ID ("VRAM")
  004h 4    Chunk Size (of whole chunk from Chunk ID and up)
  008h 4    Compression Flag (1=Compressed)
  00Ch 2    VRAM.X
  00Eh 2    VRAM.Y
  010h 2    Width in halfwords
  012h 2    Height
  014h 4    Decompressed Size (Width*Height*2)  ;\Texture Bitmaps 8bpp
  018h ..   Compressed Data                     ; (or Palettes, in last VRAM
  ...  ..   Zeropadding to 4-byte boundary      ;/chunk)
 STGE Chunks:
  000h 4    Chunk ID ("STGE")
  004h 4    Chunk Size (of whole chunk from Chunk ID and up)
  008h 4    Compression Flag (0=Uncompressed)
  00Ch ..   Unknown (stage data?)
 ANIM Chunks:
  000h 4    Chunk ID ("ANIM")
  004h 4    Chunk Size (of whole chunk from Chunk ID and up)
  008h 4    Compression Flag (0=Uncompressed)
  00Ch ..   Unknown (animation sequence info?)
 FRAM Chunks:
  000h 4    Chunk ID ("FRAM")
  004h 4    Chunk Size (of whole chunk from Chunk ID and up)
  008h 4    Compression Flag (0=When Chunksize=14h, 1=When Chunksize>14h)
  00Ch 1    Width in bytes
  00Dh 1    Height
  00Eh 6    Unknown, looks like three signed 16bit values (maybe X,Y,Z)?
  014h (4)  Decompressed Size (Width*Height*1)  ;\Animation Frame Bitmap 8bpp
  018h (..) Compressed Data                     ; (only if Chunksize>14h)
  ...  (..) Zeropadding to 4-byte boundary      ;/
VRAM and FRAM chunks with [08h]=1 (and Chunksize>14h) are compressed:
CDROM File Compression Blues


CDROM File Archive HED/CDF (Parasite Eve 2)

Crazy Data Format (CDF) is used by Parasite Eve 2, on Disc 1 and 2:
1: PE_Disk.01 Stage0.hed Stage0.cdf Stage1.cdf Stage2.cdf Stage3.cdf Inter0.str
2: PE_Disk.02 Stage0.hed Stage0.cdf Stage3.cdf Stage4.cdf Stage5.cdf Inter1.str

STAGE0.HED and STAGE0.CDF
This uses separate header/data files. The directory is stored in STAGE0.HED:
  0000h 78h   Streaming List (03h entries, 28h-bytes each, all entries used)
  0078h 1B00h File List (360h entries, 8 bytes each, all entries used)
  1B78b 8     File List End Code (FFFFFFFFh,FFFFFFFFh)
The actual data for the files (and audio stream) is stored in STAGE0.CDF.

STAGE1.CDF .. STAGE5.CDF
  0000h 800h  Root: Folder List (100h entries, 8-byte each, unused=zeropadded)
  0800h ..    1st Folder (File/Streaming List and Data)
  ...   ..    2nd Folder (File/Streaming List and Data)
  ...   ..    etc.
Folder List entries:
  000h 4  Folder ID (usually N*100+1 decimal, increasing, eg. 101,201,301,etc.)
  004h 4  Folder Size/800h (of whole folder, with File/Stream List and Data)
  The Folder List ends with unused/zeropadded entries with ID/Size=00000000h.
Folder format:
  0000h 510h  File List      (A2h entries, 8-bytes each, unused=zeropadded)
  0510h 4     Zero           (padding to decimally-minded offset 1300 aka 514h)
  0514h 2D0h  Streaming List (12h entries, 28h-bytes each, unused=zeropadded)
  07E4h 1Ch   Zero           (padding to end of sector)
  0800h ...   Data (for Files, Audio streams, and sometimes also Movie streams)

File List entries (in STAGE0 and STAGE1-5)
  000h 4  File ID (increasing, eg. 0,1,2,3,4,etc.) (or 99) (or N*100+x)
  004h 4  File Offset/800h in in .CDF (from begin of current Folder)
For STAGE0, file list ends with ID/Offset=FFFFFFFFh at end of HED file. For STAGE1-5, file list ends with unused/zeropadded entries with ID/Offset=00000000h.
The filesize can be computed as "NextOffset-CurrOffset" (at 800h-byte resolution). Whereas, "NextOffset" can be:
  The offset of next File in File List (same as CurrOffset for 0-byte files)
  The offset of next Audio stream in Streaming List
  The offset of next Movie stream in Streaming List (if it's in .CDF, not .STR)
  The size of the current Folder (for STAGE1-5)
  The size of the whole .CDF file (for STAGE0)
For STAGE1-5, audio streams are usually stored at the end of folder (after the files). However, for STAGE0, audio streams are oddly inserted between file21000 and file30100.

File Chunks (for files within File List)
Most CDF files in STAGE0 and STAGE1-5 do contain one or more chunks with 10h-byte chunk headers (this can be considered as an additional filesystem layer, with the chunk data being the actual files).
  000h 1  Chunk Type (see below)
  001h 1  End Flag (01h=More Chunks follow, FFh=Last Chunk)
  002h 2  Unknown (usually 800h, sometimes 500h or 600h)
            (eg. 500h in stage0\file30301\chunkX)
            (eg. 600h in stage1\folder1201\file0\chunkXYZ)
  004h 4  Chunk Size/800h
  008h 4  Unknown (usually zero) (or 80xxxx00h in Chunk Type 0 files?)
  00Ch 4  Zero (0)
  010h .. Data (Chunk Size-10h bytes)
Chunk Types:
  00h=Room package            .pe2pkg
  01h=Image                   .pe2img
  02h=CLUT                    .pe2clut
  04h=CAP2 Text               .pe2cap2
  05h=Room backgrounds        .bs
  06h=SPK/MPK music program   .spk  ;stereo/mono, sound/music, single/multiple?
  07h=ASCII text              .txt     (eg. stage0\20101..20132)
 ;Reportedy also (but wrong):
 ;60h=Sounds                  .pe2snd  (but nope, that's wrong, see below)
 ;60h is a MDEC movie from Streaming List (unrelated to File List chunks),
 ;60h is 20h-byte .STR header each 800h-bytes (occurs in "stage1\folder501")
There are some chunkless files:
  stage0\40105...40198 are raw hMPK files without chunks
  stage0\11000, 20213, 20214, 20300, .., 660800 and 900000 are empty 0-byte

Streaming List Movie entries (stream type 1)
  000h 2    Stream Type (0001h=Movie)
  002h 2    Unknown (8000h or 0000h)
  004h 4    Offset/800h in current Folder of .CDF file ;<-- used when [024h]=0
  008h 4    Offset/800h in INTERx.STR file             ;<-- used when [024h]>0
  00Ch 2    Unknown (0000h)
  00Eh 2    Stream ID (increasing, usually starting at 64h aka 100 decimal)
  010h 2    Stream sub.ID (usually 0, increases +1 upon multiple same IDs)
  012h 2    Picture Width  (0140h = 320 decimal)
  014h 2    Picture Height (00F0h = 224 decimal)
  016h 2    Unknown (0000h)
  018h 2    Unknown (0000h or 0018h)   maybe 24bpp or 24fps
  01Ah 2    Unknown (73Ah or 359h or 3DCh)  (Size? but it's slighty too large?)
  01Ch 6    Unknown (zero)
  022h 2    Unknown (0 or 1) (often 1 when [024h]>0, but not always)
  024h 2    Movie number in INTERx.STR, 1 and up? (or 0=Movie is in STAGEx.CDF)
  026h 2    Unknown (0 or 1)
The size of movie streams in .CDF can be computed in similar fashion as for File List entries (see there for details).
The size of movie streams in .STR cannot be computed easily (the next stream isn't neccassarily stored at the next higher offset; even if it's within same folder). As workaround, one could create a huge list with all streams from all Folders in all STAGEx.CDFs (or scan the MDEC .STR headers in .STR file; and check when the increasing frame number wraps to next stream).
The dual offsets are oddly computed as: [004h]=[008h]+EndOfLastFileInFolder (that gives the correct value in the used entry, and a nonsensical value in the other entry).

Streaming List Audio entries (stream type 2)
  000h 2    Stream Type (0002h=Audio)
  002h 2    Unknown (806Ah or increasing 0133h,0134h,0135h)
  004h 4    Offset/800h in STAGEx.CDF file (increasing offsets)
  008h 4    Unknown (0 or 13000h or E000h)
  00Ch 2    Stage Number (0..5 = STAGE0-5)
  00Eh 2    Stream ID (1, or increasing 3Ah,3Bh,3Ch)
  010h 4    Stream sub.ID (usually 0Bh, increases +0Ah upon multiple same IDs)
  014h 2    Unknown (0 or 2B0h or 3ADh or 398h) (Size/800h minus something?)
  016h 2    Unknown (usually 20h, sometimes 0Fh)
  018h 4    Unknown (2 or 1)              ... maybe num channels ?
  01Ch 2+2  Unknown (0,0 or 800h,800h)
  020h 8    Unknown (0)
The size of audio streams can be computed in similar fashion as for File List entries (see there for details).

Audio Stream Data (stored alongsides with file data in STAGEx.CDF file)
This contains a 800h-byte header a list of 32bit indices:
  000h 800h Whatever increasing 32bit index/timing values? FFFFFFFFh=special?
  ;That header exists in stage0\ and stage3\folder101\
  ;That header doesn't exist in all files (eg. not in stage1\folder301\)
then followed by several chunk-like STM blocks with 10h-byte headers:
  000h 4  Chunk Index (increases each second chunk, from 0 and up)
  004h 4  Number of Chunk Indices
  008h 4  Fixed (02h,"STM")                                  ;2-channel Stream?
  00Ch 1  Chunk Subindex (toggles 00h or 01h per each chunk) ;ch left/right?
  00Dh 1  Chunk Size/800h
  00Eh 4  Unknown (can be 00h, 01h, 11h, 20h, 21h)
  00Fh 4  Unknown (can be A0h or C0h)
  010h .. Data (Chunk Size-10h bytes) (looks like SPU-ADPCM audio)
After the last STM chunk, there is more unknown stuff:
  000h 0   Number of ADPCM blocks?            (eg. 28h    or 49h)
  004h 4   Size of extra data block in bytes  (eg. 13900h or 24200h)
  008h 38h Zerofilled
  040h 8   Zerofilled (maybe 1st sample of 1st SPU-ADPCM block)
  048h ..  Looks like more SPU-ADPCM block(s), terminated by ADPCM end flag(s)
  ...  ..  Zerofilled (padding to end of last 800h-byte sector)

Movie Stream Data (stored in .CDF, or in separate INTERx.STR file)
The movies are usually stored in INTERx.STR (except, some have them stored in STAGEx.CDF, eg. stage1\folder501, stage1\folder801, stage2\folder2101, stage2\folder3001).
The data consists of standard .STR files (with 20h-byte headers on each 800h-byte sector), with the MDEC data being in huffman .BS format (with .BS header... per frame?).
And, supposedly interleaved with XA-ADPCM audio sectors...?

PE_DISK.01 and PE_DISK.02
The presence of these files is probably used to detect which disc is inserted. The file content is unknown (looks like 800h-byte random values).

Note
Reportedly "Files inside archive may be compressed with custom LZSS compression" (unknown if/when/where/really/which files).


CDROM File Archive IND/WAD (MTV Music Generator)

MTV Music Generator (IND/WAD) (MagDemo30: JESTER\WADS\ECTS.IND and .WAD)
ECTS.IND contains FOLDER info:
  0000h 20h   Name/ID ("Music 2", zeropadded)
  0020h 4     Unknown (110000h)
  0024h 4     Filesize-1000h (size excluding last 1000h-byte padding)
  0028h 4     Unknown (17E0h)
  002Ch 4     Unknown (5)
  0030h N*10h Folder List, starting with Root in first 10h-byte
  2CF0h 4     Small Padding (34h-filled)
  2CF4h 1000h Final Padding (34h-filled)
 Folder List entries that refer to Child Folders in ECTS.IND:
  000h 8     Folder Name ("EXTRA*~*", zeropadded if less than 8) ("" for root)
  008h 2     Self-relative Index to first Child folder (positive)
  00Ah 2     Number of Child Folders (0..7FFFh)
  00Ch 4     Always 0007FFFFh (19bit Offset=7FFFFh, plus 13bit Size=0000h)
 Folder List entries that refer to File Folders in ECTS.WAD:
  000h 8     Folder Name ("EXTRA*~*", zeropadded if less than 8)
  008h 2     Self-relative Index to Parent folder (negative)
  00Ah 2     Number of Child Folders (always 8000h=None)
  00Ch 4     Offset and Size in ECTS.WAD
 The 32bit "Offset and Size" entry consists of:
  0-18   19bit Offset/800h in ECTS.WAD
  19-31  13bit Size/800h-1 in ECTS.WAD
ECTS.WAD contains FILE info and actual FILE data:
 There are several File Folders (at the locations specified in ECTS.IND).
 The separate File Folders look as so:
  000h 4     Number of files (N)
  004h N*10h File List
  ...  ..    34h-Padding to 800h-byte boundary
  ...  ..    File Data area
 File List entries:
  000h 8     File Name ("NAMELIST", "ACIDWO~1", etc.) (00h-padded if shorter)
  008h 4     Offset/800h (always from begin of WAD, not from begin of Folder)
  00Ch 4     Filesize in bytes
 The first file in each folder is called "NAMELIST" and contains this:
  000h 20h   Long Name for Parent Folder (eg. "Backgrounds", zeropadded)
  020h 20h   Long Name for this Folder   (eg. "Extra 1", zeropadded)
  040h N*20h Long Names for all files in folder (except for NAMELIST itself)
 For example, Long name for "ACIDWO~1" would be "Acidworld". Short names are
 uppercase, max 8 chars, without spaces (with "~N" suffix if the long name
 contains spaces or more than 8 chars). Many folder names are truncated to
 one char (eg. "D" for Long name "DTex"), in such cases short names CAN be
 lowercase (eg. "z" for  Long name "zTrans").
 The Long Names are scattered around in the NAMELIST files in ECTS.WAD file,
 so they aren't suitable for lookup (unless when loading all NAMELIST's).


CDROM File Archive GAME.RSC (Colonly Wars Red Sun)

Colony Wars Red Sun (MagDemo31: CWREDSUN\GAME.RSC, 13Mbyte)
  0000h 4     Offset to Bonkers List (2794h)
  0004h F*8   Folder List                      (80h bytes, 10h entries)
  0084h N*14h File List(s) for each folder     (2710h bytes, 1F4h entries)
  2794h 4     Number of Bonkers     (FE3h)
  2798h B*8   Bonkers List                     (7F18h bytes, FE3h entries)
  A6B0h 8     Unknown (zerofilled)
  A6B8h ..    File Data area
Folder List entries:
  000h 4     Offset to File List for this folder   ;\both zero when empty
  004h 4     Number of Files in this folder        ;/
File List entries:
  000h 10h   Filename ("FILENAME_EXT", zeropadded)
  010h 3     Index (in Bonkers list) (000h..Fxxh)
  013h 1     Folder Number where the file is stored (00h..0Fh)
Bonkers List entries:
  000h 4     File Offset (to Data, inreasing, 4-byte aligned, A6B8h and up)
  004h 4     Folder Number where the file is stored (00h..0Fh)
Offsets/Indices in Folder/File list are unsorted (not increasing).
Offsets in Bonkers List are increasing (so filesizes can be computed as size=next-curr, except, the LAST file must be computed as size=total-curr).
There is no "number of folders entry" nor "folder list end marker", as workaround, while crawling the folder list, search the smallest file list offset, and treat that as folder list end offset.
In the demo version, all File List entries for Folder 5 are pointing to files with filesize=0, however, the Bonkers List has a lot more "hidden" entries that are marked to belong to Folder 5 with nonzero filesize.
Note: Older Colony Wars titles did also have a GAME.RSC file (but in different format, without folder structure).


CDROM File Archive BIGFILE.DAT (Soul Reaver)

Legacy of Kain: Soul Reaver - BIGFILE.DAT
Legacy of Kain: Soul Reaver (MagDemo26: KAIN2\BIGFILE.DAT)
  000h 2     Number of Folders (175h in retail, 0Ah in demo)
  002h 2     Zero
  004h N*8   Folder List (8-byte per Folder)
  ...  ..    Zeropadding (to 800h-byte boundary)
  ...  ..    1st Folder (with File List, and File Data for that folder)
  ...  ..    2nd Folder (with File List, and File Data for that folder)
  ...  ..    3rd Folder (with File List, and File Data for that folder)
  ...  ..    etc.
Folder List entries:
  000h 2     Unknown (somehow randomly increases from -8000h to +7E8Fh)
  002h 2     Number of Files in this Folder (eg. 97h)
  004h 4     Offset to Folder (usually 800h-aligned)
Folder format:
  000h 2     Number of Files (same value as FolderistEntry[002h]) ;\encrypted
  002h 2     Zero                                                 ; by 16bit
  004h N*10h File List (10h-byte per Folder)                      ; XOR value
  ...  ..    Zeropadding (to 800h-byte boundary)                  ;/
  ...  ..    File Data for this folder                            ;-unencrypted
File List entries:
  000h 4     Unknown (random? filename hash? encrypted name?)
  004h 4     File Size in bytes
  008h 4     File Offset (usually 800h-aligned)
  00Ch 4     Unknown (random? filename hash? encrypted name?)
Encryption:
The file header, the first some Folder headers (those in first quarter or so), and (all?) File Data is unencrypted (aka XORed with 0000h).
The Folder headers at higher offsets are encrypted with a 16bit XOR value. That XOR value is derived from Subchannel Q via LibCrypt:
CDROM Protection - LibCrypt
When not having the Subchannel data (or when not knowing which Folders are encrypted or unencrypted), one can simply obtain the encryption key from one of these entries (which will be key=0000h when unencrypted):
  key = FileListEntry[000h] XOR FolderListEntry[002h]  ;encrypted num entries
  key = FileListEntry[002h]                            ;encrypted Zero
  key = FileListEntry[zeropadding, if any]             ;encrypted Zeropadding
LibCrypt seems to be used only in PAL games, unknown if the Soul Reaver NTSC version does also have some kind of encryption.


CDROM File Archive FF8 IMG (Final Fantasy VIII)

FF8 is quite a mess without clear directory structure. Apart from SYSTEM.CNF and boot EXE, there is only one huge IMG file. There are at least two central directories: The Root directory (usually at the start of the IMG file), and the Fields directory (hidden in a compressed file that can be found in the Root directory). Moreover, there are files that exist in neither of the directories (most notably the Movies at the end of the IMG file).

IMG File
The IMG file doesn't have a unique file header, it can be best detected by checking the filename: FF8DISCn.IMG with n=1-4 for Disc 1-4 (or only FF8DISC1.IMG or FF8.EXE+FF8TRY.IMG for demo versions).
The directories contain ISO sector numbers (originated from begin of the ISO area at sector 00:02:00). Accordingly, it's best to extract data from the whole disc image (in CUE/BIN format or the like). When having only the raw IMG file, one most know/guess the starting sector number (eg. assume that the first Root File is located on the sector after the Root Directory, and convert sector numbers ISO-to-IMG accordingly).
Another oddity is that many files contain RAM addresses (80000000h-801FFFFFh), unknown how far that's relevant, and if there are cases where one would need to convert RAM addresses to IMG offsets.

Root Directory
The Root Directory is found at:
  Offset 0000h in FF8DISCn.IMG in NTSC retail versions
  Offset 2800h in FF8DISCn.IMG in PAL retail versions
  Offset 0000h in FF8DISC1.IMG in french demo version
  Offset ?????h in FF8.EXE in MagDemo23 (...maybe offset 3357Ch ?)
  Offset 33510h in FF8.EXE in japanese demo version ?
  Offset 33584h in FF8.EXE in other demo versions   ?
For detection:
  if FF8DISCn.IMG starts with 000003xxh --> assume Root at IMG offset 0
  if FF8DISCn.IMG starts with xxxxxxxxh --> assume Root at IMG offset 2800h
  if FF8TRY.IMG starts with "SmCdReadCore" --> assume Root somewhere in EXE
File List:
  000h N*8  File List entries
  ...  ..   Zeropadding to end of 800h-byte sector
File List entries:
  000h 4    ISO Sector Number (origin at 00:02:00) (unsorted, not increasing)
  004h 4    Filesize in bytes
The file list does usually end with zeropadding (unknown if that applies to all versions; namely the Demo version might end with gibberish instead of having 800h-byte sector padding).

Fields Directory
The Fields Directory is located in Root file 0002h. First of, decompress that file, then search the following byte sequences to find the start/end of the directory:
  retail.start  040005241800bf8f1400b18f1000b08f2000bd270800e00300000000
  retail.end    0000010002000300
  demo.start    76DF326F34A8D0B863C8C0EC4BE817F8
  demo.end      0000000000000000000000000000000000100010
The bytes between those start/end pattern contain the Directory, with entries in same format as Root directory:
  000h 4    ISO Sector Number (origin at 00:02:00)
  004h 4    Filesize in bytes
Notes: Root file 0002h is about 190Kbyte (decompressed), of which, the Fields Directory takes up about 8Kbytes, the remaining data contains other stuff.
The sector numbers in the Fields Directory refer to other locations in the IMG file (not to data in Root File 0002h).

Movie List
There is no known central directory for the movies (unknown if such a thing exists, or if the movie sector numbers are scattered around, stored in separate files). However, a movie list can be generated by crawling the movie headers, starting at end of IMG file:
  sector = NumSectors(IMG file)
 @@lop:
  seek(sector-1), read(buf,08h bytes)
  if first4byte[buf+0]=("SMJ",01h), or ("SMN",01h) then
    num_sectors=(byte[buf+5]+1)*(halfword[buf+6]+1)
    sector=sector-num_sectors
    AddToMovieFileList(sector, num_sectors)
    goto @@lop
  endif
That should cover all movies, which are all at the end of the IMG file (except, there's one more movie-like file elsewhere in the middle of IMG file, that file has only SMN/SMR audio sectors, without any SMJ video sectors).

PADBUG archives
PADBUG archives are used in Root files 001Eh..007Fh, most of them contain two AKAO files (except file 004Bh contains one AKAO and one TXT file).
  000h 4     Number of Files (N) (usually 2)
  004h N*8   File List
  ...  ..    File Data area
File List entries:
  000h 4     Offset in bytes (increasing, 4-byte aligned, see Quirk)
  004h 4     File Size in bytes (can be odd)
Quirk: All files are zeropadded with 1-4 bytes to 4-byte boundary (ie. files that do end on a 4-byte boundary will be nethertheless padded with 4 zeroes).
Note: The PADBUG archives resemble LNK archives in O.D.T. (though those LNK archives have a different unique 4-byte padding quirk).

Compression
CDROM File Compression LZ5 and LZ5-variants
FF8 does reportedly also use GZIP (unknown in which files).

Known/unknown sectors for US version FF8DISC1.IMG
  root sectors:       27CBh ;\
  field sectors:      D466h ; total known sectors: 36D13h
  movie sectors:     270E2h ;/
  unknown sectors:   14F49h
  total IMG sectors: 4BC5Ch

See also
https://github.com/myst6re/deling/blob/master/FF8DiscArchive.cpp
https://ff7-mods.github.io/ff7-flat-wiki/FF8/PlaystationMedia.html


CDROM File Archive FF9 IMG (Final Fantasy IX)

Final Fantasy IX (FF9.IMG, 320Mbyte) Overall format
  000h Root Directory
  800h 1st Child Folder
  ...  2nd Child Folder
  ...  3rd Child Folder
  ...  ...
  8000h ?     Last folder, with Type3, contains 1FFh x increasing 16bit numbers
  ...  Data for files in 1st Child Folder
  ...  Data for files in 2nd Child Folder
  ...  Data for files in 3rd Child Folder
  ...

IMG Root Directory
  000h 4     ID "FF9 "
  004h 4     Unknown (06h on Disc 1 of 4) (maybe version, or disc id?)
  008h 4     Number of Folder List entries (0Fh)
  00Ch 4     Unknown (01h on Disc 1 of 4) (maybe version, or disc id?)
                 (or Offset/800h to first file list?)
  010h N*10h Folder List
  ...  ..    Padding to 800h-byte boundary ("FF9 FF9 FF9 FF9 ")
Folder List entries:
  000h 4     FolderType (2=Normal, 3=Special, 4=Last entry)
  004h 4     Number of entries in File List (0..1FFh ?)
  008h 4     Offset/800h to Child Folder with File List
  00Ch 4     Offset/800h to File Data (same as 1st offs in File List) (0=Last)

IMG Child Folders (FolderType=2)
  000h N*8   File List entries (N=Number of files, from Root directory)
  N*8  8     File List END entry (ID=FFFFh, Attr=FFFFh, Offs=EndOfLastFile)
  ...  ..    Zeropadding to 800h-byte boundary
File List entries:
  000h 2     File ID (increasing, often decimal 0,10,100, or FFFFh=Last)
  002h 2     Attr (unknown purpose, eg. 0,2,3,4,8,21h,28h,2Fh,44h,114h,FFFFh)
  004h 4     Offset/800h to File Data (increasing, implies end of prev entry)

IMG Child Folders (FolderType=3)
  000h N*2   File Offsets/800h, from File Data Offset in Root (or FFFFh=None)
  N*2  2     End Offset for last file
The filesize can be computed as (NextOffs-CurrOffs)*800h, however, one must skip unused entries (FFFFh) to find NextOffs.

Nested Child Archives
Most of the files in FF9.IMG are DB archives, there are also some DOT1 archives.
CDROM File Archive FF9 DB (Final Fantasy IX)
There are various combinations of IMG, DB, DOT1 archives nested up to 4 levels deep:
  IMG\DOT1         (eg. dir01\file003C)
  IMG\DB           (eg. dir01\file2712)
  IMG\DB\DOT1      (eg. dir01\file2712\00-0411)
  IMG\DB\DOT1\DOT1 (eg. dir01\file2712\00-0443\*)
  IMG\DB\DB        (eg. dir03\file2328\1B-000*)

Folders in Root directory
  dir00 - Status/Menu/Battle/... -Text and random stuff.
  dir01 - Misc Images (Logos, Fonts, World 'mini' Map images, etc).
  dir02 - Dialog Text
  dir03 - Map models (Mini-zidane, airships, save point moogle, tent...)
  dir04 - Field models
  dir05 - Monster Data (Part I, stats, names, etc).
  dir06 - Location Data (Dungeon, Cities, etc).
  dir07 - Monster Data (Part II, 3d models)
  dir08 - Weapon Data (including models)
  dir09 - Samplebanks and Sequencer Data (ie music).
  dir0A - party members Data (including models)
  dir0B - Sound effects
  dir0C - World Map Data
  dir0D - Special effects (magic, summons...)

See also
https://ninjatoes.blogspot.com/2020/07/
https://wiki.ffrtt.ru/index.php?title=Main_Page


CDROM File Archive GTFS (Gran Turismo 2)

Gran Turismo 2 (MagDemo27: GT2\GT2.VOL, GT2.VOL\arcade\arc_carlogo) - GTFS
  000h 4     ID "GTFS"                                             ;\
  004h 4     Zero                                                  ;
  008h 2     Number of 4-byte File Offset List entries (N)         ; File(0)
  00Ah 2     Number of 20h-byte File/Folder Name List entries (F)  ;
  00Ch 4     Zero                                                  ;
  010h N*4   File Offset List (see below)                          ;/
  ...  ..    Zeropadding to 800h-byte boundary
  ...  F*20h File/Folder Name List (see below)                     ;-File(1)
  ...  ..    Zeropadding to 800h-byte boundary
  ...  ..    File Data                                             ;-File(2)
  ...  ..    Zeropadding to 800h-byte boundary
  ...        File Data                                             ;-File(3)
  ...  ..    ...
  ...        File Data                                             ;-File(N-2)
  ...  ..    Zeropadding to 800h-byte boundary
  EOF  0     End of File                                           ;-File(N-1)
That is, for N files, numbered File(0)..File(N-1):
  File(0) and File(1) = Directory information
  File(2)..File(N-2)  = Regular data files
  File(N-1)           = Offset List entry points to the end of .VOL file
File Offset List entries, in File(0):
Contains information for all files, including File(0) and File(1), and including an entry for File(N-1), which contains the end offset for the last actual file, ie. for File(N-2).
  Bit0-10  = Number of padding bytes in last sector of this file (0..7FFh)
  Bit11-31 = Offset/800h to first sector of this file (increasing)
  To compute the filesize: Size=(Entry[N+1] AND FFFFF800h)-Entry[N]
File/Folder Name List entries, in File(1):
Contains information for all files, excpet File(0), File(1), File(N-1), plus extra entries for Folders, plus ".." entries for links to Parent folders.
  000h 4     Unknown (379xxxxxh) (maybe timestamp?)
  004h 2     When Flags.bit0=0: Index of File in File Offset List (2 and up)
             When Flags.bit0=1: Index of first child in Name List, or...
             When Flags.bit0=1: Index of 1st? parent in Name List (Name="..")
  006h 1     Flags (bit0:0=File, 1=Directory; bit7:1=Last Child entry)
  007h 19h   Name (ASCII, zeropadded)
The game does use several archive formats: GTFS (including nested GTFS inside of main GTFS) and WAD.WAD and DOT1.
The game does use some GT-ZIP compressed files, and many GZIP compressed files (albeit with corrupted/zeropadded GZIP footers; due to DOT1 filesize 4-byte padding and (unneccessarily) GTFS 800h-byte padding).
CDROM File Compression GT-ZIP (Gran Turismo 1 and 2)
CDROM File Compression ZIP/GZIP/ZLIB (Inflate/Deflate)
To extract the decompressed size from the corrupted GZIP footers, one could compute the compressed "size" (excluding the GZIP header, footer, and padding), and search for a footer entry that is bigger than "size".
  size=gz_filesize
  size=size-GzipHeader(including ExtraHeader, Filename, Comment, HeaderCrc)
  size=size-GzipFooter(8)   ;initially assuming 8-byte footer (without padding)
  i=gz_filesize-4
 @@search_footer:
  if buf[i]<size then i=i-1, size=size-1 goto @@search_footer
  decompressed_size = buf[i]
Note: Above doesn't recurse the worst-case compression ratio, where compressed files could be slightly bigger than decompressed files.


CDROM File Archive Nightmare Project: Yakata

Nightmare Project: Yakata
ISO Files:
  CD.IMG      550Mbyte  Contains file 004h..FFFh
  CDRTBL.DAT  32Kbyte   Alias for file 000h (File List for file 000h..FFFh)
  FDTBL.DAT   2Kbyte    Alias for file 001h (Folder List and Disc ID)
  SLPS_010.4* 500Kbyte  Alias for file 003h (Boot EXE)
  SYSTEM.CNF  72bytes   Alias for file 002h (Boot Info)
  XXXXXXXX.   27Mbyte   Padding (zerofilled)
FDTBL.DAT (Folder List):
 FDLTBL.DAT seems to be used to divide the file list in CDRTBL.DAT into
 separate folders. The Folder List entries are containing the first file number
 for each folder. Empty folders have same file number as next entry.
 The last folder contains the specified file number plus all remaining files.
  000h 56h*2 Folder List (16bit File Numbers, increasing from 0004h to 0xxxh)
  0ACh 748h  Zerofilled
  7F4h 0Ah   Game ID (ASCII "SLPS1045",00h,00h; always so on Disc 1..3)
  7FEh 2     Disc ID (1..3 = Disc 1..3)
CDRTBL.DAT (File List):
  000h 8000h File List (1000h x 8-byte entries)
 File List entries:
  000h 4   Sector (MM:SS:FF:00 in BCD, increasing)  ;\all zero for
  004h 2   Size1  (NumFramesCh1 or NumSectors)      ; unused entries
  006h 2   Size0  (NumFramesCh0 or Zero)            ;/
 The meaning of the Size entries depends on the file type:
  Normal binaries:  [004h]=NumSectors     [006h]=0             (1 channel)
  XA-ADPCM streams: [004h]=NumSectors-50h [006h]=0             (16 channels)
  MDEC streams:     [004h]=NumFrames      [006h]=0             (audio+video)
  Special streams:  [004h]=NumFramesCh1   [006h]=NumFramesCh0  (2 channels)
 To determine the actual filesize, one must compute the difference between
  sectors for current and next used file entry (or end of CD.IMG for last file;
  or alternately assume last file to be a Normal Binary with Size=NumSectors).
 Normal Binaries:
  Contains single files (file=0/channel=0). Filetypes include TIM, VB, VH,
  other/custom file formats, and DOT1 archives.
  The DOT1 archives have 4-byte aligned offsets, but, unconventionally, with
  some offsets set to ZERO (usually the last entry, and sometimes also other
  entries):
  SEQ files (Disc1:Dir08h\File173h)       ;with ZERO entries    (=uncommon)
  SEQ files (Disc1:Dir09h\File176h..3D7h) ;with ZERO entries    (=uncommon)
  SEQ files (Disc1:Dir0Ah\File3DAh..3E6h) ;with ZERO entries    (=uncommon)
  TIM files (Disc1:Dir4Fh\File962h..983h) ;with ZERO entries    (=uncommon)
  TIM files (Disc1:Dir0Ch\File414h..426h) ;without ZERO entries (=normal DOT1)
 XA-ADPCM Streams (Disc1:Dir0Bh\File3E7h..413h):
  These contain 16 audio streams (file=1/channel=00h-0Fh). The Size entry is
  set to total size in sectors for all streams, minus 50h (ie. there appears
  to be 50h sectors appended as padding before next file).
 MDEC Streams (Disc1:Dir53h\FileBD1h..BEBh):
  These are standard STR files with MDEC video (file=0/channel=1) and
  XA-ADPCM (file=1/channel=1). There are 10 sectors per frame (8-9 video
  sectors plus 1-2 audio sectors). The total filesize is NumFrames*10+Align(8)
  sectors; the Align(8) might be there to include one final audio sector.
 Special Streams (Disc1:Dir07h\File0E9h-16Eh and Dir50h\File985h..B58h):
  These are custom STR files (non-MDEC format), perhaps containing Polygon
  streams or whatever.
  There are two channels (file=1/channel=00h-01h), each channel contains
  data that consists of 5 sectors per frame (1xHeader plus 4xData).
  The sectors have STR ID=0160h, and STR Type as follows:
    0000h=Whatever special, channel 0 header (sector 0)
    0400h=Whatever special, channel 1 header (sector 1)
    0001h=Whatever special, channel 0 data   (sector 2,4,6,8)
    0401h=Whatever special, channel 1 data   (sector 3,5,7,9)
  The File List size entries contain Number of Frames for each channel (either
  of these entries may be zero, or bigger/smaller/same than the other entry).
  The smaller channel is padded to same size as bigger channel (ie. total
  filesize is "max(NumFramesCh0,NumFramesCh1)*10 sectors"; though that formula
  doesn't always hold true, for example, Disc1:Dir50h\FileA2Dh and FileB1Bh
  are bigger or smaller than expected).


CDROM File Archive FAdj0500 (Klonoa)

Klonoa (MagDemo08: KLONOA\FILE.IDX+FILE.BIN)
 FILE.IDX
  000h 8     ID "FAdj0500"
  008h 38h   RAM addresses       (80xxxxxxh, 0Ch words)
  038h 4     Zero
  03Ch 4     RAM address         (80xxxxxxh)
  040h N*10h File List (including Folder start/end markers)
 FILE.BIN
  000h ..    File Data area (split into filesizes from FILE.IDX)
File List entries:
 Type 0 (Folder End):
  000h 4     Type (0=Folder End)
  000h 4     Zero
  008h 4     RAM address         (always 801EAF8Ch)
  00Ch 4     Zero
 Type 1.a (Folder Start):
  000h 4     Type (1=Folder Start)
  000h 4     Folder Offset/800h  (offset of FIRST file in this Folder)
  008h 4     RAM address         (always 801EAF8Ch)
  00Ch 4     Folder Size/800h    (size of ALL files in this Folder)
 Type 1.b (Force Offset, can occur between Files within a Folder):
  000h 4     Type (1=Same as Folder Start)
  000h 4     Folder Offset/800h  (offset of NEXT file in this Folder)
  008h 4     RAM address         (always 801EAF8Ch)
  00Ch 4     Folder Size/800h    (zero for Force Offset)
 Type 2 (File entries, within Folder Start/End):
  000h 4     Type (2=File)
  004h 4     Filesize in bytes   (4-byte aligned?)
  008h 4     RAM address 1       (80xxxxxxh, or zero)
  00Ch 4     RAM address 2       (80xxxxxxh)
File Offsets are usually 4-byte aligned (at offset+filesize from previous entry). Except, the first file after Folder Start (and Force Offset) is 800h-byte aligned.
The archive contains DOT1 archives, OA05 archives, Ulz compression, and TIM, TMD, VAB, SEQ, VB files.


CDROM File Archives in Hidden Sectors

Hidden Sector Overview
Xenogears, Chrono Cross, and Threads of Fate contain only two files in the ISO filesystem (SYSTEM.CNF and the boot executable). The CDROMs contain standard ISO data in Sector 10h-16h, followed by Hidden stuff in Sector 17h and up:
  Sector 10h (00:02:16)  Volume Descriptor (CD001)      ;\
  Sector 11h (00:02:17)  Volume Terminator (CD001)      ;
  Sector 12h (00:02:18)  Path Table 1                   ;
  Sector 13h (00:02:19)  Path Table 2                   ; standard ISO
  Sector 14h (00:02:20)  Path Table 3                   ;
  Sector 15h (00:02:21)  Path Table 4                   ;
  Sector 16h (00:02:22)  Root Directory                 ;/
  Sector 17h (00:02:23)  Hidden ID                      ;\
  Sector 18h (00:02:24)  Hidden Directory               ; hidden directory
  Sector ..  (00:02:xx)  Hidden Unknown                 ;/
  Sector ..  (00:02:xx)  Hidden Files... (referenced via Hidden Directory)
Note: Like normal files, all hidden entries have their last sector flagged as SM=89h (that applies to all three Hidden ID, Directory, Unknown entries, and to all Hidden Files). For details, see:
CDROM XA Subheader, File, Channel, Interleave

Xenogears (2 discs, 1998)
 Sector 17h (Hidden.ID)
  000h 0Eh  ID ("DS01_XENOGEARS"=Disc 1, or "DS02_XENOGEARS"=Disc 2)
  00Eh 7F2h Zerofilled
 Sector 18h..27h
  000h N*7  File List entries
 Sector 28h (Hidden.Unknown)
  Seems to contain a list of 16bit indices 0000h..1037h,FFFFh in File List
  (that, as raw list indices, regardless of the directory structure)
  000h      Unknown 0016 0018 FFFF FFFF 01A8 FFFF FFFF FFFF  ;\
  010h      Unknown FFFF FFFF FFFF FFFF 0A35 0A3A 0D35 0AD3  ; as so on Disc 2
  020h      Unknown 0A22 0A2E 0A2F FFFF FFFF FFFF FFFF FFFF  ; (values<>FFFFh
  030h      Unknown 0014 0001 0013 FFFF 0075 FFFF FFFF FFFF  ; on Disc 1
  040h      Unknown 0C10 0C14 0C15 0C19 0F52 FFFF FFFF FFFF  ; are 5 less, eg.
  050h      Unknown 0F4C 0B6E 0C4D 1037 0C09 0BAD FFFF FFFF  ; 0011,0013,FFFF..)
  060h      Unknown 002E 0034 FFFF FFFF FFFF FFFF FFFF FFFF  ;
  070h      Unknown FFFF FFFF FFFF FFFF                      ;/
  078h 2    Disc Number      (0001h=Disc 1, 0002h=Disc 2)
  07Ah 786h Zerofilled
 Sector 29h 1st file
File List entries:
  000h 3    24bit Offset (increasing sector number, or 0=special)
  003h 4    32bit Size   (filesize in bytes, or negative or 0=special)
The Offset/Size can have following meanings:
  offset=curr,    size=+N    file at sector=curr, size N bytes
  offset=curr,    size=-N    begin of sub-directory, with N files
  offset=curr,    size=0     empty file, size 0 bytes
  offset=0,       size=0     unused file entry
  offset=FFFFFFh, size=0     end of root-directory
Notes: The Hidden.Directory size seems to be hardcoded to 10h sectors (alternately, one could treat the sector of the 1st file entry as end of Hidden.Directory plus Hidden.Unknown).
Root entry 0004h and 0005h are aliases for ISO files SYSTEM.CNF and boot EXE. There seem to be no nested sub-directories (but there are several DOT1 child archives, in root- and sub-directories, eg. 00DCh\0000h\*).

Chrono Cross (2 discs, 1999,2000)
Threads of Fate (aka Dewprism) (1 disc, 1999,2000)
 Sector 17h (Hidden.ID)
  000h 2    Disc Number      (0001h=Disc 1, 0002h=Disc 2)
  002h 2    Number of Discs? (0002h) (always 2, even if only 1 disc)
  004h 2+2  Sector and Size for Hidden.ID        (Sector=0017h, Size=002Ch)
  008h 2+2  Sector and Size for Hidden.Directory (Sector=0018h, Size=60E0h)
  00Ch 2+2  Sector and Size for Hidden.Unknown   (Sector=0025h, Size=0022h)
  010h 10h  Zerofilled
  020h 0Ch  Title ID ("CHRONOCROSS",00h)      ;Chrono Cross (retail)
       09h  Title ID ("DEWPRISM",00h)         ;Threads of Fate (retail)
       10h  Title ID ("DEWPRISM_TAIKEN",00h)  ;Threads of Fate (demo)
  0xxh 7xxh Zerofilled (unused, since Hidden.ID has only Size=2Ch/29h/30h)
 Sector 18h..24h (Hidden.Directory)
  000h N*4  File List entries
  ...  ..   Zeropadding (till Size=60E0h, aka 6200 entries)
  ...  720h Zeropadding (till end of 800h-byte sector)
 Sector 25h (Hidden.Unknown)
  Seems to contain a list of 16bit indices 0000h..1791h,FFFFh in File List
  (though many of the listed indices are unused file list entries)
  000h 2    Disc Number      (0001h=Disc 1, 0002h=Disc 2)
  002h 10h  Unknown 0000 1791 1777 1775 00ED 09DF FFFF 0002    ;\same on
  012h 10h  Unknown 0025 0943 10E3 FFFF FFFF 0C77 0FD9 0FA3    ;/Disc 1+2
  022h ..   Zerofilled (unused, since Hidden.ID has only Size=0022h)
 Sector 26h  1st file (same as boot EXE in ISO)
File List entries:
  0-22   Sector number
  23     Flag (0=Normal, 1=Unused entry)
  24-31  Number of unused bytes in last sector, div8 (0..FFh = 0..7F8h bytes)
The directory is just a huge list of root files (without any folder structure; many of the root files do contain DOT1 child archives though).
Root entry 0000h and 0001h are aliases for ISO files boot EXE and SYSTEM.CNF.
Filesizes can be computed as follows (that works for all entries including last used entry; which is followed by some unused entries with bit23=1):
  filesize = ([addr+4]-[addr] AND 7FFFFFh)*800h - ([addr+3] AND FFh)*8
Unused entries with bit23=1 have Sector pointing to end of previous file (needed for filesize calculation). There are some zeropadded entries at end of list (with whole 32bit zero). There are hundreds of dummy txt files (24-byte "It's CDMAKE Dummy!",0Dh,0Ah,,0Dh,0Ah,20h and File08xxh: 8-byte "dummy",0,0,0) although those are real used file entries, each occupying a whole separate 800h-byte sector.

Threads of Fate (demo version) (MagDemo33: TOF\DEWPRISM.HED+.EXE+.IMG)
The demo version is using the same directory format as retail version (but with Virtual Sector numbers in HED+EXE+IMG files instead of Hidden Sectors).
  TOF\DEWPRISM.HED (6000h bytes)    VirtSector=1Ah,  PhysSector=A0A5h
  TOF\DEWPRISM.EXE (97800h bytes)   VirtSector=26h,  PhysSector=A0B1h
  TOF\DEWPRISM.IMG (19EA800h bytes) VirtSector=155h, PhysSector=A1E0h
The demo's Virtual Sectors start at 1Ah (instead of 17h), to convert them to Physical Sectors: Subtract 1Ah, then add starting Sector Number of HED file. The HED file contains Hidden.ID, Hidden.Directory, and Hidden.Unknown.


CDROM File Archive HED/DAT/BNS/STR (Ape Escape)

Ape Escape KKIIDDZZ.HED/.DAT/.BNS/.STR
  000h 52Ch List for .DAT file    ;value 0000h..6FFFh = sector 0..6FFFh in DAT
  52Ch D4h  Zerofilled
  600h C4h  List for .BNS file    ;value 7000h..71AFh = sector 0..1AFh in BNS
  6C4h 3Ch  Zerofilled
  700h 50h  List for .STR file(s) ;raw CDROM sector numbers from 00:02:00
  750h B0h  Zerofilled
List entries, for all three lists (32bit values):
  0-19   File Offset/800h (20bit)
  20-31  File Size/800h   (12bit)
The sector numbers in DAT and BNS are basically counted from begin of the .DAT file (which has 7000h sectors in retail version, and the .BNS file does follow right thereafter on the next sector) (the demo version (MagDemo22: KIDZ\*) has only 105Ah sectors in .DAT, and the BNS entries at offset 600h start with 105Ah accordingly).
There are 29 STR files in DEMO\*.STR and STR\*.STR, and 20 of them (?) are referenced in HED ? There are also several .ALL files in above folders.
Note: Most of the STR files in Ape Escape contain polygon animation streams rather than BS compressed bitmaps. Ape Escape is (c)1999 by Sony.
  .HED is 2048 bytes
  .DAT is 58720256 bytes = 3800000h bytes  ;div800h would be 7000h
  .BNS is 884736 bytes = D8000h bytes      ;div800h would be 1B0h
  .STR's: 7D3Bh+150 = 7DD1h = sector for STR\LAB.STR
Some files contain RLE compressed TIMs:
CDROM File Compression TIM-RLE4/RLE8
Some files contain raw headerless SPU-ADPCM (eg. DAT file 00Ah).


CDROM File Archive WAD.WAD, BIG.BIN, JESTERS.PKG (Crash/Herc/Pandemonium)

Below are two slightly different formats. WAD.WAD has unused entries 00h-filled. The PKG format has them FFh-filled, and does additionally support Folders, and does have a trailing ASCII string. There's also a difference on whether or not to apply alignment to empty 0-byte files.
However, the formats can appear almost identical (unused entries, 0-byte files, and folders are optional, without them, the only difference would be the presence of the ASCII string; which does exist only in 800h-byte aligned PKG's though).

WAD.WAD (Crash/Crash)
Used by Crash Bandicoot 3 (DRAGON\WAD.WAD, plus nested WADs inside of WAD.WAD)
Used by Crash Team Racing (SPYR02\WAD.WAD, plus nested WADs inside of WAD.WAD)
Used by Madden NFL'98 (MagDemo02: TIBURON\.DAT except PORTRAIT,SPRITES,XA.DAT)
Used by N2O (MagDemo09, N2O\PSXMAP.TRM and N2O\PSXSND.SND)
Used by Speed Racer (MagDemo10: SPDRACER\ALL1.BIN, with 0-byte, unpadded eof)
Used by Gran Turismo 2 (MagDemo27: GT2\GT2.OVL = 128Kbyte WAD.WAD with GZIP's)
Used by Jonah Lomu Rugby (LOMUDEMO\SFX\*.VBS, ENGLISH\*.VBS)
Used by Judge Dredd (*.CAP and *.MAD)
Used by Spyro 2 Ripto's Rage (SPYRO2\WAD.WAD, and nested WAD's therein)
Used by Spyro 3 Year of the Dragon (SPYRO3\WAD.WAD, and nested WAD's therein)
Used by Men: Mutant Academy (MagDemo33: PSXDATA\WAD.WAD\*, childs in PWF)
  000h N*8  File List
  ...  ..   Zeropadding to 4-byte or 800h-byte boundary (or garbage padding)
  ...  ..   File Data...
The File List can contain Files, and Unused entries:
  000h 4    Offset in bytes (4- or 800h-byte aligned, increasing) ;\both zero
  004h 4    Size in bytes (always multiples of 800h bytes)        ;/when Unused
The Offset in first entry implies size of the File List (the list has no end-marker other than the following zeropadding; which doesn't always exist, ie. not in 4-byte aligned files, and not in case of garbage padding).
The last entry has Offset+Size+Align = Total WAD filesize (except, Speed Racer doesn't have alignment padding after the last file).
The WAD.WAD format doesn't have folder entries, however, it is often used with nested WADs inside of the main WAD, which is about same as folders.
The alignment can be 4-byte or 800h-byte: N2O uses 4-byte for the main WADs. Madden NFL '98 uses 800h-byte for main WAD and 4-byte for child WADs (file 08h,0Ah,0Ch in TIBURON\MODEL01.DAT and file 76h in PIX01.DAT). Crash Bandicoor 3 and Crash Team Racing use 800h-byte for both main & child WADs (although with garbage padding instead of zeropadding in child WAD headers).
Unused entries have Offset=0, Size=0.
Empty 0-byte files (should) have Size=0 and Offset=PrevOffs+PrevSize+Align (except, Speed Racer has Offset=PrevOffs+PrevSize, ie. without Align for 0-byte files).

X-Men: Mutant Academy (MagDemo33,50: PSXDATA\WAD.WAD)
This does resemble standard WAD.WAD, but with leading 800h-byte extra stuff.
  000h 4     ID ("PWF ")                                ;\
  004h 4     Total Filesize (707800h)                   ;
  008h 4     Unknown (1)                                ; extra stuff
  00Ch 4     Number of files (N)                        ;
  010h 7F0h  Zerofilled                                 ;/
  800h N*8   File List                                  ;\
  ...  ..    Zerofilled (padding to 800h-byte boundary) ; standard WAD.WAD
  ...  ..    File Data area                             ;/
 File List entries:
  000h 4     File Offset in bytes (increasing, 800h-byte aligned)
  004h 4     File Size in bytes
The archive contains child archives in DOT1 format, and in standard WAD.WAD format (without PWF header).

PKG (Herc/Pandemonium/UnholyWar)
Used by Pandemonium II (JESTERS.PKG, with Files+Folders+Unused entries)
Used by Herc's Adventure (BIG.BIN, with Files+Unused entries, without Folders)
Used by Unholy War (MagDemo12:CERBSAMP.PKG, with 0-byte files and nested PKG's)
Used by 102 Dalmatians (MagDemo40: PTTR\PSXDEMO.PKG)
  000h N*8  File List
  ...  ..   ASCII string (junk, but somewhat needed as nonzero end marker)
  ...  ..   Zeropadding to 800h-byte boundary; not in 4-byte aligned nested PKG
  ...  ..   File Data...
The File List can contain Files, Folders, and Unused entries. The overall format of the list entries is:
  000h 4    Offset in bytes (increasing, or 0=First child)  ;\both FFFFFFFFh
  004h 4    Size in bytes (always nonzero)                  ;/when Unused
Files and Folders do have exactly the same format, the only difference is that Folders will have Offset=00000000h in the NEXT list entry (in other words, the folder entry is followed by child entries, which start with Offset=0).
Offsets for Root entries are 800h-byte aligned, relative to begin of PKG file.
Offsets for Child entries are 4-byte aligned, relative to Parent Folder Offset.
The last Child entry has Offset+Size+Align(4) = Parent Folder Size.
The last Root entry has Offset+Size+Align(800h) = Total PKG filesize.
The last Root entry is usually followed by the ASCII string (which looks like junk, but it is useful because it equals to NextOffset=Nonzero=NoChilds).
  Example
  00003800h,00000666h   ;root00h          (file 666h bytes, padded=800h)
  00004000h,00000300h   ;root01h\..       (folder 300h bytes, padded=800h)
  00000000h,000000FDh   ;root01h\child00h (file FDh bytes, padded=100h)  ;\300h
  FFFFFFFFh,FFFFFFFFh   ;root01h\child01h (unused)                       ; byte
  00000100h,000001FDh   ;root01h\child02h (file 1FDh bytes, padded=200h) ;/
  00004800h,00001234h   ;root02h          (file 1234h bytes, padded=1800h)
  00006000h,00001234h   ;root03h          (file 1234h bytes, padded=1800h)
  FFFFFFFFh,FFFFFFFFh   ;root04h          (unused)
  00007800h,00001234h   ;root05h          (file 1234h bytes, padded=1800h)
  etc.
Notes: Unused entries can occur in both root and child folders (except, of course, not as first or last entry in child folders). Folders seem to occur only in root folder (although the format would allow nested folders).
Alternately, instead of Folders, one can use nested PKG's (the nested ones are using 4-byte align, without ASCII string and zeropadding in header).


CDROM File Archive BIGFILE.BIG (Gex)

Gex (GXDATA\BIGFILE.BIG and nested BIG files therein)
  000h 4     Number of Files (eg. F4h)
  004h 0Ch   Zero
  010h N*10h File entries
  ...  4     Archive ID (eg. 00000000h, FF53EC8Bh, or 83FFFFFFh)
  ...  ..    Zeropadding to 800h byte boundary
  ...  ..    File Data
File Entries:
  000h 4   Archive ID (same value as in above header)
  004h 4   Filename checksum or so (randomly ordered, not increasing)
  008h 4   Filesize in bytes
  00Ch 4   Fileoffset (800h-byte aligned) (increasing)
Filetypes in the archive include...
  looks like a lot of raw data without meaningful file headers...
  file C3h,ECh are raw SPU-ADPCM
  file 08h,09h are nested BIG archives, but with FileEntry[00h]=FF53EC8Bh
  file D9h,DAh are nested BIG archives, but with FileEntry[00h]=83FFFFFFh
FileEntry[04h] sometimes has similar continous values (maybe caused by similar filenames, and using a simple checksum, not CRC32).


CDROM File Archive BIGFILE.DAT (Gex - Enter the Gecko)

Gex - Enter the Gecko - BIGFILE.DAT
Used by Gex 2: Enter the Gecko (BIGFILE.DAT)
Used by Gex 3: Deep Cover Gecko (MagDemo20: G3\BIGFILE.DAT) -- UNSORTED
Used by Akuji (MagDemo18: AKUJI\BIGFILE.DAT)
Used by Walt Disney World Racing Tour (MagDemo35: GK\BIGFILE.DAT) -- UNSORTED
  000h 4     Number of Files      (C0h)
  004h N*18h File entries
  ...  ..    Zeropadding to 800h byte boundary
  ...  ..    File Data
File Entries:
  000h 4     Random
  004h 4     Filesize in bytes (uncompressed size)
  008h 4     Filesize in bytes (compressed size, or 0=uncompressed)
  00Ch 4     Fileoffset (800h-byte aligned) (increasing, unless UNSORTED)
  010h 4     Random
  014h 4     Random (or ascii in 1st file)
LZ Decompression:
  @@collect_more:
   flagbits=[src]+[src+1]*100h+10000h, src=src+2    ;16bit flags, unaligned
  @@decompress_lop:
   if dst>=dst.end then goto @@decompress_done
   flagbits=flagbits SHR 1
   if zero then goto @@collect_more
   if carry=0 then
     [dst]=[src], dst=dst+1, src=src+1
   else
     len=([src] AND 0Fh)+1), disp=([src] AND 0F0h)*10h+[src+1], src=src+2
     if len=1 or disp=0 then goto invalid   ;weirdly, these are left unused
     for i=1 to len, [dst]=[dst-disp], dst=dst+1, next i
   endif
   goto @@decompress_lop
  @@decompress_done:
   ret
Filetypes in the archive include...
  standard TIM  (eg. file 01h,02h)
  malformed TIM (eg. file 0Fh,14h) (with [8]=2*cx*cy+4 instead 2*cx*cy+0Ch)
  crippled VAB  (eg. file 0Eh,13h) (with hdr=filesize-4 plus raw ADPCM samples)
  several DNSa  (eg. file 0Dh,12h,17h,BCh) SND sound? (also used by kain)
  PMSa          (eg. Gex 3, World Racing) (SMP spu-adpcm samples)
  there seem to be no nested DAT files inside of the main DAT file
Note: same malformed TIMs are also in Legacy of Kain (folder0004h\file0013h).


CDROM File Archive FF9 DB (Final Fantasy IX)

DB Archive
  000h 1   ID (DBh)
  001h 1   Number of Types
  002h 2   Zero (0)
  004h N*4 Type List
  ...  ..  File Lists & File Data for each Type
Type List entries:
  000h 3   Offset to File List (self-relative, from current entry in Type List)
  003h 1   Data Type (00h..1Fh)
File List:
  000h 1   Data type (00h..1Fh) (same as in Type List)
  001h 1   Number of Files
  002h 2   Zero (0)
  004h N*2 File ID List (unique ID per type) (different types may have same ID)
  ...  ..  Zeropadding to 4-byte boundary
  ...  N*4 Offset List (self-relative, from current entry in Offset List)
  ...  4   End Offset  (first-relative, from first entry in Offset List)
  ...  ..  File Data (referenced from above Offset List)

Data Types
  00h  Misc (DOT1 Archives, or other files)
  01h  Unused?
  02h  Reportedly 3D Model data (vertices,quads,triangles,texcoords)
  03h  Reportedly 3D Animation sequences
  04h  TIM Texture
  05h  Reportedly Scripts (hdr="EV")              (eg. dir04\file32\1B-0001)
  06h  ?                                          (eg. dir02\file*)
  07h  Sound "Sequencer Data" (hdr="AKAO")        (eg. dir09\file*)
  08h  Sound? tiny files (hdr="AKAO")             (eg. dir04\file32\1B-0001)
  09h  Sound Samples (hdr="AKAO")                 (eg. dir0B\file*)
  0Ah  Reportedly Field Tiles and Field Camera parameters
  0Bh  Reportedly Field Walkmesh                  (eg. dir04\file32\1B-0001)
  0Ch  Reportedly Battle Scene geometry           (eg. dir06\file*)
  0Dh  ?                                          (eg. dir01\file01)
  0Eh  Unused?
  0Fh  Unused?
  10h  ?                                          (eg. dir05\file*)
  11h  ?                                          (eg. dir05\file*)
  12h  Reportedly CLUT and TPage info for models  (eg. dir04\file32\1B-0001)
  13h  Unused?
  14h  ?                                          (eg. dir05\file*)
  15h  Unused?
  16h  ?  (eg. dir04\file32\1B-0001)
  17h  ?  (eg. dir04\file32\1B-0000)
  18h  Sound (hdr="AKAO")  (eg. dir04\file32\1B-0001)
  19h  ?  (eg. dir04\file32\1B-0001)
  1Ah  ?  (eg. dir06\file*)
  1Bh  DB Archives (ie. further DB's nested inside of the parent DB archive)
  1Ch  ?  (eg. dir04\file32\1B-0001)
  1Dh  ?  (eg. dir03\file2328\1B-0001)
  1Eh  ?  (eg. dir04\file32\1B-0001)
  1Fh  ?  (eg. dir04\file32\1B-0001)
  20h..FFh Unused?


CDROM File Archive Ace Combat 2 and 3

Ace Combat 2 (Namco 1997) (ACE2.DAT and ACE2.STH/STP)
There are two archives, stored in three files:
  ACE2.DAT Directory for Data in ACE2.DAT itself         ;normal binary data
  ACE2.STH Directory for Data in separate ACE2.STP file  ;streaming data
Directory Format:
  000h 4    Unknown (1)
  004h 4    Number of entries (N)
  008h N*8  File List
File List entries (64bit):
  0-27   28bit Size/N (DAT=Size/4, STP=Size/800h)
  28-31  4bit  Type or Channel Number (see below)
  32-63  32bit Offset/800h in ACE2.STP or ACE2.DAT file
The files are interleaved depending on the Type/Channel number:
  File    Bit28-31 Channel Sector types...             Interleave Notes
  DAT     0        ch=0    DDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDD 1:1   data (normal)
  DAT     2        ch=0    DDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDD 1:1   data (exe)
  STH     0-6      ch=0-6  S.......S.......S.......S....... 1:8   stereo
  STH     8        ch=1    vvvvvvvSvvvvvvvSvvvvvvvSvvvvvvvS 1:1   video+stereo
  Whereas D=data, S=Stereo/Audio, v=video, .=other channels
Note: The DAT file does additionally contain PreSizeDOT1 and DOT1 child archives.
Demo: The archives in demo version (MagDemo01: ACE2.*) contain only a handful of files; the two EXE files in demo DAT archive are only 800h-byte dummy files, and demo STP is corrupted: Recorded as CDROM image with 920h-byte sectors, instead of as actual CD-XA sectors).

Ace Combat 3 Electrosphere (Namco 1999) (ACE.BPH/BPB and ACE.SPH/SPB)
There are two archives, stored in four files:
  ACE.BPH Directory for Data in separate ACE.BPB file  ;normal binary data
  ACE.SPH Directory for Data in separate ACE.SPB file  ;streaming data
Directory Format:
  000h 4    ID "AC3E" (=Ace Combat 3 Electrosphere)
  004h 4    Type (BPH=3=Data?, SPH=1=Streaming?)
  008h 2    BCD Month/Day?     (Japan=0427h, US=1130h)
  00Ah 2    BCD Year (or zero) (SPH=1999h, BPH=0)
  00Ch 4    Unknown (SPH=0, BPH/US=16CFh or BPH/JP=1484h)
  010h 4    Number of entries (N)
  014h N*8  File List
File List entries (64bit), when Bit31=1 (normal entries):
  0-18   19bit Size/N           (BPH=Size/4, SPB=Size/800h)
  19-23  5bit  Channel Number   (BPH=0, SPH=0..1Fh)
  24-26  3bit  Channel Interval (BPH=0, SPH=1 SHL N, eg. 3=Interval 1:8)
  27     1bit  Video Flag       (0=No, 1=Has Video sectors)
  28     1bit  Audio Flag       (0=No, 1=Has Audio sectors)
  29     1bit  Always 1 (except special entries with Bit31=0, see below)
  30     1bit  Unknown (US: Always 1, Japan: 0 or 1)
  31     1bit  Always 1 (except special entries with Bit31=0, see below)
  32-63  32bit Offset/800h in ACE.BPB or ACE.SPB file   (or 0 when bit31=0 ?)
File List entries (64bit), when Bit31=0:
  For unknown purpose, the normal entries with Bit31=1 are occassionally   followed by one or more entries with Bit31=0.
  Unknown if those entries do affect the actual storage (like switching to
  different channel numbers, or jumping to non-continous sector numbers).
  That unknown stuff exists in Japanese version only, not in US version.
  0-18   19bit Unknown (maybe some snippet size value in whatever units?)
  19-23  5bit  Always 0     (instead of Channel)
  24-27  4bit  Same as in most recent entry with Bit31=1
  28-31  4bit  Always 5     (instead of Flags)
  32-63  32bit Always 0     (instead of Offset)
The files are interleaved depending on the Channel Interval setting (and with types data/audio/video depending on Flags).
  File    Bit24-31    Sector types...                  Interval  Content
  BPH.US  E0h         DDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDD 1:1       data
  SPH.US  F8h         SvvvvvvvSvvvvvvvSvvvvvvvSvvvvvvv 1:1       stereo+video
  SPH.US  FBh         S.......v.......S.......v....... 1:8       stereo+video
  SPH.US  F3h         S.......S.......S.......S....... 1:8       stereo
  SPH.US  F4h         S...............S............... 1:16      stereo
  SPH.US  F5h         M............................... 1:32      mono
  BPH.JAP E0h         DDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDD 1:1       data
  SPH.JAP B8h,F8h     SvvvvvvvSvvvvvvvSvvvvvvvSvvvvvvv 1:1       stereo+video
  SPH.JAP B9h         Svvv....vvvv....Svvv....vvvv.... 1:2 (4:8) stereo+video
  SPH.JAP BAh,FAh     Mv......vv......vv......vv...... 1:4 (2:8) mono+video
  SPH.JAP BBh,FBh     S.......v.......S.......v....... 1:8       stereo+video
  SPH.JAP B3h,F3h     S.......S.......S.......S....... 1:8       stereo
  SPH.JAP B5h,F5h     M............................... 1:32      mono
  Whereas D=data, S=Stereo/Audio, M=Mono/Audio, v=Video, .=Other channels
As shown above, interval 1:2 and 1:4 are grouped as 4:8 and 2:8 (ie. 4 or 2 continous sectors per 8 sectors).
The Subheader's Channel number is specified in the above directory entries, Subheader's File number is fixed (0 for BPB, and 1 for SPB).
CDROM XA Subheader, File, Channel, Interleave
The SPB file is about 520Mbyte in both US and Japan, however, the Japanese version does reportedly contain more movies and some storyline that is missing in US/EU versions.
The BPB file contains DOT1 child archives, and Ulz compressed files.
CDROM File Compression Ulz/ULZ (Namco)
The SPB file contains movies with non-standard STR headers (and also uncommon: interleaved videos on different channels, at least so in the japanese version).
Demo: The archives do also exist on the demo version (MagDemo30: AC3\*), but the .SPB file is corrupted: Recorded as a RIFF/CDXAfmt file, instead of as actual CD-XA sectors).


CDROM File Archive NSD/NSF (Crash Bandicoot 1-3)

NSD/NSF versions
  v0  Crash Bandicoot Prototype (oldest known prototype from 08 Apr 1996)
  v1  Crash Bandicoot 1         (retail: S*\*.NSD and .NSF)
  v2  Crash Bandicoot 2         (MagDemo02: CRASH\S0\*.NSD and .NSF)
  v3  Crash Bandicoot 3 Warped  (MagDemo26,50: (S0\*.NSD and .NSF)


 ____________________________________ NSD _____________________________________

Overall NSD Structure (v0 contains only the Lookup entries)
  0000h 100h*4  Lookup Table, using index=((Filename/8000h) AND FFh) ;\
  0400h 4       Number of Chunks in .NSF file                        ; Lookup
  0404h 4       Number of Files in Lookup File List (N)              ;/
  0408h 4       Level Data Filename (eg. 4F26E8DFh="DATh.L")         ;-LevelDat
  040Ch 4       Bitmap Number of Colors (100h) (P) (0=None)          ;\
  0410h 4       Bitmap Width    (200h or 1B0h) (X) (0=None)          ; Bitmap
  0414h 4       Bitmap Height   (0D8h or 090h) (Y) (0=None)          ;/
  0418h 4       Compression: Offset/800h of first uncompressed chunk ;\
  041Ch 4       Compression: Number of compressed chunks (0..40h)    ; Compress
  0420h 40h*4   Compression: Compressed Chunk List (0=unused entry)  ;/
  ...   N*8     Lookup File List                                     ;-Lookup
  ...   ..      Level Data (size/format varies, see below)           ;-LevelDat
  ...   P*2     Bitmap Palette (16bit values, 8000h..FFFFh)          ;\Bitmap
  ...   X*Y     Bitmap Pixels  (0D8h*200h)                           ;/
There are four .NSD versions, which can be distinguished via filesize:
  v0  NSD Filesize=408h + N*8                           ;-Lookup only
  v1  NSD Filesize=520h + N*8 + P*2+X*Y + 210h          ;\
  v2  NSD Filesize=520h + N*8 + P*2+X*Y + 1DCh+S*18h    ; with extra stuff
  v3  NSD Filesize=520h + N*8 + P*2+X*Y + 2DCh+S*18h    ;/
Note: v0 is mainly used by the Crash Bandicoot prototype, but the Crash Bandicoot 1 retail version does also have a few v0 files.

NSD Lookup
The lookup table allows to find files (by filenames) in the NSF files. It does merely contain the NSF chunk number, so one must load/decompress that chunk to find the file's exact size/location in that chunk.
One can create a complete file list by scanning the whole NSF file without using the NDS lookup table.
 Lookup File List entries (indexed via Lookup Table):
  00h 4   Chunk Number in .NSF file
  04h 4   Filename (five 6bit characters)
Filenames:
  0     Type (always 1=Filename) (as opposed to 0=Memory Pointer)
  1-6   5th character ;-Extension  ;\character set is:
  7-12  4th character ;\           ; 00h..09h="0..9"
  13-18 3rd character ; Name       ; 0Ah..23h="a..z"
  19-24 2nd character ;            ; 24h..3Dh="A..Z"
  25-30 1st character ;/           ;/3Eh..3Fh="_" and "!"
  31    Always zero?
Special name: 6396347Fh="NONE.!"

NSD Level Data
Level Data exists in NSD v1-v3 (v0 does also have Level Data, but it's stored in NSF file "DAT*.L" instead of in the NSD file). There are two major versions:
 Level Data in NSD v1 (or NSF v0 file DAT*.L):
  000h  4       01h                                                  ;\
  004h  4       Level Number (xxh) (same as xx in S00000xx.NSD/NSF)  ;
  008h  4       3807C8FBh = "s0_h.Z" ?                               ; LevelDat
  00Ch  4       Zero                                                 ; v1
  010h  4       Zero                                                 ;
  014h  L*4     Namelist (40h*4)                                     ;
  ...   4       5Ah                                                  ;
  ...   F8h     Zerofilled                                           ;/
 Level Data in NSD v2-v3:
  000h  4       Number of Spawn Points (S)                           ;\
  004h  4       Zero                                                 ;
  008h  4       Level Number (xxh) (same as xx in S00000xx.NSD/NSF)  ; LevelDat
  00Ch  4       Number of Objects? (can be bigger than below list)   ; v2/v3
                  (eg. 1BDh or A5h or E4h)                           ;
  010h  L*4     Namelist for Objects?  (v2=40h*4, or v3=80h*4)       ;
  ...   4       Unknown, always 5Ah (maybe just list end marker?)    ;
  ...   C8h     Zerofilled                                           ;
  ...   S*18h   Spawn Points                                         ;/

NSD Bitmap
This bitmap is displayed while loading the level.

NSD Compression Info
Compression is only used in v1 (v2-v3 do also have the compression entries at [418h..51Fh], but they are always zerofilled).
 Compressed Chunk List entries at [420h..51Fh]:
  0-5   Compressed Chunk Size/800h (1..1Fh=800h..F800h bytes, 20h..3Fh=Bad?)
  6-31  Compressed Chunk Offset/800h
Note: Crash Bandicoot 1 retail does also have a few uncompressed files (either v0 files without compression info, or v1 files with zerofilled compression info).

 ____________________________________ NSF _____________________________________

NSF files consist of 64Kbyte chunks (compressed chunks are smaller, but will be 64Kbyte after decompression). Each chunk can contain one or more file(s). That implies that all files must be smaller than 64Kbyte (larger textures or ADPCM samples must be broken into multiple smaller files).
All files (except Textures) are NSF Child Archives which contain one or more smaller files/items.

NSF Chunk Types
 N*8Kbyte-Compressed-chunks:
  000h 2    ID, always 1235h (instead of 1234h)
  002h 2    Zero
  004h 4    Decompressed Size (max 10000h) (usually 9xxxh..Fxxxh, often Fxxxh)
  008h 4    Skip Size (max 40h or so, when last LZSS_len was 40h)
  00Ch ..   Compressed data
  ...  SK   Unused (Skip size)
  ...  ..   Final uncompressed bytes (10000h-compressed_size-skip_size)
 64Kbyte-Texture-chunks:
  000h 2    ID, always 1234h
  002h 2    Chunk Family (1=Texture)
  004h 4    Filename (five 6bit characters)
  008h 4    File Type (5=Texture)
  00Ch 4    Checksum (sum of bytes ar [0..FFFFh], with initial [0Ch]=00000000h)
  010h ...  Zerofilled
  020h ...  Texture data (raw VRAM data, FFE0h bytes?)
 64Kbyte-NonTexture-chunks:
  000h 2    ID, always 1234h
  002h 2    Chunk Family (0=Misc or 2..5=Sound)
  004h 4    Chunk Number*2+1
  008h 4    Number of Files (N) (can be 0, eg. prototype S0000003 chunk21h)
  00Ch 4    Checksum (sum of bytes ar [0..FFFFh], with initial [0Ch]=00000000h)
  010h N*4  File List (Offsets from ID=1234h to entries) (4-byte aligned)
  ...  ..   Offset for end of last File
  ...  ..   File Data (NSF Child Archives) (includes Type/Filename)
  ...  ..   Padding to 10000h-byte boundary

NSF Child Archives
  000h 4    ID, always 0100FFFFh
  004h 4    Filename (five 6bit characters)
  008h 4    File Type (01h..04h, or 06h..15h)
  00Ch 4    Item Count (I)
  010h I*4  Item List (Offsets from ID=0100FFFFh to items) (...unaligned?)
  ...  ..   Offset for end last item
  ...  ..   Data (Items)

NSF Chunk Loading and Decompression
The compression is a mixup of LZSS and RLE. Compressed chunks are max F800h bytes tall (10000h bytes after decompression).
  dst=chunk_buffer_64kbyte
  if chunksize is known (from NSD file)
    src=dst+10000h-chunksize
    diskread(fpos,src,chunksize)
  else (when parsing raw NSF file without NSD file)
    src=temp_buffer_64kbyte
    diskread(fpos,src,10000h)
  dst_start=dst, src_start=src
  if halfword[src+00h]<>1234h then   ;check ID (1234h=raw, or 1235h=compressed)
    dst_end=dst+word[src+04h]
    skip_size=word[src+08h]
    src=src+0Ch
    while dst<dst_end
      x=[src], src=src+1
      if x<80h then
        for i=0 to x-1, [dst]=[src], dst=dst+1, src=src+1, next i ;uncompressed
      else
        x=(x AND 7Fh)*100h+[src], src=src+1
        disp=x/8, len=(x AND 7)+3, if len=0Ah then len=40h
        for i=0 to len-1, [dst]=[dst-disp], dst=dst+1, next i     ;compressed
    src=src+src_skip
  if src<>dst then
    while dst<dst_start+10000h, [dst]=[src], dst=dst+1, src=src+1 ;uncompressed
  chunksize=src-src_start  ;<-- compute (when chunksize was unknown)
  fpos=fpos+chunksize      ;<-- fileposition of next chunk
As shown above, the chunk is intended to be loaded to the end of the decompression buffer, so trailing uncompressed bytes would be already in place without needing further relocation (despite of that intention, the actual game code is uselessly relocating src to dst, even when src=dst).
Note: All compressed files seem to have an uncompressed copy with same filename in another chunk (the NSD Lookup table does probably(?) point to the compressed variant, which should reduce CDROM loading time).

 _________________________________ Filetypes __________________________________

Filetype Summary
Below shows File Type, Chunk Family, Extension (5th character of filename), the version where the type is used, 4-letter type names (as found in the EXE files), and a more verbose description.
  Typ Family Ext Ver  Name Description
  00h -      !   -    NONE Nothing
  01h 0      V   all  SVTX Misc.Vertices
  02h 0      G   all  TGEO Misc.Model         ;\changed format in v2-v3 ?
  03h 0      W   all  WGEO Misc.WorldScenery  ;/
  04h 0      S   all  SLST Misc.UnknownSLST
  05h 01h    T   all  TPAG Texture.VRAM
  06h 0      L   v0   LDAT Misc.LevelData     ;-stored in NSD in v1-v3
  07h 0      Z   all  ZDAT Misc.Entity        ;-changed format in v2-v3 ?
  08h -      -   -    CPAT Internal?
  09h -      -   -    BINF Internal?
  0Ah -      -   -    OPAT Internal?
  0Bh 0      C   all  GOOL Misc.GoolBytecode
  0Ch 02h    A   v0   ADIO OldSound.Adpcm     ;\type 0Ch
  0Ch 03h    A   all  ADIO Sound.Adpcm        ;/
  0Dh 0      M   all  MIDI Misc.MidiMusic     ;-changed format in v1-v3 ?
  0Eh 04h    N   all  INST Sound.Instruments
  0Fh 0      D   v0-1 IMAG Misc.UnknownIMAG   ;\type 0Fh
  0Fh 0      X   v2-3 VCOL Misc.UnknownVCOL   ;/
  10h -      -   -    LINK Internal?
  11h 0      P   v0-1 MDAT Misc.UnknownMDAT   ;\type 11h
  11h 0      R   v3   RAWD Misc.UnknownRAWD   ;/
  12h 0      U   v0-1 IPAL Misc.Unknown      ;-Crash 1 only? (eg. S0000019.NSF)
  13h 0      B   v1-3 PBAK Misc.DemoPlayback ;-eg. in MagDemo02
  14h 0      V   v0-1 CVTX Misc.UnknownCVTX   ;\type 14h
  14h 05h    O   v2-3 SDIO Speech.Adpcm       ;/
  15h 0      D   v2-3 VIDO Misc.UnknownVIDO
As shown above, Type 0Ch is used with family 02h/03h, and Type 0Fh,11h,14h have two variants each (with different extensions). The Extensions do usually corresponding with the Types (although extension V,D are used for two different types each).

See also:
https://gist.github.com/ughman/3170834
https://dl.dropbox.com/s/fu29g6xn97sa4pl/crash2fileformat.html

Weird Note
"Sound entries don't need to be aligned as strictly for most (all?) emulators."
What does that mean???
Is there a yet unknown 16-byte DMA alignment requirement on real hardware?


CDROM File Archive STAGE.DIR and *.DAT (Metal Gear Solid)

Metal Gear Solid (MagDemo13: MGS\*)
Metal Gear Solid (MagDemo25: MGS\*)
Metal Gear Solid (MagDemo44: MGS\*) (looks same as in MagDemo13)
Metal Gear Solid (Retail: MGS\*)

Summary of ISO files in MGS folder (with filesizes for different releases)
  File        MagDemo13/44 MagDemo25  Retail/PAL
  .EXE        9C000h       9C800h     9D800h      ;-executable
  STAGE.DIR   590800h      11A7800h   42AE000h    ;-main archive
  FACE.DAT    2CA000h      3Dh (txt)  358800h     ;-face animation archive
  ZMOVIE.STR  -            -          2D4E800h    ;-movie archive
  DEMO.DAT    149B000h     3Dh (txt)  EC20000h    ;\DAT/SYM combos (the .SYM
  DEMO.SYM    88h          -          -           ; files were leaked in
  VOX.DAT     14F2000h     9F800h     B054800h    ; MagDemo13/MagDemo44 only)
  VOX.SYM     988h         -          -           ;/
  BRF.DAT     -            66800h     575800h     ;\whatever, unknown format(s)
  RADIO.DAT   16CB8h       3Dh (txt)  1AA956h     ;/

STAGE.DIR:
  000h 4     Size of File List (N*0Ch)
  004h N*0Ch Folder List
  ...  ..    Zeropadding to 800h-byte boundary
  ...  ..    Folder Data
 Folder List entries:
  000h 8     Foldername (zeropadded if less than 8 chars)  ;nickname=stg
  008h 4     Offset/800h to File List
 Folder Data (per folder):
  000h 2     Unknown (always 1) (maybe File List size/800h?)
  002h 2     Folder Size/800h (of whole folder, with file list plus file data)
  004h N*8   File List
  ...        Zeropadding to 800h-byte
  800h       Data (for files in current folder)
 File List entries:
  000h 2     File ID (checksum on name)
  002h 1     File Family (one of following chars: "cnrs")
  003h 1     File Type   (one of following chars: "abcdeghiklmoprswz",FFh)
  004h 4     File Size (or File Offset, when File Family="c")
Combinations of Family/Type characters are:
  .?a    ???? if any ???? (does NOT exist on PAL disc 1)    ;nickname=azm
  .sb    MIPS binary code  (leading)                        ;nickname=bin
  .cc    Whatever          (eg. vr10\*, s01a\*)             ;nickname=con
  .nd    Texture Archive   (leading) (contains PCX files)   ;nickname=dar
  .rd    Misc Archive      (leading) (eg. init\*)           ;nickname=dar
  .se    Sound Effects?    (trailing)                       ;nickname=efx
  .cg    Whatever, reportedly bytecode functions            ;nickname=gcx
  .ch    Whatever                                           ;nickname=hzm
  .ci    Whatever          (eg. ending\*, s01a\*)           ;nickname=img
  .ck    Whatever, model? aka "pat_xxx" files               ;nickname=kmd
  .cl    Lights, first word = size/10h                      ;nickname=lit
  .sm    Sound Music? Nested DOT1+DOTLESS Archives          ;nickname=mt3
  .co    Whatever "OARa"   (eg. d16e\*, s00a\*, s02c\*)     ;nickname=oar
  .cp    PCX bitmap        (eg. init\*)                     ;nickname=pcc
  .cr    Whatever "sNRJ1F" (eg. roll\*)                     ;nickname=rar
  .cs    Whatever          (eg. d16e\*, s01a\*)             ;nickname=sgt
  .sw    Wave Archive      (trailing)                       ;nickname=wvx
  .cz    Whatever "KMDa"   (eg. s11a, a11c, s14e, s15a)     ;nickname=zmd
  .c,FFh End of Family="c" area                             ;nickname=dar?
Files are starting on 800h-byte boundaries. Files with Family="c" are special, they contain an Offset entries instead of a Size entries, that Offsets are 4-byte aligned (relative to the 800h-byte aligned offset of the first Family="c" entry), the list of Family="c" entries is terminated by an entry with Family="c" and Type=FFh (which contains the end-offset of the last c-Family entry, aka the size of all c-Family entries).
Note: The above 3-letter nicknames are used on some webpages (unknown why, maybe they are derived from MGS filename extensions in the PC version).

FACE.DAT (face animations for video calls):
This contains several large blocks (supposedly one per stage, each block having its own file list). There is no directory to find the begin of the separate blocks, but one can slowly crawl through the file:
  NextBlock = CurrBlock + 4 + Offset(lastfile)+Size(lastfile) + Align800h
The content of each block is:
  000h 4     Number of Files in this block (eg. 19h or 1Ch)
  004h N*0Ch File List for this block
  ...  ..    File Data for this block
  ...  ..    Zeropadding to 800h-byte boundary (followed by next block, if any)
 File List entries:
  000h 2     File Type (0=Main/Eye/Mouth frames, 1=All frames are full size)
  002h 2     File ID (name checksum?)
  004h 4     Filesize in bytes
  008h 4     Offset in bytes, minus 4
Type 0 Files in FACE.DAT:
 This type use a single palette for all frames, and only the first frame is
 full 52x89pix, the other frames contain only the update sections (eg. eyes).
  000h 4     Offset to 200h-byte palette       (usually 20h)    ;\Main
  004h 4     Offset to Main Bitmap (52x89pix) (usually 220h)    ;/
  008h 4     Offset to 4th Bitmap  (usually xxxxh or 0=None)    ;\Eyes
  00Ch 4     Offset to 5th Bitmap  (usually xxxxh or 0=None)    ;/
  010h 4     Zero
  014h 4     Offset to 2nd Bitmap  (usually 143Ch or 0=None)    ;\Mouth
  018h 4     Offset to 3rd Bitmap  (usually xxxxh or 0=None)    ;/
  01Ch 4     Zero
  020h 200h  Palette (256 colors) ;\Main
  220h 1218h Main Bitmap          ;/
  1438h 4    Zero
  143Ch ..   2nd Bitmap (if any)  ;\Mouth
  ...   ..   3rd Bitmap (if any)  ;/
  ...   ..   4th Bitmap (if any)  ;\Eyes
  ...   ..   5th Bitmap (if any)  ;/
Type 1 Files in FACE.DAT:
 This type use separate palettes for each frame, all frames are full 52x89pix.
  000h 4     Number of frames
  004h N*0Ch Frame List
  ...  200h  1st Frame Palette
  ...  1218h 1st Frame Bitmap (52x89pix)
  ...  4     ?
  ...  200h  2nd Frame Palette
  ...  1218h 2nd Frame Bitmap (52x89pix)
  ...  4     ?
  ...  ..    3rd Frame ...
 Frame List entries:
  000h 4     Offset to Palette
  004h 4     Offset to Bitmap (usually at Palette+200h)
  008h 4     Unknown (often 000x000xh)
Bitmap Format (for both Type 0 and Type 1):
  000h 1     Offset X (always 00h in Main Bitmap)
  001h 1     Offset Y (always 00h in Main Bitmap)
  002h 1     Width    (always 34h in Main Bitmap, or less in 2nd-5th bitmap)
  003h 1     Height   (always 59h in Main Bitmap, or less in 2nd-5th bitmap)
  004h ..    Bitmap Pixels at 8bpp (Width*Height bytes)

DEMO.DAT, DEMO.SYM
VOX.DAT, VOX.SYM
The .DAT files contain several huge blocks, found on 800h-boundaries starting with:
  10 08 00 00 0x 00 00 00 ..
The .SYM files (if present) contain Names and .DAT Offsets/800h for those huge blocks in text format:
  "0xNNNNNNNN name",0Ah
VOX.DAT does (among others) contain SPU-ADPCM chunks with 2004h bytes or less, that is, a 1+3 byte chunk header (01h=SPU-ADPCM, 002004h=Size), plus 2000h byte or less SPU-ADPCM data.

RADIO.DAT:
Whatever, contains chunks with text messages, chunks are about as so:
  000h 4   Unknown    (eg. 36h,BFh,5Eh,00h)
  004h 4   Unknown    (eg. 03h,13h,00h,00h)
  008h 1   Unknown    (eg. 80h)
  009h 2   Chunk Size (eg. 0xh,xxh)          ;big-endian
  ..   ..  Chunk Data (Chunk Size-2 bytes) (binary stuff, and text strings)

BRF.DAT:
Contains several "folders" in this format:
  000h 4   Number of files in this folder
  004h ..  File(s)
  ...  ..  01h-padding to 800h-byte boundary
 Files have this format:
  000h ..  Filename ("name.pll",00h)
  ...  ..  Zeropadding to 4-byte boundary (aligned to begin of BRF.DAT)
  ...  4   File data size (usually a multiple of 4)
  ...  ..  File data
  ...  1   Zero (00h)
The above "folders" are then followed by several PCX files:
  000h ..  PCX file (starting with 0A,05,01,01 or 0A,05,01,08)
  ...  ..  01h-padding to 800h-byte boundary
The first part with .pll files does contain some kind of chunk sizes that could be used to find the next entry (but that would be very slow).
The second part with .PCX files doesn't have any chunk sizes at all (though one could decompress the .PCX file to find the end of each file) (also one could guess/find them by looking for 0A,05,01,01/08 on 800h-byte boundaries).

ZMOVIE.STR (movie archive with several STR files with subtitles)
CDROM File Video Streaming STR Variants

STAGE.DIR\*\*.sb - stage binary/header
This is the first file in most folders (except "init*" folders).
The file contains MIPS binary program code. And, there are ascii strings near end of .sb files, which include filenames, alike:
  "name.c",00h + garbage-padding to 4-byte boundary  ;<-- maybe source code?
  "pat_lamp",00h + zero- padding to 4-byte boundary  ;<-- name for File ID !
Those filenames do cover some (not all) of the name checksums in the STAGE.DIR folder.

STAGE.DIR\*\*.cp, STAGE.DIR\*\*.nd\.p, BRF.DAT\* - PCX bitmap files
MGS is using customized/corrupted PCX files as standard texture format (in STAGE.DIR\*\*.cp, STAGE.DIR\*\*.nd\*.p, and BRF.DAT\*).
For details on PCX format (and MGS-specific customizations), see:
CDROM File Video Texture/Bitmap (PCX)
Apart from PCX, there's also custom texture format for animated bitmaps (in FACE.DAT), and a few TIM images (in STAGE.DIR\init*\*.rd\*.r)

STAGE.DIR\*\*.nd - texture archive (with .PCX files)
STAGE.DIR\init*\*.rd - misc archive (with misc files)
These archives contain several chunks in following format:
  000h 2     File ID (checksum on name?)
  002h 1     File Type (one of following chars: "p" for .nd, or "kors" for .rd)
  003h 1     Zero (00h)
  004h 4     Chunk Size (rounded to 4-byte boundary)
  008h ..    Chunk Data
The File Type can be:
  .p    PCX bitmap                      ;-in *\*.nd archives
  .k    Whatever                        ;\
  .o    Whatever "OARa"                 ; in init*\*.rd archives
  .a    Whatever                        ;
  .r    Misc (TIM and other stuff)      ;/
There can be 1-2 texture archives per STAGE.DIR folder (both having File ID=0000h) (probably due to a memory size limit: the game does probably load one archive with max 300Kbytes, relocate its contents to VRAM, then load the next archive, if any).

STAGE.DIR\*\*.sw - wave archive
There can be one or more .sw files per stage folder (eg. two sw's in "vr*\*.sw").
  000h 4     Unknown (800h or C00h)       ;big-endian
  004h 4     Size of File List (N*10h)    ;big-endian
  008h 8     Zerofilled
  010h N*10h File List (xx,xx,xx,00,00,00,00,7F,00,00,00,0F,00,19,0A,00)
  ...  4     Unknown (40000h or 60000h)   ;big-endian
  ...  4     Size of SPU-ADPCM Data area  ;big-endian
  ...  8     Zerofilled
  ...  ..    SPU-ADPCM Data area (indexed from File List)
 File List entries:
  000h 4     Offset+Flags                 ;little-endian!
               bit0-16  Offset (from begin of SPU-ADPCM Data area)
               bit17    Unknown (0 or 1)
               bit18    Unknown (1)
               bit19-31 Unknown (0)
  004h 12    Whatever (always 00,00,00,7F,00,00,00,0F,00,19,0A,00)
The unknown fields might contain volume, ADSR, pitch or the like?

STAGE.DIR\*\*.se - sound effects? maybe short midi-like sequences or so?
  000h 80h*10h List (unused entries are 1x00000000h,3xFFFFFFFFh)
  800h ..      Data (whatever, usually 14h or more bytes per list entry)
 List entries:
  000h 1       Unknown (eg. 01h,10h,20h,A0h,80h,FFh)    ;\
  001h 1       Number of Voices? (1..3)                 ; all zero for
  002h 1       Unknown (1 or 0)                         ; unused list entries
  003h 1       Unknown (2 or 0 or 1)                    ;/
  004h 4       Offset-800h for 1st Voice?               ;-FFFFFFFFh=Unused
  008h 4       Offset-800h for 2nd Voice? (if any)      ;-FFFFFFFFh=Unused
  00Ch 4       Offset-800h for 3rd Voice? (if any)      ;-FFFFFFFFh=Unused
 Data:
  Seems to contain 4-byte entries (last entry being 00,00,FE,FF).

STAGE.DIR\*\*.sm - whatever nested archives - sound music? mide-like?
This does resemble a DOT1 Parent archive with 1-4 DOTLESS Child archives. Except, the offsets in Child archives are counted from begin of Parent archive.
 Data:
  Seems to contain 4-byte entries (last entry being 00,00,FE,FF).

File IDs
File IDs in STAGE.DIR (and maybe elsewhere, too) are computed as so:
  sum=0,
  for i=0 to len(filename)-1
    sum=sum*20h+filename[i]          ;\or so, 16bit overflows might be
    sum=(sum+sum/10000h) AND FFFFh   ;/cropped slightly differently
Examples: "abst"=1706h, "selectvr"=8167h.
Some filenames are empty (name="", ID=0000h).
Some filenames do match up with the STAGE.DIR foldername.
Some filenames do match up with strings in .sb file of current folder.
Other filenames are unknown.


CDROM File Archive DRACULA.DAT (Dracula)

Dracula - The Resurrection - DRACULA.DAT (180Mbyte)
  000h 4     Zero
  004h 4     Number of Entries (503h)
  008h 4     Zero
  00Ch 4     Random
  010h 10h   Zero
  020h N*10h File List
  ...  ..    Zeropadding to 800h-byte boundary
  ...  ..    Fild Data area
File List entries:
  000h 4     Offset/800h
  004h 4     Type (see below for info on different file types)
  008h 4     Filesize in bytes
  00Ch 4     Random (or 0 when Filesize=0)
Most of the .DAT file consists of groups of 3 files (with type 01h/40h, 20h and 400h; of which the files with type 20h and 400h may have Size=0=empty).
  Type=00000001h Cubemap           ;\either one of these
  Type=00000040h Cubemap.empty     ;/
  Type=00000020h Cubemap.overlay?  ;\these have size=0 when unused
  Type=00000400h Cubemap.sounds    ;/
There are some general purpose files with other types at end of .DAT file:
  Type=00000000h Archive with TIMs         (Size=AB74h)  (" RSC3.1V")
  Type=00000004h Unknown                   (Size=16164h) (00000064h)
  Type=00000008h Related to DRACULA1.STR   (Size=1000h)  (" RTS1.1V")
  Type=00001000h Unknown                   (Size=2000h)  ("BXFS1.1V")
  Type=00008000h Unknown                   (Size=71Dh)   ("  CM1.1V")
  Type=00020000h Unknown                   (Size=3B9h)   (" GSM0.1V")
  Type=02000000h Unknown                   (Size=0h)     (empty)
  Type=00000100h Related to DRACULA1.XA    (Size=1000h)  ("RAAX1.1V")
  Type=00000010h Unknown                   (Size=450h)   (" HYP0.1V")
  Type=00100000h Unknown                   (Size=4014h)  (" xFS1.1V") (x=A1h)
  Type=00000080h Unknown                   (Size=258F4h) (00000010h)
  Type=00000200h TIM (gui charset)         (Size=6E9Eh)  (TIM)
  Type=00010000h TIM (gui buttons)         (Size=10220h) (TIM)
  Type=00040000h Unknown                   (Size=2C4h)   (" TES0.1V")
  Type=00002000h TIM (gui book pages)      (Size=1040h)  (TIM)
  Type=00000800h Cubemap ;\as Type 01h,    (Size=4092Ch) (" RIV3.1V")
  Type=00004000h Cubemap ;/but [10h,14h]=0 (Size=4092Ch) (" RIV3.1V", too)
Type 01h - Cubemap:
  000h 8     Name, ASCII, padded with leading spaces (eg. " RIV3.1V")
  008h 4     Something (0, 1 or 2) (unknown, this isn't number of list entries)
  00Ch 4     Zero
  010h 4     Offset to Ext data (ACh)                       ;\ext data
  014h 4     Size of Ext data (eg. 0 or 84h)                ;/
  018h 6*4   Offsets to Side 0-5                            ;\cubemap sides
  030h 6*4   Sizes of Side 0-5 (0, 10220h, or 10820h)       ;/
  048h 44h   Zerofilled
  08Ch 20h   Name, ASCII (eg. "DEBUT0.VR", zeropadded)
  0ACh ..    Ext Data (if any)
  ...  ..    Cubemap TIM sides (if any)
 Note: The cubemap TIMs have 100h or 400h colors (in the latter case: 100h  colors for each quarter of the 8bpp bitmap).
 Note: The TIMs can be arranged as 3D-cubemap with six sides, or as hires
 2D-bitmap (composed of four TIMs, and 2 empty TIMs with size=0).
Type 40h - Empty Cubemap:
  Same as Type 01h, but size is always 0ACh (and all seven Size entries are 0)
Type 400h - Sound VAG's:
  000h 8     Name, ASCII, padded with leading spaces (eg. " XFS0.1V")
  008h 4     Zero
  00Ch 4     Number of Files (N) (max 10h)
  010h N*10h File List (100h bytes, zeropadded when less than 10h files)
  110h ..    File Data (VAG files)
 File List entries:
  000h 4     Unknown (55F0h, 255F0h or 20000h)
  004h 4     File ID (01010000h, increasing, or other when above=2xxxxh)
  008h 4     Offset in bytes                                ;\.VAG files
  00Ch 4     Filesize in bytes                              ;/
Type 20h - Cubemap overlays, polygons, effects or so?:
  000h 8      Name, ASCII, padded with leading dot (eg. ".MNA4.1V")
  008h 4      Zero
  00Ch 4      Random
  010h 4      Unknown 01h
  014h 4      Total Number of 40h-byte blocks (01h..[018h]) (H)
  018h 4      Total Number of 120h-byte blocks (eg. 1Fh,31h) (N)
  01Ch 4      Total Number of 1Ch-byte blocks (eg. 1Eh, 50h, F7h) (M)
  020h 4      Unknown 0 or 1 (in file 4EAh)
  024h 4      Unknown 01h
  028h 6*4    Offsets to Side 0-5 (at end of file and up) (or 0)  ;\cubemap
  040h 6*4    Sizes of Side 0-5   (10220h, or 10820h)     (or 0)  ;/sides
  058h H*40h  40h-byte blocks
  ...  N*120h 120h-byte blocks (related to offsets in 40h-byte blocks)
  ...  M*1Ch  1Ch-byte blocks  (related to offsets in 120h-byte blocks)
  ...  ..     Unknown data     (related to offsets in 1Ch-byte blocks)
  ...  ..     Ext data         (related to Ext offsets in 40h-byte blocks)
  FILE DOES END HERE!
  (below is allocated in above header, but not actually stored in the file)
  (maybe allocated as rendering buffer?)
  ...  -      Cubemap TIM sides
 The 40h-byte blocks are:
  000h 20h    Name (eg. "FLAMMES", zeropadded)
  020h 4      Unknown 01h or 00h
  024h 4      Offset to 120h-byte blocks (usually 98h, or higher)
  028h 4      Unknown 00h
  02Ch 4      Number of 120h-byte blocks (01h..[018h])
  030h 4      Unknown 01h
  034h 4      Ext Offset                ;\usually all zero
  038h 4      Ext Size (3C000h)         ; (except, nonzero in file 4EAh)
  03Ch 4      Ext Random (checksum?)    ;/
 The 120h-byte blocks are:
  000h 18h*4  List with Offsets to 1Ch-byte blocks (usually 4 entries nonzero)
  060h 18h*4  List with Zeroes
  0C0h 18h*4  List with Numbers of 1Ch-byte blocks (usually max 4 entries)
 The 1Ch-byte blocks are:
  000h 4      Unknown 04h
  004h 4      Width   20h or 10h
  008h 4      Height  20h or 10h or 30h
  00Ch 4      Unknown 60h or 10h
  010h 4      Unknown 00h or 30h
  014h 4      Offset to Unknown Data
  018h 4      Size of Unknown Data (Width*Height*1)
Type 00h - TIMs:
  000h 8      Name (" RSC3.1V")
  008h 8      Zerofilled
  010h 4      Number of used entries (1Fh) (max 80h)
  014h 80h*4  Offset List    (offsets to files) (A14h and up)
  214h 80h*4  Zero List      (zerofilled)
  414h 80h*4  Size List      (filesizes)
  614h 80h*4  Width List     (0Ch,18h,34h,2Ch) (in pixels)
  814h 80h*4  Height List    (0Ch,24h,34h,2Ch)
  A14h ..     Data (TIM files, with mouse pointers)


CDROM File Archive Croc 1 (DIR, WAD, etc.)

Croc 1 (MagDemo02: CROC\*) (plus more files in retail version)
CROCFILE.DIR and CROCFILE.1:
 CROCFILE.DIR:
  000h 4     Number of Entries (N)
  004h N*18h File List
  ...  4     Checksum (sum of all of the above bytes)
 CROCFILE.1:
  000h ..    File Data (referenced from .DIR)
 File List entries:
  000h 0Ch   Filename ("FILENAME.EXT", zeropadded if shorter)
  00Ch 4     File Size in bytes (can be odd) (including 8 byte for size/chksum)
  010h 4     File Offset in .1 file (unaligned, can be odd, increasing)
  014h 4     Zero (0)
CROCFILE.DIR\MP*.MAP (and MAP files inside of MAP*.WAD and MP090-100_*.WAD):
  000h 4    Size-8 of whole file (or Size-0 for those in MP*.WAD)
  004h 4    Flags? (usually 0Ch or 14h)
  008h 1    Filename length                (including trailing 00h, if any)
  009h ..   Filename ("P:\CROC\EDITOR\MAPS\..\*.MAP") (+00h in MAP05*.WAD)
  ...  ..   Unknown
  ...  1    Description length
  ...  ..   Description (eg. "Default New Map")
  ...  ..   Unknown
  ...  (4)  Checksum of whole file (sum of all bytes) (not in MP*.WAD)
CROCFILE.DIR\*.WAD:
 MAP*.WAD:
  000h 4    Size-8 of whole file
  004h ..   MAP file(s) (each with size/checksum, same format as MP*.MAP)
  ...  4    Checksum of whole file (sum of all of the above bytes)
 CROC.WAD, CROCSLID.WAD, EXCLUDE.WAD, MP*.WAD, OPTIONS.WAD, SWIMCROC.WAD:
  000h 4    Size-8 of whole file
  004h 4    Offset-8 to SPU-ADPCM data area
  008h ..   Data File area (model.MOD anim.ANI, bytecode.BIN, header.CVG, etc.)
  ...  ..   SPU-ADPCM data area (if any, note in CROCSLID.WAD and OPTIONS.WAD)
  The Data File area contains several "files" but doesn't have any directory
  with filename/offset/size. The only way to find the separate files seems to
  be to detect the type/filesize of each file, and then advance to next file
  (bytecode.BIN files start with a size entry, but files like .MOD or .ANI
  require parsing their fileheader for computing filesize).
  Note: The PC version reportedly has .WAD files bundled with .IDX file (that
  makes it easier to find files and filenames).
  Note: The STRAT.DIR file contains a list of filenames used in .WAD files
  (but lacks info on offset/size, so it isn't really useful).
CROCFILE.DIR\*.BIN:
 Sound.BIN Files (CROCFILE.DIR\AMBI*.BIN, MAP*.BIN, JRHYTHM.BIN, REVERB.BIN):
  000h 4    Size of .SEQ file                   ;\if any (not in REVERB.BIN)
  004h ..   SEQ file (starting with ID "pQES")  ;/
  ...  4    Size of .VH file                    ;\always present
  ...  ..   VH file (starting with ID "pBAV")   ;/
  ...  ..   VB file (sample data, SPU-ADPCM data, up to end of file)
 Music.BIN files (MAGMUS.BIN, MUSIC.BIN):
  000h 4      Size-8 of whole file (118h)
  004h ..     Increasing 32bit values ;sector numbers in PACK*.STR files or so?
  ...  4      Unknown (2EEh or 258h) (aka 750 or 600 decimal)
  ...  ..     Zeropadding
  11Ch 4      Checksum (sum of all of the above bytes)
  Note: MUSIC.BIN has an extra copy (without chksum) in EXCLUDE.WAD\MUSIC.BIN
 Ascii.BIN files (CREDITS*.BIN, MNAME.BIN):
  000h 4      Size-8 of whole file
  004h (2)    Type or so? (02h,01h) (only in CREDITS*.BIN, not in MNAME.BIN)
  ...  ..     Ascii strings (each string is: len,"text string",unknown)
  ...  4      Checksum (sum of all of the above bytes)
 Texture.BIN files (type 4) (STILLGO.BIN, STILLST.BIN, STILLTL.BIN):
  000h 2      Type (4=Texture/uncompressed, with 0Eh-byte list entries)
  002h 1      Zero (maybe Extra6byte as in type 5,6 Texture.BIN files)
  003h 2      Number of List entries (N) (always 4B0h in all three files)
  005h 2      Number of Texture Pages (usually 2)
  007h 2      Zero (maybe Unknown/Animation as in type 5,6 Texture.BIN files)
  009h N*0Eh  Polygon List (?,?,?,?,?,?, x1,y1, x2,y1, x1,y2, x2,y2)
  ...  40000h Texture Page uncompressed data (two pages, 20000h bytes each)
  ...  4      Checksum (sum of all of the above bytes)
 Texture.BIN files (type 5,6) (ENDTEXT*.BIN, FONT.BIN, FRONTEND.BIN,
 OUTRO.BIN, PUBLISH.BIN, STILL*.BIN, TB*.BIN, TK*.BIN, TPAGE213.BIN):
  000h 4      Zero (0)               (in TPAGE213.BIN: Size-8 of whole file)
  004h 2      Type (6=Texture/RLE16) (in TPAGE213.BIN: 5=Texture/uncompressed)
  006h 1      Extra6byte flag/size (0=None, 3=Extra6byte: TB*.BIN, TPAGE*.BIN)
  ...  (6)    Extra6byte data (unknown purpose, only present when [006h]=3)
  ...  2      Number of Polygon List entries (N)
  ...  2      Number of Texture Pages (usually 1) (in TK*_ENM.BIN: usually 2)
  ...  2      Number of Unknown Blocks (0=None, or 1,2,4,8)
  ...  (..)   Unknown Block(s), if any
  ...  2      Number of Animation Blocks (0=None)
  ...  (..)   Animation Block(s), if any
  ...  N*0Ch  Polygon List (?,?,?,?, x1,y1, x2,y1, x1,y2, x2,y2)  ;x,y or y,x?
  ...  (4)    Texture Page compressed size (T1) ;\only when [004h]=Type=6
  ...  (T1)   Texture Page compressed data      ;/
  ...  (4)    Texture Page compressed size (T2) ;\only when [004h]=Type=6
  ...  (T2)   Texture Page compressed data      ;/     and NumPages=2
  ...  20000h Texture Page uncompressed data    ;-only when [004h]=Type=5
  ...  4      Checksum (sum of all of the above bytes)
  Unknown Block(s):
  (Unknown purpose, each Unknown Block has the format shown below)
  000h 2    Unknown (looks like some index value, different for each entry)
  002h 2    Number of Unknown Items (eg. 1 or 2 or 4)
  004h ..   Unknown Items (NumItems*6 bytes) (three halfwords each?)
  Animation Block(s):
  (This is supposedly used to update portions of the Texture Page for
  animated textures, each Animation Block has the format shown below)
  000h 2    Number of Bitmap Frames in this Animation (usually 8)
  002h 2    Bitmap Width (in halfword units)
  004h 2    Bitmap Height
  006h 2    Unknown (1 or 3)                    ;\
  008h 2    Unknown (C10h, CC8h, 1E8h, or xxxh) ; maybe vram X,Y address?
  00Ah 2    Unknown (0)                         ;/
  00Ch ..   Bitmap Frames (Width*2*Height*NumFrames bytes, uncompressed)
  Croc 1 RLE16 compression:
  This is using unsigned little-endian 16bit LEN/DATA pairs, LEN can be:
   0000h..7FFFh --> Load one halfword, fill 1..8000h halfwords
   8000h..FFFFh --> Copy 1..8000h uncompressed halfwords
  BUG: Texture pages should be 20000h bytes (256x256 halfwords), but for
  whatever reason, the size of decompressed data can be 1FFEAh, 1FFF0h,
  1FFFAh, 20000h, or 20002h.
 Bytecode.BIN (inside of .WAD files):
  000h 4    Size of whole file
  004h ..   Whatever bytecode (starting with initial 16bit program counter?)
 Unknown.BIN (last 1-2 file(s) in EXCLUDE.WAD file):
  000h 4     Number of entries (N)
  004h N*18h Whatever
  ...  4     Checksum (sum of above bytes)
  Unknown purpose, retail version has one such file (with 0Ah entries), demo
  version has two such files (with 0Ah and 4Eh entries. The files start with:
  0A,00,00,00,00,00,00,00,00,00,64,00,00,00,EB,FF,...  ;demo+retail
  4E,00,00,00,00,00,64,00,00,00,50,00,00,00,64,00,...  ;demo
CROCFILE.DIR\*.MOD
 Demo version has one .MOD file in CROCFILE.DIR (retail has more such files):
  000h 2     Number of Models (N) (1 or more) (up to ECh exists)     ;\header
  002h 2     Flags (0 or 1)                                          ;/
  004h N*Var SubHeadersWithData  ;see below                          ;-data
  ...  4     Checksum (sum of all of the above bytes)                ;-checksum
  SubHeadersWithData(N*Var):
  004h 4     Radius                                                  ;\
  008h 48h   Bounding Box[9*8] (each 8byte are 4x16bit: X,Y,Z,0)     ; for each
  050h 4     Number of Vertices (V)                                  ; model
  054h V*8   Vectors (4x16bit: X,Y,Z,0)                              ;
  ...  V*8   Normals (4x16bit: X,Y,Z,0)                              ;
  ...  4     Number of Faces (F) (aka Polygons?)                     ;
  ...  F*14h Faces   (8x16bit+4x8bit: X,Y,Z,0,V1,V2,V3,V4, Tex/RGB)  ;
  ...  2     Number of collision info 1? (X)     ;\                  ;
  ...  2     Number of collision info 2? (Y)     ; only if           ;
  ...  X*2Ch Collision info 1?                   ; Flags.bit0=1      ;
  ...  Y*2Ch Collision info 2?                   ;/                  ;/
 There are further .MOD models inside of .WAD files, with slightly
 re-arranged entries (and additional reserved/garbage fields):
  000h 2     Number of Models (N) (1 or more) (up to ECh exists)     ;\
  002h 2     Flags (0 or 1)                                          ; header
  004h 4     Reserved/garbage (usually 224460h) (or 22C9F4h/22DF54h) ;/
  008h (4)   Number of Models WITH Data arrays (M)                   ;\
  00Ch (M*2) Model Numbers WITH Data arrays (increasing, 0..N-1)     ; ext.hdr
  ...  (..)  Padding to 4-byte boundary (garbage, usually=M)         ;/
  ...  N*68h Subheader(s)   ;see below                               ;-part 1
  ...  N*Var DataArray(s)   ;see below                               ;-part 2
  Subheaders(N*68h):
  000h 4     Radius                                                  ;\
  004h 48h   Bounding Box[9*8] (each 8byte are 4x16bit: X,Y,Z,0)     ; for each
  04Ch 4     Number of Vertices (V)                                  ; model
  050h 4     Reserved/garbage (usually 0022xxxxh)                    ;
  054h 4     Reserved/garbage (usually 0022xxxxh)                    ;
  058h 4     Number of Faces (F) (aka Polygons?)                     ;
  05Ch 4     Reserved/garbage (usually 0022xxxxh)                    ;
  060h 2     Number of collision info1? (X)                          ;
  062h 2     Number of collision info2? (Y)                          ;
  064h 4     Reserved/garbage (usually 0022xxxxh) or xxxxxxxxh)      ;/
  DataArrays(N*Var) with sizes V,F,X,Y from corresponding Subheader:
  (if ext.hdr is present, then below exists only for models listed in ext.hdr)
  000h V*8   Vectors (4x16bit: X,Y,Z,0)                              ;\
  ...  V*8   Normals (4x16bit: X,Y,Z,0)                              ; for each
  ...  F*14h Faces   (8x16bit+4x8bit: X,Y,Z,0,V1,V2,V3,V4, Tex/RGB)  ; model
  ...  X*2Ch Collision info 1?                                       ;
  ...  Y*2Ch Collision info 2?                                       ;/
 The ext.hdr mentioned above exists only in some .MOD files (usually in one of
 the last chunks of MP*.WAD). Files with ext.hdr have N>1, Flags=1 (but files
 without ext.hdr can also have those settings). Files with ext.hdr do usually
 have uncommon garbage values at hdr[4], which isn't too helpful for detection.
 The only way to detect models with ext.hdr seems to be to check if the ext.hdr
 contains valid increasing entries in range 0..N-1.
 WAD's that do contain a model with ext.hdr do usually also contain an extra
 100h-byte file, that file contains N bytes for model 0..N-1 (plus zeropadding
 to 100h-byte size), the bytes are supposedly redirecting models without Data
 Arrays to some other data source.
 The 100h-byte files don't have any header or checksum, they contain up to 9Ch
 entries (so there's always some zeropadding to 100h), the existing 100h-byte
 files contain following values in first 4 bytes (as 32bit value):
  04141401h, 0C040017h, 01010101h, 09030503h, 0A0B0A0Bh, 03020102h, 0C060900h,
  00060501h, 04040201h, 01010203h, 01030201h, 05000302h, 0C040317h, or Zero.
  To distinguish from other files: BIN/MAP files start with a 4-byte aligned
  Size value; if Size=0 or (Size AND 3)>0 or Size>RemainingSize then it's
  probably a 100h-byte file. Best also check if last some bytes are zeropadded.
 Exceptions:
  Retail MP090..MP100_*.WAD has model with ext.hdr, but no 100h-byte file
  Demo MP041_00.WAD has model with ext.hdr, with zerofilled 100h-byte file
 Note: Some models have ALL models listed in ext.hdr (which is about same as
 not having any ext.hdr at all; except, they ARE bundled with 100h-byte file).
CROCFILE.DIR\MP*.DEM
 Some (not all) MP*.WAD files are bundled with MP*.DEM files, supposedly
 containing data for demonstration mode. There are two versions:
  demo version:   size 2584h (9604 decimal) (some files with partial checksum)
  retail version: size 0E10h (3600 decimal) (without checksum)
CROCFILE.DIR\CROCWALK.ANI:
 Animation data, there is only one such file in CROCFILE.DIR:
  000h 2       Value (100h)
  002h 2       Number of Triggers (T) (2)
  004h (T*2)   Trigger List (with 2x8bit entries: FrameNo, TriggerID)
  ...  ..      Probably, Padding to 4-byte boundary (when T=odd)
  ...  4       Number of entries 1 (X)
  ...  X*18h   Whatever Array 1
  ...  4       Number of entries 2 (Y) (usually/always 64h)
  ...  X*Y*4   Whatever Array 2
  ...  4       Number of entries 3 (Z) (usually/always 0Ah)
  ...  X*Z*18h Whatever Array 3
 There are further .ANI files inside of .WAD files:
  000h 2       Value (100h or 200h)                         ;Animation Speed?
  002h 2       Number of Triggers (T) (0, 1, 2, 3, 5, or 9)
  004h 4       Garbage/Pointer (usually 224460h) (or zero)
  008h 4       Number of entries 1 (X) (1 or more)          ;Num Frames
  00Ch 4       Garbage/Pointer (usually 22C9F4h) (or 224460h or 22DF54h)
  010h 4       Number of entries 2 (Y) (usually 64h) (or 0) ;Num Vertices (?)
  014h 4       Garbage/Pointer
  018h 4       Number of entries 3 (Z) (usually 0Ah) (or 6 or 9)
  01Ch 4       Garbage/Pointer
  020h (T*2)   Trigger List (with 2x8bit entries: FrameNo, TriggerID)
  ...  ..      Padding to 4-byte boundary (garbage, usually=X)
  ...  X*18h   Whatever Array 1
  ...  X*4     Garbage/Pointers (0021EE74h,0021EE74h,xxx,...)
  ...  X*Y*4   Whatever Array 2   ;Vertex 3x10bit?            ;only if Y>0
  ...  (X*4)   Garbage/Pointers (0021EE74h,0021EE74h,xxx,...) ;only if Y>0
  ...  X*Z*18h Whatever Array 3
CROCFILE.DIR\TCLD.CVG:
 There is only one such file in CROCFILE.DIR:
  000h 4      Size-8 of whole file
  004h 4      Unknown (0)
  008h 4      Unknown (1)
  00Ch ..     SPU-ADPCM data
  ...  4      Checksum (sum of all of the above bytes)
 There are further .CVG files inside of .WAD files, these consist of two
 parts; 0Ch-byte Headers (in the data file area), and raw SPU-ADPCM data
 (in the spu-adpcm data area at end of the .WAD file):
  Header(0Ch):
  000h 4      Size+8 of data part
  004h 4      Unknown (0)
  008h 4      Unknown (0 or 1)
  Data(xxxx0h):
  000h ..     SPU-ADPCM data (starting with sixteen 00h bytes)
STRAT.DIR (in retail version with extra copy in CROCFILE.DIR\STRAT.DIR):
 This file contains a list of filenames for files inside of .WAD files, but
 it does NOT tell where those files are (in which WAD at which offset).
  000h 4     Number of Entries (N)
  004h N*xxh File List (retail=14h bytes, or demo=18h bytes per entry)
  ...  4     Checksum (sum of all of the above bytes)
 List entries are:
  demo:   entrysize=18h  ;Filename(0Ch)+Size(4)+Zeroes(8)
  retail: entrysize=14h  ;Filename(0Ch)+        Zeroes(8)
 The list contains hundreds of filenames, with following extensions:
  *.BIN  byte-code strategies
  *.MOD  models
  *.ANI  animations
  *.CVG  spu-adpcm voice data
 These "filenames" seem to be actually solely used as "memory handle names":
  MemoryHandle(#1) = LoadFile("FILENAME.BIN")  ;<-- names NOT used like this
  MemoryHandle("FILENAME.BIN") = LoadFile(#1)  ;<-- names used like this
PACK*.STR (retail version only):
  Huge files with XA-ADPCM audio data
MAGMUS.STR (demo version only):
  Huge mis-mastered 24Mbyte file (contains several smaller XA-ADPCM blocks,
  accidentally stored in 800h-byte FORM1 data sectors, instead of 914h-byte
  FORM2 audio sectors).
ARGOLOGO.STR, FOXLOGO.STR
  MDEC movies
COPYRIGHT.IMG, WARNING.IMG
  Raw bitmaps (25800h bytes, uncompressed, 320x240x16bpp)
CUTS\*.AN2 (looks like cut-scenes with polygon-streaming):
CDROM File Video Polygon Streaming
Note: MOD/ANI files contain many Reserved/Garbage/Pointer entries which are replaced by pointers after loading (the initial values seem to have no purpose; they are aften set to constants with value 002xxxxxh which could be useful for file type detection, but they vary in different game versions).
See also:
https://github.com/vs49688/CrocUtils/ (for PC version, PSX support in progress)


CDROM File Archive Croc 2 (DIR, WAD, etc.)

Croc 2 (MagDemo22: CROC2\CROCII.DIR\T*.WAD+DEM)
Disney's The Emperor's New Groove (MagDemo39: ENG\KINGDOM.DIR\T*.WAD+DEM)
Disney's Aladdin in Nasira's Rev. (MagDemo46: ALADDIN\ALADDIN.DIR\T*.WAD+DEM)
Harry Potter: Philosopher's Stone (POTTER.DIR\T*.WAD+DEM)
Harry Potter: Chamber of Secrets (POTTER.DIR\T*.WAD+DEM)
Overall .WAD format:
  000h 4      Total Filesize+/-xx (-4 or +800h or +1800h)
  004h 4+4+.. XSPT Chunk        ;Textures
  ...  4+4+.. XSPS Chunk        ;SPU-ADPCM Sound (if any, not in all .WAD's)
  ...  4+4+.. FINU Chunk        ;...whatever Data...?  ;Potter games only
  ...  4+4+.. XSPL Chunk        ;...whatever Data...?  ;Potter games only
  ...  4+4+.. XSPD Chunk        ;...whatever Data...?
  ...  4+4+.. TROP Chunk        ;...whatever Data...?  ;Potter games only
  ...  4+4    DNE Chunk         ;End marker (in Harry Potter: with data!)
XSPT Chunk (Textures):
  000h 4        Chunk Name "XSPT" (aka TPSX backwards)
  004h 4        Chunk Size (excluding 8-byte Name+Size)
  008h 4        Chunk Flags (02h or 06h or 0Eh)  ;02h in Croc 2
  00Ch (20h)    Name (eg. "Default new map", zeropadded)  ;\if Flags bit2=1
  ...  (804h)   Unknown ... SAME as in XSPD chunk !!!     ;/
  ...  4        Number of List 1 entries (N1) (xxh..xxxh) ;\
  ...  4        Number of Texture Pages (1..4)            ; List 1 and NumPages
  ...  N1*0Ch   List 1 Whatever (6B 2F xx 00..)           ;/
  ...  4        Number of List 2 entries (N2) (0..xxh)    ;\
  ...  4        Unknown (2 or 7)                          ; List 2
  ...  N2*04h   List 2 Whatever (halfwords?) (if N2>0)    ;/
  ...  (5*C00h) Whatever, 5*C00h, Palette+Stuff?          ;-if Flags bit3=1
  ...  ..       RLE16 compressed Texture Pages            ;-Texture bitmap
 RLE16 Texture notes:
  Compressed data consists of signed little-endian 16bit LEN+DATA pairs:
   LEN=0000h        --> invalid/unused
   LEN=0001h..7FFFh --> copy LEN halfwords from src
   LEN=8000h..FFFFh --> load ONE halfword as fillvalue, fill -LEN halfwords
  Compressed size is everything up to end of XSPT chunk
  Decompressed size is 20000h*NumTexturePages (=20000h,40000h,60000h or 80000h)
  That is: Width=256 halfwords, height 256*NumTexturePages lines. There seems
  to be only one RLE16 compression block for all Texture Pages, rather than one
  RLE16 block for each Page.
 BUG #1: Decompressed data in Aladding/Emperor does often contain only
  1FFFEh,3FFFEh,5FFFEh,7FFFEh bytes (the decompressed data has correct size
  when appending ONE halfword with random/zero value).
 BUG #2: Compressed data in Croc 2 ends with a RLE16 length value (-LEN), but
  lacks the corresponding RLE16 filldata (the decompressed data is 7FFFEh when
  filling those LEN halfwords with random/zero values).
XSPS Chunk (SPU-ADPCM Sound) (if any, isn't present in all .WAD files):
  000h 4      Chunk Name "XSPS" (aka SPSX backwards)       ;\
  004h 4      Chunk Size (excluding 8-byte Name+Size)      ; header
  008h 4      Chunk Flags (0 or 3 or 7)                    ;/
  00Ch 4      Number of Sounds (N1) (1..xxh)               ;\always present
  010h N1*14h Sound List                                   ;/
  ...  (4)     VAB/VH Size                                 ;\if Flags=3 or 7
  ...  (..)    VAB/VH Header                               ;/   (bit0 or bit1?)
  ...  (4)     Unknown (2 or 4)                            ;-if Flags=3 or 7
  ...  (4)     Whut (N2)                                   ;\if Flags.bit2=1
  ...  (N2*10h) Whut List (4 words: xxh,10h,xxxx00h,xxxx0h);/
  ...  4       Size of all Part 1 Sound Data blocks               ;\always
  ...  ..      SPU-ADPCM Sound Data (referenced from Sound List)  ;/
  ...  (4)     Size of all Part 2 Sound Data blocks (+8)          ;\if Flags=
  ...  (..)    SPU-ADPCM Sound Data (referenced from Sound List?) ;    3 or 7
  ...  (8)     Zero                                               ;/
 Sound List entries (as in FESOUND.WAD):
  000h 4    Sample Rate in Hertz (AC44h=44100Hz, 5622h=22050Hz, 3E80h=16000Hz)
  004h 2    Sample Rate Pitch    (1000h=44100Hz, 0800h=22050Hz, 05CEh=16000Hz)
  006h 2    Unknown (7Fh)
  008h 4    Unknown (1)          (1)               (8)
  00Ch 4    Unknown (42008Fh)    (1FC0001Fh)       (40008Fh)
  010h 4    Filesize             (xxx0h)           (xxx0h)
XSPD Chunk:
  000h 4     Chunk Name "XSPD" (aka DPSX backwards)
  004h 4     Chunk Size (excluding 8-byte Name+Size)
  008h 4     Flags-and/or-other stuff ? (eg. 00000094h or 0A801094h)
  00Ch 804h  Unknown ... SAME as in XSPT chunk !!!
  810h ..    Unknown ...
DNE Chunk (End marker):
  000h 4     Chunk Name " DNE" (aka END backwards)
  004h 4     Chunk Size (0)           (except, in Harry Potter: nonzero)
  ...  ..    Data (usually none such) (except, in Harry Potter: with data!)
Additional DEM files (always 1774h bytes) (if any, not all .WAD's have .DEM's):
  000h 4     Number of entries (N) (always 2EEh, aka 750 decimal) (or 258h)
  004h N*8   Whatever entries... maybe data for demonstration mode?
See also:
http://wiki.xentax.com/index.php/Argonaut_WAD


CDROM File Archive Alien Resurrection (WAD)

Alien Resurrection (PACK.BIN\*.WAD)
  000h 4    Always 100h
  004h 4    Number of 4-byte entries in TXF footer          (0..25h)
  008h 4    Number of ...? (usually same as above, or less) (0..25h)
  00Ch 4    Number of ...?                                  (0..0Ah)
  010h 4    Number of Files      (N)                        (0..8)
  014h 4    Trailer Part Size 1? (a bit smaller than Trailer Total Size)
  018h 4    Trailer Part Size 2? (0..170h) (usually multiple of 4)
  01Ch 4    Trailer Total Size   (TS)
  020h N*8  File List    (2x32bit: Type, Size)
  ...  ..   Zeropadding to 800h-byte boundary
  800h ..   File Data    (with zeropadding to 800h-byte boundary, each)
  ...  TS   Trailer      (with zeropadding to 800h-byte boundary)
File Types:
  00h,"FXT"   (aka TXF backwards)  Textures
  00h,"PAM"   (aka MAP backwards)  Map
  00h,"BVC"   (aka CVB backwards)  CVB
  00h,"NIB"   (aka BIN backwards)  Binary ("CMD " or "pQES"+"pBAV")
  00h,"DVC"   (aka CVD backwards)  CVD (there can be several CVDs)
  00h,"TAR"   (aka RAT backwards)  Rat
Note: Additional Filetypes in PACK.BIN (not in WAD) include .TUK (some kind of (un-)aligned DOT1's with text strings), .TXF (as in WAD), .CVD (as in WAD), .CVS (SPU-ADPCM), .TIM (either WxHxN or Malformed TIM with +2 bytes), .DEM (some kind of demo data).


CDROM File Archive Headerless Archives

Headerless Archives
Some games use files that contain several files badged together. For example,
  PSX Resident Evil 2, COMMON\DATA\*.DIE contains TIM+VAB badged together
  PSX Resident Evil 2, COMMON\DATA\*.ITP contains 1000h-byte aligned TIMs
  Blaster Master, DATA\MENU\*\*.PRT contains three smaller TIMs badged together
  Blaster Master, DATA\MENU\*\*.BG contains three bigger TIMs badged together
  Misadventures of Tron Bonne, KATWA\*.BIN has headerless archives (TIM+audio)
  Headerless BSS files contain several BS files with huge padding inbetween
To some level one could detect & resolve such cases, eg. TIM contains information about the data block size(s), if the file is bigger, then there may be further file(s) appended.
Some corner cases may be: Files with odd size may insert alignment padding before next file. Archives with 800h-byte filesize resolution will have zeropadding (or garbage) if the real size isn't a mutiple of 800h. Regardless of that two cases, archives may use zeropadding to 800h-byte or even 10000h-byte boundaries (as workaround one could skip zeroes until reaching a well-aligned nonzero word or double word (assuming that most files start with nonzero values; though not always, eg. raw ADPCM or raw bitmaps).


CDROM File Compression

Compressed Bitmaps
  .BS used by several games (and also in most .STR videos)
  .GIF used by Lightspan Online Connection CD
  .JPG used by Lightspan Online Connection CD
  .BMP with RLE4 used by Lightspan Online Connection CD (MONOFONT, PROPFONT)
  .BMP with RLE8+Delta also used by Online Connection CD (PROPFONT\ARIA6.BMP)
  .PCX with RLE used by Jampack Vol. 1 (MDK\CD.HED\*.pcx)
  .PCX with RLE used by Hot Wheels Extreme Racing (MagDemo52: US_01293\MISC\*)
  .PCX with RLE used by Metal Gear Solid (slightly corrupted PCX files)

Compressed Audio
  .XA uses XA-ADPCM (and also used in .STR videos)
  .VAG .VB .VAB uses SPU-ADPCM

Compressed Files
CDROM File Compression LZSS (Moto Racer 1 and 2)
CDROM File Compression LZSS (Dino Crisis 1 and 2)
CDROM File Compression LZSS (Serial Experiments Lain)
CDROM File Compression LZSS.8/32 and LZ+RLE+DELTA (Viewpoint)
CDROM File Compression LZSS.ZOO (Fossil Fuckers)
CDROM File Compression Ulz/ULZ (Namco)
CDROM File Compression SLZ/01Z (chunk-based compressed archive)
CDROM File Compression LZ5 and LZ5-variants
CDROM File Compression PCK (Destruction Derby Raw)
CDROM File Compression GT-ZIP (Gran Turismo 1 and 2)
CDROM File Compression GT20 and PreGT20
CDROM File Compression HornedLZ
CDROM File Compression LZS (Gundam Battle Assault 2)
CDROM File Compression BZZ
CDROM File Compression RESOURCE (Star Wars Rebel Assault 2)
CDROM File Compression TIM-RLE4/RLE8
CDROM File Compression RLE_16
CDROM File Compression PIM/PRS (Legend of Mana)
CDROM File Compression BPE (Byte Pair Encoding)
CDROM File Compression RNC (Rob Northen Compression)
CDROM File Compression Darkworks
CDROM File Compression Blues
CDROM File Compression Z (Running Wild)
CDROM File Compression ZAL (Z-Axis)
CDROM File Compression EA Methods
CDROM File Compression ZIP/GZIP/ZLIB (Inflate/Deflate)
CDROM File Compression LArc/LHarc/LHA (LZS/LZH)
CDROM File Compression UPX
CDROM File Compression LZMA
CDROM File Compression FLAC audio
Some other archvies that aren't used by any PSX games, but, anyways...
CDROM File Compression ARJ
CDROM File Compression ARC
CDROM File Compression RAR
CDROM File Compression ZOO
CDROM File Compression nCompress.Z
CDROM File Compression Pack.z (Huffman)
CDROM File Compression Freeze/Melt.F (LZHUF-based)
CDROM File Compression Octal Oddities (TAR, AR, CPIO, RPM)
CDROM File Compression MacBinary, BinHex, PackIt, StuffIt, Compact Pro
CDROM File Compression CP/M Squeeze, Crunch, CrLZH, LBR

Compressed Archives
Some Archives have "built-in" compression.
CDROM File Archive WAD (Doom)
CDROM File Archive BIGFILE.DAT (Gex - Enter the Gecko)


CDROM File Compression LZSS (Moto Racer 1 and 2)

Moto Racer 1 ("LZSS" with len+2) (MagDemo03: MRDEMO\IMG\*.TIM)
Moto Racer 2 ("LZSS" with len+3) (MagDemo16: MR2DEMO\IMG\*.TIM and .TPK)
  000h 4     ID "LZSS"
  004h 4     Decompressed Size
  008h ..    Compressed Data
This LZSS variant is unusually using 6bit len and 10bit disp. And, there are two versions: Moto Racer 1 uses len+2, and Moto Racer 1 uses len+3. There is no version information in the header, one workaround is to decompress the whole file with len+2, and, if the resulting size is too small, retry with len+3. Observe that the attempt with len+2 may cause page faults (eg. if the sum of len values is smaller than disp; so allocate some extra space at begin of compression buffer, or do error checks),
  @@collect_more:
   flagbits=[src]+100h, src=src+1    ;8bit flags
  @@decompress_lop:
   flagbits=flagbits SHR 1
   if zero then goto @@collect_more
   if carry=1 then
     [dst]=[src], dst=dst+1, src=src+1
   else
     disp=([src]+[src+1]*100h) AND 3FFh, len=([src+1]/4)+2_or_3, src=src+2
     if disp=0 then goto @@decompress_done
     for i=1 to len, [dst]=[dst-disp], dst=dst+1, next i
   endif
   goto @@decompress_lop
  @@decompress_done:
   ret


CDROM File Compression LZSS (Dino Crisis 1 and 2)

Dino Crisis 1 and 2 (PSX\DATA\*.DAT and *.DBS and *.TEX, File type 7,8)
Dino Crisis LZSS Decompression for files with type 7 and 8:
  @@collect_more:
   flagbits=[src]+100h, src=src+1    ;8bit flags
  @@decompress_lop:
   flagbits=flagbits SHR 1
   if zero then goto @@collect_more
   if carry=1 then
     [dst]=[src], dst=dst+1, src=src+1
   else
     disp=[src]+[src+1]*100h AND FFFh, len=[src+1]/10h+2, src=src+2
     if disp=0 then error
     for i=1 to len, [dst]=[dst-disp], dst=dst+1, next i
   endif
   if src<src_end then goto @@decompress_lop
   ret
The compressed file & archive header don't contain any info on the decompressed size (except, for compressed bitmaps, the archive header does contain width/height entries, nethertheless the decompressed file is usually BIGGER then width*height*2 (it can contain padding, plus 8 bytes).


CDROM File Compression LZSS (Serial Experiments Lain)

Serial Experiments Lain is using LZSS compression for TIMs (in SITEA.BIN, SITEN.BIN), and for Transparency Masks (in LAPKS.BIN).

Serial Experiments Lain (7MB SITEA.BIN on Disc 1, 5MB SITEB.BIN on Disc 2)
These are huge 5-7 Mbyte files with hundreds of chunks. Each chunk contains one compressed TIM.
 Each chunk is having this format:
  000h 4     Chunk ID "napk"
  004h 4     Decompressed size
  008h ..    LZSS compressed TIM data
  ...  ..    Zeropadding to 800h-byte boundary
Unknown how the game is accessing chunks (there is no chunk size info, so one would need read the whole file (or at least first 4-byte of each 800h-byte sector) for finding chunks with ID="napk").

Serial Experiments Lain (LAPKS.BIN on Disc 1 and 2)
This a huge 14Mbyte file with 59 chunks. Each chunk contains one or more 24bpp .BS images with black background (the images in each chunk are forming a short animation sequence; width/height may vary because all images are cropped to rectangles containing non-black pixels).
 Each chunk is having this format:
  000h 4     Chunk ID "lapk"
  004h 4     Chunk size (excluding 8-byte chunk header, excluding zeropadding)
  008h 4     Number of Files in this Chunk (N)
  00Ch N*0Ch File List
  ...  ..    File Data (bitmaps in .BS v0 format with uncommon headers)
  ...  ..    Zeropadding to 800h-byte boundary
 File List entries:
  000h 4     Offset in bytes (zerobased, from begin of File Data area)
  004h 2     Bitmap Width/2 + some 3bit value in LSBs?
  006h 2     Bitmap Height
  00Ch 4     Zero
 File Data (bitmaps in .BS v0 format with uncommon headers):
  000h 2     Bitmap Width
  002h 2     Bitmap Height
  004h 2     Quant for Y1,Y2,Y3,Y4
  006h 2     Quant for Cr,Cb
  008h 4     Size of compressed BS Bitstream plus 4 ;Transparency at [008h]+0Ch
  00Ch 2     Size/2 of MDEC data (after huffman decompression, without padding)
  00Eh 2     BS Version (0) (actually MSBs of above Size, but it's always 0)
  010h ..    BS Bitstream with DC and AC values (Huffman compressed MDEC data)
  ...  4     Transparency Mask Decompressed Size (Width*Height*2/8) (=2bpp)
  ...  ..    Transparency Mask LZSS-compressed data
BUG: The chunksize at C3A800h is set to 4C614h but should be 4D164h (the next chunk starts at C88000h).
Unknown how the game is accessing chunks (crawling all chunks would be exceptionally slow due to CDROM seek times, and won't work with the BUGGED chunksize).

Decompression function
This LZSS variant is unusually using 8bit len and 8bit disp.
   dst_end=dst+[src], src=src+4   ;decompressed size
  @@collect_more:
   flagbits=([src] SHL 24)+800000h, src=src+1    ;8bit flags
  @@decompress_lop:
   if dst=dst_end then goto @@decompress_done
   flagbits=flagbits SHL 1    ;32bit shift with carry-out/zeroflag
   if zero then goto @@collect_more
   if carry=0 then
     [dst]=[src], dst=dst+1, src=src+1
   else
     disp=[src]+1, len=[src+1]+3, src=src+2
     for i=1 to len, [dst]=[dst-disp], dst=dst+1, next i
   endif
   goto @@decompress_lop
  @@decompress_done:
   ret


CDROM File Compression LZSS.8/32 and LZ+RLE+DELTA (Viewpoint)

Used in Viewpoint SPRT bitmaps.

Decompress Viewpoint Method=0 Uncompressed
  for i=1 to dst_len, [dst]=[src], src=src+1, dst=dst+1
  ret
Used by Viewpoint fonts\*, screens\*, and in (some) streams\*\ files.

Decompress Viewpoint Method=1 LZ+RLE+DELTA
  dst_end=dst+((dst_len+1) and not 1))   ;dst_buf_size must be multiple of 2 !
  dst_start=dst
 @@decompress_lop:
  code=LittleEndian16bit[src], src=src+2
  len=code AND FFFh, code=code/1000h
  if code=0                                                        ;\RLE copy
    for i=1 to len, [dst+0..1]=[src+0..1], src=src+2, dst=dst+2    ;/
  elseif code=1                                                    ;\
    fillval=[src+0..1], src=src+2                                  ; RLE fill
    for i=1 to len, [dst+0..1]=fillval, dst=dst+2                  ;/
  elseif code=3..4                                                 ;\
    from=dst-8000h, if from<dst_start then from=dst_start          ; LZ
    if code=3 then from=from+LittleEndian16bit[src]*2, src=src+2   ;  <-- far
    if code=4 then from=from+(len AND FFh)*2, len=len/100h         ;  <-- near
    for i=1 to len, [dst+0..1]=[from+0..1], from=from+2, dst=dst+2 ;/
  else  ;code=2 or code=5 or code=6..0Fh                           ;\
    for i=1 to len                                                 ;
      steps=LittleEndain16bit[src+0..1], src=src+2  ;4x4bit steps  ; Delta
      for j=1 to 4                                                 ;
        x=steps AND 0Fh, steps=steps/10h                           ;
        if code=2 and x>7 then x=8-x                               ;  <-- +/-N
        if code=5 then x=x                                         ;  <-- +N
        if code>5 then x=0-x                                       ;  <-- -N
        if dst>dst_start then x=x+[dst-1] else x=x+(whatever/zero) ;
        [dst]=x, dst=dst+1                                         ;/
  if dst<>dst_end then goto @@decompress_lop
  code=LittleEndian16bit[src]   ;overshot, nonsense read after dst_end
  ret
Used by Viewpoint streams\level2\* and many streams\*\VCOV\*.
BUG: Many SPRT's start with code=2, which seems to rely on [dst_start-1]=00h (or maybe it relies on some leftover from previous SPRT). And those files use code=2 with large amounts of zeroes, which would be better compressed with code=1.

Decompress Viewpoint Method=2 LZSS.32
  dst_end=dst+((dst_len+3) and not 3))   ;dst_buf_size must be multiple of 4 !
  collected_bits=LittleEndian32bit[src+0], curr_bit=1           ;-fetch 32x1bit
  collected_codes=LittleEndian32bit[src+4], src=src+8           ;-fetch 2x16bit
 @@decompress_lop:
  if dst=dst_end then goto @@decompress_done                    ;-end check
  if (collected_bits and curr_bit)=0                            ;\copy 4-byte
    [dst+0..3]=[src+0..3], src=src+4, dst=dst+4                 ;/uncompressed
  else
    disp=(collected_codes and 3FFh)*4                                 ;\
    len=(collected_codes/400h) and 3Fh                                ; copy
    for i=1 to len, [dst+0..3]=[dst-disp+0..3], src=src+4, dst=dst+4  ;/
    collected_codes=collected_codes/10000h                      ;\
    if collected_codes=0 then                                   ; fetch
      collected_codes=LittleEndian32bit[src+4], src=src+8       ;/
  curr_bit=curr_bit*2
  if curr_bit AND FFFFFFFFh=0 then  ;fetch more (even if already at dst_end ?!)
    collected_bits=LittleEndian32bit[src+0], curr_bit=1         ;-fetch
  goto @@decompress_lop
 @@decompress_done:
  ret
Used by Viewpoint streams\level1\*\*.

Decompress Viewpoint Method=3 LZSS.8
  dst_end=dst+dst_len
  collected_bits=LittleEndian32bit[src], src=src+4, curr_bit=1  ;-fetch 32x1bit
  collected_codes=LittleEndian32bit[src], src=src+4             ;-fetch 2x16bit
  collected_bytes=LittleEndian32bit[src], src=src+4, numbytes=4 ;-fetch 4x8bit
 @@decompress_lop:
  if dst=dst_end then goto @@decompress_done                    ;-end check
  if (collected_bits and curr_bit)=0                            ;\copy 1-byte
    [dst]=collected_bytes AND FFh, dst=dst+1                    ;/uncompressed
    collected_bytes=collected_bytes/100h, numbytes=numbytes-1      ;\
    if numbytes=0                                                  ; fetch
      collected_bytes=LittleEndian32bit[src], src=src+4, numbytes=4;/
  else
    disp=(collected_codes and 3FFh)                             ;\copy
    len=(collected_codes/400h) and 3Fh                          ; compressed
    for i=1 to len, [dst]=[dst-disp], src=src+1, dst=dst+1      ;/
    collected_codes=collected_codes/10000h                      ;\
    if collected_codes=0 then                                   ; fetch
      collected_codes=LittleEndian32bit[src+4], src=src+8       ;/
  curr_bit=curr_bit*2
  if curr_bit AND FFFFFFFFh=0 then  ;fetch more (even if already at dst_end ?!)
    collected_bits=LittleEndian32bit[src+0], curr_bit=1         ;-fetch
  goto @@decompress_lop
 @@decompress_done:
  ret
Used by Viewpoint streams\level6.str\*\*.


CDROM File Compression LZSS.ZOO (Fossil Fuckers)

Jarret & LaBonte Stock Car Racing (2000) (MagDemo38: WTC\*.ZOO)
  0000h 4     Decompressed Size                          ;\1st sector
  0004h 7FCh  Garbage                                    ;/
  0800h 4     Decompressed Size (same as above)          ;\2nd sector
  0804h 7FCh  LZSS compressed data, part 1               ;/
  1000h 800h  LZSS compressed data, part 2               ;-3rd sector
  1800h 800h  LZSS compressed data, part 3               ;-4th sector
  ...   ..    etc.
Note: The file format & compression method is unrelated to ZOO archives (to distinguish between the formats: ZOO archives have [0014h]=FDC4A7DCh, the LZSS.ZOO files have [0014h]=Garbage).

Porsche Challenge (1997) (SRC\*.*)
Both compressed and uncompressed files are starting with 4-byte headers:
 Compressed (with size.bit31=0):
  0000h 4     Decompressed Size                          ;\1st sector
  0004h 7FCh  LZSS compressed data, part 1               ;/
  0800h 800h  LZSS compressed data, part 2               ;-2nd sector
  1000h 800h  LZSS compressed data, part 3               ;-3rd sector
  ...   ..    etc.
 Uncompressed (with size.bit31=1):
  0000h 4     Uncompressed Size, plus 80000000h          ;\uncompressed
  0004h ..    Uncompressed Data                          ;/
There aren't any meaningful headers or file extensions for detecting these files, however, one can detect the CDROM as a whole by checking for the following game codes (in root directory file names or SYSTEM.CNF):
  SCUS-94187 Porsche Challenge NTSC-U   ;-known to use this compression format
  SIPS-60016 Porsche Challenge NTSC-J   ;\
  SCPS-45117 Porsche Challenge ASIA     ; probably thise are using it, too
  SCES-00409 Porsche Challenge PAL      ;/
And then, expect all files in the ISO filesystem to start with the above 4-byte headers - except, the following files contain raw data without such headers:
  \CDFAT.DAT              ;whatever
  \SYSTEM.CNF             ;boot info
  \Sxxx_nnn.nn            ;boot exe (name depends on region)
  \SRC\CAR.EXE            ;another exe
  \SRC\MENU\STREAM\*.STR  ;mdec video streams
  \SRC\MUSIC\*.MVB        ;spu-adpcm streams

Decompression functions
  decompress_zoo_file:
   if LittleEndian32bit[src+14h]=FDC4A7DCh then refuse   ;refuse ZOO archives
   if LittleEndian32bit[src]<>LittleEndian32bit[src+800h] then refuse
   src=src+804h   ;skip header and garbage
   call decompress_body
   ret
  ;---
  decompress_porsche_file:
   if gamecode<>(SCUS-94187, SIPS-60016, SCPS-45117, SCES-00409) then refuse
   if filename=(CDFAT.DAT, *.CNF, *.MVB, *.STR) or [src]="PS-X EXE" then refuse
   dst_len=LittleEndian32bit[src], src=src+4
   if dst_len AND 80000000h then
     for i=1 to dst_len AND 7FFFFFFFh, [dst]=[src], src=src+1, dst=dst+1
   else
     call decompress_body
   ret
  ;---
  decompress_body:
   next=src+7FCh                       ;end of 1st sector
  @@sector_lop:
   decompress_sector
   src=next, next=src+800h             ;next sector
   if src<src_end then goto @@sector_lop
   ret
  ;---
  decompress_sector:
  @@collect_more:
   flagbits=([src] SHL 24)+800000h, src=src+1    ;8bit flags
  @@decompress_lop:
   flagbits=flagbits SHL 1    ;32bit shift with carry-out/zeroflag
   if zero then goto @@collect_more
   if carry=0 then
     [dst]=[src], dst=dst+1, src=src+1
   else
     disp=[src]*100h+[src+1], src=src+2
     if disp=FFFFh then goto @@decompress_done
     len=(disp/800h)+3, disp=(disp AND 7FFh)+1
     for i=1 to len, [dst]=[dst-disp], dst=dst+1, next i
   endif
   goto @@decompress_lop
  @@decompress_done:
   ret


CDROM File Compression Ulz/ULZ (Namco)

Ulz/ULZ uses fairly normal LZSS compression, unusually with variable Len/Disp ratio, three separate data streams (flg/lz/dta), and rather weird end check in version=0.

Ulz Format (Ace Combat 3 Electrosphere, Namco)
Ulz Format (Klonoa, MagDemo08: KLONOA\FILE.IDX\*)
  000h 4    ID ("Ulz",1Ah) (parts lowercase)
  004h 3    Decompressed Size in bytes
  007h 1    Version (0 or 2)
  008h 3    Offset to Uncompressed data   <-- reportedly can be 0 in version=0?
  00Bh 1    Number of Disp bits (DispBits=N, LenBits=16-N) (usually 0Ah..0Dh)
  00Ch 4    Offset to Compressed data
  010h ..   Compression Flags   (32bit entries)
  ...  ..   Uncompressed data   (8bit entries)
  ...  ..   Zeropadding to 4-byte boundary
  ...  ..   Compressed data     (16bit entries)
Most files use version=2 (eg. US:ACE.BPH\0006h\000Fh contains DOT1 with TIMs).
Some files use version=0 (eg. US:ACE.BPH\0048h\*\* contains TIMs).

ULZ Format (Time Crisis, Namco)
  000h 4    ID ("ULZ",1Ah) (all uppercase)
  004h 2    Zero
  006h 1    Version (0 or 2)
  007h 1    Number of Disp bits (DispBits=N, LenBits=16-N) (usually 0Ah..0Dh)
  008h 4    Offset to Uncompressed data
  00Ch 4    Offset to Compressed data
  010h 4    Decompressed Size in bytes
  014h ..   Compression Flags   (32bit entries)
  ...  ..   Uncompressed data   (8bit entries)
  ...  ..   Zeropadding to 4-byte boundary
  ...  ..   Compressed data     (16bit entries)
Most files use version=2 (eg. EUR: AD*\TIM*.FHT\*)
Some files use version=0 (eg. EUR: AD4\TIM0_0.FHT\0018h, 0019h)

Ulz/ULZ Decompression Function
  if [src+00h]="Ulz",1Ah then
    version   = Byte[src+07h]
    disp_bits = Byte[src+0Bh]
    dst_end   = LittleEndian24bit[src+04h] + dst
    src_dta   = LittleEndian24bit[src+08h] + src
    src_lz    = LittleEndian32bit[src+0Ch] + src
    src_flg   = src + 10h
    add_len   = 3
    flg_1st   = 31  ;process flag bit31 first
  if [src+00h]="ULZ",1Ah then
    version   = Byte[src+06h]
    disp_bits = Byte[src+07h]
    src_dta   = LittleEndian32bit[src+08h] + src
    src_lz    = LittleEndian32bit[src+0Ch] + src
    dst_end   = LittleEndian32bit[src+10h] + dst
    src_flg   = src + 14h
    add_len   = 2
    flg_1st   = 0   ;process flag bit0 first
  collected = 80000000h   ;initially empty, plus stop bit
 @@decompress_lop:
  if version=2 AND dst=dst_end then goto @@decompress_done
  flag = collected AND 80000000h
  collected=collected*2
  if collected=0
    collected = LittleEndian32bit[src_flg], src_flg=src_flg+4
    if flg_1st=0 then ReverseBitOrder(collected)  ;or make custom/faster code
    flag = collected AND 80000000h
    if version=0 AND collected=0 then goto @@decompress_done
    if version=0 then collected=collected*2       ;<-- has implied stop bit
    if version=2 then collected=collected*2 + 1   ;<-- shift-in stop bit
  if flag=0     ;compressed
    disp = LittleEndian16bit[src_lz], src_lz=src_lz+2
    len  = (disp SHR disp_bits) + add_len
    disp = (disp AND ((1 shl disp_bits)-1)) + 1
    for i=1 to len, [dst]=[dst-disp], dst=dst+1, next i
  else          ;uncompressed
    [dst]=[src_dta], dst=dst+1, src_dta=src_dta+1
  goto @@decompress_lop
 @@decompress_done:
  ret
Note: Version=2 has 32 flags per 32bit. Version=0 has 31 flags and 1 stop bit per 32bit, plus 32 null bits at end of data (which is all rather wasteful, there's no good reason to use version=0).


CDROM File Compression SLZ/01Z (chunk-based compressed archive)

SLZ/01Z files are Chunk-based archives with one or more compressed chunk(s).
Used by Hot Shots Golf 2 (retail: DATA\F0000.BIN\*, MagDemo31/42: HSG2\MINGOL2.BIN\*)

SLZ/01Z chunk headers
The archive consists of Chunk(s) in following format:
  000h 3     ID (either "01Z" or "SLZ", both are used)
  003h 1     Method (00h=Uncompressed, 01h=LZSS, 02h=LZSS+FILL)
  004h 4     Compressed size (SIZ) (same as decompressed when Method=0)
  008h 4     Decompressed size
  00Ch 4     Distance to next chunk, if any (SIZ+10h+Align4, or 0=None)
  010h SIZ   Compressed data

SLZ/01Z decompression function:
   method=byre[src+3]
   len=word[src+8]
   src=src+10h
   if method=0 then
     for i=1 to len, [dst]=[src], dst=dst+1, src=src+1, next i
     goto @@decompress_done
   dst_end = dst+len
  @@collect_more:
   flagbits=[src]+100h, src=src+1    ;8bit flags
  @@decompress_lop:
   if method=2 AND dst=dst_end then goto @@decompress_done
   flagbits=flagbits SHR 1
   if zero then goto @@collect_more
   if carry=1 then
     [dst]=[src], dst=dst+1, src=src+1
   else
     disp=([src]+[src+1]*100h) AND 0FFFh, len=([src+1]/10h)+3, src=src+2
     if method=1 AND disp=0 then goto @@decompress_done
     if method=2 AND len=12h then     ;special fill mode...
       len=disp/100h+3, val=disp AND FFh               ;len=3..12h
       if len=3 then len=val+13h, val=[src], src=src+1 ;len=13h..112h
       for i=1 to len, [dst]=val, dst=dst+1, next i    ;len=4..112h
     else
       for i=1 to len, [dst]=[dst-disp], dst=dst+1, next i
   endif
   goto @@decompress_lop
  @@decompress_done:
   ret


CDROM File Compression LZ5 and LZ5-variants

Original LArc LZ5 (method "-lz5-")
LZ5 was used by LArc compression tool from 1988/1989, decompression is also supported by LHarc/LHA. LZ5 is basically LZSS compression, but with some oddities:
  LZ5 is often implemented with a ringbuf (instead of actual sliding window)
  LZ5 uses absolute ringbuf indices (instead of relative sliding dest indices)
  LZ5 requires the ringbuf to be initially prefilled with constants
  LZ5 ringbuf is 1000h bytes tall and starts with write index FEEh
LArc was discontinued in 1989, but LZ5-variants have been kept used on PSX and Nintendo DSi; those variants are just using the raw compression, without LArc archive headers.

DSi Dr. Mario (DSiware, Nintendo/Arika, 2008-2009)
 INFO.DAT
  encrypted directory with filename, offset and compressed/uncompressed size
 GAME.DAT
  000h 4   ID "ALZ1"
  004h ... ALZ1 Compressed data (with size as defined in INFO.DAT)
  ...  4   ID "ALZ1"
  ...  ... ALZ1 Compressed data (with size as defined in INFO.DAT)
  ...

PSX Final Fantasy VII (FF7)
ALZ1 compression is used in various folders (ENEMY*, STAGE*, STARTUP, MAGIC, FIELD, MINI, MOVIE, WORLD) with various filename extensions (.LZS .BSX .DAT .MIM .TIZ .PRE .BSZ .TXZ).
  000h 4   Compressed Size       ;=Filesize-4
  004h ..  ALZ1 Compressed data (Filesize-4 bytes)
Detection can be more or less reliably done by checking [000h]=Filesize-4, one could also check the filename extensions, although .DAT doesn't qualify as unique extension.
The file doesn't contain any info on the decompressed size, so one cannot know the decompression buffer size without first decompressing the file.
Note: For whatever reason, the game does also have one GZIP compressed file (BATTLE\TITLE.BIN).

PSX Final Fantasy VIII (FF8)
About same as FF7, but detection is less reliable because there are no filenames or extensions, and the file header is somewhat randomly set to [000h]=(Filesize-4)+0..7, unknown why, maybe it's allocating dummy bytes to last some compression flags.
  000h 4   Compressed Size+0..7  ;=(Filesize-4)+0..7
  004h ..  ALZ1 Compressed data (Filesize-4 bytes)
ALZ1 is used in four Root files (0001h,0002h,0017h,001Ah), and in many Field files, and maybe in further files elsewhere.

Dragon Seeds (*.DAT\*)
  000h 4   Compressed Size       ;=(Filesize-4-Padding)
  004h ..  ALZ1 Compressed data (Filesize-4-(0..3) bytes)
  ...  ..  Zeropadding to 4-byte boundary
About same as FF7, with trailing padding.

Vampire Hunter D (EFFECT\*.TPK, SOUND\*.SLH, MAPFILE\*\*, CHRHEAD\*)
  000h 4     Decompressed size
  004h 4     Compressed size (including 8-byte header, without padding, if any)
  008h ..    DECODE_S compressed data (containing TIM, SEQ, VAB, TPK, or BO3!)
  ...  (..)  Optional padding to 4-byte boundary (eg. in MAPFILE\0BEh\*)
The decompresion is almost same as ALZ1 (but with 8-byte header, and with ringbuf[FEEh..FFFh] left uninitialized). The compression is used in various files:
  EFFECT\*.TPK --> compressed TPK's
  MAPFILE\*    --> compressed TIM's
  MAPFILE\88Ah --> compressed SEQ's
  SOUND\*.SLH  --> compressed VAB's
  CHRHEAD\*    --> compressed TIM's VAB's and BO3!'s
Note: The game does also support another DECODE_D decompression function (but unknown if/which files are using that format). The decompression functions can be found by looking for the "decode_s.c" and "decode_d.c" error strings in the EXE file.

PSX Ultimate Fighting Championship (MagDemo38: UFC\CU00.RBB\383h\*)
  000h 8     ID "00zLATAD" (aka DATALz00 backwards)               ;\PreHeader
  008h 4     Total Filesize excluding PreHeader+Padding (SIZ+0Ch) ;/
  00Ch 4     Unknown (always 1000h)                               ;\
  010h 4     Compressed data size                       (SIZ)     ; Header
  014h 4     Decompressed data size                               ;/
  018h SIZ   zLATAD Compressed data                               ;-Data
  ...  ..    Padding to 4-byte boundary                           ;-Padding

Ninja (MagDemo13: NINJA\LOADPICS\*.PAK and NINJA\VRW\FOREST.VRW\*)
  000h 8     ID "VRAM-WAD"
  008h 4     Compressed size (Filesize-Padding-10h)
  00Ch 4     Decompressed size       (18000h, 28000h, 40000h bytes)
  010h ..    VRAMWAD Compressed data (192x256, 320x256, 512x256 halfwords)
  ...  (..)  Padding to 4-byte boundary (if any, in files in .VRW archives)
Observe that Ninja is using the same ID="VRAM-WAD" for .PAK files and .VRW archives (if [008h]=Filesize-Padding-10h then it's a compressed .PAK file, otherwise it's a .VRW archive; whereas, those .VRW archives do themselves contain several .PAK files).

PSX Power Spike (MagDemo43: POWER\GAME.IDX\*.BIZ)
BIZ compression is used in BIZ archives (which are nested in IDX/HUG archive). The compressed & decompressed size is stored in the BIZ archive.
Note: Power Spike 20h-filled initial BIZ ringbuf is required for sky pixels in:
  MagDemo43: POWER\GAME.IDX\PERSOS\PSX\CUSTOM\TEXTURE\NFIELD.BIZ\LPORJ.PSI

PSX Army Men Air Attack 2 (MagDemo40: AMAA2\*.PCK\*.PAK)
SCRATCH compression is used in PAK archives (which are nested in PCK archive). The compressed & decompressed size is stored in the PAK archive.
Note: The decompressor uses half of the 1Kbyte Scratchpad RAM at 1F800000h as ringbuf (hence the name and unusual small 200h-byte ringbuf size).

Alice in Cyberland (ALICE.PAC\*.FA2)
  000h ..   FA2 Compressed .FA archive
The decompressor is at 80093A3Ch (but the code isn't permanently in memory), and it's by far one of the worst decompression functions in compilerland.

Decompression
   DEFAULT = ALZ1 or BIZ or LZ5 or DECODE_S
   if DEFAULT then wr=0FEEh, mask=FFFh    ;\
   if VRAMWAD then wr=0FEEh, mask=FFFh    ; initial ringbuf write index
   if zLATAD  then wr=0000h, mask=FFFh    ; and ringbuf mask (size-1)
   if SCRATCH then wr=01BEh, mask=1FFh    ;
   if FA2     then wr=00EFh, mask=0FFh    ;/
   if FA2     then len2=0
   initialize_ringbuf_content (see below)
   numbits=0
  @@decompress_lop:
   if dst>=dst.end then goto @@decompress_done
   if numbits=0
     flagbits=[src], numbits=8, src=src+1    ;8bit flags
   numbits=numbits-1
   if VRAMWAD or FA2 then flagbits SHL 1, else flagbits=flagbits SHR 1
   if carry=1 then
     dta=[src], [dst]=dta, ringbuf[wr AND mask]=dta
     dst=dst+1, wr=wr+1, src=src+1
   else
     if DEFAULT then rd=[src]+([src+1]/10h)*100h), len=([src+1] AND 0Fh)+3
     if zLATAD  then rd=[src]+([src+1] AND 0Fh)*100h), len=([src+1]/10h)+3
     if SCRATCH then rd=[src]+([src+1]/80h)*100h), len=([src+1] AND 7Fh)+3
     if VRAMWAD then rd=[src+1]+([src]/10h)*100h), len=([src] AND 0Fh)+3
     if FA2     then rd=[src], len=len2, len2=0, src=src+1
     if FA2 and len=0 then len=[src]/10h+2, len2=([src] AND 0Fh)+2, src=src+1
     if FA2=0   then src=src+2
     for i=1 to len   ;read ringbuf[rd] (instead of relative [dst-rd])
       dta=ringbuf[rd AND mask], [dst]=dta, ringbuf[wr AND mask]=dta
       dst=dst+1, wr=wr+1, rd=rd+1
     next i
   endif
   goto @@decompress_lop
  @@decompress_done:
   ret

Initial Ringbuf Content
  if ALZ1 or zLATAD then
    ringbuf[000h..FFFh]=(00h)              ;zeroes
  if VRAMWAD or DECODE_S then
    ringbuf[000h..FEDh]=(00h)              ;zeroes
    ringbuf[FEEh..FFFh]=(uninitialized)    ;uninitialized, don't use
  if BIZ then
    ringbuf[000h..FEDh]=(20h)              ;ascii space
    ringbuf[FEEh..FFFh]=(uninitialized)    ;uninitialized, don't use
  if SCRATCH then
    ringbuf[000h..1BFh]=(00h)              ;zeroes
    ringbuf[1C0h..1FFh]=(uninitialized)    ;uninitialized, don't use
  if FA2 then
    ringbuf[000h..0FFh]=(00h)              ;zeroes
  if LZ5 then
    ringbuf[000h..CFFh]=(000h..CFFh)/0Dh   ;increasing, repeated 0Dh times each
    ringbuf[D00h..DFFh]=(00h..FFh)         ;increasing
    ringbuf[E00h..EFFh]=(FFh..00h)         ;decreasing
    ringbuf[F00h..F7Fh]=(00h)              ;zeroes
    ringbuf[F80h..FEDh]=(20h)              ;ascii space
    ringbuf[FEEh..FFFh]=(should be 00h)    ;see note, better don't use
Note: The last 12h bytes in LZ5 are 00h in LArc v3.33 (though unknown if that's intended and stable), LHarc source code did accidentally set them to 20h (which is reportedly fixed in later LHA versions).


CDROM File Compression PCK (Destruction Derby Raw)

Destruction Derby Raw (MagDemo35: DDRAW\*.PCK,EXE,DAT)
  000h 3     Decompressed size (24bit, little-endian)
  003h 1     Unused (0)
  004h ...   LZSS compressed data, starting with 30bit+2bit flags
The compression is used in some ISO files, which can be detected as:
  [03h]=00h, [04h]=00h, [08h]="PS-X EXE"                ;DDRAW\*.EXE
  [03h]=00h, [04h] AND FCh=00h, [08h]="BC",04h,40h,0,0  ;DDRAW\LDPICS\*.PCK
The compression is also used in nested PTH+DAT archives (where the whole DAT is compressed), which can be detected by checking if the sum of the PTH filesizes exceeds the DAT filesize.

Self-decompressing GUI code in PSX BIOS for SCPH-7000 and up
The PSX BIOS seems to use the same LZSS format for the self-decompressing GUI code (with GUI/decompression starting at 80030000h).

Decompression function
   dst_end=dst+LittleEndian24bit[src], src=src+4
  @@collect_more:
   flagbits=BigEndian32bit([src]), src=src+4
   dispbits=14-(flagbits AND 03h), flagbits=(flagbits OR 3)-1
   dispmask=(1 SHL dispbits)-1
  @@decompress_lop:
   flagbits=flagbits SHL 1    ;32bit shift with carry-out/zeroflag
   if zero then goto @@collect_more
   if carry=0 then
     [dst]=[src], dst=dst+1, src=src+1
   else
     disp=BigEndian16bit[src], src=src+2
     len=(disp SHR dispbits)+3
     disp=(disp AND dispmask)+1
     for i=1 to len, [dst]=[dst-disp], dst=dst+1, next i
   endif
   id dst<dst_end then goto @@decompress_lop
  @@decompress_done:
   ret


CDROM File Compression GT-ZIP (Gran Turismo 1 and 2)

BS iki Video
IKI is a rather uncommon variant of the .STR video format (used by Gran Turismo 1 and 2, Legend of Legaia, Legend of Dragoon, Omega Boost, Um Jammer Lammy).
IKI videos have a custom .BS header, including some GT-ZIP compressed data:
  000h 2   MDEC Size/4 (after huffman decompression) (rounded to 80h/4 bytes)
  002h 2   File ID (3800h)
  004h 2   Bitmap Width in pixels     ;instead quant
  006h 2   Bitmap Height in pixels    ;instead version
  008h 2   Size of GT-ZIP compressed data (plus 2-byte alignment padding)
  00Ah ..  GT-ZIP compressed DC/Quant values (plus 2-byte alignment padding)
  ...  ..  Huffman compressed AC data blocks (Cr,Cb,Y1,Y2,Y3,Y4, Cr,Cb,Y1,Y2..)
The number of blocks is NumBlocks=(Width+15)/16*(height+15)/16*6. The size of the decompressed GT-ZIP data is NumBlocks*2.

Gran Turismo 1 (MagDemo10: GT\*.DAT) - headerless
Gran Turismo 1 (MagDemo15: GT\*.DAT) - headerless
  000h ..    Compressed Data (without header)
This is used for compressing files inside of GT-ARC archives (or in one case, for compressing the whole GT-ARC archive). The GT-ARC directory contains additional compression info, see GT-ARC description for details.
The file GT\GAMEFONT.DAT is also GT-ZIP compressed, but lacks any ID or info on decompressed size, and there are at least two GAMEFONT.DAT versions (in MagDemo10 va MagDemo15), both versions are 8000h bytes when decompressed, and compressed data starts with 00,FF,FF,00,00,00,80,00,00,01,17,07.

Gran Turismo 2 (MagDemo27: GT2\GT2.VOL\arcade\arc_other.tim\*) - with header
  000h 0Ch   ID "@(#)GT-ZIP",0,0
  00Ch 4     Decompressed Size
  010h ..    Compressed Data (unknown compressed size due to below padding)
  ...  ..    Zeropadding to 4-byte boundary (when stored in DOT1 archives)
This is used for compressing some files in one DOT1 archive (most other files in Gran Turismo 2 are using GZIP compression; with corrupted/zeropadded GZIP footers).

Decompression function
   if [src]="@(#)GT-ZIP",0,0 then dst.end=dst+[src+0Ch], src=src+10h
  @@collect_more:
   flagbits=[src]+100h, src=src+1    ;8bit flags
  @@decompress_lop:
   if src>=src.end then goto @@decompress_done  ;(when src.end is known)
   if dst>=dst.end then goto @@decompress_done  ;(when dst.end is known)
   flagbits=flagbits SHR 1
   if zero then goto @@collect_more
   if carry=0 then
     [dst]=[src], dst=dst+1, src=src+1
   else
     len=[src], src=src+1, disp=[src], src=src+1                 ;len, disp
     if disp>=80h then disp=(disp-80h)*100h+[src], src=src+1     ;longer disp
     for i=1 to (len+3), [dst]=[dst-(disp+1)], dst=dst+1, next i
   endif
   goto @@decompress_lop
  @@decompress_done:
   ret

Notes
Depending on the source, only the compressed or decompressed size may be known:
  Source                    Compressed Size           Decompressed Size
  Compressed GAMEFONT.DAT   In ISO Filesystem         Unknown (n/a)
  Compressed GT-ARC         In ISO Filesystem         Unknown (n/a)
  Files in GT-ARC           In GT-ARC                 In GT-ARC
  Files with GT-ZIP header  Unknown (due to padding)  In GT-ZIP
  DC values in IKI videos   Unknown (due to padding)  From Width*Height
Gran Turismo 1 has ID "@(#)GT-ZIP" (and "@(#)G.T-ZIPB" whatever that is) stored in Main RAM (though unknown if/which/any files do have those IDs).
Gran Turismo 2 has ID "@(#)GT-ZIP" in "GT2\GT2.VOL\arcade\arc_other.tim\*", apart from that, it does mainly use GZIP compressed files.


CDROM File Compression GT20 and PreGT20

GT20 Compressed Files
Used by Rollcage (MagDemo19: ROLLCAGE\SPEED.IMG\*)
Used by Rollcage Stage II (MagDemo31: ROLLCAGE\SPEED.IDX\*)
Used by Sydney 2000 (MagDemo37: OLY2000\DEMO.IDX\* and OLY2000\GTO\*.GTO)
Reportedly also Chill (PS1) (*.GTO)
Reportedly also Ducati World: Racing Challenge
Reportedly also Martian Gothic: Unification (PS1) (*.GT20)
  000h 4     ID ("GT20"=Compressed) (or reportedly "NOGT"=Uncompressed)
  004h 4     Size of decompressed data in bytes
  008h 4     Overlap for in-situ decompression (usually 3, or sometimes 7)
  00Ch 4     Size of Leading Zeropadding in bytes (0..7FFh)
  010h ..    Leading Zeropadding (0..7FFh bytes)
  ...  ..    Compressed Data
The Leading Zeropadding can be used to arrange the data to end on a sector boundary (useful when loading the file in units of whole sectors, and wanting to load it to the end of the decompression buffer).
 DecompressGT20:
  src=src+word[src+0Ch]+10h      ;skip header and any leading zeropadding
  collected=00000001h  ;end-bit
 @@lop:
  if GetBit=0
    [dst]=[src], dst=dst+1, src=src+1               ;uncompressed byte
  else
    if GetBit=0
      disp=byte[src]-100h, src=src+1                ;disp=(-100h..-1)
      len=(GetBit*2)+(GetBit*1)+2                   ;len=(2..5)
    else
      tmp=halfword[src], src=src+2
      disp=(tmp/8)-2000h                            ;disp=(-2000h..-1)
      len=(tmp AND 7)+2                             ;len=(2..9)
      if len=2
        tmp=byte[src], src=src+1
        if (tmp AND 80h) then disp=disp-2000h       ;disp=(-4000h..-1)
        len=(len AND 7Fh)+2                         ;len=(2..81h)
        if len=3 then goto decompression_done
        if len=2 then len=halfword[src], src=src+2  ;len=(0..FFFFh)
    for i=1 to len, [dst]=[dst+disp], dst=dst+1, next i
  goto @@lop
 ;---
 GetBit:
  collected=collected SHR 1
  if zero then collected=(word[src] SHR 1)+80000000h, src=src+4
  return carry (from shift right)
Note: Uncompressed files can reportedly contain "NOGT" in the header, however, Rollcage does have compressed files (with GT20 header), and raw uncompressed files (without any NOGT header).
See also: https://zenhax.com/viewtopic.php?t=13175 (specs)
See also: http://wiki.xentax.com/index.php/GT20_Archive (blurp)

Pre-GT20 Compressed Files
Used by Bloody Roar 1 (MagDemo06: BL\*.DAT\*)
Used by Bloody Roar 2 (MagDemo22: ASC,CMN,EFT,LON,SND,ST5,STU\*.DAT\*)
  000h 4    Compression Method (0=None, 2=Compressed, Other=Invalid)
  004h 4    Compressed Size (SIZ) (same as decompressed when method=0)
  008h 4    Decompressed Size
  00Ch SIZ  Compressed Data
  ...  ..   Garbagepadding to 4-byte boundary (in 4-byte aligned DAT files)
This is apparently on older version of what was later called GT20. The PreGT20 decompression works as so:
 DecompressPreGT20:
  src=src+0Ch                    ;skip header
  collected=80h  ;end-bit
 @@lop:
  if GetBit=1
    [dst]=[src], dst=dst+1, src=src+1               ;uncompressed byte
  else
    if GetBit=0
      len=(GetBit*2)+(GetBit*1)+2                   ;len=(2..5)
      disp=byte[src]-100h, src=src+1                ;disp=(-100h..-1)
    else
      tmp=bigendian_halfword[src], src=src+2
      disp=(tmp/8)-2000h                            ;disp=(-2000h..-1)
      len=(tmp AND 7)+2                             ;len=(2..9)
      if len=2
        len=byte[src]+1, src=src+1                  ;len=(1..100h)
        if len=1 then goto decompression_done
    for i=1 to len, [dst]=[dst+disp], dst=dst+1, next i
  goto @@lop
 ;---
 GetBit:
  collected=collected SHL 1    ;8bit shift
  if zero then collected=(byte[src] SHL 1)+01h, src=src+1
  return carry (from 8bit shift left)
Note: Uncompressed files with Method=0 exist in Bloody Roar 2 (CMN\SEL01.DAT).
Bloody Roar 1 (MagDemo06) has decompressor at 8016DD64h (method 0 and 2).
Bloody Roar 2 (MagDemo22) has decompressor at 8015C8C0h (method 0 and 2).


CDROM File Compression HornedLZ

Used by Project Horned Owl (*.BIN\*) (and within self-decompressing EXE)

HornedLZ Detection
The easiest way to detect HornedLZ files is to check first 4 bytes:
  B3 10 00 4F ..    Compressed TIM with TIM Type=00h (4bpp without CLUT)
  DB 10 00 3F ..    Compressed TIM with TIM Type=08h,09h,etc.
Alternately, one could check the Chunktype (in the parent archive):
  Type=05h can be uncompressed .TXT or HornedLZ-compressed .TIM
    (check if 2nd data byte is ASCII or 10h)
  Type=0Fh is a DOT1 archive with HornedLZ-compressed .TIMs
    (parse the DOT1 archive and treat its contents as compressed .TIMs)
  Type=10h contains Deflated TIMs
    (a completely different compression method)

DecompressHornedLZ:
  collected=01h  ;end-bit
 @@lop:
  if GetBit=1
    [dst]=[src], dst=dst+1, src=src+1               ;uncompressed byte
  else
    if GetBit=1
      tmp=[src], src=src+1
      len=tmp/40h+2, disp=tmp or (-40h)       ;len=(2..05h), disp=(-40h..-1)
    else
      tmp=[src]*100h+[src+1], src=src+2
      len=tmp/1000h+2, disp=tmp or (-1000h)   ;len=(2..11h), disp=(-1000h..-1)
      if len=2 then
        len=[src]+2, src=src+1                ;len=(2..101h)
        if len=2 then goto decompression_done
    for i=1 to len, [dst]=[dst+disp], dst=dst+1, next i
  goto @@lop
 ;---
 GetBit:
  collected=collected SHR 1
  if zero then collected=([src] SHR 1)+80h, src=src+1
  return carry (from shift right)
Note: The end code has all bits zero, except, disp is don't care (it's usually FFFh).


CDROM File Compression LZS (Gundam Battle Assault 2)

Gundam Battle Assault 2 (DATA\*.PAC\*, with ID="lzs")
  000h 4     ID ("lzs",00h)
  004h 4     Zerofilled
  008h 4     Fixed (must be 1) (method/version?)
  00Ch 14h   Zerofilled
  020h 2     Fixed (must be 3) (method/version?)
  022h 2     Offset to Compressed Data minus 20h (usually 38h-20h)
  024h 4     Decompressed Size
  028h 2     Flagsize (must be 08h, 10h, or 20h) (usually 20h=32bit)
  02Ah 2     Lensize  (must be 02h..07h)         (usually 05h=5bit)
  02Ch 4     Compressed Size (total filesize, including "lzs" header)
  030h 8     Name? (always "000000",00h,00h)
  038h ..    Compressed data (usually at offset 38h)
decompress_gundam_lzs:
   dst_end = dst+littleendian32bit[src+24h]
   flg_bits = littleendian16bit[src+28h]   ;8,16,32
   len_bits = littleendian16bit[src+2Ah]   ;2..7
   len_mask = (1 shl len_bits)-1           ;03h..7Fh
   src=src+littleendian16bit[src+22h]+20h
   collected_bits=0
  @@collect_more:
   for i=0 to flg_bits/8-1    ;read 8bit/16bit/32bit little-endian
     collected_bits=collected_bits+([src] SHL (i*8)), src=src+1
   num_collected=flg_bits
  @@decompress_lop:
   if dst=dst_end then goto @@decompress_done
   if num_collected=0 then goto @@collect_more
   num_collected=num_collected-1
   flagbits=flagbits SHR 1
   if carry=1 then
     [dst]=[src], dst=dst+1, src=src+1
   else
     temp=bigendian16bit[src], src=src+2
     len=(temp AND len_mask)+3
     disp=(temp SHR len_bits), if disp=0 then goto @@decompress_error
     for i=1 to len, [dst]=[dst-disp], dst=dst+1, next i
   endif
   goto @@decompress_lop
  @@decompress_done:
   ret


CDROM File Compression BZZ

Used in .BZZ archives. Note that there are three slightly different .BZZ archive formats (they are all using the same BZZ compression, only the BZZ archive headers are different).
  Jersey Devil .BZZ (MagDemo10: JD\*.BZZ)
  Bugs Bunny: Lost in Time (MagDemo25: BBLIT\*.BZZ)
  The Grinch (MagDemo40: GRINCH\*.BZZ)
Neither the file header nor the archive directory entries do contain any information about the decompressed size. Best workaround might be to decompress the file twice (without storing the output in 1st pass, to determine the size of the decompression buffer for 2nd pass).

BZZ Decompression
The compression is fairly standard LZSS, except that it supports non-linear length values, and it does support uncommon Len/Disp pairs like 7bitLen/9bitDisp (though usually, it does use standard 4bitLen/12bitDisp).
  decompress_bzz:
   method=byte[src], src=src+1       ;method (00h..1Fh) ;usually/always 0Bh)
   shifter  = ((method/8) and 3)     ;00h..03h                ;usually 1
   len_bits = ((method and 7) xor 7) ;07h..00h                ;usually 4
   len_mask = (1 shl len_bits)-1     ;7Fh..00h                ;usually 0Fh
   threshold=len_mask/2, if threshold>07h then threshold=13h  ;usually 07h
   for i=0 to len_mask
     if i>threshold then len_table[i] = ((i-threshold) shl shifter)+threshold+3
     else len_table[i] = i+3 ;method=18h max=(7Fh-13h)*8+13h+3=376h=886 decimal
   next i                    ;method=0Hh max=(0Fh-07h)*2+07h+3=1Ah=26 decimal
   num_flags=bigendian24bit[src]+1, src=src+3   ;NUM24+1
  @@collect_more:
   if src>=src_end then goto @@decompress_error
   flagbits=[src]+100h, src=src+1    ;8bit flags
  @@decompress_lop:
   flagbits=flagbits SHR 1
   if zero then goto @@collect_more
   if carry=1 then
     if src>=src_end then goto @@decompress_error
     [dst]=[src], dst=dst+1, src=src+1
   else
     if src+1>=src_end then goto @@decompress_error
     temp=bigendian16bit[src], src=src+2
     len=len_table[temp AND len_mask]
     disp=temp SHR len_bits, if disp=0 then goto @@decompress_error
     for i=1 to len, [dst]=[dst-disp], dst=dst+1, next i
   endif
   num_flags=num_flags-1, if num_flags>0 then goto @@decompress_lop
  @@decompress_error:
   ret
Bug: Files can randomly contain NUM24 or NUM24+1 codes (that seems to be due to a compressor bug or different compressor versions; the two variants are unfortunately randomly mixed even within the same game).
And, compressed files are padded to 4-byte boundary (making it impossible to distinguish between "NUM24+1" and "NUM24+padding").
  Case 1) source has NUM24+1 codes
           --> decode all NUM24+1 codes (otherwise output will be too small)
  Case 2) source has NUM24 codes (and enough padding for another code)
           --> decode all NUM24+1 codes (for compatibility with case 1)
           --> output will have some constant garbage byte(s) appended
           --> exception: omit last code if it contains invalid disp=0
  Case 3) source has NUM24 codes (and not enough padding for another code)
           --> decode only NUM24 codes (abort if NUM24+1 exceeds src_end)
           --> output should (probably) have correct size
           --> never exceed src_end which would be highly unstable


CDROM File Compression RESOURCE (Star Wars Rebel Assault 2)

Star Wars Rebel Assault 2 (RESOURCE.*\*)
BallBlazer Champions (*.DAT)
 decompression function:
  base=src, method=[src], dst_end=dst+BigEndian24bit[src+1], src=src+4
 @@decompress_lop:
  if dst>=dst_end then goto @@decompress_done
  if [src] AND 80h then
    if method=01h then
      len=([src]-80h)/8+3, disp=(BigEndian16bit[src] AND 7FFh)+1, src=src+2
    else  ;method=02h
      len=([src]-80h)+4, disp=(BigEndian16bit[src+1])+1, src=src+3
    for i=1 to len, [dst]=[dst-disp], dst=dst+1
  else    ;uncompressed
    len=[src]+1, src=src+1
    for i=1 to len, [dst]=[src], src=src+1, dst=dst+1
  goto @@decompress_lop
 @@decompress_done:
  src=(src+3) AND NOT 3
  if LittleEndian32bit[src]<>crc(base, src-base) then error
  ret
Note: Compression is (normally) used only in Top-level RESOURCE.* and *.DAT archives (not in Nested archives). The Top-level archives do also contain some uncompressed files (which contain data that is compressed on its own: SPU-ADPCM audio, or encrypted BS bitmaps).

Special case for BallBlazer Champions
Normally only Top-level archives contain compression, however, there are also some Nested archives with compression in BallBlazer Champions:
  STD_BBX.DAT\s*t\tp_a\*    ;\double compression, Top-level is ALSO compressed
  BBX_INTR.DAT\data1\pics\* ;/
  BBX_INTR.DAT\Stad\pics\*  ;\
  BBX_INTR.DAT\Stad\wire\*  ; Nested archives with compression
  BBX_INTR.DAT\Subtitl\*    ;
  BBX_INTR.DAT\Subtitl\sub\*;/
The Nested archives don't have any compression flag or decompressed size entries (so there's no good way for detecting compression in nested files).


CDROM File Compression TIM-RLE4/RLE8

Ape Escape (Sony 1999) (MagDemo22: KIDZ\*) has several compressed and uncompressed TIMs in headerless archives, the archives can contain:
  Compressed 4bpp RLE4-TIM with uncompressed CLUT ;\only 4bpp can be compressed
  Compressed 4bpp RLE8-TIM with uncompressed CLUT ;/
  Uncompressed 4bpp TIM with uncompressed CLUT    ;\only this type/combinations
  Uncompressed 8bpp TIM with uncompressed CLUT    ; are allowed if uncompressed
  Uncompressed 16pp TIM without CLUT              ;/
  End code 00000000h (plus more zeropadding)      ;-end of headerless archive
The compression method is indicated by changing a reserved halfword in the TIM header:
  hdr[02h]=Method (0000h=Uncompressed, 0001h=RLE4, 0002h=RLE8)
The rest of the bytes in TIM header and in CLUT section are same as for normal TIMs. The Bitmap section is as follows:
Decompressed size must be computed as Width*Height*2. The Section Size entry contains Section header size, plus compressed size, plus padding to 4-byte boundary.
Method=0001h (RLE4):
 @@decompress_lop:
  color=[src]/10h, len=([src] AND 0Fh)+1, src=src+1
  for i=1 to len, putpixel(color), next i               ;len=1..10h
  if numpixels<Width*Height*4 then goto @@decompress_lop
Method=0002h (RLE8):
 @@decompress_lop:
  color1=[src]/10h, color2=[src] AND 0Fh, src=src+1
  if color1=color2
    len=[src]+2, src=src+1
    for i=1 to len, putpixel(color1), next i            ;len=2..101h
  else
    putpixel(color1), if numpixels<Width*Height*4 then putpixel(color2)
  for i=1 to len, putpixel(color)       ;len=1..10h
  if numpixels<Width*Height*4 then goto @@decompress_lop
The decompression functions in Ape Escape (MagDemo22: KIDZ\*) are found at:
  80078760h ape_escape_load_tim_archive
  8007894Ch ape_escape_decompress_with_4bit_lengths
  800789FCh ape_escape_decompress_with_8bit_lengths
Examples for compressed TIMs are found at:
  RLE8: Ape Escape, MagDemo22: KIDZ\KKIIDDZZ.HED\DAT\file004h\1stTIM
  RLE4: Ape Escape, MagDemo22: KIDZ\KKIIDDZZ.HED\DAT\file135h\1stTIM
  RLE8: Ape Escape, MagDemo22: KIDZ\KKIIDDZZ.HED\DAT\file139h\1stTIM
Being made by Sony, this might be an official (but late) TIM format extension, unknown if there are any other games using that compression.


CDROM File Compression RLE_16

Apocalypse (MagDemo16: APOC\CD.HED\*.RLE)
Spider-Man (MagDemo31,40: SPIDEY\CD.HED\*.RLE)
Spider-Man 2 (MagDemo50: HARNESS\CD.HED\*.RLE)
  000h 8     ID "_RLE_16_"
  008h 4     Decompressed Size (usually 3C008h) (33408h=Apocalypse warning.rle)
  00Ch ..    RLE Compressed Data (usually a .BMR bitmap)
This is using simple RLE compression with 16bit len/data units (suitable for 16bpp VRAM data). The compression ratio ranges from not so bad to very bad.

Decompression
  src=src+0Ch                                       ;skip ID and size
 @@decompress_lop:
  len=halfword[src], src=src+2
  if len=0000h then goto @@decompress_done          ;end-code
  if (len AND 8000h)=0 then
    for i=1 to len, halfword[dst]=halfword[src], dst=dst+2, src=src+2, next i
  else
    fillvalue=halfword[src], src=src+2
    for i=1 to len-8000h, halfword[dst]=fillvalue, dst=dst+2, next i
  goto @@decompress_lop
 @@decompress_done:
  ret

Other RLE16 variants
A similar RLE16 variant is used in Croc 1, and another variant in Croc 2.
CDROM File Archive Croc 1 (DIR, WAD, etc.)
CDROM File Archive Croc 2 (DIR, WAD, etc.)


CDROM File Compression PIM/PRS (Legend of Mana)

Legend of Mana (.PIM/.PRS)
  000h 1   Unknown (always 01h) (maybe File ID or Compression method)
  001h ..  Compressed data  ;for TIM: usually 00,10, F0,00, 00,0x, F0,00, ...
Compression codes are:
  nn,data[nn+1]  ;nn=00..EF len=nn+1   [dst]=data[1]             ;-uncompressed
  F0,xn                     len=n+3    [dst]=0x         ;1x4bit  ;\
  F1,nn,xx                  len=nn+4   [dst]=xx         ;1x8bit  ;
  F2,nn,yx                  len=nn+2   [dst]=0x,0y      ;2x4bit  ; RLE fill
  F3,nn,xx,yy               len=nn+2   [dst]=xx,yy      ;2x8bit  ;
  F4,nn,xx,yy,zz            len=nn+2   [dst]=xx,yy,zz   ;3x8bit  ;/
  F5,nn,xx,data[nn+4]       len=nn+4   [dst]=xx,data[1]          ;\interleaved
  F6,nn,xx,yy,data[nn+3]    len=nn+3   [dst]=xx,yy,data[1]       ; fill combo
  F7,nn,xx,yy,zz,data[nn+2] len=nn+2   [dst]=xx,yy,zz,data[1]    ;/
  F8,nn,xx                  len=nn+4   [dst]=xx    ;xx=xx+1      ;\
  F9,nn,xx                  len=nn+4   [dst]=xx    ;xx=xx-1      ; fill with
  FA,nn,xx,ss               len=nn+5   [dst]=xx    ;xx=xx+ss     ; signed step
  FB,nn,xx,yy,ss ;ss=signed len=nn+3   [dst]=xx,yy ;yyxx=yyxx+ss ;/
  FC,xx,ny                  len=n+4    [dst]=[dst-yxx-1]         ;\
  FD,xx,nn                  len=nn+14h [dst]=[dst-xx-1]          ; LZ compress
  FE,xn                     len=n+3    [dst]=[dst-x*8-8]         ;/
  FF                        len=0      end                       ;-end code
The compression is used for several files in Legend of Mana:
  BIN\*.BIN       ---> packed misc binary
  MAP\*\FDATA.PRS ---> packed resource, whatever
  MAP\*\MAP*.PRS  ---> packed MPD resource, "SKmapDat"
  WM\WMTIM\*.PIM  ---> packed TIM image, 384x384x4bpp, bad compression ratio
  WM\WMAP\*.PAT   ---> packed loaddata
  WM\WMAP\*.PIM   ---> packed TIM image, 320x256x16bit, with UNCOMPRESSED dupe


CDROM File Compression BPE (Byte Pair Encoding)

Byte Pair Encoding (BPE) does replace the most common byte-pairs with bytes that don't occur in the data. That does work best if there are unused bytes (eg. ASCII text, or 8bpp bitmaps with less than 256 colors).

Bust A Groove (MagDemo18: BUSTGR_A\*.BPE)
Bust-A-Groove 2 (MagDemo37: BUSTAGR2\BUST2.BIN\*)
  000h 4     ID "BPE_"
  004h 4     Total Filesize of compressed file including header (big-endian)
  ...  ..    Compression block(s)
 Each compression block contains:
  000h ..    Dictionary info
  ...  2     Size of compressed data (big-endian)
  ...  ..    Compressed data
The decompression function in Bust A Groove (MagDemo18) is at 80023860h, the heap is in 1Kbyte Scratchpad RAM at 1F800208h, so heap size should be max 1F8h bytes (assuming that the remaining Scratchpad isn't used for something else). The fileheader lacks info about the decompressed size.

Legend of Dragoon (MagDemo34: LOD\OVL\*.OV_ and LOD\SECT\*.BIN\*)
  000h 4     Decompressed size (little-endian)
  004h 4     ID "BPE",1Ah
  008h ..    Compression block(s)
  ...  ..    End code (00000000h) (aka last block with Blocksize=0)
 Each compression block contains:
  000h 4     Size of decompressed block (little-endian) (or 0=End code)
  004h ..    Dictionary info
  ...  ..    Compressed data
  ...  ..    Padding to 4-byte boundary
Max nesting appears to be 2Ch, the decompression function allocates a 30h-byte heap on stack, and fetches source data in 32bit units (occupying 4 heap bytes), the decompressor does then remove 1 byte from heap, and adds 2 bytes in case of nested codes.

BPE Decompression for Bust-A-Groove and Legend of Dragoon
  if [src+0]="BPE_" then type=GROOVE                                    ;\
  if [src+4]="BPE",1Ah then type=DRAGOON                                ;
  if type=GROOVE then src_end = src+BigEndian32bit[src+4]               ; hdr
  if type=DRAGOON then dst_end = dst+LittleEndian32bit[src+0]           ;
  src=src+8                                                             ;/
 @@block_lop:
  if type=DRAGOON then                                                  ;\blk
    dst_blk_end = dst+LittleEndian32bit[src]+4, src=src+4               ; len
    if dst=dst_blk_end then goto @@decompress_done                      ;/
  for i=00h to FFh, dict1[i]=i, next i                                  ;\
  i=00h                                                                 ;
 @@dict_lop:                                                            ; dict
  num=[src], src=src+1                                                  ;
  if num>7Fh then i=i+(num-7Fh), num=0, if i=100h then goto @@dict_done ;
  for j=0 to num                                                        ;
    a=[src], src=src+1                                                  ;
    if a<>i then b=[src], src=src+1, dict1[i]=a, dict2[i]=a             ;
    i=i+1                                                               ;
  if i<100h then goto @@dict_lop                                        ;
 @@dict_done:                                                           ;/
  if type=GROOVE then                                                   ;\blk
    src_blk_end = src+BigEndian16bit[src]+2, src=src+2                  ;/len
  i=0                                                                   ;\
 @@data_lop:                                                            ;
  if i=0 then                                                ;\         ; data
    if type=GROOVE and src=src_blk_end then goto @@data_done ; get data ;
    if type=DRAGOON and dst=dst_blk_end then goto @@data_done; from src ;
    x=[src], src=src+1                                       ; or heap  ;
  else                                                       ;          ;
    i=i-1, x=heap[i]                                         ;/         ;
  a=dict1[x]                                    ;-xlat                  ;
  if a=x then                                   ;\                      ;
    [dst]=x, dst=dst+1                          ; output data to        ;
  else                                          ; dst or heap           ;
    b=dict2[x], heap[i]=b, heap[i+1]=a, i=i+2   ;/                      ;
  goto @@data_lop                                                       ;
 @@data_done:                                                           ;/
  if type=GROOVE and src<src_end then goto @@block_lop                  ;\next
  if type=DRAGOON then src=(src+3) AND not 3, goto @@block_lop          ;/blk
 @@decompress_done:
  if type=DRAGOON and dst<>dst_end then error
  ret

Electronic Arts
Electronic Arts games support several compression methods, including a BPE variant. That BPE variant is a bit unusual: It does have only one compression block (with a single dictionary for the whole file), and uses escape codes for rarely used bytes.
CDROM File Compression EA Methods


CDROM File Compression RNC (Rob Northen Compression)

Pro-Pack aka Rob Northen Compression (RNC)
PRO-PACK is a compression tool for DOS and Amiga, bundled with decompression functions for PC, Amiga, PSX, Mega Drive, Game Boy, SNES and Atari Lynx.
  000h 3    ID ("RNC")
  003h 1    Compression Method (01h or 02h) (or 00h=uncompressed)
  004h 4    Size of Uncompressed Data                  ;big-endian
  008h (4)  Size of Compressed Data (SIZ)              ;big-endian     ;\
  00Ch (2)  CRC16 on Uncompressed Data ;\with initial  ;big-endian     ; method
  00Eh (2)  CRC16 on Compressed Data   ;/value 0000h   ;big-endian     ; 1..2
  010h (1)  Leeway (difference between compressed and uncompressed data; only
              in largest pack block, if larger than decompressed data) ;
  011h (1)  Number of pack blocks (or 00h=Not specified)               ;/
  ...  SIZ  Compressed Data (or uncompressed data for method 0)
  ...  (..) Zeropadding to 800h-byte boundary-4 ;\in PSX Heart of Darkness
  ...  (4)  Unknown                             ;/
The compressed data consists of interleaved bit- and byte-streams, the first 2 bits of the bit stream are ignored.

RNC Method 0 - uncompressed
The 8-byte Method 0 headers are ONLY used inside of "RNCA" archives (uncompressed single files are simply stored as raw data, without any RNC header).

RNC Method 1 - custom Huffman trees
The bit-stream is read in little-endian (!) 16bit units (the 1st bit being in bit0 of 1st byte), the bit-stream is interleaved with uncompressed bytes.
 decompress_rnc_method_1:
  num_blocks=[src+11h], src=src+12h
  dummy=GetBits(2)              ;skip/ignore first 2 bits
 @@block_lop:
  GetTree(rawlen_tree)
  GetTree(disp_tree)
  GetTree(lzlen_tree)
  num_items=GetBits(16)
  goto @@item_injump
 @@item_lop:
  disp=GetHuffCode(disp_tree)+1
  len=GetHuffCode(lzlen_tree)+2
  for i=1 to len, [dst]=[dst-disp], dst=dst+1
 @@item_injump:
  len=GetHuffCode(rawlen_tree)    ;can be 0=none
  for i=1 to len, [dst]=[src], src=src+1, dst=dst+1   ;with optional decrypt
  num_items=num_items-1    ;AND FFFFh (in DOS version, at least)
  if num_items<>=0 then @@item_lop
  num_blocks=num_blocks-1  ;AND FFh   (in DOS version, at least)
  if num_blocks<>00h then goto @@block_lop
  ret
 ;---
 GetTree(tree)
  ;note: below can have num=0=none (eg. very small uncompressed blocks
  ;may leave the disp and lzlen trees unused/uninitialized).
  num=GetBits(5)                               ;number of symbols (00h..10h)
  for i=0 to num-1, codesizes[i]=GetBits(4)    ;sizes (1..15 bits, or 0=unused)
  lzh_explode_tree(tree,codesizes,num)         ;alike LHA trees
  ret
 ;---
 GetCode(tree):
  val=GetHuffCode(tree)
  if val>1 then val=(1 SHL (val-1)) + GetBits(val-1)
  return val
Limits for 16bit DOS version are disp<=8000h and sum(rawlen+lzlen)<=7FF0h.

RNC Method 2 - hardcoded Huffman trees
The bit-stream is read in 8bit units (the 1st bit being in bit7), the bit-stream is interleaved with uncompressed bytes.
  0     + Byte(DATA[1])              Copy 1 Byte from Source
  1000  + Dist + Byte(X)             Copy 4 Bytes from Dest-(Dist+X+1)
  10010 + Dist + Byte(X)             Copy 6 Bytes from Dest-(Dist+X+1)
  10011 + Dist + Byte(X)             Copy 7 Bytes from Dest-(Dist+X+1)
  1010  + Dist + Byte(X)             Copy 5 Bytes from Dest-(Dist+X+1)
  10110 + Dist + Byte(X)             Copy 8 Bytes from Dest-(Dist+X+1)
  10111 + nnnn + Byte(DATA[12..72])  Copy nnnn*4+12 Bytes from Source
  110   + Byte(X)                    Copy 2 Bytes from Dest-(X+1)
  1110  + Dist + Byte(X)             Copy 3 bytes from Dest-(Dist+X+1)
  1111  + Byte(0) + 0 + zeropadding  End of last pack block
  1111  + Byte(0) + 1                End of non-last pack block
  1111  + Byte(L) + Dist + Byte(X)   Copy L+8 Bytes from Dest-(Dist+X+1) ;L>00h
Dist values:
  0      = 0000h            1000   = 0200h
  110    = 0100h            1001   = 0300h
  111000 = 0C00h            101000 = 0800h
  111001 = 0D00h            101001 = 0900h
  11101  = 0600h            10101  = 0400h
  111100 = 0E00h            101100 = 0A00h
  111101 = 0F00h            101101 = 0B00h
  11111  = 0700h            10111  = 0500h
The purpose of the pack blocks isn't quite clear, it might be related to memory restrictions on old CPUs. In PSX Heart of Darkness they are chosen so that the decompressed data is max 3000h bytes per block. Unknown if the next block may copy data from previous block.

RNC Archives (rarely used)
Apart from compressing single files, Pro-Pack can also store multiple files in .rnc archives (when using C or A instead of P in commandline).
  000h 4   ID ("RNCA") (RNC Archive)                                 ;\
  004h 2   Offset to End of Folder list                 (big-endian) ; header
  006h 2   CRC16 on Folder List (initial value 0000h)   (big-endian) ;
  008h ..  Folder List                                               ;/
  ...  ..  Data (RNC compressed files, each starting with "RNC",0xh) ;-data
  ...  4   Zero                                                      ;-end
 Folder List entries:
  000h 2   Offset to End of File list                   (big-endian)
  ...  ..  Folder Path ("DIR\SUBDIR\",00h) (or "",00h for root)
  ...  ..  File List
  ...  1   File List end marker (00h)
 File List entries:
  000h ..  Filename ("FILENAME.EXT",00h)
  ...  4   Offset to Data for this file                 (big-endian)

RNC1old and RNC2old (based on Atari/Amiga Pack-Ice)
  000h 4    ID ("RNC",01h or 02h) (as in newer RNC files, but without CRCs)
  004h 4    Size of Uncompressed Data                  ;big-endian
  008h 4    Size of Compressed Data (SIZ)              ;big-endian
  00Ch SIZ  Compressed data (processed backwards, fetched in 8bit units)
Differences between RNCold and Pack-Ice are: Changed header ID, swapped compressed/uncompressed size header entries, the compressed size excludes the 0Ch-byte headersize. And the Atari picture filter feature is completely removed (the bitstream ends with the last compression bit, without the usual trailing filter flag).
And, following compresion parameters are changed:
  rawlen_bits  = (1,1,2,2,3,8,15)                              ;-pack-ice
  rawlen_bits  = (1,1,2,2,3,10)                                ;-rnc1old
  rawlen_bits  = (1,1,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16)  ;-rnc2old
  maxlzlenbits = 10                                            ;\pack-ice
  maxdispbits  = 12                                            ;/and rnc1old
  maxlzlenbits = ([src+0Ch+src_len-1]/10h)+1                   ;\rnc2old
  maxdispbits  = ([src+0Ch+src_len-1] AND 0Fh)+1               ;/
Note: rnc2old rawlen can be max 10000h bytes.

RNC in whatever UK games
RNC is used in a number of games by UK developers (notably Bullfrog and Traveller's Tales), including Sonic 3D: Flickies' Island, Blam! Machinehead, Dungeon Keeper 2, Magic Carpet, Syndicate and Syndicate Wars.

RNC in Amiga Games
  Method 1: Syndicate
  Method RNC1old: Heimdall
  Method RNC2old: Knightmare

RNC in PSX Games
  Method 2: Demolition Racer (MagDemo27: DR\DD.DAT\*.RNC)
  Method 2: Heart of Darkness (IMAGES\US.TIM)
  Method 2: Jonah Lomu Rugby (LOMUDEMO\GFX\*.PAK)
  Method 2: NBA Jam: Tournament Edition (*.RNC, headerless .BIN/.GFX archives)
  Method 2: Test Drive 5 (MagDemo13: TD5.DAT\*.RNC)
  Method 2: Test Drive Off-Road 3 (MagDemo27: TDOR3\TDOR3.DAT\*.rnc)

RNC in Mega Drive games
  3 Ninjas Kick Back
  Addams Family
  Addams Family Values
  The Adventures of Mighty Max
  Asterix and the Great Rescue
  Asterix and the Power of the Gods
  The Incredible Hulk
  The Itchy & Scratchy Game (unreleased)
  Marsupilami
  Mortal Kombat
  Mr. Nutz
  Outlander
  The Pagemaster
  RoboCop 3
  Spirou
  Spot Goes to Hollywood
  Stargate
  Street Racer
  Tinhead
  Tintin in Tibet
  World Championship Soccer II

Links
  http://aminet.net/package/util/pack/RNC_ProPack - official tool & source code
  https://segaretro.org/Rob_Northen_compression - description (contains bugs)


CDROM File Compression Darkworks

Used by Alone in the Dark The New Nightmare (FAT.BIN\LEVELS\*\chunks)

Decompression
The decompressor is designed to hook the sector loading function: It does decompress incoming sectors during loading, and forwards the decompressed data to the original sector loading function. The decompressed data is temporarily stored in two small Dict buffers (which do also serve as compression dictionary).
 decompress:
  dictsize=1000h, dict0=alloc(dictsize), dict1=alloc(dictsize)
  src=load_next_800h_byte_sector  ;load first sector
  dst=dict0                       ;temp dest in current dict
  dst_base=dst                    ;memorize start of newly decompressed data
 @@decompress_lop:
  if [src]=00h then                                             ;\
    esc=[src+1], src=src+1                                      ;
    forward_to_actual_dest(source=dst_base, len=dst-dst_base)   ; escape
    if esc=0 or esc>4 then esc=2 (or warn_invalid_escape_code)  ;
    if esc=1 then goto @@decompress_done                        ;
    if esc=2 or esc=4 then src=load_next_800h_byte_sector       ;
    if esc=3 or esc=4 then swap(dict0,dict1), dst=dict0         ;
    dst_base=dst                                                ;/
  elseif ([src] AND 03h)=0 then                                 ;\
    len=[src]/4+2, dat=[src+1], src=src+2                       ; fill 8bit
    for i=1 to len, [dst]=dat, dst=dst+1                        ;/
  elseif ([src] AND 03h)=1 then                                 ;\
    len=[src]/4+([src+2] AND 40h)+4                             ;
    ptr=[src+1]+([src+2] AND 3Fh)*100h                          ; LZ compressed
    if ptr+len>dictsize then error (exceeds allocated dictsize) ;
    if ([src+2] AND 80h) then ptr=ptr=dict1 else ptr=ptr=dict0  ;
    src=src+3                                                   ;
    for i=1 to len, [dst]=[ptr], ptr=ptr+1, dst=dst+1           ;/
  elseif ([src] AND 03h)=2 then                                 ;\
    len=[src]/4+3, dat0=[src+1], dat1=[src+2], src=src+3        ; fill 16bit
    for i=1 to len, [dst]=dat0, [dst+1]=dat1, dst=dst+2         ;/
  elseif ([src] AND 03h)=3 then                                 ;\
    len=[src]/4+1, src=src+1                                    ; uncompressed
    for i=1 to len, [dst]=[src], src=src+1, dst=dst+1           ;/
  goto @@decompress_lop
 @@decompress_done:
  dealloc(dict0), dealloc(dict1)
  ret
There are one or more escape codes per sector (one to indicate the end of the sector, plus further escape codes to swap the Dict buffers whenever the current Dict is full).
The original decompressor is doing the forwarding in 800h-byte units, so Dict swapping may be only done when dict0 contains a multiple of 800h bytes (aka dictsize bytes).
For whatever reason, there are only 4Kbyte per Dict allocated (although the 14bit LZ indices could have addressed up to 16Kbyte per Dict).


CDROM File Compression Blues

Blue's Clues: Blue's Big Musical (VRAM and FRAM chunks in *.TXD)
Decompression function:
  if LittleEndian32bit[src+08h]<>1 then error  ;compression flag
  dst_end=dst+LittleEndian32bit[src+14h], src=src+18h, num_collected=0
 @@decompress_lop:
  if GetBit=1 then
    [dst]=[src], src=src+1, dst=dst+1           ;code 1 uncompressed byte
  elseif GetBit=1 then
    len=[src], src=src+1                        ;code 01 fill or end code
    if len=00h then goto @@decompress_done
    len=len+1, fillvalue=[dst-1]
    for i=1 to len, [dst]=fillvalue, dst=dst+1
  else
    len=GetBit*2+GetBit
    if len=0 then                               ;code 0000 long LZ range
      len=[src] AND 0Fh, disp=[src]/10h+[src+1]*10h-1000h, src=src+2
    else                                        ;code 00xx short LZ range
      disp=[src]-100h, src=src+1
    len=len+1
    for i=1 to len, [dst]=[dst+disp], dst=dst+1
  goto @@decompress_lop
 @@decompress_done:
  if dst<>dst_end then error
  ret
 ;---
 GetBit:
  if num_collected=0 then collected=[src], src=src+1, num_collected=8
  collected=collected*2
  return (collected/100h) AND 1


CDROM File Compression Z (Running Wild)

Running Wild (MagDemo15: RUNWILD\*.BIN\*.Z and *.z)
  decompress_z:
   src=src+4            ;skip 32bit decompressed size entry
  @@reload_lop:
   load_table1          ;table for first 9bits
   load_table2          ;table for codes longer than 9bits
  @@decompress_lop:
   sym=get_symbol()
   if sym<100h then [dst]=sym, dst=dst+1, goto @@decompress_lop
   if sym=100h then goto @@escape
   len=sym-0FCh                         ;change 101h..140h to 05h..44h
   disp=((get_symbol()-101h)*40h)       ;change 101h..140h to 00h..3Fh*40h
   disp=((get_symbol()-101h) or disp)+1 ;change 101h..140h to 00h..3Fh+above+1
   copy len bytes from dst-disp to dst
   goto @@decompress_lop
  @@escape:
   if GetBits(1)=0 then goto @@reload_lop
   ret
  ;-----
  load_table1:
   t=0
  @@load_lop:
   x=GetBits(10h)
   if x and 8000h then num=1 else num=(1 shl (9-(x/400h)))
   for i=1 to num, table1[t]=x, t=t+1, next i
   if t<200h then goto @@load_lop
   ret
  ;-----
  load_table2:
   num=GetBits(9)*2      ;can be 0=none, max=3FEh
   if num>0 then for i=0 to num-1, table2[i]=GetBits(9), next i
   ret
  ;-----
  get_symbol:
   ;returns a value in range 0..140h:
   ;  00h..FFh   = data 00h..FFh   (or unused for disp codes)
   ;  100h       = escape          (or unused for disp codes)
   ;  101h..140h = length 05h..44h (or 6bit fraction of 12bit disp)
   ;  141h..3FFh = would be possible for short codes, but shouldn't be used
   x=table1[PeekBits(9)]
   if (x and 8000h)=0 then SkipBits(x/400h), return (x and 3FFh)  ;-short code
   SkipBits(9)   ;skip first 9 bits, and process futher bit(s)..  ;\
   x=x-0C000h    ;change C000h..C1FFh and up to 000h..1FFh        ; long code
  @@lop:                                                          ; (with more
   x=table2[x*2+GetBits(1)]             ;branch node0/node1       ; than 9bit)
   if x>=141h then x=x-141h, goto @@lop                           ;
   return x                                                       ;/
The bitstream is fetched in little endian 16bit units (the first bit is in bit7 of second byte). PeekBits returns the next some bits without discarding them, SkipBits does discard them, GetBits does combine PeekBits+SkipBits.
Note: The decompression function in Running Wild (MagDemo15) is at 80029D10h.


CDROM File Compression ZAL (Z-Axis)

Thrasher: Skate and Destroy (MagDemo27: SKATE\ASSETS\*.ZAL) (Z-Axis)
Dave Mirra Freestyle BMX (MagDemo36: BMX\ASSETS\*.ZAL) (Z-Axis)
Dave Mirra Freestyle BMX (MagDemo46: BMX\ASSETS\*.ZAL) (Z-Axis)
ZAL compression is used in ZAL archives. The archive header contains compressed and decompressed size for each file (and a compression flag indicating whether the archive is compressed at all).

ZAL Decompression
  if src_len=0 then goto @@decompress_done      ;empty (without end code)
  lzlen=0, rawlen=0
  if [src]=10h..FFh then                                ;\special handling
    rawlen=[src]-11h, src=src+1                         ; for code=10h..FFh
    if rawlen<=0 then goto @@decompress_error           ;/at begin of source
 @@decompress_lop:
  memcopy(dst-disp,dst,lzlen)   ;copy compressed bytes
  memcopy(src,dst,rawlen)       ;copy uncompressed bytes
  code=[src], src=src+1
  if code=00h..0Fh then
    if rawlen=0   ;when OLD rawlen=0...
      lzlen=0, rawlen=code+3                            ;\
      if rawlen=3 then                                  ;
        while [src]=00h, rawlen=rawlen+FFh, src=src+1   ;
        rawlen=rawlen+[src]+0Fh, src=src+1              ;/
    else          ;when OLD rawlen>0, and depending on OLD lzlen...
      rawlen=code AND 03h
      disp=code/4+[src]*4, src=src+1
      if lzlen=0 then disp=disp+801h, lzlen=3, else then disp=disp+1h, lzlen=2
  if code=10h..1Fh then
    lzlen=(code AND 07h)+2
    if lzlen=2 then
      while [src]=00h, lzlen=lzlen+FFh, src=src+1
      lzlen=lzlen+[src]+07h, src=src+1
    rawlen=[src] AND 03h, disp=[src]/4+[src+1]*40h+(code/8 AND 1)*4000h+4000h
    src=src+2
    if disp=4000h AND code=11h then goto @@decompress_done    ;end code
    if disp=4000h AND code<>11h then goto @@decompress_error
  if code=20h..3Fh then
    lzlen=code-20h+2
    if lzlen=2 then
      while [src]=00h, lzlen=lzlen+FFh, src=src+1
      lzlen=lzlen+[src]+1Fh, src=src+1
    rawlen=[src] AND 03h, disp=[src]/4+[src+1]*40h+1, src=src+2
  if code=40h..FFh then
    rawlen=code AND 03h
    lzlen=(code/20h)+1
    disp=((code/4) AND 07h)+([src]*8)+1, src=src+1
  goto @@decompress_lop
 @@decompress_done:
  ret


CDROM File Compression EA Methods

Electronic Arts Compression Headers
The files start with a 16bit big-endian Method value, with following bits:
  0-7     ID (usually FBh) (or 31h for Method 4A31h with 16bit sizes)
  8       Extended Header (usually 0) (or 1 for headers with extra entries)
  9-14    Used to distinguish different methods
  15      Extended Size (usually 0 for 24bit sizes) (or 1 for 32bit sizes)
The most common Method values are:
  10FBh = LZSS Compression (RefPack)
  90FBh = LZSS Compression (RefPack, with 32bit size) (not on PSX)
  30FBh = Huffman Compression
  32FBh = Huffman Compression with filter
  34FBh = Huffman Compression with dual filter
  46FBh = BPE Byte-Pair Encoding
  4AFBh = RLE Run-Length Encoding
  4A31h = RLE Run-Length Encoding, with 16bit size
  C0FBh = File Archive (not a compression method)
Most or all PSX files have Bit8=0, but anyways, the decompressor does support skipping extra header entries in files with Bit8=1 (with all methods except RLE).
Most or all PSX files have Bit15=0, games for newer consoles can reportedly have Method=90FBh (unknown if anything like B2FBh or CAFBh does also exist).
Most or all PSX files have Bit0-7=FBh (supposedly short for Frank Barchard), the 16bit mode with Bit0-7=31h is supported for Method=4A31h only (the decompressor would also accept invalid methods like 1031h or 3431h, but doesn't actually support 16bit mode for those).

Compression Formats
CDROM File Compression EA Methods (LZSS RefPack)
CDROM File Compression EA Methods (Huffman)
CDROM File Compression EA Methods (BPE)
CDROM File Compression EA Methods (RLE)

Usage in PSX games
The compression can be used to compress whole files:
  PGA Tour 96, 97, 98 (*.* and *.VIV\*) (with method 10FBh)
  Need for Speed 3 Hot Pursuit (*.Q* with method 10FBh, 30FBh, 32FBh)
Or to compress texture bitmaps inside of .PSH file chunks:
  FIFA - Road to World Cup 98 (*.PSH chunk C0h/C1h with method 10FBh)
  Sled Storm (MagDemo24: ART3\LOAD*.PSH chunk C0h/C1h with method 10FBh)
  WCW Mayhem (MagDemo28: WCWDEMO\*.BIG\*.PSH with chunk C0h/C1h with 10FBh)
The decompressor supports further methods (like 34FBh, 46FBh, 4AFBh), but there aren't any files or chunks known to actually use those compression formats.

Note: Some compressed files are slightly larger than uncompressed files (eg. filesizes for PGA Tour 96, 97, 98 COURSES\*\*.VIV\*.mis are compressed=58h, uncompressed=50h).

See also
http://wiki.niotso.org/RefPack - LZ method


CDROM File Compression EA Methods (LZSS RefPack)

RefPack
  000h 2     Method (10FBh, or 11FBh,90FBh,91FBh) (big-endian)
  ...  (3/4) Compressed size   (24bit or 32bit)   (optional)
  ...  3/4   Uncompressed size (24bit or 32bit)   (big-endoan)
  ...  ..    Compressed data
The compression is some kind of LZSS/LZH variant (similar to Z-Axis .ZAL files). The compressed data consists of a big-endian bit-stream (or byte-stream, as all codes are multiples of 8bits). The Compression codes are:
  0ddzzzrrdddddddd                  rawlen=r(2), lzlen=z(3)+3,  disp=d(10)+1
  10zzzzzzrrdddddddddddddd          rawlen=r(2), lzlen=z(6)+4,  disp=d(14+1
  110dzzrrddddddddddddddddzzzzzzzz  rawlen=r(2), lzlen=z(10)+5, disp=d(17)+1
  111rrrrr                          rawlen=r(5)*4+4, lzlen=0
  111111rr                          rawlen=r(2), lzlen=0, endflag=1
refpack_decompress:
  method=BigEndian16bit[src], src=src+2
  if (method AND 100h)>0 then src=src+3+method/8000h ;compressed size, if any
  if (method AND 8000h]=0 then dst_size=BigEndian24bit[src], src=src+3
  if (method AND 8000h)>0 then dst_size=BigEndian32bit[src], src=src+4
  endflag=0
 @@decompress_lop:
  if ([src] AND 80h)=0 then
    rawlen=[src] AND 03h
    lzlen=([src] AND 1Fh)/4+3
    disp=([src] AND 60h)*8+[src+1]+1
    src=src+2
  elseif ([src] AND 40h)=0 then
    rawlen=[src+1]/40h
    lzlen=[src] AND 3Fh+4
    disp=([src+1] AND 3Fh)*100h+[src+2]+1
    src=src+3
  elseif ([src] AND 20h)=0 then
    rawlen=[src] AND 03h
    lzlen=([src] AND 0Ch)*40h+[src+3]+5
    disp=([src] AND 10h)*1000h+[src+1]*100h+[src+2]+1
    src=src+4
  elseif ([src] AND FCh)=FCh then
    rawlen=[src] AND 03h
    lzlen=0
    src=src+1, endflag=1
  else
    rawlen=([src] AND 1Fh)*4+4
    lzlen=0
    src=src+1
  for i=1 to rawlen, [dst]=[src], src=src+1, dst=dst+1, next i
  for i=1 to lzlen, [dst]=[dst-disp], dst=dst+1, next i
  if endflag=0 then goto @@decompress_lop
  if (dst-dst_base)<>dst_size then error
  ret


CDROM File Compression EA Methods (Huffman)

Huffman
  000h 2    Method (30FBh..35FBh) (big-endian)
  ...  (3)  Extra 3 bytes (only present if Method.bit8=1)
  ...  3    Decompressed Size     (big-endian)
  ...  1    Escape code
  ...  ..   Number of codes per width
  ...  ..   Data placement for each code
  ...  ..   Compressed Data

Huffman
  decompress_ea_huffman:
   method=GetBits(16)    ;3xFBh                     ;-get method (30FBh..35FBh)
   if method AND 100h then dummy=GetBits(24)        ;-skip extra (if any)
   dst_size=GetBits(24)                             ;-get uncompressed size
   ESC=GetBits(8)                                   ;-get escape code
   huffwidth=0, huffcode=0, totalnumcodes=0         ;\
   while (huffcode shl (10h-huffwidth))<10000h      ;
     num=GetVarLenCode                              ; get num codes per width
     huffwidth=huffwidth+1                          ;
     numcodes_per_width[width]=num                  ;
     totalnumcodes=totalnumcodes+num                ;
     huffcode=(huffcode*2)+num                      ;/
   for i=0 to FFh, data_defined_flags[i]=00h        ;\
   dat=FFh, index=0                                 ;
   while index<totalnumcodes                        ;
     n=GetVarLenCode+1               ;-             ; get/assign data values
     while n>0  ;search Nth notyet defined entry    ;
       dat=(dat+1) AND FFh  ;wrap in 8bit range!    ;
       if data_defined_flags[dat]=0 then n=n-1      ;
     data_defined_flags[dat]=1                      ;
     data_values[index]=dat, index=index+1          ;/
   huffcode=0000h, index=0                          ;\
   InitEmptyHuffTree(data_tree)                     ;
   for width=1 to huffwidth                         ;
     for i=1 to numcodes_per_width[width]           ; create huffman tree
       dat=data_values[index], index=index+1        ;
       CreateHuffCode(data_tree,dat,huffcode,width) ;
       huffcode=huffcode+(1 shl (10h-width)         ;/
  @@decompress_lop:                                 ;\
   dat=GetHuffCode(data_tree)                       ;
   if dat<>ESC                                      ;
     [dst]=dat, dst=dst+1                           ; decompress
   else                                             ;
     num=GetVarLenCode                              ;
     if num=0 then                                  ;
       if GetBits(1)=1 then goto @@decompress_done  ;
       [dst]=GetBits(8), dst=dst+1                  ;
     else                                           ;
       dat=[dst-1]                                  ;
       for i=0 to num-1, [dst]=dat, dst=dst+1       ;
   goto @@decompress_lop                            ;/
  @@decompress_done:
   if (dst-dst_base)<>dst_size then error                 ;-error check
   dst=dst_base, x=00h, y=00h                             ;\
   if (method AND FEFFh)=32FBh                            ; optional final
     for i=0 to dst_size-1, x=x+[dst+i], [dst+i]=x        ; unfiltering
   if (method AND FEFFh)=34FBh                            ;
     for i=0 to dst_size-1, x=x+[dst+i], y=y+x, [dst+i]=y ;/
   ret
  ;------------------
  GetVarLenCode:
   num=2
   while GetBits(1)=0, num=num+1
   return (GetBits(num)+(1 shl num)-4)
  GetBits(num):
   return "num" bits, fetched from big-endian bitstream
  GetHuffCode(data_tree):
   ...
  InitEmptyHuffTree(data_tree):
   ...
  CreateHuffCode(data_tree,dat,huffcode,width):
   ...
  numcodes_per_width[10h]   ;9bit numcodes per width 0..15 (entry[0]=unused)
  data_values[100h]         ;8bit data values for up to 100h huffman codes
  data_defined_flags[100h]  ;1bit flags for data(00h..FFh)



CDROM File Compression EA Methods (BPE)

Byte-Pair Encoding
  000h 2    Method (46FBh or 47FBh) (big-endian)
  ...  (5)  Extra 5 bytes (only present if Method=47FBh)
  ...  3    Decompressed Size       (big-endian)
  ...  1    Escape code
  ...  1    Number of Dict entries (N)
  ...  N*3  Dict (each 3 bytes: Index,Dat1,Dat2)
  ...  ..   Compressed Data
decompress_bpe:
  method=BigEndian16bit[src], src=src+2
  if method=47FBh then src=src+5
  dst_size=BigEndian24bit[src], src=src+3
  esc=[src], src=src+1
  num=[src], src=src+1
  for i=0 to FFh, dict1[i]=i    ;initially default=self (uncompressed bytes)
  for i=1 to num, j=[src], dict1[j]=[src+1], dict2[j]=[src+2], src=src+3
 @@decompress_lop:
  x=[src], src=src+1
  if x=dict1[x] then
    if x=esc then x=[src], src=src+1, if x=00h then goto @@decompress_done
    [dst]=x, dst=dst+1
  else
    heap[0]=x, i=1
    while i>0
      i=i-1, x=heap[i], a=dict1[x]
      if a=x then [dst]=x, dst=dst+1                    ;\output data to
      else b=dict2[x], heap[i]=b, heap[i+1]=a, i=i+2    ;/dst or heap
  goto @@decompress_lop
 @@decompress_done:
  if (dst-dst_base)<>dst_size then error
  ret


CDROM File Compression EA Methods (RLE)

Run-Length Encoding
  000h 2    Method (4AFBh=24bit or 4A31h=16bit) (big-endian)
  ...  2/3  Decompressed Size (24bit or 16bit)  (big-endian)
  ...  ..   Compressed Data
Compression codes are:
  00h..3Fh  Copy 0..3Fh uncompressed bytes
  40h..7Fh  Load new fillbyte and fill 0..3Fh bytes
  80h..BFh  Use old fillbyte and fill 0..3Fh bytes (initial fillbyte=00h)
  C0h..FFh  Copy 0..3Fh bytes with constant value in upper 4bit
decompress_bpe:
  method=BigEndian16bit[src], src=src+2
  if (method AND 00FFh)=31h then dst_size=BigEndian16bit[src], src=src+2
  if (method AND 00FFh)<>31h then dst_size=BigEndian24bit[src], src=src+3
  fillbyte=00h  ;initially zero
 @@decompress_lop:
  type=[src]/40h, len=[src] AND 3Fh, src=src+1, dst_size=dst_size-len
  if type=0 then                                          ;\uncompressed bytes
    for i=1 to len, [dst]=[src], src=src+1, dst=dst+1     ;/
  elseif type=1 then                                      ;\
    fillbyte=[src], src=src+1                             ; fill with new dat
    for i=1 to len, [dst]=fillbyte, dst=dst+1             ;/
  elseif type=2 then                                      ;\fill with old dat
    for i=1 to len, [dst]=fillbyte, dst=dst+1             ;/
  elseif type=3 then
    x=[src], [dst]=x, src=src+1, dst=dst+1, x=x AND F0h
    for i=2 to len      ;<-- or so?
      if (i AND 1)=0 then [dst]=x+([src]/10h) dst=dst+1
      if (i AND 1)=1 then [dst]=x+([src] AND 0Fh), dst=dst+1, src=src+1
  if dst_size<>0 then goto @@decompress_lop
  ret


CDROM File Compression ZIP/GZIP/ZLIB (Inflate/Deflate)

Inflate/Deflate is a common (de-)compression algorithm, used by ZIP, ZLIB, and GZIP.

Inflate - Core Functions
Inflate - Initialization & Tree Creation
Inflate - Headers and Checksums

PSX Disk Images
In PSX cdrom-images, ZLIB is used by the .CDZ cdrom-image format:
CDROM Disk Image/Containers CDZ
In PSX cdrom-images, Inflate is used by .PBP and .CHD cdrom-image formats:
CDROM Disk Images PBP (Sony)
CDROM Disk Images CHD (MAME)

PSX Games
In PSX games, ZLIB is used by:
  Twisted Metal 4 (MagDemo30: TM4DATA\*.MR\* and *.IMG\*)
  Kula Quest / Kula World / Roll Away (*.PAK) (*.PAK\*)
  (and probably more games... particulary files starting with "x")
In PSX games, GZIP is used by:
  Final Fantasy VII (FF7) (BATTLE\TITLE.BIN)
  Gran Turismo 2 (MagDemo27: GT2\*) (with corrupted/zeropadded GZIP footers)
  Mat Hoffman's Pro BMX (old demo) (MagDemo39: BMX\BMXCD.HED\TITLE_H.ZLB)
In PSX games, Inflate (with slightly customized block headers) is used by:
  Mat Hoffman's Pro BMX (new demo) (MagDemo48: MHPB\FE.WAD+STR)
In PSX games, Inflate (with ignored block type, dynamic tree only) is used by:
  Project Horned Owl (COMDATA.BIN, DEMODATA.BIN, ROLL.BIN, ST*DATA.BIN)
In PSX games, ZIP is used by:
  Komocchi (DUMMY.BIN, a dummy padding file containing .MP3 pop songs)


Inflate - Core Functions

tinf_uncompress(dst,src)
 tinf_init()                    ;init constants (needed to be done only once)
 tinf_align_src_to_byte_boundary()
 repeat
  bfinal=tinf_getbit()          ;read final block flag (1 bit)
  btype=tinf_read_bits(2)       ;read block type (2 bits)
  if btype=0 then tinf_inflate_uncompressed_block()
  if btype=1 then tinf_build_fixed_trees(), tinf_inflate_compressed_block()
  if btype=2 then tinf_decode_dynamic_trees(), tinf_inflate_compressed_block()
  if btype=3 then ERROR         ;reserved
 until bfinal=1
 tinf_align_src_to_byte_boundary()
 ret

tinf_inflate_uncompressed_block()
 tinf_align_src_to_byte_boundary()
 len=LittleEndian16bit[src+0]                             ;get len
 if LittleEndian16bit[src+2]<>(len XOR FFFFh) then ERROR  ;verify inverse len
 src=src+4                                                ;skip len values
 for i=0 to len-1, [dst]=[src], dst=dst+1, src=src+1, next i    ;copy block
 ret

tinf_inflate_compressed_block()
 repeat
  sym1=tinf_decode_symbol(tinf_len_tree)
  if sym1<256
   [dst]=sym1, dst=dst+1
  if sym1>256
   len  = tinf_read_bits(length_bits[sym1-257])+length_base[sym1-257]
   sym2 = tinf_decode_symbol(tinf_dist_tree)
   dist = tinf_read_bits(dist_bits[sym2])+dist_base[sym2]
   for i=0 to len-1, [dst]=[dst-dist], dst=dst+1, next i
 until sym1=256
 ret

tinf_decode_symbol(tree)
 sum=0, cur=0, len=0
 repeat                         ;get more bits while code value is above sum
  cur=cur*2 + tinf_getbit()
  len=len+1
  sum=sum+tree.table[len]
  cur=cur-tree.table[len]
 until cur<0
 return tree.trans[sum+cur]

tinf_read_bits(num) ;get N bits from source stream
 val=0
 for i=0 to num-1, val=val+(tinf_getbit() shl i), next i
 return val

tinf_getbit() ;get one bit from source stream
 bit=tag AND 01h, tag=tag/2
 if tag=00h then tag=[src], src=src+1, bit=tag AND 01h, tag=tag/2+80h
 return bit

tinf_align_src_to_byte_boundary()
 tag=01h   ;empty/end-bit (discard any bits, align src to byte-boundary)
 ret


Inflate - Initialization & Tree Creation

tinf_init()
 tinf_build_bits_base(length_bits, length_base, 4, 3)
 length_bits[28]=0, length_base[28]=258
 tinf_build_bits_base(dist_bits, dist_base, 2, 1)
 ret

tinf_build_bits_base(bits,base,delta,base_val)
 for i=0 to 29
  bits[i]=min(0,i-delta)/delta
  base[i]=base_val
  base_val=base_val+(1 shl bits[i])
 ret

tinf_build_fixed_trees()
 for i=0 to 15, tinf_len_tree.table[i]=0, next i      ;[0..15]=0   ;len tree...
 tinf_len_tree.table[7,8,9]=24,152,112  ;number of 7bit/8bit/9bit huffcodes
 for i=0 to 23,  tinf_len_tree.trans[i+0]  =i+256, next i  ;[0..23]   =256..279
 for i=0 to 143, tinf_len_tree.trans[i+24] =i+0,   next i  ;[24..167] =0..143
 for i=0 to 7,   tinf_len_tree.trans[i+168]=i+280, next i  ;[168..175]=280..287
 for i=0 to 111, tinf_len_tree.trans[i+176]=i+144, next i  ;[176..287]=144..255
 for i=0 to 15, tinf_dist_tree.table[i]=0, next i  ;[0..15]=0        ;\dist
 tinf_dist_tree.table[5]=32             ;number of 5bit huffcodes    ; tree
 for i=0 to 31, tinf_dist_tree.trans[i]=i, next i  ;[0..31]=0..31    ;/
 ret

tinf_decode_dynamic_trees()
 hlit  = tinf_read_bits(5)+257           ;get 5 bits HLIT (257-286)
 hdist = tinf_read_bits(5)+1             ;get 5 bits HDIST (1-32)
 hclen = tinf_read_bits(4)+4             ;get 4 bits HCLEN (4-19)
 for i=0 to 18, lengths[i]=0, next i
 for i=0 to hclen-1                      ;read lengths for code length alphabet
  lengths[clcidx[i]]=tinf_read_bits(3)   ;get 3 bits code length (0-7)
 tinf_build_tree(code_tree, lengths, 19) ;build code length tree
 for num=0 to hlit+hdist-1               ;decode code lengths for dynamic trees
  sym = tinf_decode_symbol(code_tree)
  len=1, val=sym                         ;default (for sym=0..15)
  if sym=16 then len=tinf_read_bits(2)+3, val=lengths[num-1] ;3..6 previous
  if sym=17 then len=tinf_read_bits(3)+3, val=0              ;3..10 zeroes
  if sym=18 then len=tinf_read_bits(7)+11, val=0             ;11..138 zeroes
  for i=1 to len, lengths[num]=val, num=num+1, next i
 tinf_build_tree(tinf_len_tree,  0,      hlit)    ;\build trees
 tinf_build_tree(tinf_dist_tree, 0+hlit, hdist)   ;/
 ret

tinf_build_tree(tree, first, num)
 for i=0 to 15, tree.table[i]=0, next i     ;clear code length count table
 ;scan symbol lengths, and sum code length counts...
 for i=0 to num-1, x=lengths[i+first], tree.table[x]=tree.table[x]+1, next i
 tree.table[0]=0
 sum=0          ;compute offset table for distribution sort
 for i=0 to 15, offs[i]=sum, sum=sum+tree.table[i], next i
 for i=0 to num-1  ;create code to symbol xlat table (symbols sorted by code)
  x=lengths[i+first], if x<>0 then tree.trans[offs[x]]=i, offs[x]=offs[x]+1
 next i
 ret

tinf_data
 clcidx[0..18] = 16,17,18,0,8,7,9,6,10,5,11,4,12,3,13,2,14,1,15   ;constants


 typedef struct TINF_TREE:
   unsigned short table[16]     ;table of code length counts
   unsigned short trans[288]    ;code to symbol translation table


 TINF_TREE tinf_len_tree   ;length/symbol tree
 TINF_TREE tinf_dist_tree  ;distance tree
 TINF_TREE code_tree       ;temporary tree (for generating the dynamic trees)
 unsigned char lengths[288+32]   ;temporary 288+32 x 8bit ;\for dynamic tree
 unsigned short offs[16]         ;temporary 16 x 16bit    ;/creation


 unsigned char  length_bits[30]
 unsigned short length_base[30]
 unsigned char  dist_bits[30]
 unsigned short dist_base[30]


Inflate - Headers and Checksums

tinf_gzip_uncompress(dst, destLen, src, sourceLen)
 src_start=src, dst_start=dst                 ;memorize start addresses
 if (src[0]<>1fh or src[1]<>8Bh) then ERROR   ;check id bytes
 if (src[2]<>08h) then ERROR                  ;check method is deflate
 flg=src[3]                                   ;get flag byte
 if (flg AND 0E0h) then ERROR                 ;verify reserved bits
 src=src+10                                                 ;skip base header
 if (flg AND 04h) then src=src+2+LittleEndian16bit[src]     ;skip extra data
 if (flg AND 08h) then repeat, src=src+1, until [src-1]=00h ;skip file name
 if (flg AND 10h) then repeat, src=src+1, until [src-1]=00h ;skip file comment
 hcrc=(tinf_crc32(src_start, src-src_start) & 0000ffffh))   ;calc header crc
 if (flg AND 02h) then x=LittleEndian16bit[src], src=src+2  ;get header crc
 if (flg AND 02h) then if x<>hcrc then ERROR                ;verify header
 tinf_uncompress(dst, destLen, src, src_start+sourceLen-src-8)  ;----> inflate
 crc32=LittleEndian32bit[src], src=src+4   ;get crc32 of decompressed data
 dlen=LittleEndian32bit[src], src=src+4    ;get decompressed length
 if (dlen<>destLen) then ERROR                              ;verify dest len
 if (crc32<>tinf_crc32(dst_start,dlen)) then ERROR          ;verify crc32
 ret

tinf_quasijarus_uncompress(dst, destLen, src, sourceLen)
 src_start=src, dst_start=dst                 ;memorize start addresses
 if (src[0]<>1fh or src[1]<>A1h) then ERROR   ;check id bytes
 src=src+2                                    ;skip header
 tinf_uncompress(dst, destLen, src, sourceLen-0Ah)          ;----> inflate
 crc32=LittleEndian32bit[src], src=src+4   ;get crc32 of decompressed data
 dlen=LittleEndian32bit[src], src=src+4    ;get decompressed length
 if (dlen<>destLen) then ERROR                              ;verify dest len
 if (crc32<>tinf_crc32(dst_start,dlen)) then ERROR          ;verify crc32
 ret

tinf_zlib_uncompress(dst, destLen, src, sourceLen)
 src_start=src, dst_start=dst         ;memorize start addresses
 hdr=BigEndian16bit[src], src=src+2   ;get header
 if (hdr MOD 31)<>0 then ERROR        ;check header checksum (modulo)
 if (hdr AND 20h)>0 then ERROR        ;check there is no preset dictionary
 if (hdr AND 0F00h)<>0800h then ERROR ;check method is deflate
 if (had AND 0F000h)>7000h then ERROR ;check window size is valid
 tinf_uncompress(dst, destLen, src, sourceLen-6)      ;------> inflate
 chk=BigEndian32bit[src], src=src+4                   ;get data checksum
 if src-src_start<>sourceLen then ERROR               ;verify src len
 if dst-dst_start<>destLen then ERROR                 ;verify dst len
 if a32<>tinf_adler32(dst_start,destLen)) then ERROR  ;verify data checksum
 ret

tinf_adler32(src, length)
 s1=1, s2=0
 while (length>0)
  k=max(length,5552)    ;max length for avoiding 32bit overflow before mod
  for i=0 to k-1, s1=s1+[src], s2=s2+s1, src=src+1, next i
  s1=s1 mod 65521, s2=s2 mod 65521, length=length-k
 return (s2*10000h+s1)



CDROM File Compression LArc/LHarc/LHA (LZS/LZH)

LHA (formerly LHarc) is an old DOS compression tool with backwards compatibility for LArc. LHA appears to have been particulary popular in Japan, and in the Amiga scene.
LHA archives are used by some PSX games:
  PSX Championship Surfer (MagDemo43: HWX\*.DAT)                ;method lh5
  PSX Net Yaroze Demo Disc SLED-01340 (DATA\JAPAN\*.FPC\*.LZH)  ;method lh5
And, there are various PSX games with compression based on LArc's method lz5:
CDROM File Compression LZ5 and LZ5-variants

Overall File Format
Default archive filename extension is .LZH for LHarc/LHA (lh*-methods), or .LZS for LArc (lz*-methods).
Archives can contain multiple files, and are usually terminated by a 00h-byte:
  LHA Header+Data for 1st file
  LHA Header+Data for 2nd file
  End Marker (00h)
There is no central directory, one must crawl all headers to create a list of files in the archive.
Caution: There is a hacky test file (larc333\initial.lzs) with missing end byte (it does just end at filesize).
LHA Header v2 Headersize=xx00h would conflict with End Byte (as workaround, insert a Nullbyte between Ext.Headers and Data to change Headersize to xx01h.

LHA Header v0 (with [14h]=00h)
  00h     1   Header Size (Method up to including Extended Area) (=16h+F+E)
  01h     1   Header Checksum, sum of bytes at [02h+(0..15h+F+E)]
  02h     5   Compression Method (eg. "-lh0-"=Uncompressed)
  07h     4   Compressed Size
  0Bh     4   Uncompressed Size
  0Fh     2   Last modified time (in MS-DOS format)
  11h     2   Last modified date (in MS-DOS format)
  13h     1   MS-DOS File attribute (usually 20h)
  14h     1   Header level (must be 00h for v0)
  15h     1   Path\Filename Length
  16h     (F) Path\Filename (eg. "PATH\FILENAME.EXT")
                     '\' may apper in the 2nd byte of Shift_JIS, processing
                     of Shift_JIS is indispensable when you need full
                     implementation of reading Pathname.
  16h+F   2   CRC16 (with initial value 0000h) on uncompressed file
  18h+F   (E) Extended area (used by UNIX in v0)
  18h+F+E ..  Compressed data
Note: Reportedly, old LArc files don't have CRC16 (unknown if that is true, the ONLY known version is LArc v3.33, which DOES have CRC16, if older versions didn't have that CRC then they did perhaps behave as if E=(-2)?).

LHA Header v1 (with [14h]=01h)
  00h     1   Header Size (Method up to including 1st Ext Size) (=19h+F+E)
  01h     1   Base Header Checksum, sum of bytes at [02h+(0..18h+F+E)]
  02h     5   Compression Method (eg. "-lh0-"=Uncompressed)
  07h     4   Skip size (size of all Extended Headers plus Uncompressed Size)
  0Bh     4   Uncompressed Size
  0Fh     2   Last modified time (in MS-DOS format)
  11h     2   Last modified date (in MS-DOS format)
  13h     1   Reserved     (must be 20h) (but is 02h on Amiga)
  14h     1   Header level (must be 01h for v1)
  15h     1   Length of Filename (or 00h when name is in Extended Header)
  16h     (F) Filename (eg. "FILENAME.EXT; path (if any) is in Extended Header)
  16h+F   2   CRC16 (with initial value 0000h) on uncompressed file
  18h+F   1   Compression Tool OS ID (eg. "M"=MSDOS)
  19h+F   (E) Extended area (unused in v1, use Ext Headers instead)
  19h+F+E 2   Size of 1st Extended Header (0000h=None)
  1Bh+F+E ..  Extended Header(s) (optional stuff)
  ...     ..  Compressed data

LHA Header v2 (with [14h]=02h)
  00h     2   Header Size (whole Header including all Extended Headers)
  02h     5   Compression Method (eg. "-lh0-"=Uncompressed)
  07h     4   Compressed Size
  0Bh     4   Uncompressed Size
  0Fh     4   Last modified date and time (seconds since 1st Jan 1970 UTC)
  13h     1   Reserved     (must be 20h) (but is 02h on Amiga)
  14h     1   Header level (must be 02h for v2)
  15h     2   CRC16 (with initial value 0000h) on uncompressed file
  17h     1   Compression Tool OS ID (eg. "M"=MSDOS)
  18h     2   Size of first Extended Header (0000h=None)
  1Ah     ..  Extended Header(s) (filename and optional stuff)
  ...     0/1 Nullbyte (End-Marker conflict: change Headersize xx00h to xx01h)
  ...     ..  Compressed data

LHA Header v3 (with [14h]=03h)
Kinda non-standard (supported only in late japanese LHA beta versions): Allows Header and Ext.Headers to exceed 64Kbyte, which is rather useless.
  00h     2   Word size for 32bit Header entries (always 4=32bit)
  02h     5   Compression Method (eg. "-lh0-"=Uncompressed)
  07h     4   Compressed Size
  0Bh     4   Uncompressed Size
  0Fh     4   Last modified date and time (seconds since 1st Jan 1970 UTC)
  13h     1   Reserved     (must be 20h)
  14h     1   Header level (must be 03h for v3)
  15h     2   CRC16 (with initial value 0000h) on uncompressed file
  17h     1   Compression Tool OS ID (eg. "M"=MSDOS)
  18h     4   Header Size (whole Header including all Extended Headers)
  1Ch     4   Size of first Extended Header (00000000h=None)
  20h     ..  Extended Header(s) (filename and optional stuff)
  ...     ..  Compressed data

Compression Methods
  Method Len    Window
  -lz4-  -  -   -        LArc Uncompressed File
  -lh0-  -  -   -        LHA  Uncompressed File
  -lhd-  -  -   -        LHA  Uncompressed Directory name entry
  -lzs-  2..17  2Kbyte   LArc LZSS-Compressed  (rare, very-very old)    ;-15bit
  -lz5-  3..17  4Kbyte   LArc LZSS-Compressed  (LArc srandard)          ;-16bit
  -lh1-  3..60  4Kbyte   LHA  LZHUF-Compressed (old LHA standard)
  -lh2-  3..256 8Kbyte   LHA  Obscure test     (used in self-extractor)
  -lh3-  3..256 8Kbyte   LHA  Obscure test     (experimental)
  -lh4-  3..256 4Kbyte   LHA  AR002-Compressed (rare, for small RAM)    ;\4bit
  -lh5-  3..256 8Kbyte   LHA  AR002-Compressed (new LHA standard)       ;/
  -lh6-  3..256 32Kbyte  LHA  AR002-Compressed (rare)                   ;\
  -lh7-  3..256 64Kbyte  LHA  AR002-Compressed (rare)                   ; 5bit
  -lh8-  3..256 64Kbyte  LHA  AR002-Compressed (accidently same as lh7) ;
  -lh9-  3..256 128Kbyte LHA  AR002-Compressed (unimplemented proposal) ;
  -lha-  3..256 256Kbyte LHA  AR002-Compressed (unimplemented proposal) ;
  -lhb-  3..256 512Kbyte LHA  AR002-Compressed (unimplemented proposal) ;
  -lhc-  3..256 1Mbyte   LHA  AR002-Compressed (unimplemented proposal) ;
  -lhe-  3..256 2Mbyte   LHA  AR002-Compressed (unimplemented proposal) ;
  -lhx-  3..256 512Kbyte LHA  AR002-Compressed (rare)                   ;/
Apart from above methods, there are various other custom hacks/extensions.

Extended Headers
  00h     1   Extension Type (00h..FFh, eg. 01h=Filename)
  01h     ..  Extension Data
  ...     2/4 Size of next Extended Header (0=None) (v1/v2=16bit, v3=32bit)
Extension Type values:
  00h   CRC16 on whole Header with InitialValue=0000h and InitialCrcEntry=0000h
  01h   Filename
  02h   Directory name (with FFh instead of "\", and usually with trailing FFh)
  3Fh   Comment (unspecified format/purpose)
  40h   MS-DOS File attribute of MS-DOS format
  41h   Windows FILETIME for last access, creation, and modification
  42h   Filesize (uncompressed and compressed size, when exceeding 32bit)
  50h   Unix Permission
  51h   Unix User ID and Group ID
  52h   Unix Group name
  53h   Unix User name (owner)
  54h   Unix Last modified time in time_t format
  7Dh   Capsule offs/size (if the OS adds extra header/footer to the filebody)
  7Eh   OS/2 Extended attribute
  7Fh   Level 3 Attribute in Unix form and MS-DOS form
  FFh   Level 3 Attribute in Unix form
Note: There appears to be no MAC specific format (instead, the LHA MAC version is including a MacBinary header in the compressed files).

See also
The site below has useful links with info about headers (see LHA Notes), source code, and test archives:
  http://fileformats.archiveteam.org/wiki/LHA


CDROM File Compression UPX

UPX Compression (used in AmiDog's GTE test)
UPX is a tool for creating self-decompressing executables. It's most commonly used for DOS/Windows EXE files, but it does also support consoles like PSX. The PSX support was added in UPX version 1.90 beta (11 Nov 2002).
  000h 88h      Standard PS-X EXE header
  088h 20h      Unknown
  0A8h 4        ASCII ID "UPX!"
  0ACh 1Eh      Unknown
  0CAh 9Ah      ASCII "$info: This file is ..."
  164h 69Ch     Zerofilled
  800h ..       Leading zeropadding (to make below end on 800h-byte boundary)
  ...  ..       Decompression stub
  ...  ..       Compressed data (ending on 800h-byte boundary)


CDROM File Compression LZMA

LZMA is combining LZ+Huffman+Probabilities. The LZ+Huffman bitstream is rather simple (using hardcoded huffman trees), the high compression ratio is reached by predicting probabilities for the bitstream values (that is, the final compressed data is smaller than the bitstream).

LZMA Bitstreams
  000h 1   Ignored byte (usually 00h, unknown purpose)
  001h ..  Bitstream with actual compression codes
  ...  ..  EOS end code (end of stream) (optional)
  ...  ..  Ignored byte (present in case of Normalization after last code)
  ...  ..  Padding to byte-boundary
Apart from the bitstream, one must know several parameters (which may be hardcoded, or stored in custom file headers in front of the bitstream):
  Three decompression parameters: lc, lp, pb
  Decompressed size (required if the bitstream has no EOS end code)
  Dictionary size (don't care when decompressing the whole file to memory)
  Presence/Absence of EOS end code

.lzma files (LZMA_Alone format from LZMA SDK)
  000h 1   Parameters (((pb*5)+lp)*9)+lc  (usually 5Dh)         ;\
  001h 4   Dictionary Size in bytes       (usually 10000h)      ; Header
  005h 8   Decompressed Size in bytes     (or -1=Unknown)       ;/
  00Dh 1   LZMA ignored 1st byte of bitstream (00h)             ;\LZMA
  00Eh ..  LZMA bitstream (with optional EOS end code)          ;/
The files are often starting with 5Dh,00h,00h. However, there's no real File ID, and there's no CRC, the format is rather unsuitable for file sharing.
The end of the bitstream is indicated by EOS end code, or by Decompressed Size entry (or both).

.lz files (LZIP)
LZIP files can contain one or more "LZIP Members" plus optional extra data:
  000h ..  LZIP Member(s)
  ...  ..  Optional extra data (if any) (eg. zeropadding or some SHA checksum)
Whereas, a normal .lz file contains only one "Member", without extra data.
Each of the "LZIP Member(s)" is having following format:
  000h 5   ID and version ("LZIP",01h)                          ;\LZIP Header
  005h 1   Dictionary size (5bit+3bit code, see below)          ;/
  006h ..  LZMA bitstream (with lc=3, lp=0, pb=2) (with EOS end code)
  ...  4   CRC32 on uncompressed data                           ;\
  ...  8   Size of uncompressed data                            ; LZIP Footer
  ...  8   Size of compressed data (including header+footer)    ;/
The dictionary size should be 1000h..20000000h bytes, computed as so:
  temp = 1 SHL (hdr[005h] AND 1Fh)
  dict_size = temp - (temp/10h)*(hdr[005h]/20h)
The LZIP format doesn't really allow to determine the uncompressed size before decompression (one must either decompress the whole file to detect the size, or one could try to find the Footer at end of file; which requires weird heuristics because the LZIP manual is explicitely stating that it's valid to append extra data after the Footer).
  http://www.nongnu.org/lzip/manual/lzip_manual.html#File-format

.chd (MAME compressed CDROM and HDD images)
The CHD format has its own headers and supports several compression methods including LZMA. Leaving apart the CHD specific headers, the raw LZMA bitstreams are stored as so:
  000h ..  LZMA bitstream (with lc=3, lp=0, pb=2) (without EOS end code)

.xz files (XZ Utils)
This is a slightly overcomplicated format with LZMA2 compression and optional filters.
CDROM File Compression XZ

.7z files (7-Zip archives)
  000h 6   ID ("7z",BCh,AFh,27h,1Ch)
  ...  ..  ..
The 7z format defines many compression methods. The ones normally used are LZMA2 (default for 7-Zip 9.30 alpha +), LZMA (default for 7-Zip prior to 9.30 alpha), PPMd, and bzip2.
http://fileformats.archiveteam.org/wiki/7z

LZMA2 (used in .7z and .xz files)
LZMA2 is a container format with LZMA chunks. The LZMA function is slightly customized: It can optionally skip some LZMA initialization steps (and thereby re-use the dictionary/state from previous chunks). The chunks are:
 ChunkID=00h - Last chunk:
  000h 1   Chunk ID (00h=End)
 ChunkID=01h..02h - Uncompressed chunks:
  000h 1   Chunk ID (01h=Uncompressed+ResetDictionary, 02h=Uncompressed)
  001h 2   Uncompressed Data Size-1     (big-endian)
  003h ..  Uncompressed Data (to be copied to destination and dictionary)
  Note: The uncompressed data is stored in LZMA dictionary, and
  the last uncompressed byte is updating the LZMA prevbyte.
 ChunkID=03h..7Fh - Invalid chunks:
  000h 1   Chunk ID (03h..7Fh=Invalid)
 ChunkID=80h..FFh - LZMA-compressed chunks:
  000h 1   Chunk ID (80h/A0h/C0h/E0h + Upper5bit(UncompressedSize-1))
  001h 2   LSBs(UncompressedSize-1)       (big-endian)
  003h 2   CompressedSize-1               (big-endian)
  005h (1) Parameters (((pb*5)+lp)*9)+lc  (only present if ChunkID=C0h..FFh)
  ...  ..  LZMA bitstream (without EOS end code)
LZMA status gets reset depending on the Chunk ID:
  ChunkID  dict/prev  lc/lp/pb  state  dist[0-3]  probabilities  code/range
  01h      reset      -         -      -          -              -
  02h      -          -         -      -          -              -
  80h+n    -          -         -      -          -              reset
  A0h+n    -          -         reset  reset      reset          reset
  C0h+n    -          reset     reset  reset      reset          reset
  E0h+nn   reset      reset     reset  reset      reset          reset
  (Note: Those resets occur before processing the chunk data)
Note: dict/prev reset means that previous byte is assumed to be 00h (and old dictionary content isn't used, somewhat allowing random access or multicore decompression).
Apart from the chunks, LZMA2 does usually contain a Dictionary Size byte:
  Dictionary Size byte (00h..28h = 4K,6K,8K,12K,16K,24K,..,2G,3G,4G)
 Which can be decoded as so:
  if (param AND 1)=0 then dict_size=1000h shl (param/2)
  if (param AND 1)=1 then dict_size=1800h shl (param/2)
  if param=28h then dict_size=FFFFFFFFh   ;4GB-1
  if param>28h then error
 In .xz files, that byte is stored alongsides with the Filter ID.

LZMA Source code
Compact LZMA decompression ASM code can be found here:
  https://github.com/ilyakurdyukov/micro-lzmadec
Above code is for self-decompressing executables (for plain LZMA, ignore the stuff about EXE/ELF headers). The two "static" versions are size-optimized (they contain weird and poorly commented programming tricks, and do require additional initialization code from "test_static.c"). For normal purposes, it's probably better to port the 64bit fast version to 32bit (instead of dealing with the trickery in the 32bit static version).


CDROM File Compression XZ

Overall Structure of .xz File
  000h ..  Stream(s)
Note: To determine the total uncompressed size, one must process the file backwards, starting at footer of last stream.

Stream
  000h 6   Header ID (FDh,"7zXZ",00h) (FDh,37h,7Ah,58h,5Ah,00h) ;\
  006h 2   Checksum Type (0000h, 0100h, 0400h or 0A00h)         ; Header
  008h 4   Header CRC32 on above 2 bytes                        ;/
  00Ch ..  Compressed Block(s)                                  ;-Block(s)
  ...  ..  Index List                                           ;-Index
  ...  4   Footer CRC32 on below 6 bytes                        ;\
  ...  4   Index List Size/4-1                                  ; Footer
  ...  2   Checksum Type (must be same as in Header)            ;
  ...  2   Footer ID ("YZ") (59h,5Ah)                           ;/
  ...  ..  Optional Zeropadding (multiple of 4 bytes)           ;-Padding
 Checksum Type (for Block checksums):
  0000h=None
  0100h=CRC32 (little-endian)
  0400h=CRC64 (little-endian)
  0A00h=SHA256 (big-endian)
  Other=Reserved

Index List
  000h 1    Index Indicator (00h) (as opposed to 01h..FFh in Block Headers)
  001h VL   Number of Records (must be same as number of Blocks in Stream)
  ...  ..   Index Record(s)
  ...  ..   Zeropadding to 4-byte boundary
  ...  4    CRC32 on above bytes
 Index Record:
  000h VL   Unpadded Block Size (BlockHeader + CompressedData + 0 + Checksum)
  ...  VL   Uncompressed Block Size

Compressed Block
  000h 1    Block Header Size/4-1 (01h..FFh = 8..400h bytes)           ;\
  001h 1    Block Flags                                                ;
  002h (VL) Compressed Size     ;present if Flags.bit6 = 1             ; Header
  ...  (VL) Uncompressed Size   ;present if Flags.bit7 = 1             ;
  ...  ..   Filter Info 0 (LAST filter when DECOMPRESSING)             ;
  ...  (..) Filter Info 1       ;present if Flags.bit0-1 = 1,2,3       ;
  ...  (..) Filter Info 2       ;present if Flags.bit0-1 = 2,3         ;
  ...  (..) Filter Info 3       ;present if Flags.bit0-1 = 3           ;
  ...  ..   Zeropadding to 4-byte boundary                             ;
  ...  (..) Optional Zeropadding (multiple of 4 bytes)                 ;
  ...  4    CRC32 on above bytes                                       ;/
  ...  ..   Compressed Data                                            ;-Data
  ...  ..   Zeropadding to 4-byte boundary                             ;-Pad
  ...  (..) Checksum on uncompressed Data (None/CRC32/CRC64/SHA256)    ;-Check
 Block Flags:
  0-1  Number of filters-1                (0..3 = 1..4 filters)
  2-5  Reserved (0)
  6    Compressed Size field is present   (0=No, 1=Present)
  7    Uncompressed Size field is present (0=No, 1=Present)
 Filter Info:
  000h VL   Filter ID
  ...  VL   Size of Filter Properties
  ...  ..   Filter Properties
 Filter IDs:
  03h                        Delta Filter       (with 1 byte param)
  04h..09h                   Executable Filters (with 0 or 4 byte param)
  21h                        LZMA2 Compression  (with 1 byte param)
  300h..4FFh                 Reserved to ease .7z compatibility
  20000h..7FFFFh             Reserved to ease .7z compatibility
  2000000h..7FFFFFFh         Reserved to ease .7z compatibility
  xxxxxxxxxxxxxxxxh          Custom Registered IDs (obtained from Lasse Collin)
  3Frrrrrrrrrriiiih          Custom Random IDs (40bit random+16bit filterno)
  4000000000000000h and up   Reserved for internal use (don't use in xz files)
Note: The first decompression filter must be LZMA2, which reads from compressed data stream, and writes to decompressed data (and also implies the size of compressed/decompressed data). The other filters (if any) are unfiltering the decompressed data.

Filter 21h: LZMA2 Compression Method
This "filter" is the actual compression method (XZ supports only one method).
It can be combined with BCJ/Delta filters (whereas, LZMA2 must be always used as LAST compression filter, aka FIRST decompression filter).
 The filter parameter is 1 byte tall:
  Dictionary Size byte (00h..28h = 4K,6K,8K,12K,16K,24K,..,2G,3G,4G)
 The compressed data contains:
  LZMA2 chunks (with LZMA-compressed data and/or uncompressed data)

Filter 03h: Delta Filter
The filter parameter is 1 byte tall:
  Distance-1 (00h..FFh = distance 1..100h)
 unfilter_delta(buf,len,param_byte):
  dist=byte(param)+1, i=dist   ;init dist and skip first some unfiltered bytes
  while i<len, byte(buf[i]) = buf[i]+buf[i-dist], i=i+1

Filter 04h-09h: Executable Branch/Call/Jump (BCJ) Filters
These filters can replace relative jump addresses by absolute values.
  ID   Parameters    Alignment  Description
  04h  0 or 4 bytes  1 byte     80x86 filter (32bit or 64bit)
  05h  0 or 4 bytes  4 bytes    PowerPC filter (big endian)
  06h  0 or 4 bytes  16 bytes   IA64 filter
  07h  0 or 4 bytes  4 bytes    ARM filter (little endian)
  08h  0 or 4 bytes  2 bytes    ARM Thumb filter (little endian)
  09h  0 or 4 bytes  4 bytes    SPARC filter
  0Ah,0Bh                       Inofficial hacks/proposals for ARM64?
The filter parameter field can 0 or 4 bytes tall:
  if param_size=0 then offset=00000000h
  if param_size=4 then offset=LittleEndian32bit(param)
 Nonzero offsets are intended for executables with multiple sections and
 cross-section jumps. The offset shall/must match the filter's alignment.
 unfilter_bcj_x86(buf,len,offset):
  i=0, len=len-4, offset=offset+4
  while i<len
    x=byte[buf+i], i=i+1
    if (x AND FEh)=E8h                     ;Opcode=E8h or E9h
      x=LittleEndian32bit[buf+i]
      if ((x+01000000h) AND FE000000h)=0   ;MSB=00h or FFh
        LittleEndian32bit[buf+i]=SignExpandLower25bit(x-i-offset)
      i=i+4
 unfilter_bcj_arm(buf,len,offset):
  i=0, len=len/4, offset=(offset+8)/4
  while i<len
    x=LittleEndian32bit[buf+i*4]
    if (x AND FF000000h)=EB000000h
      LittleEndian32bit[buf+i*4]=((x-i-offset) and 00FFFFFFh)+EB000000h
    i=i+1
 unfilter_bcj_armthumb(buf,len,offset):
  i=0, len=len/2-1, offset=(offset+4)/2
  while i<len
    x=LittleEndian32bit[buf+i*2]
    if (x AND F800F800h)=F800F000h
      msw=LittleEndian16bit[buf+i*2+0] AND 7FFh
      lsw=LittleEndian16bit[buf+i*2+2] AND 7FFh
      x=msw*800h+lsw-i-offset
      LittleEndian16bit[buf+i*2+0]=F000h+(7FFh and (x/800h))
      LittleEndian16bit[buf+i*2+2]=F800h+(7FFh and (x/1))
    i=i+1
 unfilter_bcj_sparc(buf,len,offset):
  i=0, len=len/4, offset=offset/4
  while i<len
    x=BigEndian32bit[buf+i*4]
    if (x AND FFC00000h)=40000000h or (x AND FFC00000h)=7FC00000h
      x=SignExpandLower23bit(x-i-offset)
      BigEndian32bit[buf+i*4]=(x AND 3FFFFFFFh)+40000000h
    i=i+1
 unfilter_bcj_powerpc(buf,len,offset):
  i=0, len=len/4, offset=offset/4
  while i<len
    x=BigEndian32bit[buf+i*4]
    if (x AND FC000003h)=48000001h
      BigEndian32bit[buf+i*4]=(((x/4-i-offset) AND 00FFFFFFh)*4)+48000001h
    i=i+1
 unfilter_bcj_ia64(buf,len,offset):
  i=0, len=len/10h, offset=offset/10h
  xlat[0..1Fh]=0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,4,4,6,6,0,0,7,7,4,4,0,0,4,4,0,0
  while i<len
    flags=xlat[byte[buf] and 1Fh]       ;shared 5bit for three 41bit opcodes
    for slot=0 to 2
      if flags and (1 shl slot)         ;process three 41bit opcodes
        bitbase=slot*41+5
        hi=byte[buf+(bitbase+37)/8] shr ((bitbase+37) and 7) and 0Fh
        lo=LittleEndian16bit[buf+(bitbase+9)/8] shr ((bitbase+9) and 7) and 07h
        if hi=5 and lo=0
          mid=LittleEndian32bit[buf+(bitbase+13)/8]
          x=mid shr ((bitbase+13) and 7)
          x=x and 8FFFFFh, if (x and 800000h) then x=x-700000h
          x=x-i-offset
          x=x and 1FFFFFh, if (x and 100000h) then x=x+700000h
          mid=mid AND NOT (8FFFFFh shl ((bitbase+13) and 7))  ;strip old
          mid=mid OR x shl ((bitbase+13) and 7))              ;place new
          LittleEndian32bit[buf+(bitbase+13)/8]=mid           ;apply
    i=i+1, buf=buf+10h

Cyclic Redundancy Checks (CRCs)
CRC32 uses 32bit (with polynomial=EDB88320h). CRC64 does basically use the same function (with 64bit values and polynomial=C96C5795D7870F42h).

Endianness and Variable Length (VL) Integers
Little-endian is used for 16bit/32bit/64bit values (Flags, Sizes, CRCs).
Big-endian is used for 256bit SHA256 and for values within LZMA2 chunks.
Variable length integers (marked VL in above tables) are used for Sizes and IDs, these values may contain max 63bit, stored in 1-9 bytes:
  decode_variable_len_integer:
   i=0, num=0
  @@lop:
   x=[src], src=src+1, num=num+((x and 7Fh) shl i), i=i+7
   if x AND 80h then goto @@lop
   return num

Notes and References
XZ Utils for Windows is claimed to work on Win98 (that is, it will throw an error about missing MSVCRT.DLL:___mb_cur_max_func). XZ Utils for DOS does work on Win98.
Official XZ file format specs for can be found at:
  https://tukaani.org/xz/format.html
If your browser can't break the https encryption, try this link:
  http://web.archive.org/web/20220603034213/https://tukaani.org/xz/format.html
The BCJ filters aren't documented in XZ specs, but are defined in XZ source code, see src\liblzma\simple\*.c). There's also this mail thread about semi-official ARM64 filters:
  https://www.mail-archive.com/xz-devel@tukaani.org/msg00537.html


CDROM File Compression FLAC audio

FLAC is a lossless audio compression format.

FLAC file format
  000h 4   FLAC ID ("fLaC")
  004h ..  Metadata block with STREAMINFO
  ...  ..  Metadata block(s) with further info (optional)
  ...  ..  FLAC Frame(s)
The whole file can be read as big-endian bitstream (although bitstream reading is mainly required for the Frame bodies) (the Frame header/footer and Metadata blocks are byte-aligned and can be read as byte-stream).
Metadata Block format:
  1bit    Last Metadata block flag (1=Last, 0=More blocks follow)
  7bit    Block Type (see below)
  24bit   Size of following metadata in bytes (N)
  N*8bit  Metadata (depending on Type)
Metadata Block Types:
  00h = STREAMINFO
  01h = PADDING
  02h = APPLICATION
  03h = SEEKTABLE
  04h = VORBIS_COMMENT
  05h = CUESHEET
  06h = PICTURE
  ..  = Reserved
  7Fh = Invalid (to avoid confusion with a frame sync code)
FLAC METADATA_BLOCK_STREAMINFO (272bit = 22h bytes)
  16bit  Minimum Block size in samples (10h..FFFFh)  ;\min=max implies
  16bit  Maximum Block size in samples (10h..FFFFh)  ;/fixed blocksize
  24bit  Minimum Frame size in bytes (or 0=Unknown)
  24bit  Maximum Frame size in bytes (or 0=Unknown)
  20bit  Sample rate in Hertz (01h..9FFF6h = 1..655350 Hz)
  3bit   Number of channels-1 (00h..07h = 1..8 channels)
  5bit   Bits per sample-1    (03h..1Fh = 4..32 bits) (max 24bit implemented)
  36bit  Total number of samples per channel (or 0=Unknown)
  128bit MD5 on unencoded audio data (...in which format? endian/interleave?)

More info
The FLAC file format is documented here:
  https://xiph.org/flac/format.html
Above requires new browser with strong https, alternately try the link below:
  http://web.archive.org/web/20201208111432/https://xiph.org/flac/format.html
Source code for a compact FLAC decoder can be found here:
  https://www.nayuki.io/page/simple-flac-implementation


CDROM File Compression ARJ

ARJ archives contain several chunks
  Main header chunk
  Local file chunk(s)
  Chapter chunk(s), backup related, exist only in newer archives
  End Marker

ARJ main "comment" header, with [00Ah]=2
This is stored at the begin of the archive. The format is same as for local file header (but with file-related entries set to zero, or to global security settings).
  000h 2   ARJ ID (EA60h, aka 60000 decimal)
  002h 2   Header size (from 004h up to including Filename+Comment) (max 2600)
  004h 1   Header size (from 004h up to including Extra Data) (1Eh+extra)
  005h 1   Archiver version number (01h..0xh)
  006h 1   Minimum archiver version to extract (usually 01h)
  007h 1   Host OS
  008h 1   ARJ Flags (bit0-7, see below)
  009h 1   Security version (2 = current)
  00Ah 1   File Type        (must be 2=ARJ Comment in main header)
  00Bh 1   Reserved/Garbage (LSB of Archive creation Date/Time, same as [00Ch])
  00Ch 4   Date/Time when archive was created
  010h 4   Date/Time when archive was last modified
  014h 4   Zero  (or Secured Archive size, excluding Security and Protection)
  018h 4   Zero  (or Security envelope file position) (after End Marker)
  01Ch 2   Zero  (or Filespec position in filename) (0) (what is that??)
  01Eh 2   Zero  (or Security envelope size in bytes) (78h, if any)
  020h 1   Zero  (or >2.50?: Encryption version, 0-1=Old, 2=New, 4=40bit GOST)
  021h 1   Zero  (or >2.50?: Last chapter (eg. 4 when having chapter 1..4)
  022h (1) Extra data: ARJ Protection factor                         ;\extra,
  023h (1) Extra data: ARJ Flags (bit0=ALTVOLNAME, bit1=ReservedBit) ; if any
  024h (2) Extra data: Spare bytes                                   ;/
  ...  ..  Filename, max 500 bytes ("FILENAME.ARJ",00h)
  ...  ..  Comment, max 2048 bytes ("ASCII Comment",00h)
  ...  4   CRC32 on Header (from 004h up to including Comment)
  ...  2   Size of 1st extended header (usually 0=none)
  ...  (0) Extended Header(s?) (usually none such)

ARJ local file header, with [00Ah]=0,1,3,4
This occurs at the begin of each file in the archive.
  000h 2   ARJ ID (EA60h, aka 60000 decimal)
  002h 2   Header size (from 004h up to including Filename+Comment) (max 2600)
  004h 1   Header size (from 004h up to including Extra Data) (1Eh+extra)
  005h 1   Archiver version number
  006h 1   Minimum archiver version to extract (usually 01h)
  007h 1   Host OS
  008h 1   ARJ Flags (bit0,2-5)
  009h 1   Method
  00Ah 1   File Type (0=Binary, 1=Text, 3=Directory Name, 4=Volume Name)
  00Bh 1   Reserved/Garbage (LSB of Archive update Date/Time?)
  00Ch 4   Date/Time modified
  010h 4   Filesize, compressed (max 7FFFFFFFh)
  014h 4   Filesize, uncompressed
  018h 4   CRC32 on uncompressed file data
  01Ch 2   Zero  (or Filespec position in filename) (what is that??)
  01Eh 2   File access mode (aka MSDOS file attribute) (20h=Normal)
  020h 1   Zero  (or >2.50?: first chapter of file's lifespan)
  021h 1   Zero  (or >2.50?: last chapter of file's lifespan)
  022h (4) Extra data: Extended file position (maybe for split?)  ;\extra,
  026h (4) Extra data: Date/Time accessed                  ;\ARJ  ; 0,4 or 10h
  03Ah (4) Extra data: Date/Time created                   ; 2.62 ; bytes
  03Eh (4) Extra data: Original file size even for volumes ;/     ;/
  ...  ..  Filename, max 500 bytes ("PATH/FILENAME.EXT",00h)
  ...  ..  Comment, max 2048 bytes ("ASCII Comment",00h)
  ...  4   CRC32 on Header (from 004h up to including Comment)
  ...  2   Size of 1st extended header (usually 0=none)
  ...  (0) Extended Header(s?) (usually none such)
  ...  ..  Compressed file data
Entry 3Eh might be meant to contain Original Size of TEXT files (with CR,LFs), however, the entry is just set to 00000000h in ARJ 2.75a. Or maybe it's meant to mean size of whole file (in split-volumes)?

ARJ backup "chapter" header (ARJ >2.50?) (exists in 2.75a), with [00Ah]=5
This is rarely used and supported only in newer ARJ versions. The format is same as for local file header (but with file-related entries being nonsense in TECHNOTE; in practice, those nonsense values seem to be zero).
  000h 2   ARJ ID (EA60h, aka 60000 decimal)
  002h 2   Header size (from 004h up to including Filename+Comment) (max 2600)
  004h 1   Header size (from 004h up to including Extra Data) (1Eh+extra)
  005h 1   Archiver version number (eg. 0Ah=2.75a)
  006h 1   Minimum archiver version to extract (usually 01h)
  007h 1   Host OS
  008h 1   ARJ Flags (usually 00h)
  009h 1   Method (usually 01h, although chapters have no data)  what file???
  00Ah 1   File Type (must be 5=ARJ Chapter)
  00Bh 1   Reserved/Garbage (LSB of Chapter Date/Time, same as [00Ch])
  00Ch 4   Date/Time stamp created
  010h 4   Zero  (or reportedly, ?)                              what question?
  014h 4   Zero  (or reportedly, ?)                              what question?
  018h 4   Zero  (or reportedly, original file's CRC32)          what file???
  01Ch 2   Zero  (or reportedly, entryname position in filename) what file???
  01Eh 2   Zero  (or reportedly, file access mode)               what file???
  020h 1   Chapter range start (01h=First chapter?)              what range???
  021h 1   Chapter range end   (contains same value as above)    what range???
  022h (4) Extra data: Extended file position (usually none such)what extra???
  ...  ..  Filename ("<<<001>>>",00h for First chapter)
  ...  ..  Comment  ("",00h)
  ...  4   CRC32 on Header (from 004h up to including Comment)
  ...  2   Size of 1st extended header (usually 0=none)
  ...  (0) Extended Header(s?) (usually none such)

ARJ End Marker (with [002h]=0000h)
This is stored at the end of the archive.
  000h 2   ARJ ID (EA60h, aka 60000 decimal)
  002h 2   Header size (0=End)
Note: The End Marker may be followed by PROTECT info and Security envelope.

ARJ Method [009h]
  0 = stored (uncompressed)
  1 = compressed most (default) (Window=6800h=26Kbyte, Chars=255, Tree=31744)
  2 = compressed medium         (Window=5000h=20Kbyte, Chars=72, Tree=30720)
  3 = compressed less           (Window=2000h=8Kbyte, Chars=32, Tree=30720)
  4 = compressed least/fastest  (Window=6800h? or 8000h?)
  8 = no data, no CRC  ;\unknown if/where that is used (maybe only used
  9 = no data          ;/internally, and never stored in actual files?)

ARJ File Type [00Ah]
  0 = binary file (default)
  1 = text file (with converted line breaks, via -t1 switch)
  2 = ARJ comment header (aka ARJ main file header)
  3 = directory name
  4 = volume label (aka disc name)
  5 = ARJ chapter label (aka begin of newer backup sections)

ARJ Flags (in Main [008h])
  0  GARBLED
  1  OLD_SECURED   has old signature (with signature in Main Header?)
  1  ANSIPAGE      ANSI codepage used by ARJ32 (for what? for "FILENAME.ARJ"?)
  2  VOLUME        presence of succeeding volume
  3  ARJPROT
  4  PATHSYM       archive name translated ("\" changed to "/")
  5  BACKUP        obsolete
  6  SECURED       has new signature (in security envelope?)
  7  ALTNAME       dual-name archive
ARJ Flags (in Local [008h])
  0  GARBLED       passworded file
  1  NOT USED
  2  VOLUME        continued file to next volume (file is split)
  3  EXTFILE       file starting position field (for split files)
  4  PATHSYM       filename translated ("\" changed to "/")
  5  BACKUP_FLAG   obsolete
ARJ Flags (in Chapter [008h])
  0  GARBLED                          ;\
  1  RESERVED                         ;
  2  VOLUME                           ; what does that mean in Chapters???
  3  EXTFILE                          ;
  4  PATHSYM                          ;/
  5  BACKUP        obsolete < 2.50a   ;-how can obsolete exist in Chapters???
  6  RESERVED

Host OS [007h]
  0=MSDOS, 1=PRIMOS, 2=UNIX, 3=AMIGA, 4=MACDOS (aka MAC-OS)
  5=OS/2, 6=APPLE GS, 7=ATARI ST, 8=NEXT
  9=VAX VMS, 10=WIN95, 11=WIN32 (aka WinNT or so?)

ARJ Method 1-3 (LHA/LZH compression)
These methods are same as LHA's "-lh6-" compression method (albeit the three ARJ methods are allocating slighly less memory for the sliding window).

ARJ Method 4 (custom fastest compression)
 @@decompress_lop:
  if dst>=dst_end then goto @@decompress_done
  width=count_ones(max=7), len = get_bits(width) + (1 shl width)+1
  if len=2 then
    [dst]=get_bits(8), dst=dst+1
  else ;len>=3
    width=count_ones(max=4)+9, disp = get_bits(width) + (1 shl width)-1FFh
    for i=1 to len, [dst]=[dst-disp], dst=dst+1, next i
  goto @@decompress_lop
 @@decompress_done:
  ret
 ;---
 count_ones(max):
  num=0
 @@lop:
  if get_bits(1)=1 then
    num=num+1, if num<max then goto @@lop
  return num
get_bits(N) is same as in method 1-3 (fetching N bits, MSB first, starting with bit7 of first byte).

ARJ Glossary & Oddities
BACKUPs seem to keep old files (instead overwrting them by newer files)
CHAPTERs seems to be a new backup type (instead of [008h].Bit5=Backup flag).
COMMENTS can be text... with ANSI.SYS style ANSI escape codes?
DATE/TIME stamps seem to be MSDOS format (16bit date plus 16bit time)
EXTENDED headers seem to be unused, somewhat inspired on LHA format but with CRC32 instead CRC16 (unknown if the "1st extended header" can be followed by 2nd, 3rd, and further extended headers in LHA fashion) (bug: older ARJ versions are reportedly treating the extended CRC32 as 16bit value).
GARBLED seems to refer to encrypted password protected archives.
PROTECTED seems to mean Error Correction added in newer ARJ archives.
SECURED seems to mean archive with signature from registered manufacturers.
SPLIT aka VOLUMEs means large ARJ's stored in fragments on multiple disks.
TEXT (aka [00Ah]=1 aka -t1 switch aka "C Text" aka "7-bit text") converts linebreaks from CR,LF to LF to save memory (the uncompressed size and uncompressed CRC32 entries refer to that converted LF format, not to the original CR,LF format; the official name "7-bit text" is nonsense: All characters are stored as 8bit values, not 7bit values).
TIMEBOMB causes newer ARJ versions to refuse to work (and request the user to check for non-existing newer updates) (eg. ARJ 2.86 is no longer working, ARJ 2.75a does still work without timebomb).

See also
The various ARJ versions include .TXT or .DOC files (notably, ARJ.TXT is user manual, TECHNOTE.TXT contains hints on the ARJ file format). There's also an open source version.


CDROM File Compression ARC

ARC Archives
ARC is an old DOS and CP/M compression tool from 1985-1990. ARC files contain chunks in following format:
  000h 1     Fixed ID (1Ah)
  001h 1     Compression Method (00h..1Fh)
  002h 13    Filename ("FILENAME.EXT",00h) (garbage-padded if shorter)
  00Fh 4     Filesize, compressed
  013h 4     File Timestamp in MSDOS format
  017h 2     CRC16 with initial value 0000h on uncompressed/decrypted file
  019h (4)   Filesize, uncompressed  ;<-- not present for Method=1
  ...  ..    Compressed file data (size as stored in [00Fh])
The chunksize depends on the Method:
  Method 00h and 1Fh --> Chunksize=02h       (archive/subdir end markers)
  Method 01h         --> Chunksize=19h+[0Fh] (old uncompressed ARC archives)
  Others Methods     --> Chunksize=1Dh+[0Fh] (normal case)
Compression Methods (aka "header versions"):
  00h     End-of-archive marker (1Ah,00h)
  01h     ARC v?     Uncompressed (with short 19h-byte header)
  02h     ARC v?     Uncompressed (with normal 1Dh-byte header)
  03h     ARC v?     Packed    (RLE90)                   Used for small files
  04h     ARC v?     Squeezed  (RLE90+Huffman)           Based on CP/M Squeeze
  05h     ARC v4.00  Crunched  (OldRandomizedLZW)        Derived from LZWCOM
  06h     ARC v4.10  Crunched  (RLE90+OldRandomizedLZW)  Alike CP/M Crunch v1.x
  07h     ARC vBeta? Crunched  (RLE90+NewRandomizedLZW)  Leaked beta version?
  08h     ARC v5.00  Crunched  (RLE90+ClearGap12bitLZW)  Most common ARC method
  09h     Inofficial Squashed  (ClearGap13bitLZW)        Used by PKARC/PKPAK
  0Ah     ARC v7.xx  Trimmed   (RLE90+LZHUF)             Based on LHArc lh1
  0Ah     Inofficial Crushed   (RLE90+LZW/LZMW?)         PAK
  0Bh     Inofficial Distilled (LZ77+Huffman)            PAK v2.0
  14h-1Dh ARC v6.0 Used/reserved for Information items:
  14h     Archive info
  15h     Extended File info (maybe a prefix(?) for actual file entries?)
  16h     OS-specific info
  1Eh-27h ARC v6.0 Used/reserved for Control items:
  1Eh     ARC v6.00 Subdir (nested ARC-like format, created by the "z" option)
  1Fh     ARC v6.00 End-of-subdir marker (1Ah,1Fh)
  48h     Not used in ARC  ;\Hyper archives start with 1Ah,48h or 1Ah,53h
  53h     Not used in ARC  ;/(an unrelated format that also starts with 1Ah)
  80h-xxh Not used in ARC  ;-Spark archives (ARC-like, with extended headers)
Information items use standard 1Dh-byte headers (with [002h]="",00h, [00Fh]=SizeOfAllItem(s), [019h]=Junk. The data part at offset 01Dh can contain one or more item(s) in following format:
  000h 2     Item size (LEN)
  002h 1     Item Subtype
  003h ..    Item Data (LEN-3 bytes)
Information item types as used by ARC 6.0:
  Method=14h, Subtype=0  Archive description          (eg. "Comment blah",00h)
  Method=14h, Subtype=1  Archive creator program name (eg. "ARC 7.12 ...",00h)
  Method=14h, Subtype=2  Archive modifier program name
  Method=15h, Subtype=0  File description             (eg. "Comment blah",00h)
  Method=15h, Subtype=1  File long filename (if not MS-DOS "8.3" filename)
  Method=15h, Subtype=2  File extended date-time info (reserved)
  Method=15h, Subtype=3  File Icon                    (reserved)
  Method=15h, Subtype=4  File attributes (see below)  (eg. "RWHSN",00h)
  Method=16h, Subtype=.. Operating system info        (reserved)
File attributes can contain following uppercase chars:
  R=ReadAccess, W=WriteAccess, H=HiddenFile, 1=SystemFile, N=NetworkShareable

Sub-directories
Sub-directories are implemented as nested ARC files - about same as when storing the sub-directory files in SUBDIR.ARC, and including that SUBDIR.ARC file in the main archive with Method 02h. Except that:
It's using Method 1Eh (instead Method 02h), with filename SUBDIR (instead SUBDIR.ARC), and with [019h]=Nonsense (instead uncompressed size), and the nested file ends with Method 1Fh (instead Method 00h).

RLE90 (run-length compression with value 90h used as escape code)
ARC does use raw RLE90 for small files (eg. 4-byte "aaaa"). ARC does also use RLE90 combined with other methods (perhaps because ARC wasn't very fast, compressing 100Kbytes could reportedly take several minutes; and without RLE90 pre-compression it might have been yet slower).
  90h,00h       Output 90h, but DON'T change prevbyte    ;<-- ARC
  90h,00h       Output 90h, and DO set prevbyte=90h      ;<-- BinHex
  90h,00h       Output 90h, and UNKNOWN what to do       ;<-- StuffIt
  90h,01h..03h  Output prevbyte 00h..02h times (this is not useful)
  90h,04h..FFh  Output prevbyte 03h..FEh times (this does save memory)
  xxh           Output xxh, and memorize prevbyte=xxh
 arc_decompress_rle90:
  src_end = src+src_size
  prevbyte = <initially undefined in ARC source code>
 @@decompress_lop:
  if src>=src_end then goto @@decompress_done
  x=[src], src=src+1
  if x<>90h then
    [dst]=x, dst=dst+1, prevbyte=x    ;output x, and memorize prevbyte=x
  else  ;x=90h
    x=[src], src=src+1
    if x=00h then
      [dst]=90h, dst=dst+1            ;output 90h, but DO NOT change prevbyte
      if BinHex then prevbyte=90h     ;for BinHex, DO change prevbyte
    else
      for i=1 to x-1, [dst]=prevbyte, dst=dst+1, next i
  goto @@decompress_lop
RLE90 is used by ARC (and Spark and ArcFS), StuffIt, and BinHex (some of these may handle "prevbyte" differently; the handling in ARC is somewhat stupid as it cannot compress repeating 90h-bytes).

Squeeze
Used for ARC Method 04h, CP/M Squeeze, and Amiga LHW Method 0Ah.
  000h 2    Number of Tree entries (0..100h) (when 0, assume tree=FEFFh,FEFFh)
  002h N*4  Tree entries (16bit node0, 16bit node1)
  ...  ..   Huffman bitstream (starting in bit0 of first byte)
  ...  ..   Maybe supposedly padding to byte boundary?
 The 16bit nodes are:
  0000h..00FFh  Next Tree index
  0100h..FEFEh  Invalid
  FEFFh         End of compressed data
  FF00h..FFFFh  Data values FFh..00h (these are somewhat inverted/reversed)
 arc_decumpress_squeeze:
  if [src]=0000h then tree=empty_tree, else tree=src+2  ;-start tree
  InitBitstreamLsbFirst(src+2+[src]*4)                  ;-start bitstream
 @@decompress_lop:
  index=0000h                                           ;\
  while index<FEFFh                                     ; huffman decode
    index=[tree+index*4+GetBits(1)*2]                   ;/
  if index>FEFFh then                                   ;-check end code
    [dst]=(index XOR FFh) AND FFh), dst=dst+1           ;-store data
    goto @@decompress_lop
  return
 empty_tree dw FEFFh,FEFFh   ;upen empty tree, ARC defines two 1bit END codes
http://fileformats.archiveteam.org/wiki/Squeeze

RandomizedLZW
Below can decompress ARC (method=5,6,7) and also Crunch .xZx v1 (method=1).
 arc_decompress_randomized_lzw:
  num_free=1000h, stack=empty, oldcode=-1
  for i=0 to FFFh, lzw_parent[i]=EEEEh    ;mark all codes as unused
  if method=1 then create_code(0000h,00h) ;create end code (cpm crunch v1)
  for i=0 to FFh, create_code(FFFFh,i)    ;codes for 00h..FFh with parent=none
 @@decompress_lop:
  if method>1 and and src>=src_end then goto @@decompress_done
  code=GetBitsMsbFirst(12), i=code
  if method=1 and code=0 then goto @@decompress_done  ;end code (cpm crunch v1)
  if lzw_parent[i]=EEEEh then i=oldcode, push(oldbyte)  ;-for KwKwK strings
  while lzw_parent[i]<>FFFFh, push(lzw_data[i]), i=lzw_parent[i]
  oldbyte=lzw_data[i], [dst]=oldbyte, dst=dst+1
  if oldcode<>-1 then create_code(oldcode,oldbyte)
  oldcode=code
  while stack<>empty, [dst]=pop(), dst=dst+1
  goto @@decompress_lop
 @@decompress_done:
  ret
 ;---
 create_code(parent,data):
  if num_free=0 then goto @@no_further_codes, else num_free=num_free-1  ;-full
  i=(parent+data) AND 0000FFFFh                                         ;\
  if method=7 then i=(i*3AE1h) AND FFFh         ;new "fast" randomizer  ;
  else i=i OR 800h, i=((i*i)/40h) AND FFFh      ;old "slow" randomizer  ;
  if lzw_parent[i]=EEEEh then goto @@found_free                         ; alloc
  while lzw_sibling[i]>0000h, do i=lzw_sibling[i]    ;find chain end    ; code
  e=i, i=(i+65h) AND FFFh     ;memorize chain end & do some random skip ;
  while lzw_parent[i]<>EEEEh, do i=(i+1) AND FFFh    ;find a free code  ;
  lzw_sibling[e]=i    ;weirdly, i=0 will make it behave as sibling=none ;
 @@found_free:                                                          ;/
  lzw_data[i]=data, lzw_parent[i]=parent, lzw_sibling[i]=0000h          ;-apply
 @@no_further_codes:
  ret
Codes are always 12bit (unlike normal LZW that often starts with 9bit codes).
There won't be any new codes created if the table is full, the existing codes can be kept used if they do match the remaining data (unfortunatly this LZW variant has no Clear code for resetting the table when they don't match).
Instead of just using the first free entry, code allocation is using some weird pseudo-random-sibling logic (which is totally useless and will slowdown decompression, but compressed files do contain such randomized codes, so it must be reproduced here).

ClearGapLZW
This is more straight non-randomized LZW with Clear codes (and weird gaps after Clear codes). The compression (and gaps) are same as for nCompress (apart from different headers):
CDROM File Compression nCompress.Z
  ARC Method 8 with 1-byte header (0Ch) --> nCompress 3-byte header 1Fh,9Dh,8Ch
  ARC Method 9 without header           --> nCompress 3-byte header 1Fh,9Dh,8Dh
Method 8 does have 0Ch as first byte (indicating max 12bit codesize, this must be always 0Ch, the ARC decoder supports only that value). Method 9 uses max 13bit codesize (but doesn't have any leading codesize byte).

LZHUF
This is based on LHArc lh1. Like lh1, it does have 13Ah data/len codes, and 1000h distance codes. There are two differences:
  Differences          LHArc method lh1        ARC method 0Ah
  Data/len codes:      100h..139h=Len(3..3Ch)  100h=End, 101h..139h=Len(3..3Bh)
  Initial dictionary:  20h-filled              Uninitialized

Notes
ARC file/directory names are alphabetically sorted, that does apply even when adding files to an existing archive (they are inserted at alphabetically sorted locations rather than being appended at end of archive).
ARC files can be encrypted/garbled with password (via "g" option), the chunk header doesn't contain any flags for indicating encrypted files (except, the CRC16 will be wrong when not supplying the correct password).
ARC end-marker (1Ah,00h) may be followed by additional padding bytes, or by additional information from third-party tools:
  PKARC/PKPAK adds comments (starting with "PK",AAh,55h)
  PAK adds extended records (described in PAK.DOC file in the v2.51)

See also
http://fileformats.archiveteam.org/wiki/ARC_(compression_format)
https://www.fileformat.info/format/arc/corion.htm
http://cd.textfiles.com/pcmedic/utils/compress/arc520s.zip - source code
https://github.com/ani6al/arc - source code, upgraded with method 9 and 4
https://entropymine.wordpress.com/2021/05/11/arcs-trimmed-compression-scheme/
http://www.textfiles.com/programming/FORMATS/arc-lbr.pro - benchmarks


CDROM File Compression RAR

RAR is a compression format for enthusiastic users (who love to download the latest RAR version before being able to decompress those RAR files).

RAR v1.3 (March 1994, used only in RAR 1.402)
This format was only used by RAR 1.402, and discontinued after three months when RAR 1.5 got released.
 File Header:
  000h 4     ID "RE~^" (aka 52h,45h,7Eh,5Eh)
  004h 2     Header Size  (usually 0007h, or bigger when Comment/Ext1 exist)
  006h 1     Archive Flags (80h or xxh)
  ...  (2)   Archive Comment Size   ;\Only present when ArchiveFlags.bit1=1
  ...  (..)  Archive Comment Data   ;/
  ...  (2)   Ext1 Size              ;\Only present when ArchiveFlags.bit5=1
  ...  (..)  Ext1 Data              ;/
  ...  ..    Unknown (TECHNOTE hints sth can be here, when bigger HeaderSize?)
 Archive Flags:
  0   Volume   (maybe related to split-volume on several floppies?)
  1   Comment
  2   Unknown? (non-english description is in 1.402's TECHNOTE.DOC)
  3   Unknown? (non-english description is in 1.402's TECHNOTE.DOC)
  4   Unknown? (non-english description is in 1.402's TECHNOTE.DOC)
  5   EXT1
  6   Unspecified (maybe unused)
  7   Unspecified (maybe unused, but... it's usually 1)
 File Data blocks:
  000h 4     Filesize, compressed
  004h 4     Filesize, uncompressed
  008h 2     Checksum on uncompressed? file (sum=LeftRotate16bit(sum+byte[i])
  00Ah 2     Header Size (usually 0015h+FilenameLength)
  00Ch 4     File Modification Timestamp in MSDOS format
  010h 1     File Attribute in MSDOS format (20h=Normal)
  011h 1     Flags
  012h 1     Version (0=0.99, 1=1.00, 2=1.30) (always 2 in public version)
  013h 1     Filename Length
  014h 1     Method (00h=m0a=Stored, 03h=m3a=Default) (1..5 = fastest..best)
  ...  (2)   File Comment Length        ;\Only present if FileFlags.bit3=1
  ...  (..)  File Comment Data          ;/
  ...  ..    Filename ("PATH\FILENAME.EXT", without any end marker)
  ...  ..    Unknown (TECHNOTE hints sth can be here, when bigger HeaderSize?)
  ...  ..    Compressed file data
 File Flags:
  0   Unknown? (non-english description is in 1.402's TECHNOTE.DOC)
  1   Unknown? (non-english description is in 1.402's TECHNOTE.DOC)
  2   Unknown? (non-english description is in 1.402's TECHNOTE.DOC)
  3   Comment  (non-english description is in 1.402's TECHNOTE.DOC)
  4-7 Unspecified (maybe unused)

RAR 1.5 (June 1994) and newer
Overall Chunk Format:
  000h 2    Chunk Header CRC; Lower 16bit of CRC32 on [002h..HdrSize-1 or less]
  002h 1    Chunk Type (72h..7Ah)
  003h 2    Chunk Flags
  005h 2    Chunk Header Size
  007h (4)  Data block size    ;<-- Only present if Flags.bit15=1
  ...  ..   Header values (depending on Chunk Type and Chunk Header Size)
  ...  ..   Data block         ;<-- Only present if Flags.bit15=1
 Chunk Types:
  72h="r"=Marker block (with "r" being 3rd byte in ID "Rar!",1Ah)
  73h="s"=Archive header
  74h="t"=File header
  75h="u"=Old style Comment header (nested within Type 73h/74h)
  76h="v"=Old style Authenticity information
  77h="w"=Old style Subblock
  78h="x"=Old style Recovery record
  79h="y"=Old style Authenticity information
  7AH="z"=Subblock
 Chunk Flags:
  0-13   Flags, meaning depends on Chunk Type
  14     If set, older RAR versions (before 1.52 or so?) will ignore the
               block and remove it when the archive is updated. If clear, the
               block is copied to the new archive file when the archive is
               updated;
               or does "older" mean older than the "archiver version"?
  15     Data Block present (0=No, 1=Yes, with size at [007h])

Type 72h, Marker Block (MARK_HEAD)
This 7-byte ID occurs at the begin of RAR files (or after the executable in case of self-extracting files).
  000h 7       ID ("Rar!",1Ah,07h,00h) (or "Rar!",1Ah,07h,01h for RAR 5.0)
 The above ID can be somewhat parsed as normal chunk header, as so:
  000h 2       Faux CRC          (6152h, no actual valid CRC)
  002h 1       Chunk Type        (72h)
  003h 2       Faux Flags        (1A21h, no actual meaning)
  005h 2       Chunk Header size (0007h)

Type 73h, Archive Header (MAIN_HEAD)
  000h 2       CRC32 AND FFFFh of fields HEAD_TYPE to RESERVED2
  002h 1       Chunk Type: 73h
  003h 2       Archive HeaderFlags
  005h 2       Header size (usually 000Dh) (plus Comment Block, if any)
  007h 2       RESERVED1 (0000h)
  009h 4       RESERVED2 (0000011Dh)
  ...  (..)    Comment block ;<-- only present if Flags.bit1=1
  ...  (..)    Reserved for additional blocks
 Archive Header Chunk Flags:
  0     Volume attribute (archive volume) (split-volume? volume-label? what?)
  1     Archive comment present              ;<-- used only before RAR 3.x
          RAR 3.x uses "the separate comment block" and does not set this flag.
  2     Archive lock attribute
  3     Solid attribute (solid archive)
  4     New volume naming scheme (0=Old="name.???", 1=New="name.partN.rar")
  5     Authenticity information present     ;<-- used only before RAR 3.x
  6     Recovery record present
  7     Chunk headers are encrypted
  8     First volume                         ;<-- set only by RAR 3.0 and later
  9-13  Reserved for internal use
  14-15 See overall Chunk Format

Type 74h, File Header (File in Archive)
  000h 2     CRC32 AND FFFFh on HEAD_TYPE to FILEATTR and file name
  002h 1     Header Type: 74h
  003h 2     Bit Flags
  005h 2     File header full size including file name and comments
  007h 4     Compressed file size (can be bigger than uncompressed)
  00Bh 4     Uncompressed file size
  00Fh 1     Operating system used for archiving
  010h 4     CRC32 on uncompressed file
  014h 4     File Modification Timestamp in MSDOS format
  018h 1     RAR version needed to extract file (Major*10+Minor) (min=0Fh=1.5)
  019h 1     Compression Method (usually 35h in RAR 1.52)
  01Ah 2     Filename size
  01Ch 4     File Attribute in MSDOS format (20h=Normal, Upper24bit=whatever=0)
  ...  (..)  Comment block                      ;-Only present if Flags.bit3=1
  ...  (4)   MSBs of compressed file size       ;\Only present if Flags.Bit8=1
  ...  (4)   MSBs of uncompressed file size     ;/
  ...  ..    Filename ("PATH\FILENAME.EXT")
  ...  (..)  Filename extra fields (see Flags.bit9+bit11)
  ...  (8)   Encryption SALT                    ;-Only present if Flags.Bit10=1
  ...  (..)  Extended Time, variable size       ;-Only present if Flags.Bit12=1
  ...  (..)  * other new fields may appear here.
  ...  ..    Compressed file data
 File Chunk Flags:
  0     File continued from previous volume
  1     File continued in next volume
  2     File encrypted with password
  3     File comment present              ;<-- used only before RAR 3.x
          RAR 3.x uses the separate comment block and does not set this flag.
  4     Information from previous files is used (solid flag) ;RAR 2.0 and later
  5-7   Dictionary bits (for RAR 2.0 and later)
  8     64bit Filesizes (for files "larger than 2Gb")
  9     Unicode Filename, this can be in Dual or Single name form:
          Dual name:   "NormalName",00h,"UnicodeName"   ;<-- in UTF-8 or what?
          Single name: "UnicodeName"                    ;<-- in UTF-8
  10    Header contains 8-byte Encryption SALT entry
  11    Backup File (with version number ";n" appended to filename)
  12    Extended Time field present
  13-14 -
  15    Data Block present (always 1=With 32bit size at [007h], or 64bit size)
 Dictionary Bits (bit5-7)
  00h=Dictionary Size 64 Kbyte
  01h=Dictionary Size 128 Kbyte   ;\
  02h=Dictionary Size 256 Kbyte   ; RAR 2.0 and up
  03h=Dictionary Size 512 Kbyte   ;
  04h=Dictionary Size 1024 Kbyte  ;/
  05h=Dictionary Size 2048 Kbyte  ;\RAR ?? and up
  06h=Dictionary Size 4096 Kbyte  ;/
  07h=File is a directory         ;-RAR 2.0 and up
 Operating System Indicators:
  00h=MS DOS
  01h=OS/2
  02h=Windows
  03h=Unix
  04h=Mac OS
  05h=BeOS
  ??h=Android?
 Compression Method:
  35h=Default in RAR 1.52 (used even when file is too small to be compressed)
  xxh=Other methods (unknown values)
  30h=Stored (RAR 2.00 supports uncompressed small files and -m0 switch)
  N/A=Stored (RAR 1.52 simply ignores "-m0" switch, and enforces "-m1" or so)

Type 75h, Comment block:
  000h 2    Header CRC of fields from HEAD_TYPE to COMM_CRC
  002h 1    Chunk Type: 75h
  003h 2    Chunk Flags (unknown if/which flags are used)
  005h 2    Chunk Header size (0Eh+Compressed comment size)
  007h 2    Uncompressed comment size
  009h 1    RAR version needed to extract comment
  00Ah 1    Packing Method
  00Ch 2    Comment CRC
  00Eh ..   Compressed comment data

Sub-formats
The RAR format is comprised of many sub-formats that have changed over the years. The different formats and their descriptions are as follows:
  * 1.3 (Does not have the RAR! signature)
        o There is difficulty finding information regarding this sub-format.
  * 1.5
        o Utilizes a proprietary compression method that is not public.
        o Considered the root model of subsequent formats.
        o A detailed list of information can be found here.
  * 2.0
        o Utilizes a proprietary compression method that is not public.
        o Based off of version 1.5 of the RAR file format.
  * 3.0
        o Utilizes the PPMII and Lempel-Ziv (LZSS)] algorithms.
        o Encryption now uses cipher block chaining (AES?-CBC) instead of AES
        o Based off of version 1.5 of the RAR file format.

See also
Older RAR versions did include a TECHNOTE file describing the file format of those versions (TECHNOTE for 1.402 exist in unknown-language only, perhaps russian, and TECHNOTE was discontinued somewhere between 2.5 and 2.9).
There is official decompression source code for newer RAR versions.


CDROM File Compression ZOO

ZOO Archives
 File Header:
  000h 20   Text Message (usually "ZOO #.## Archive.",1Ah,00h,00h)
  014h 4    ID (FDC4A7DCh) (use this ID for detection, and ignore above text)
  018h 4    Offset to first Chunk          (22h or 2Ah+commentsize?)
  01Ch 4    Offset to first Chunk, negated (-22h or -2Ah-commentsize?)
  020h 1+1  Version needed to extract (Major,Minor) (usually 1,01 or 2,00)
  022h (1)  Archive Header Type (01h)                           ;\
  023h (4)  Offset to Archive Comment (0=None)                  ; v2.00 and
  027h (2)  Length of Archive Comment (0=None)                  ; up only
  029h (1)  Version Data (01h or 03h)          "HVDATA"         ;/
 File Chunks:
  000h 4    ID (FDC4A7DCh)
  004h 1    Type of directory entry (1=Old, 2=New, with extra entries)
  005h 1    Compression method (0=Stored, 1=LZW/default, 2=LZH)
  006h 4    Offset to next Chunk
  00Ah 4    Offset to File Data
  00Eh 4    File Modification Date/time in MSDOS format
  012h 2    CRC16 on uncompressed file (with initial value 0000h)
  014h 4    Filesize, uncompressed
  018h 4    Filesize, compressed
  01Ch 1+1  Version needed to extract (Major,Minor) (usually 1,00 or 2,01)
  01Eh 1    Deleted flag (0=Normal, 1=Deleted)
  01Fh 1    File structure (unknown purpose)
  020h 4    Offset of comment field (0=None)
  024h 2    Length of comment field (0=None)
  026h 13   Short Filename ("FILENAME.EXT",00h, garbage padded if shorter)
  033h (1)  Unknown (4Fh) (or 00h when with comment?)              ;-Type=1
  033h (2)  Length of 038h and up (0Ah+longname+dirname)           ;\
  035h (1)  Timezone (signed) (7Fh=Unknown)                        ;
  036h (2)  CRC16 on Header (000h..037h+[033h], with [036h]=0000h) ;
  038h (1)  Length of Long Filename (0=None, use Short Filename)   ;
  039h (1)  Length of Directory name (0=None)                      ; Type=2
  03Ah (..) Long Filename  ("longfilename.ext",00h) (if any)       ;
  ...  (..) Directory name ("/path",00h)            (if any)       ;
  ...  (2)  System ID (0=Unix, 1=DOS, 2=Portable) (but for DOS=0)  ;
  ...  (3)  File Attributes (24bit)               (but for DOS=0)  ;
  ...  (1)  Backup Flags (bit7=On, bit6=Last, bit0-3=Generation)   ;
  ...  (2)  Backup File Version Number (for backup copies)         ;/
  ...  5    File Leader aka Fudge Factor ("@)#(",00h)              ;\
  ...  ..   File Data                                              ; All types
  ...  ..   File Comment (if any) (ASCII, "Text string",0Ah)       ;/
 Last Chunk:
  000h 4     ID (FDC4A7DCh)
  004h (30h) Zerofilled                                            ;-Type 1
  004h (1)   Fixed (02h)                                           ;\
  005h (31h) Zerofilled                                            ; Tyoe 2
  036h (2)   CRC16 on Header (with [036h]=0000h) (always 83FCh)    ;/
  ...  (..)  Comments may be stored here (if added after archive creation)
  ...  (..)  Padding, if any (1Ah-filled in some files)

Notes:
Method LZW is quite straight, the bitstream is fetched LSB first, codesize is initially 9bit, max 13bit, with two special codes (100h=Clear, 101h=Stop), there aren't any gaps after clear codes, the unusual part is that the bitstream does start with a clear code.
Method LZH is slower, requires Zoo 2.10, and is used only when specifiying "h" option in commandline. LZH has 8Kbyte window, same as LHA's "lh5", with an extra end marker (blocksize=0000h=end).
Comments may be stored anywhere in the middle or at the end of the archive (even after the zerofilled last chunk) (depending on whether the comment or further files where last added to the archive).
Zoo is from 1986-1991, long filenames were supported only for OSes that did support them at that time (ie. not for DOS/Windows).
When adding new files, Zoo defaults to maintain backups of old files in the archive (older files are marked as "deleted" via [01Eh]=1, but are kept in the archive; until the user issues command "P" for repacking/removing deleted files) (Zoo 2.xx can additionally use a "generation" limit of 0..15, which means to keep 0..15 older copies).
All offsets are originated from begin of archive.

Zoo Tiny format (single-file) (commandline "z" option)
This format is called Tiny in Zoo source code, but isn't documented in the Zoo manual or Zoo help screen. Tiny can contain only a single file (alike gzip). The purpose appears to be using Tiny as temporary files when moving files from one archive to another (without needing to decompress & recompress the file), for example:
  zoo xz source.too testfile.txt     ;extract to tiny/temp file testfile.tzt
  zoo az dest.zoo   testfile.txt     ;import from tiny/temp file testfile.tzt
The tiny/temp file extensions have the middle character changed to "z" (eg. "tzt" instead of "txt").
Going by zoo source code, the format should look as so:
  000h 2   Zoo Tiny ID (07FEh)
  002h 1   Type (01h)
  003h 1   Compression Method
  004h 4   Date/time in MSDOS format
  008h 2   CRC16 on uncompressed file, or what (?)
  00Ah 4   Filesize, uncompressed
  00Eh 4   Filesize, compressed
  012h 1   Major_ver
  013h 1   Minor_ver
  014h 2   Comment size (0=None)
  016h 13  Short Filename
  023h ..  File data     ... plus comment, if any?
But, files from Zoo DOS version are reportedly starting with 07h,01h (instead FEh,07h,01h).
And, using Zoo DOS version with "z" option in Win98 does merely display "Zoo: FATAL: I/O error or disk full."

Zoo Filter format (for modem streaming) (commandline "f" command)
This command is documented in the Zoo manual, although it isn't actually supported in Zoo DOS version. The intended purpose is to use Zoo as a filter to speedup modem transfers.
Going by some information snippets, the transfer format appears to be somewhat as so:
  000h 2   Zoo Filter ID (32h,5Ah)
  ...  ..  Compressed data
  ...  2   CRC16 on uncompressed file, or what (?)
The transfer uses stdin/stdout instead of source/dest filenames (although, the OS commandline interface may allow to assign filenames via ">" and "<").
There is no compression method entry (so both sides must know whether they shall use LZW or LZH).
Unknown if there are any transfer size entries, or LZW/LZH end codes, or maybe the streaming is infinite (with CRCs inserted here ot there)?


CDROM File Compression nCompress.Z

nCompress is some kind of a Gzip predecessor. The program was originally called "compress" and later renamed to "ncompress" (and sometimes called "(n)compress"). Compressed files have uppercase ".Z" attached to their original name.

nCompress.Z
The header is rather small and lacks info on decompressed size (ie. the one must process the whole bitstream to determine the size, and accordingly, the fileformat doesn't allow padding to be appended at end of file). To detect .Z files, examine the first three bytes, and best also check that the leading 9bit codes don't exceed num_codes (with num_codes increasing from 101h and up for each new code).
  000h 2    ID (1Fh,9Dh)
  002h 1    Mode (MaxBits(9..16) + bit7=WithClearCode) (usually 90h)
  003h ..   ClearGapLZW compressed data
Compression is relative straight LZW, resembling 8bit GIFs, with 9bit initial codesize, with preset codes 000h..0FFh=Data and (optional) 100h=Clear code (there is no End code). Codes are allocated from 101h and up (100h and up if without Clear code).
  BUG: MaxBits=9 does accidentally act as MaxBits=10 (although without
  actually using more than 200h codes, the 10bit codes always have MSB=0).
The bitstream is fetched LSB first (starting in bit0 of first byte). The decoder is prefetching groups of eight codes (N-bytes with eight N-bit codes), the odd part is that Clear codes are discarding those prefetched bytes (so Clear codes will be followed by Gaps with unused bytes).
A similar gap occurs when not using clear codes (when Mode.bit7=0): In that case the gap does accur when switching from 9bit to 10bit codesize (other codesize changes do always occur on code-group boundaries, so there won't be any gaps there).
Note: ClearGapLZW is also used by ARC Method 8 and 9.


CDROM File Compression Pack.z (Huffman) 

 Old:
  000h 2   ID (1Fh,1Fh)
  002h 2   Uncompressed size, bit16-31               (Little-Endian)
  004h 2   Uncompressed size, bit0-15                (Little-Endian)
  006h 2   Number of tree entries (min=2, max=400h?) (Little-Endian)
  008h ..  Tree (8bit or 24bit per entry)
  ...  ..  Compressed data (16bit Little-Endian, 1st bit = MSB of 2nd byte)
 New:
  000h 2   ID (1Fh,1Eh)
  002h 4   Uncompressed size, bit31-0                (Big-Endian)
  006h 1   Max codesize (CS)
  008h CS  Tree, number of huffcodes with codesize=(1,2,3,..)
  ...  ..  Tree, data values for each huffcode
  ...  ..  Compressed data



CDROM File Compression Freeze/Melt.F (LZHUF-based)

Freeze (compressor) and Melt (decompressor) are LZHUF-based compression tools. File extension is uppercase .F (or .lzc).

Freeze v1
  000h 2   ID (1Fh,9Eh)
  002h ..  Compressed Data (LZHUF, with EndCode, 13Bh codes)

Freeze v2
  000h 2   ID (1Fh,9Fh)
  002h 3   Custom Disp Code Sizes (LittleEndian24bit, see below)
  005h ..  Compressed Data (LZHUF, with EndCode, 1FFh codes, specials)
 Custom Disp Code Sizes:
  bit0     Number of 1bit codes (v1=0)
  bit1-2   Number of 2bit codes (v1=0)
  bit3-5   Number of 3bit codes (v1=1)
  bit6-9   Number of 4bit codes (v1=3)
  bit10-14 Number of 5bit codes (v1=8)
  bit15    Zero
  bit16-21 Number of 6bit codes (v1=12)
  bit22-23 Zero

InitFreezeCodeSizes:
  id=LittleEndian16bit[src], src=src+2
  if id=9E1Fh then    ;Freeze v1
    numdatacodes=13Bh, withendcode=1, displsbs=6
    buf[0..7]=0,0,1,3,8,12,24,16  ;<-- this will make standard LZHUF values
  elseif id=9F1Fh then  ;Freeze v2
    numdatacodes=1FFh, withendcode=1, displsbs=7
    x=LittleEndian24bit[src+02h], src=src+3
    if (x AND C08000h)<>0 then error
    buf[0]=(x SHR 0) AND 01h                      ;Number of 1bit codes (v1=0)
    buf[1]=(x SHR 1) AND 03h                      ;Number of 2bit codes (v1=0)
    buf[2]=(x SHR 3) AND 07h                      ;Number of 3bit codes (v1=1)
    buf[3]=(x SHR 6) AND 0Fh                      ;Number of 4bit codes (v1=3)
    buf[4]=(x SHR 10) AND 1Fh                     ;Number of 5bit codes (v1=8)
    buf[5]=(x SHR 16) AND 3Fh                     ;Number of 6bit codes (v1=12)
    count=62, weight=256, shift=7
    for i=0 to 5
      count=count-buf[i], weight=weight-(buf[i] SHL shift), shift=shift-1
    x=weight-count, buf[6]=x, if x<0 then error   ;Number of 7bit codes (v1=24)
    x=count*2-weight, buf[7]=x, if x<0 then error ;Number of 8bit codes (v1=16)
  else
    error
  k=0, for i=0 to 7, for j=1 to buf[i], codesizes[k]=i+1, k=k+1
  if k>64 then error
  lzh_explode_tree(disp_tree,codesizes,k)

LZHUF Variants
  Tool        Method Ext   NumCodes EndCode Len       DispLsbs DispCodes Dict
  LHA/LHarc   -lh1-  .lzh  13Ah     -       N+3-100h  6bit+1   Fixed     20h's
  Amiga LHW   Frozen .lbr  13Ah     -       N+3-100h  6bit+1   Fixed     20h's
  CP/M ARC    Trim   .arc  13Ah     100h    N+3-101h  6bit+1   Fixed     -
  CP/M CrLZH  v1     .xYx  13Bh !   100h    N+3-101h  6bit+1   Fixed     20h's
  CP/M CrLZH  v2     .xYx  13Bh !   100h    N+3-101h  5bit+1 ! Fixed     20h's
  Unix Freeze v1     .F    13Bh !   100h    N+3-101h  6bit+1   Fixed     -
  Unix Freeze v2     .F    1FFh !   100h    N+3-101h  7bit+1 ! Variable  20h's
  Amiga DMS   Deep   .dms  13Ah     -       N+3-100h  8bit+1 ! Fixed     00h's
  Amiga LhLib Lh     -     13Dh !   13Ch !  N+1-100h  6bit   ! Fixed     -
Note: Upon 8000h steps, the LhLib variant simply stops to update the datalen codes (instead of halving the code frequencies).


CDROM File Compression Octal Oddities (TAR, AR, CPIO, RPM)

Below are file formats with unix/linux-style octal numbers (unknown if they are serious about using that formats, or if they do consider them as decently amusing, or whatever).

Compression
TAR and CPIO are uncompressed archives, however, they are usually enclosed in a compressed Gzip file (or some other compression format like nCompress, Bzip2).

TAR format (1979)
  0000h ..        TAR Chunk(s)
  ...   400h      TAR End Marker (400h bytes zerofilled)
  ...   ..        Zerofilled (whatever further padding)
TAR Chunk format:
  000h 100 text   Filename ("path/filename.ext",00h)
  064h 8   octal  Mode Flags
  06Ch 8   octal  User ID
  074h 8   octal  Group ID
  07Ch 12  octal  Filesize
  088h 12  octal  File modification time (seconds since 01 Jan 1970)
  094h 8   octal  Header Checksum (sum of byte[0..1F3h], with [94h..9Bh]=20h)
  09Ch 1   text   Type (00h or "0" for normal files)
  09Dh 100 text   Whatever link name
  101h 8   text   Tar ID (6x00h or "ustar",00h,"00" or "ustar  ",00h)
  109h 32  text   User Name (owner)
  129h 32  text   Group Name
  149h 8   octal  Device major  ;\device number (when Type="4")
  151h 8   octal  Device minor  ;/
  159h 155 ?      Whatever prefix         ;-when ID="ustar",00h,"00" or 6x00h
  159h 131 ?      Whatever prefix         ;\
  1DCh 12  octal  File access time        ; when ID="ustar  ",00h
  1E8h 12  octal  File status-change time ;/
  1F4h 12  -      Zeropadding to 200h-byte boundary
  200h ..  -      File data (Filesize bytes)
  ...  ..  -      Zeropadding to 200h-byte boundary
TAR numeric values are weirdly stored as octal ASCII strings, often decorated with leading or trailing spaces. For example, 8-byte octal value 123o (53h) can look as so (with "." meaning 00h end-byte):
  "0000123."  <-- normal weirdness, with leading zeroes and end-byte ("."=00h)
  "  123 . "  <-- extra weird, leading/trailing spaces, mis-placed end-byte
  "   123  "  <-- extra weird, leading/trailing spaces, without end-byte
See also: https://www.gnu.org/software/tar/manual/html_node/Standard.html

AR Format (1971) (linker libraries)
These archives are often used as a linker library containing ELF.o files. Common archive extensions: *.a *.lib or Debian *.deb *.udeb.
The file header is plain ASCII with numbers stored as decimal/octal strings. The filenames and values are 20h-padded.
  000h 8   text    ID ("!<arch>",0Ah)     ;reportedly "!<thin>",??h is similar?
  008h ..  -       File entries
 File entries:
  000h 16  text    Filename
  010h 12  decimal File modification Timestamp (in seconds)
  01Ch 6   decimal Owner ID
  022h 6   decimal Group ID
  028h 8   octal   File Mode (type and permission)
  030h 10  decimal Filesize in bytes (SIZ)
  03Ah 2   fixed   Fixed (60h, 0Ah)
  03Ch SIZ -       Data
  ...  ..  -       Padding to 2-byte boundary (0Ah-filled)
The Timestamp, Owner/User ID and File Mode entries may be blank (they are 20h-filled in "//" files).
There are two different ways to indicate long filenames (both using a special name with "nn" being decimal characters):
  Filename="#1/nn" --> Long Filename is stored in first "nn" bytes of Data
  Filename="/nn"   --> Long Filename,0Ah is stored at offset "nn" in file "//"
The first file in the archive (named "/" or "__.SYMDEF" or similar) does usually contain a summary of linker symbols.
Some archives have the filenames terminated by "/" (then followed by the usual 20h-padding).
  Used in Amiga ADFLibPPC.lha\Bin\AmigaPPC\libadf.a
  See also: http://justsolve.archiveteam.org/wiki/AR
  See also: https://en.wikipedia.org/wiki/Ar_(Unix)

CPIO Format (1977) (and MAC .PAX files)
  0000h ..        CPIO Chunk(s) (with actual files)
  ...   57h       CPIO Chunk    (with filename "TRAILER!!!",00h)
  ...   ..        Zeropadding to 200h-byte boundary (not always present)
The chunks are simple, but they do exist in five weirdly different variants:
  Align 2, Binary, little-endian (but partial "big-endian" for 2x16bit pairs)
  Align 2, Binary, big-endian
  Align 1, Ascii, octal strings
  Align 4, Ascii, hexadecimal lowercase strings, checksum=0)
  Align 4, Ascii, hexadecimal lowercase strings, checksum=sum of bytes in file)
Binary, little-or-big-endian:
  000h 2   binary 16bit ID (71C7h)                      ;-little-or big endian
  002h 2   binary 16bit  dev                                    ;\
  004h 2   binary 16bit  ino                                    ; same
  006h 2   binary 16bit  mode                                   ; endianness
  008h 2   binary 16bit  uid                                    ; as in ID
  00Ah 2   binary 16bit  gid                                    ;
  00Ch 2   binary 16bit  nlink                                  ; (but be aware
  00Eh 2   binary 16bit  rdev                                   ; of the fixed
  010h 2   binary 16bit File modification time, upper 16bit  ;\ ; upper/lower
  012h 2   binary 16bit File modification time, lower 16bit  ;/ ; 16bit order
  014h 2   binary 16bit Filename size (including ending 00h)    ; for time and
  016h 2   binary 16bit Filesize, upper 16bit                ;\ ; filesize)
  018h 2   binary 16bit Filesize, lower 16bit                ;/ ;/
  01Ah ..  text   Filename, terminated by 00h ("path/filename",00h)
  ...  ..  binary Zeropadding to 2-byte boundary
  ...  ..  binary File data (Filesize bytes)
  ...  ..  binary Zeropadding to 2-byte boundary
Ascii/octal CPIO Chunk format:
  000h 6   octal  18bit ID "070707" (=71C7h)
  006h 6   octal  18bit dev    ;\unique file id
  00Ch 6   octal  18bit ino    ;/within archive
  012h 6   octal  18bit Mode (file attributes)
  018h 6   octal  18bit User ID of owner
  01Eh 6   octal  18bit Group ID
  024h 6   octal  18bit nlink (related to duplicated dev/ino?)
  02Ah 6   octal  18bit rdev (system-defined info on char/blk devices)
  030h 11  octal  33bit File modification time
  03Bh 6   octal  18bit Filename size (including ending 00h)
  041h 11  octal  33bit Filesize
  04Ch ..  text   Filename, terminated by 00h ("path/filename",00h)
  ...  ..  binary File data (Filesize bytes)
Ascii/hex CPIO Chunk format:
  000h 6   hex    24bit ID "070701"=Without Checksum, or "070702"=With Checksum
  006h 8   hex    32bit  ino (does that 32bit value include 16bit "dev"?)
  00Eh 8   hex    32bit  mode
  016h 8   hex    32bit  uid
  01Eh 8   hex    32bit  gid
  026h 8   hex    32bit  nlink
  02Eh 8   hex    32bit  mtime
  036h 8   hex    32bit Filesize
  03Eh 8   hex    32bit  devmajor
  046h 8   hex    32bit  devminor
  04Eh 8   hex    32bit  rdevmajor
  056h 8   hex    32bit  rdevminor
  05Eh 8   hex    32bit Filename size (including ending 00h)
  066h 8   hex    32bit Checksum, sum of all bytes in file, zero when ID=070701
  06Eh ..  text   Filename, terminated by 00h ("path/filename",00h)
  ...  ..  binary Zeropadding to 4-byte boundary
  ...  ..  binary File data (Filesize bytes)
  ...  ..  binary Zeropadding to 4-byte boundary
CPIO numeric values are weird octal ASCII strings (eg. 6-byte "000123"), but, unlike TAR, without extra oddities like spaces or end-bytes.
https://www.systutorials.com/docs/linux/man/5-cpio/

RPM Format (1997) (BIG-ENDIAN)
RPM files contain Linux installation packages. The RPM does basically contain a CPIO archive bundled with additional header/records with installation information.
  000h 60h File Header      (officially called "Lead" instead of "Header")
  060h ..  Signature Record (contains "Header Record" in "Signature format")
  ...  ..  Padding          (to 8-byte boundary)
  ...  ..  Info Record      (called "Header" and also uses "Signature format")
  ...  ..  Archive file     (usually a GZIP compressed CPIO) (called "Payload")
File Header (aka Lead) (60h bytes):
  000h 4    File ID (EDh,ABh,EEh,DBh)     (aka octal string "\355\253\356\333")
  004h 1    Major version (3)
  005h 1    Minor version (0)
  006h 2    Type (0=Binary Package, 1=Source Package)
  008h 2    Architecture ID (defined in ISO/IEC 23360)
  00Ah 66   Package name, terminated by 00h
  04Ch 2    Operating System ID (1)
  04Eh 2    Signature Type (5)
  050h 16   Reserved space (officially undefined, usually zerofilled)
Signature/Info Records (10h+N*10h+SIZ bytes):
  000h 4     Record ID (8Eh,ADh,E8h,01h)  (aka octal string "\216\255\350\001")
  004h 4     Reserved (zerofilled)        (aka octal string "\000\000\000\000")
  008h 4     Number of Item List entries  (N)
  00Ch 4     Size of Item Data            (SIZ)
  010h N*10h Item List (4x32bit each: Tag, Type, Offset, Size)
  ...  SIZ   Item Data (referenced via Offset/Size entries in above list)
Item Type values:
  00h=NULL         Not Implemented
  01h=CHAR         Unknown, maybe unsigned 8bit         (unaligned)
  02h=INT8         Unknown, maybe signed 8bit           (unaligned)
  03h=INT16        Unknown, maybe signed 16bit          (align2)
  04h=INT32        Unknown, maybe signed 323bit         (align4)
  05h=INT64        Reserved, maybe signed 643bit        (maybe align8)
  06h=STRING       Variable, NUL terminated string      (unaligned)
  07h=BIN          Unknown, reportedly 1-byte size???   (unaligned)
  08h=STRING_ARRAY Variable, Sequence of NUL terminated strings (unaligned)
  09h=I18NSTRING   Variable, Sequence of NUL terminated strings (unaligned)
Item Tag values:
  There are dozens of required & optional tag values defined.
RPM source code packages are often bundled with a .spec file (inside of the CPIO archive), that .spec file contains source code in text format for creating the RPM header/records.

File Extensions
 Basic extensions:
  .cpio (CPIO)
  .pax  (CPIO for MAC)
  .rpm  (RPM installation package for RPM package manager)
  .spec (RPM source file for creating RPM header/records)
  .tar  (TAR, tape archive)
 Double extensions (and short forms like tgz):
  .tgz  short for .tar.gz  (gzip)
  .tbz  short for .tar.bz2 (bzip2)
  .txz  short for .tar.xz  (XZ)
  .tlz  short for .tar.lz  (Lzip) or .tar.lzma (LZMA_Alone)
  .tzst short for .tar.zst (zstandard)
  .tsz  short for .tar.sz  (Sunzip)
  .taz  short for .tar.Z   (nCompress or possibly some other compressed format)
  .tz   short for .tar.Z   (nCompress or possibly some other compressed format)
  .spm  short for .src.rpm (RPM source code package)


CDROM File Compression MacBinary, BinHex, PackIt, StuffIt, Compact Pro

Below are related to MAC filesystems (where the file body consists of separate Data and Resource forks), and file type/creator values (resembling filename extensions).

MacBinary I,II,III format (v1,v2,v3)
MacBinary contains a single uncompressed file, used for transferring MAC files via network, or storing MAC files on non-MAC filesystems.
PackIt/StuffIt archives do often have leading MacBinary headers. MacBinary doesn't have any unique filename extension (.bin may be used, more often it's using the same extension as the enclosed file, eg. .sit if it contains a StuffIt archive).
Also, archives without explicit MAC support may use MacBinary format within compressed files (eg. LZH archives created with LHA MAC version).
  000h 1   Old version number, must be kept at zero for compatibility
  001h 1   Length of filename (1..63) (though v3 says 1..31)
  002h 63  Filename (only "length" bytes are significant)
  041h 4   File type    (normally expressed as four characters)
  045h 4   File creator (normally expressed as four characters)
  049h 1   Finder flags, bit8-15 (see [065h] for bit0-7)
  04Ah 1   Zero (must be 00h for compatibility)
  04Bh 2   File Vertical position within its window
  04Dh 2   File Horizontal position within its window
  04Fh 2   File Window or folder ID
  051h 1   Protected flag (bit0=Protected, whatever that is)
  052h 1   Zero (must be 00h for compatibility)
  053h 4   Filesize, Data Fork     (0=None)
  057h 4   Filesize, Resource Fork (0=None)
  05Bh 4   File Timestamp, creation
  05Fh 4   File Timestamp, last modification
  063h 27  v1:    Reserved (zerofilled)
  063h 2   v2/v3: Length of Get Info comment (if any, usually 0000h)
  065h 1   v2/v3: Finder Flags, bit0-7 (see [049h] for bit8-15)
  066h 6   v2:    Reserved (zerofilled)
  066h 4   v3:    ID ("mBIN"=MacBinary III)
  06Ah 1   v3:    Script of file name (from fdScript field of an fxInfo record)
  06Bh 1   v3:    Extended Finder flags (from fdXFlags field of fxInfo record)
  06Ch 8   v2/v3: Reserved (zerofilled)
  074h 4   v2/v3: Length of "total files" when "packed files are unpacked", uh?
  078h 2   v2/v3: Extended Header size (reserved for future, always 0000h)
  07Ah 1   v2/v3: MacBinary II uploader version           (81h=v2, 82h=v3)
  07Bh 1   v2/v3: MacBinary II downloader minimum version (81h=v2)
  07Ch 2   v2/v3: CRC16-XMODEM on [000h..07Bh]
  07Eh 2   Reserved for computer type and OS ID (0000h)
  ...  ..  Extended Header (if any, maybe stored here? when [078h]>0)
  ...  ..  Padding to 80h-byte boundary
  ...  ..  Data Fork (if any)
  ...  ..  Padding to 80h-byte boundary
  ...  ..  Resource Fork (if any)
  ...  ..  Padding to 80h-byte boundary
  ...  ..  Get Info comment (if any, usually none)
CRC16-XMODEM: http://www.sunshine2k.de/coding/javascript/crc/crc_js.html

BinHex 4.0 (.hqx) (ASCII, RLE90, big-endian)
Decoding binhex files is done via following steps (in that order):
  1) ASCII to BINARY conversion (similar to BASE64)
  2) RLE90 decompression of whole file (header+data+resource+crc's)
  3) Processing the header+data+resource from the decompressed binary
  4) For Multipart files, repeat above steps for each part
ASCII to BINARY:
  The file may start with some text message, comments, description. Skip any
  such text lines until reaching a line that contains this 45-byte ID string:
    (This file must be converted with BinHex 4.0)
  That line should be followed by following characters (each char representing
  6bit binary value, MSB first, first char is bit7-2 of first byte):
    !"#$%&'()*+,-    char(21h..2Dh) --> bin(00h..0Ch)
    0123456          char(30h..36h) --> bin(0Dh..13h)
    89               char(38h..39h) --> bin(14h..15h)
    @ABCDEFGHIJKLMN  char(40h..4Eh) --> bin(16h..24h)
    PQRSTUV          char(50h..56h) --> bin(25h..2Bh)
    XYZ[             char(58h..5Bh) --> bin(2Ch..2Fh)
    `abcdef          char(60h..66h) --> bin(30h..36h)
    hijklm           char(68h..6Dh) --> bin(37h..3Ch)
    pqr              char(70h..72h) --> bin(3Dh..3Fh)
    :                char(3Ah)      --> start/end marker
    CR/LF            char(0Dh/0Ah)  --> linebreaks per 64 chars (CR and/or LF)
    SPC/TAB          char(09h/20h)  --> blanks (reportedly in some files)
RLE90 Decompression:
  RLE90 decompression is same as in ARC files, except, code 90h,00h is handled
  differently: ARC keeps prevbyte=unchanged, BinHex sets prevbyte=90h.
  RLE90 compression is somewhat optional: 90h must be encoded as 90h,00h,
  but many encoders don't bother to compress repeating bytes (eg. many files
  contain "!!!!!!!!" chars aka uncompressed 00h-filled bytes).
  There is no way to know the decompressed size before decompression (either
  decompress the whole file and allocate more memory as needed, or decompress
  only the header (filename+16h bytes) and then compute decompressed size as
  filename+16h+data+2+resource+2 bytes).
Decompressed Binary (big-endian):
  The decompressed binary contains following data (similar as MacBinary):
    00h   1    Length of Filename (1..63)
    01h   ..   Filename ("FILENAME.EXT")
    01h+N 1    Version (00h)
    02h+N 4    File Type
    06h+N 4    File Creator
    0Ah+N 2    Finder Flags
    0Ch+N 4    Filesize, uncompressed, Data Fork
    10h+N 4    Filesize, uncompressed, Resource Fork
    14h+N 2    Header CRC16-XMODEM on uncompressed 14h+N bytes
    16h+N ..   Data Fork
    ...   2    Data Fork CRC16-XMODEM on uncompressed Data Fork
    ...   ..   Resource Fork
    ...   2    Resource Fork CRC16-XMODEM on uncompressed Resource Fork
    ...   ..   Padding (might reportedly occur in some files)
  Caution: There is a document that does claim that the CRC field should be be
  set to 0000h before CRC calculation, and that the CRC would be computed on
  Size+2 bytes (up to including he CRC field), that appears to be nonsense,
  the CRC is computed on Size+0 bytes, not Size+2.
Multipart files:
  Emails or other text documents may contain multiple binhex files, if so,
  each part should be reportedly followed by a line containing:
    --- end of part NN ---
  Unknown if there are any .hqx files with such multipart stuff.
  Unknown if the next part starts with "(This file must.." or just with ":".
Note: Many files with .hqx extension are actually raw .sit or .cpt files (maybe because somebody had removed the binhex encoding without altering the filename extension).

PackIt (.pit) (Macintosh) (1986) (big-endian)
MAC File Type,Creator IDs = "PIT ","PIT " <-- normal (=uncompressed?)
MAC File Type,Creator IDs = "PIT ","UPIT" <-- other (=compressed?)
 Bitstream for Uncompressed File Entries:
  32bits    Uncompressed Header[000h..003h] (Method/Crypto="PMag")
  ..bits    Uncompressed Header[004h..061h] (uncompressed size = 5Eh)
  ..bits    Uncompressed Data+Resource+CRC  (uncompressed size = Data+Rsrc+2)
 Bitstream for Compressed File Entries:
  32bits    Uncompressed Header[000h..003h] (Method/Crypto="PMa4")
  ..bits    Compressed Huffman Tree         (for decoding following bits)
  ..bits    Compressed Header[004h..061h]   (uncompressed size = 5Eh)
  ..bits    Compressed Data+Resource+CRC    (uncompressed size = Data+Rsrc+2)
  ..bits    Padding to 8bit-boundary        (byte align next File Entry)
 Bitstream for Archive End Marker (after last file):
  32bits    Uncompressed Header[000h..003h] (Method/Crypto="PEnd")
 File Entry Format:
  000h 4    Method/Crypto (usually "PMag"=Uncompressed, "PMa4"=Huffman)
  004h 1    Filename length
  005h 63   Filename ("FILENAME", garbage padded)
  044h 4    File Type
  048h 4    File Creator
  04Ch 2    Finder flags
  04Eh 2    Locked?
  050h 4    Filesize, uncompressed, Data fork
  054h 4    Filesize, uncompressed, Resource fork
  058h 4    Timestamp, creation
  05Ch 4    Timestamp, modification
  060h 2    CRC16-XMODEM on [004h..05Fh]
  ...  ..   Data Fork
  ...  ..   Resource Fork
  ...  2    CRC16-XMODEM on uncompressed Data+Resource forks
 Method/Crypto:
  "PEnd" = Archive End marker (4-byte end marker, without filename etc.)
  "PMag" = Uncompressed
  "PMa1" = Uncompressed, Encrypted Simple
  "PMa2" = Uncompressed, Encrypted DES
  "PMa3" = Uncompressed, Encrypted reserved
  "PMa4" = Huffman
  "PMa5" = Huffman, Encrypted Simple
  "PMa6" = Huffman, Encrypted DES
  "PMa7" = Huffman, Encrypted reserved
 Decompression:       ;for PackIt (and also for StuffIt method 03h)
  InitBitstreamMsbFirst(src)             ;-src is after "PMa4" PackIt ID
  tree=GetMem(200h*4)                    ;-alloc tree (probably less needed)
  num_entries=0                          ;\init tree
  root=GetTreeEntry                      ;/
  while dst<dst_end                      ;-decompress, till end...
    index=root                           ;\
    while index<FF00h                    ; huffman decode
      index=[tree+index*4+GetBits(1)*2]  ;/
    [dst]=index AND FFh, dst=dst+1       ;-store data
  return
 ;---
 GetTreeEntry:
  if GetBits(1)=1 then
    return GetBits(8)+FF00h            ;-final data entry
  else
    index=num_entries                  ;-current index
    num_entries=num_entries+1          ;-alloc next index
    [tree+index*4+0*2] = GetTreeEntry  ;-recursive call for node0
    [tree+index*4+1*2] = GetTreeEntry  ;-recursive call for node1
    return index
http://www.network172.com/early-mac-software/packit-source-code/ - official

StuffIt (.sit) (Macintosh) (old format) (1987) (big-endian)
MAC File Type,Creator IDs = "SIT!","SIT!" (version=01h).
MAC File Type,Creator IDs = "SITD","SIT!" (version=02h).
MAC File Type,Creator IDs = "APPL","STi0" (whatever, with ID="ST65")
 StuffIt Archive Header:
  000h 4    ID ("SIT!", short for StuffIt)
            Reportedly, there are several alternate IDs:
              "SIT!","ST46","ST50","ST60","ST65","STin","STi2","STi3","STi4"
            Unknown why, and if some do differ somehow (ST65 appears to be
            same as SIT!) (for STi, the "i" might be short for it? installer?)
  004h 2    Number of entries in root directory
  006h 4    Total size of archive
  00Ah 4    ID ("rLau", short for Raymond Lau)
  00Eh 1    Version number (01h=v1.x-v1.5.x, 02h=v1.6-v4.5)
  00Fh 7    Reserved (zerofilled)                          ;-when version=01h
  00Fh 1    Unknown (C6h or FFh)                           ;\
  010h 4    Offset to first root entry (16h or elsewhere!) ; when version=02h
  014h 2    Unknown (0001h or FFFFh)                       ;/
 File Entries:
  000h 1    Compression method, Resource fork
  001h 1    Compression method, Data fork
  002h 1    Filename length (1..63 for version=01h, 1..31 for version=02h)
  003h 1Fh  Filename ("FILENAME.EXT", garbage padding)
  022h 20h  Filename further chars                         ;-when version=01h
  022h 2    Filename+size CRC                              ;\
  024h 2    Unknown (always 0000h or 0986h?)               ; when version=02h
  026h 4    Unknown Resource fork related    ;maybe window ;
  02Ah 4    Unknown Data fork related        ;coords ?     ;
  02Eh 1    Unknown Data fork related                      ;
  02Fh 1    Unknown Resource fork related                  ;
  030h 2    Number of child entries (excluding End marker) ;
  032h 4    Offset to previous entry                       ;
  036h 4    Offset to next entry                           ;
  03Ah 4    Offset to parent entry                         ;
  03Eh 4    Offset to first child (or -1 for file entries) ;/
  042h 4    File type     (eg. "APPL")
  046h 4    File creator  (eg. "ACTA")
  04Ah 2    Finder flags  (2100h)
  04Ch 4    Creation date
  050h 4    Modification date
  054h 4    Filesize, uncompressed, Resource fork  (0=None)
  058h 4    Filesize, uncompressed, Data fork      (0=None)
  05Ch 4    Filesize, compressed, Resource fork    (0=None)
  060h 4    Filesize, compressed, Data fork        (0=None)
  064h 2    CRC16 on uncompressed(?) Resource fork (0=None)
  066h 2    CRC16 on uncompressed(?) Data fork     (0=None)
  068h 1    Pad bytes for encrypted Resource? (00h)
  069h 1    Pad bytes for encrypted Data?     (00h)
  06Ah 2    Unknown Data fork related     (0000h, or 0004h=Encrypted?)
  06Ch 2    Unknown Resource fork related (0000h, or 0004h=Encrypted?)
  06Eh 2    CRC16 on Header [000h..06Dh] with initial=0000h
  070h ..   Compressed Data, Resource fork (if any) (size=[05Ch])
  ...  ..   Compressed Data, Data fork     (if any) (size=[060h])
 StuffIt Methods:
  00h Uncompressed
  01h RLE90        (same as... unknown if this is like BinHex, or like ARC)
  02h ClearGapLZW  (same as nCompress, 14bit, with Clear(+gap), no Stop code)
  03h Huffman      (same as PackIt "PMa4" method)
  05h LZHUF        (same as LHA "lh1" method)
  06h Fixed Huffman  Segmented. PackBits, then optional Huffman coding.
                       The set of Huffman codes is predefined, but the meaning
                       of a code can be different in each segment
  08h MW (Miller-Wegman, presumably LZMW)
  0Dh LZ+Huffman   (?)                             ;-StuffIt and StuffIt5
  0Eh Installer    (uh?)
  0Fh Arsenic      (BWT and arithmetic coding)     ;-StuffIt5 only?
  1xh Encrypted methods (same as above, plus encryption)
  20h Folder start                                 ;\StuffIt (not StuffIt5)
  21h Folder end                                   ;/
Common methods are 02h,03h,0Dh (rarely also 00h,01h,05h) (and 0Fh for StuffIt5).
Folders have BOTH methods set to 20h. Uncompressed Data size is WHAT? (maybe sum of all decompressed files in that folder?) Compressed Data size is size in SIT file including 70h-byte folder end-marker. The Folder END marker has both methods set to 21h. The Folder END marker has NONSENSE data size entries?
When version=01h (eg. blackfor.sit), folder/file entries start at offset 16h, and are ordered as so:
  Folder start
    Child entries
    Folder end
  Folder start
    Child entries
    Folder end
When version=02h (eg. cabletron.sit), folder/file entries start at offset from archive header [010h] (which can be anywhere at offset 16h, or near end of archive), and are ordered as specified in file header entries [022h..041h].

StuffIt 5 (.sit) (Macintosh, Windows) (1997) (big-endian)
 StuffIt Archive Header:
  000h 82   ID "StuffIt (c)1997",...,"/StuffIt/",0Dh,0Ah,1Ah,00h)
  052h 1    Version (always 05h)
  053h 1    Flags (can be 00h, 10h, 80h) (bit4=what?, bit7=Encrypted)
  054h 4    Total size of archive
  058h 4    Offset to first entry in root directory (64h, plus Extra Data)
  05Ch 2    Number of entries in root directory
  05Eh 4    Same as [058h] (maybe one is 1st entry, and other is Header size)?
  062h 2    Header CRC16 on [000h..[05xh]-1] with [062h]=0000h and initial=0
  064h ..   Extra Data (see below)
  ...  ..   File/Folder entries
 Extra data can be:
  None (when [58h]=64h)                                  ;with Flags=00h
  05h,76h,35h,B9h,87h,11h             ;maybe 05h=Length? ;with Flags=80h=crypto
  0Dh,A5h,A5h,"Reserved",A5h,A5h,00h) ;maybe 0Dh=Length? ;with Flags=10h=what?
 File/Folder entries:
  000h ..   Base Header
  ...  ..   OS Header (depending on OS Type in Base Header)
  ...  ..   Resource fork (if any) (MAC only, not Windows)
  ...  ..   Data fork     (if any)
 Base Header:
  000h 4    ID (A5A5A5A5h) (or B4B4B4B4h=corrupted charset conversion maybe?)
  004h 1    OS Type (1=Mac, 3=Windows)
  005h 1    Unknown (0)
  006h 2    Base Header size (41h)  (30h+IV?+Filename+Comment)
  008h 1    Unknown (0) (maybe Flags MSB?)
  009h 1    Flags (bit3=Comment, bit6=Folder, bit5=Encrypted)
  00Ah 4    Timestamp, Creation     (Mac OS format, seconds since 1904)
  00Eh 4    Timestamp, Modification (Mac OS format, seconds since 1904)
  012h 4    Offset of previous entry          (0=None)
  016h 4    Offset of next entry              (0=None)
  01Ah 4    Offset of parent folder entry     (0=None)
  01Eh 2    Filename size (F)
  020h 2    Base Header CRC-16 on [000h..[006h]-1]
  022h (4)  Offset of first child entry in folder (FFFFFFFFh=End) ;\Folder
  026h (4)  Size of complete directory                            ; (if Flags
  02Ah (4)  Unknown                                               ; bit6=1)
  02Eh (2)  Number of child entries (excluding folder End marker) ;/
  022h (4)  Data fork uncompressed size                           ;\
  026h (4)  Data fork compressed size                             ;
  02Ah (2)  Data fork CRC-16 (0 for method 0Fh)                   ; File
  02Ch (2)  Data fork Unknown (0000h)                             ; (if Flags
  02Eh (1)  Data fork compression method (00h,0Dh,0Fh)            ; bit6=0)
  02Fh (1)  Data fork Encryption IV? size                         ;
  ...  (..) Data fork Encryption IV? data                         ;/
  ...  ..   File/Folder name ("FILENAME.EXT")
  ...  (2)  Comment size (K)                                      ;\Comment
  ...  (2)  Comment Unknown (0)                                   ; (if Flags
  ...  (..) Comment data                                          ;/bit3=1)
 OS Header for Mac (OS=1):
  000h 2       Flags2 (bit0=HasResource, bit4=same as archive header [053h] ?)
  002h 2       CRC16 on OS Header (with [002h]=0000h, initial=0)
  004h 4       Mac OS file type     ;\
  008h 4       Mac OS file creator  ; as so for Files
  00Ch 2       Mac OS Finder flags  ; (seems to contain
  00Eh 2       Mac OS Unknown       ; other stfuff/junk
  010h 4       Mac OS Unknown       ; for Folders)
  014h 4       Mac OS Unknown       ;
  018h 4       Mac OS Unknown       ;
  01Ch 4       Mac OS Unknown       ;
  020h 4       Mac OS Unknown       ;/
  024h (4)     Resource fork uncompressed size               ;\
  028h (4)     Resource fork compressed size                 ; only if
  02Ch (2)     Resource fork CRC-16 (0 for method 0Fh)       ; Flags2
  02Eh (2)     Resource fork Unknown                         ; bit0=1
  030h (1)     Resource fork compression method              ;
  031h (1)     Resource fork Encryption IV? size             ;
  ...  (..)    Resource fork Encryption IV? data             ;/
 OS Header for Windows (OS=3):
  000h 2       Flags 2 (bit4=same as archive header [053h] ?)
  002h 2       CRC16 on OS Header (with [002h]=0000h, initial=0)
  004h 4       Windows File Attribute (20h=Normal, 10h=Folder)
  008h 08h     Windows Zerofilled
  010h 4       Windows Timestamp last accessed?
  014h 4       Windows Unknown (0005xxxxh)
  018h 08h     Windows Zerofilled
StuffIt 5 seems to only use 00h, 0Dh and 0Fh. See "StuffItSpecs" for descriptions of the algorithms.

StuffIt X (.sitx) (Macintosh, Windows) (20xx?)
 StuffIt Archive Header:
  000h 8    ID "StuffIt!" (reportedly "StuffIt?" also exists)
  008h ..   Unknown...
The StuffIt X headers are somehow compressed/compacted (there are very few 00h bytes even when filesize entries should have zeroes in MSBs).
https://github.com/incbee/Unarchiver/blob/master/XADMaster/XADStuffItXParser.m

Compact Pro aka Compactor (.cpt) (Macintosh) (1990s) (big-endian)
MAC File Type,Creator IDs = "PACT","CPCT".
Compact Pro (originally called Compactor) was a MAC archiver competing with StuffIt. There's also a DOS tool (ExtractorPC) for extracting .cpt files on PCs (albeit released in .EXE.sit.hqx format, making it unlikely that PC users could have used it).
 Archive header:
  000h   1   File ID           (always 01h)
  001h   1   Volume number     (01h for single-volume, Other=Unknown)
  002h   2   Random Volume ID? (...must be same in all split volume files?)
  004h   4   Offset to Footer  (from begin of file)
  008h   ..  Compressed files  (resource+data fork pairs)
  ...    ..  Footer            (directory information)
 Footer format:
  000h   4   CRC32 XOR FFFFFFFFh on following bytes
  004h   2   Number of entries in root folder (including all child entries)
  006h   1   Comment length (usually 00h=None)
  007h   N   Comment
  007h+N ..  File/Folder entries
 Folder entries, with [000h].bit=1:
  000h   1   Foldername length (N), plus bit7=Type (1=Folder)
  001h   N   Foldername ("FOLDERNAME")
  001h+N 2   Number of entries in this folder (including all child entries)
 File entries, with [000h].bit=0:
  000h   1   Filename length (N), plus bit7=Type (0=File)
  001h   N   Filename ("FILENAME.EXT")
  001h+N 1   Volume number (01h for single-volume, Other=Unknown)
  002h+N 4   Offset to compressed Resource (followed by compressed Data)
  006h+N 4   File type
  00Ah+N 4   File creator
  00Eh+N 4   Timestamp, creation     (seconds since 1904)
  012h+N 4   Timestamp, modification (seconds since 1904)
  016h+N 2   Finder flags
  018h+N 4   CRC32 XOR FFFFFFFFh on uncompressed Resource + Data forks
  01Ch+N 2   Method/Flags (see below)
  01Eh+N 4   Filesize, uncompressed, Resource fork
  022h+N 4   Filesize, uncompressed, Data fork
  026h+N 4   Filesize, compressed, Resource fork
  02Ah+N 4   Filesize, compressed, Data fork
 Method/Flags:
  0     Encryption               (0=None, 1=Encrypted, unknown how)
  1     Method for Resource fork (0=RLE8182, 1=RLE8182+LZSSHUF)
  2     Method for Data fork     (0=RLE8182, 1=RLE8182+LZSSHUF)
  3-15  Unknown/unused           (0)
 Note: RLE8182 and RLE8182+LZSSHUF are also used by Mac DiskDoubler.
RLE8182 Compression:
 This is same as RLE90, with two-byte escape code (81h,82h instead of 90h):
  81h,82h,00h       Output 81h,82h
  81h,82h,01h..03h  Output prevbyte 00h..02h times (this is not useful)
  81h,82h,04h       Output prevbyte 03h times (useful if prev=81h, next=82h)
  81h,82h,05h..FFh  Output prevbyte 04h..FEh times (this does save memory)
  81h,xxh           Output 81h, and then process xxh
  81h,padding       Output 81h, at end of file (with padding<>82h)
  xxh               Output xxh (unless it is 81h)
 Note: prevbyte is the previous output byte (ie. that stored at [dst-1]).
 If the uncompressed file ends with 81h, then the compressed file MUST contain
 a dummy padding byte (the RLE decoder in macutils sets a prefix flag upon 81h,
 but doesn't output it to dst until receiving the padding byte, which could be
 81h, or any value other than 82h).
LZSSHUF Compression:
 This uses LZSS-style flag bits (to distinguish between data and len/disp),
 combined with three Huffman trees (for data, len, disp values). The sliding
 window is 2000h bytes (8Kbytes). The format appears to be a simplified variant
 or LHA compression (but gets complicated by inventing weird corner cases).
DecompressLzsshuf:
  if uncompressed_size=0 then goto @@all_done   ;-empty (eg. for unused forks)
  [dst+0000h..1FFCh]=uninitialized              ;\
  [dst+1FFDh..1FFFh]=00h,00h,00h                ; prefill sliding window
  dst+dst+2000h                                 ;/
 @@block_lop:
  InitBitstreamMsbFirst(src)
  GetLzsshufTree(data_tree,100h)  ;tree for data=00h..FFh
  GetLzsshufTree(len_tree,40h)    ;tree for len=00h..3Fh (0,1 usually unused)
  GetLzsshufTree(disp_tree,80h)   ;tree for dispUpper7bit=00h..7Fh
  block_org=src, blocksize=0      ;block origin (after above trees)
 @@decompress_lop:
  if src>=src_end then goto @@all_done  ;<-- this may overshoot on padding bits
  if out>=out_end then goto @@all_done  ;<-- more precise; if RleOnTheFly
  if blocksize>=1FFF0h AND type=CompactPro then goto @@block_done
  if blocksize>=0FFF0h AND type=Disc Double then goto @@block_done
  if GetBits(1)=1 then
    [dst]=GetHuffCode(data_tree), dst=dst+1, blocksize=blocksize+2
  else
    len=GetHuffCode(len_tree)+0, blocksize=blocksize+3
    disp=GetHuffCode(disp_tree)*40h+GetBits(6), if disp=0000h then disp=2000h
    for i=1 to len, [dst]=[dst-disp], dst=dst+1, next i
  if RleOnTheFly then forward above byte(s) to RLE (which advances "out" ptr)
  goto @@decompress_lop
 @@block_done:
  ;the decoder does prefetch data in 16bit units, and it does always have
  ;16..31 bits prefetched, these bits are discarded at block end...
  src=src+2+((src-block_org) AND 1) ;discard 16..31 bits (till 16bit-boundary)
  goto @@block_lop                  ;start next block, with new trees
 @@all_done:
  ret
GetLzsshufTree(tree,max):
  num=GetBits(8)*2, if num>max then goto error ;number of symbols (00h and up)
  for i=0 to num-1, codesizes[i]=GetBits(4)    ;sizes (1..15 bits, or 0=unused)
  lzh_explode_tree(tree,codesizes,num)         ;alike LHA trees
  ret
Minor Corner cases:
  Disp=0 acts as Disp=2000h (don't care when using ringbuf[index AND 1FFFh])
  Len=0..1 could be definied in the len_tree (but are usually size=0bit=unused)
  Unknown if disp_tree & len_tree can be empty (when using data_tree only)?
  RLE ending with 81h,padding should only output 81h (see RLE8182 description)
Incomplete Trees
  A few .cpt files (eg. ABC's-1.09.cpt.hqx\..\Colin's ABC's\Message.h) have
  incomplete trees (like only one disp code, "0"=DispUpper7bit=00h, without
  defining any further huffman codes like "1" or "1xxx").
  This isn't much of a problem (except, one may need to remove incomplete tree
  error checking in the "lzh_explode_tree" function).
End of Last Block
  End of Last Block is usually determined by forwarding the LZSSHUF output
  directly to the RLE8182 decompressor (which does then check if uncompressed
  size is reached) (marked "RleOnTheFly" in above sample code).
  Alternately, one could decompress in separate steps (LZSSHUF to tempbuf, and
  then tempbuf to RLE8182), but that requires to deal with padding bits.
    - padding seems to be 16..31 bits (?) alike at end of blocksize
    - padding bits are (always?) zeroes, which act as flag=0=compressed
    - compressed data occupies at least flg(1),len(1),disp(1),displsbs(6)=9bits
  That can lead to decoding a few extra codes (with lengths up to 3Fh each),
  so the tempbuf must have trailing space for writing that garbage padding.
  And, those padding bits tend to translate to disp=0000h (aka disp=2000h),
  which can cause reads from the whole sliding window, so tempbuf requires
  2000h leading bytes to avoid page faults (not just the 3 initialized bytes).
See also:
https://github.com/dgilman/macutils/blob/master/macunpack/cpt.c - source code
https://github.com/MacPaw/XADMaster/wiki/CompactProSpecs - confused anti-specs

Self-Extracting Archives (SEA)
The abbreviation SEA (and extension .sea) is used for several self-extracting MAC archives. The Resource fork contains an executable (as indicated by Type="APPL") which contains the decompressor, and the Data fork contains the archive.
  MAC File Type,Creator IDs = "APPL","aust" (StuffIt).
  MAC File Type,Creator IDs = "APPL","EXTR" (CompactPro).
  MAC File Type,Creator IDs = "APPL","DSEA" (DiskDoubler).
There are some oddities for .sea files found in internet:
  StuffIt .sea files: These are often raw StuffIt archives (apparently
    somebody had removed the MacBinary header and the resource fork with
    the decompressor).
  CompactPro .sea files: These are often stored as MacBinary without 80h-byte
    padding appended to the Data and Resource forks.
    That applies to "Santa.sea" but other such files have OTHER corruptions,
    which may include wrong Size and/or garbage in reserved MacBinary fields?
Note: Not to be confused with ARC archives from System Enhancement Associates (SEA).

Mac OS Data forks
The Data fork contains the "normal data" part of the file (eg. anything like .TXT .DOC .GIF .JPG .WAV .ZIP .LZH .SIT .PIT .CPT etc).

Mac OS Resource forks
The Resource fork can contain executable code resources (similar to .EXE files; with File Type="APPL"), and various other resources (fonts, icons, text strings for dialog boxes, etc). Those resources are stored in a filesystem-style archive and can be accessed with IDs and/or name strings.
 Resource fork Header:
  000h 4    Offset to Resource Data section (from start of file) (100h)
  004h 4    Offset to Resource Map section  (from start of file) (100h+DataSiz)
  008h 4    Size of Resource Data section (can be 0=None)
  00Ch 4    Size of Resource Map section
  010h F0h  Unknown (can contain filename/type.. MAYBE just garbage padding?)
  100h ..   Resource Data section, contains Data Record(s)
  ...  ..   Resource Map section
 Data Record(s) in Resource Data section (usually at offset 100h and up):
  000h 4    Size of Data for this record
  004h ..   Data for this record
 Resource Map section:
  000h 4    Offset to Resource Data section (from start of file) ;\
  004h 4    Offset to Resource Map section  (from start of file) ; same as in
  008h 4    Size of Resource Data section                        ; header
  00Ch 4    Size of Resource Map section                         ;/
  010h 4    Zero (internally used by Resource Manager, nextResourceMap)
  014h 2    Zero (internally used by Resource Manager, fileRef)
  016h 2    Map Attributes
              0-4  Zero (reserved)
              5    Zero (internally used by Resource Manager, changed)
              6    Zero (internally used by Resource Manager, need compression)
              7    Resource map is read-only
              8-15 Zero (reserved)
  018h 2    Offset to Type List (from start of resource map) (usually 1Ch ?)
  01Ah 2    Offset to Name List (from start of resource map)
  ...  ..   Type List
  ...  ..   Resource List (with one or more entry for each entry in Type List)
  ...  ..   Name List (each name consists of 8bit NameLength, plus name string)
 Type List follows the header and contains an array of resource type records.
  000h 2    Number of Type Records, minus one (FFFFh=None, 0000h=One, etc.)
  002h N*8  Type Records
 Type Record format:
  000h 4    Resource Type (four-character constant)
  004h 2    Number of Resource List entries, minus one (0000h=One, etc.)
  006h 2    Offset to first Resource List entry (from start of Type List)
 Resource List entries:
  000h 2    Resource ID (C000h..FFFFh=Special/Owned)
  002h 2    Offset to Resource Name (from start of Name List) (FFFFh=None)
  004h 1    Attributes
              0    Resource data is compressed             (0=No, 1=Compressed)
              1    Zero (internally used by Resource Manager, changed)
              2    Load Resource as soon as file is opened (0=No, 1=Preload)
              3    Resource is read-only                   (0=No, 1=Protected)
              4    Resource may not be moved in memory     (0=No, 1=Locked)
              5    Resource may be paged out of memory     (0=No, 1=Purgeable)
              6    Load Resource to        (0=Application heap, 1=System Heap)
              7    Zero (reserved)
  005h 3    Offset to Resource Data (from start of Resource Data section)
  008h 4    Zero (internally used by Resource Manager, resourcePtr)
 Note: Some (or all?) 16bit offsets are reportedly signed (max 32Kbyte), the
 24bit offsets are reportedly unsigned (max 16Mbyte).
Compressed Resources (when Attributes.bit0=1)
 Compressed resource have a standarized header, the decompression function(s)
 are supposed to be stored in separate "dmcp" resource (unknown if the OS is
 also providing standard decompression functions).
  000h 4      ID (always A89F6572h for compressed resource)
  004h 2      Always 0012h (maybe compression header size)
  006h 1      Type (08h=Type8, 09h=Type9)
  007h 1      Always 01h
  008h 4      Uncompressed resource size
  00Ch 1      For Type8: workingBufferFractionalSize               ;\
  00Dh 1      For Type8: expansionBufferSize                       ; Type8
  00Eh 2      For Type8: dcmpID (ID in "dmcp" decompress resource) ;
  010h 2      For Type8: Zero (reserved?)                          ;/
  00Ch 2      For Type9: dcmpID (ID in "dmcp" decompress resource) ;\Type9
  00Eh 4      For Type9: decompressor_specific_parameters_with_io  ;/
  012h ..     Compressed Resource Data
 http://formats.kaitai.io/compressed_resource/
Owned Resources (with Resource ID=C000h..FFFFh):
 https://github.com/kreativekorp/ksfl/wiki/Macintosh-Resource-File-Format
The upper 5bit (mask F800h) indicate the resource type of the owner, the middle 6bit (mask 07E0h) indicate the resource id of the owner, and the lower 5bit (mask 001Fh) indicate the "sub-id" of the owned resource.
  ID MSBs    Owner Type  Notes
  C000h      DRVR        driver or desk accessory
  C800h      WDEF        window definition: code to draw windows
  D000h      MDEF        menu definition: code to draw menus
  D800h      CDEF        control definition: code to draw UI widgets
  E000h      PDEF        printer driver
  E800h      PACK        utility code package/library used by the Mac OS
  F000h      cdev        control panel; owner id is set to 1
  F800h      reserved    reserved for future use
The Mac OS Resource Manager used this scheme to ensure that certain types of programs, themselves stored in resources, could find the other resources they needed even if the resources had to be renumbered to avoid conflicts. Utilities such as Font/DA Mover that were used to install and remove these programs used this scheme to ensure that all associated resources were installed or removed as well, and renumber the resources if necessary to avoid conflicts.


CDROM File Compression CP/M Squeeze, Crunch, CrLZH, LBR

CP/M File Formats
  CP/M .LBR archive (ID=1x00h, 11x20h, 2x00h) (uncompressed archive)
  CP/M .xQx squeeze (ID=76h,FFh) (compressed file, RLE90+Huffman)
  CP/M .xZx crunch  (ID=76h,FEh) (compressed file, RLE90+LZW)
  CP/M .xYx CrLZH   (ID=76h,FDh) (compressed file, LZHUF Variant)
For the compressed files, the middle character of the extension is commonly changed to Q, Z, or Y (eg. .TXT changed to .TQT for squeeze), blank extensions are changed to QQQ, ZZZ, or YYY.

Library .LBR
LBR is an uncompressed archive format. However, the contained files (or the whole archive) are often compressed with Squeeze, Crunch, or CrLZH.
First entry:
  000h 1   Status      (always 00h)
  001h 8+3 FilenameExt (always 20h-filled)
  00Ch 2   Offset/80h  (always 0000h)
  00Eh 2   Size/80h    (always nonzero) (aka directory size, NumEntries/4)
 In very old files:
  010h 10h Garbage
 In newer files:
  010h 2   CRC16 (with this field set to 0000h during calculation)
  012h 8   Date/Time (as in File entries, see there)
  01Ah 1   Pad Count   (always 00h) (directory entries are full N*80h-byte)
  01Bh 5   Reserved (zero)
File entries:
  000h 1   Status      (00h=Active, FEh=Deleted, FFh=Unused)
  001h 8+3 FilenameExt (20h-padded, when shorter than 8+3)
  00Ch 2   Offset/80h  (0000h)
  00Eh 2   Size/80h    (nonzero)
  010h 2   CRC16
  012h 2   Creation Date    (days since 31 Dec 1977)
  014h 2   Last Change Date (days since 31 Dec 1977, or 0000h=Same as Creation)
  016h 2   Creation Time    (MSDOS format, HH:MM:SS = 5:6:5 bits)
  018h 2   Last Change Time
  01Ah 1   Pad Count   (0..7Fh, number of unused bytes in last 80h-byte block)
  01Bh 5   Reserved (zero)
CP/M filesizes are usually multiples of 80h, other sizes can be defined by subtracting the "Pad Count" (Filesize = Word[00Eh]*80h-Byte[01Ah]). However, the CRC's are always computed on the whole 80h-byte sectors, including padding).

Squeeze .xQx (RLE90+Huffman)
  000h 2    ID (76h,FFh) (aka "v",FFh)                     ;\
  002h 2    Checksum (sum of all decompressed bytes)       ; header
  004h ..   Filename ("Filename.ext",00h)                  ;/
  ...  2    Tree Size (N) (0..100h)                        ;\
  ...  N*4  Tree      (2x16bit, FEFFh..00FFh)              ; compressed data
  ...  ..   Compressed data                                ;/
  ...  (2)  Timestamp ID (77h,FFh)                         ;\
  ...  (2)  Timestamp Date (MSDOS format)                  ; optional timestamp
  ...  (2)  Timestamp Time (MSDOS format)                  ; extension
  ...  (2)  Timestamp Checksum (sum of above three words)  ;/
  ...  (..) Padding to 80h-byte boundary                   ;-optional padding
Decompression: RLE90+Hufman (same as ARC method 04h).

Crunch .xZx (RLE90+LZW)
  000h 2   ID (76h,FEh) (aka "v",FEh)
  002h ..  Filename/Comment ("Filename.ext[comment]",00h)
  ...  1   Version used for compression       (10h,12h,20h,23h,24h,28h)
  ...  1   Version required for decompression (10h,20h) (v1.0, v2.0)
  ...  1   Error Detection type (00h=Checksum, other=Reserved)
  ...  1   Spare (conventionally 00h in v1.0, 00h/09h in v1.2, or 05h in v2.x)
                                                        XXX or 01h in v2.0
  ...  ..  Compressed data
  ...  2   Checksum (sum of all decompressed bytes)
  ...  ..  Padding to 80h-byte boundary (as common for CP/M files) (1Ah-filled)
Decompression:
  Crunch v1.x --> OldRandomizedLZW with added End Code (000h)
  Crunch v2.x --> PostRandomizedLZW with added special Codes (100h..103h)

CrLZH .xYx (LZHUF Variant)
  000h 2   ID (76h,FDh) (aka "v",FDh)
  002h ..  Filename/Comment ("Filename.ext[comment]",00h)
  ...  1   Version used for compression       (10h,11h,20h) (v1.x, v2.0)
  ...  1   Version required for decompression (10h,20h)     (v1.0, v2.0)
  ...  1   Error Detection type (00h=Checksum, 01h=CRC16, other=Reserved)
  ...  1   Spare (conventionally/always 05h)
  ...  ..  Compressed data
  ...  2   Checksum/CRC16 (sum of all decompressed bytes) (or rarely=CRC16 ?)
  ...  ..  Padding to 80h-byte boundary (as common for CP/M files) (1Ah-filled)
Differences to lh1 LZHUF:
  CrLZH v1/v2 uses 13Bh codes, with 100h=EndCode (same as in ARC archives)
  CrLZH v1 uses DispLsbs=6bit, although using only 2Kbyte dictionary
  CrLZH v2 uses DispLsbs=5bit, to better match 2Kbyte dictionary
        XXX support CRC instead of Checksum (if CRC is ever used?)

Filename/Comment (Crunch and CrLZH)
Filename shorter than 8 chars should be stored without space-padding, but extension should be always space-padded to 3 characters. Bit7 of the extension chars may contain Attribute flags. If present, the comment field always starts after the 3rd extension char.
Apart from "[comment]" there can be nonzero binary data after the extension (eg. "READ.ME ",<binarystuff>,00h, which seems to have three 5-byte BCD timestamps YY,MM,DD,HH,MM or so, which could lead to possible Y2K and hour/minute=00 problems).


CDROM File XYZ and Dummy/Null Files

Dummy/Null Files
Most PSX discs have huge zerofilled dummy files with about 32Mbytes, using filenames like DUMMY, NUL, NULL, or ZNULL, this is probably done to tweak the disc to have valid sector numbers at the end of disc (to help the drive head to know which sector it is on).
Of course, Sony could as well pad the discs with longer Lead-Out areas, but the dummy files may have been needed during development with CDRs (though burning such large files doesn't exactly speed up development).
There are different ways to make sure that the file is at end of the disc:
- Some CDROM burning tools may allow to specify which file is where
- Some games have the file alphabetically sorted as last file in last folder
- Some games have the file declared as audio track
- Some games (additionally) have large zeropadding at end of their archive file

XYZ Files
To reduce seek times, it can make sense to have the boot files & small files at the begin of the disc.
Some games seem to use alphabetically sorted file/folder names to tweak Movies and XA-audio to be located at the end of disc (eg. using ZMOVIE as folder name).


CDROM Protection - SCEx Strings

SCEx String
The heart of the PSX copy-protection is the four-letter "SCEx" string, encoded in the wobble signal of original PSX disks, which cannot be reproduced by normal CD writers. The last letter varies depending on the region:
  "SCEI" for Japan
  "SCEA" for America (and all other NTSC countries except Japan)
  "SCEE" for Europe (and all other PAL countries like Australia)
If the string is missing (or if it doesn't match up for the local region) then the PSX refuses to boot. The verification is done by the Firmware inside of the CDROM Controller (not by the PSX BIOS, so there's no way to bypass it by patching the BIOS ROM chip).

Wobble Groove and Absolute Time in Pregroove (ATIP) on CD-R's
A "blank" CDR contains a pre-formatted spiral on it. The number of windings in the spiral varies depending on the number of minutes that can be recorded on the disk. The spiral isn't made of a straight line (------), but rather a wobbled line (/\/\/\), which is used to adjust the rotation speed during recording; at normal drive speed, wobble should produce a 22050Hz sine wave.
Additionally, the CDR wobble is modulated to provide ATIP information, ATIP is used for locating and positioning during recording, and contains information about the approximate laser power necessary for recording, the last possible time location that lead out can start, and the disc application code.
Wobble is commonly used only on (recordable) CDRs, ie. usually NOT on (readonly) CDROMs and Audio Disks. The copyprotected PSX CDROMs are having a short CDR-style wobble period in the first some seconds, which seems to contain the "SCEx" string instead of ATIP information.

Other Protections
Aside from the SCEx string, PSX disks are required to contain region and licence strings (in the ISO System Area, and in the .EXE file headers), and the "PS" logo (in the System Area, too). This data can be reproduced with normal CD writers, although it may be illegal to distribute unlicensed disks with licence strings.


CDROM Protection - Bypassing it

Modchips
A modchip is a small microcontroller which injects the "SCEx" signal to the mainboard, so the PSX can be booted even from CDRs which don't contain the "SCEx" string. Some modchips are additionally patching region checks contained in the BIOS ROM.
Note: Although regular PSX disks are black, the hardware doesn't verify the color of the disks, and works also with normal silver disks.

Disk-Swap-Trick
Once when the PSX has recognized a disk with the "SCEx" signal, it'll be satisfied until a new disk is inserted, which is sensed by the SHELL_OPEN switch. When having that switch blocked, it is possible to insert a CDR without the PSX noticing that the disk was changed.
Additionally, the trick requires some boot software that stops the drive motor (so the new disk can be inserted, despite of the PSX thinking that the drive door is still closed), and that does then start the boot executable on the new disk.
The boot software can be stored on a special boot-disk (that do have the "SCEx" string on it). Alternately, a regular PSX game disk could be used, with the boot software stored somewhere else (eg. on Expansion ROM, or BIOS ROM replacement, or Memory Card).

Booting via BIOS ROM or Expansion ROM
The PSX can be quite easily booted via Expansion ROM, or BIOS ROM replacements, allowing to execute code that is stored in the ROM, or that is received via whatever serial or parallel cable connection from a PC.
However, even with a BIOS replacement, the protection in the CDROM controller is still active, so the ROM can't read "clean" data from the CDROM Drive (unless the Disk-Swap trick is used).
Whereas, no "clean" data doens't mean no data at all. The CDROM controller does still seem to output "raw" data (without removing the sector header, and without handling error correction, and with only limited accuracy on the sector position). So, eventually, a customized BIOS could convert the "raw" data to "clean" data.

Secret Unlock Commands
There is an "official" backdoor that allows to disable the SCEx protection by software via secret commands (for example, sending those commands can be done via BIOS patches, nocash BIOS clone, or Expansion ROMs).
CDROM - Secret Unlock Commands

Booting via Memory Card
Some games that load data from memory cards may get confused if the save data isn't formatted as how they expect it - with some fine tuning you can get them to "crash" in a manner that they do accidently execute bootcode stored on the memory card.
Requires a tools to write to the memory card (eg. parallel port cable), and the memory card data customized for a specific game, and an original CDROM with that specific game. Once when the memory card code is booted, the Disk-Swap trick can be used.


CDROM Protection - Modchips

Modchip Source Code
The Old Crow mod chip source code works like so:
  entrypoint:                   ;at power_up
    gate=input/highz
    data=input/highz
    wait 50 ms
    data=output/low
    wait 850 ms
    gate=output/low
    wait 314 ms
  loop:
    wait 72 ms                  ;pause (eighteen "1=low" bits)
    sendbyte("S")               ;1st letter
    sendbyte("C")               ;2nd letter
    sendbyte("E")               ;3rd letter
    sendbyte(...)               ;4th letter (A, E, or I, depending on region)
    goto loop
  sendbyte(char):
    sendbit(0)                  ;one start bit (0=highz)
    for i=0 to 7
      sendbit(char AND 1)       ;output data (LSB first)
      char=char/2
    next i
    sendbit(1)                  ;1st stop bit (1=low)
    sendbit(1)                  ;2nd stop bit (1=low)
    return
  sendbit(bit):
    if bit=1 then data=output/low elseif bit=0 then data=input/highz
    wait 4 ms           ;4ms per bit = 250 bits per second
    return
That is, 62 bits per transfer at 250bps = circa 4 transfers per second.

Connection for the data/gate/sync signals:
For older PSX boards (data/gate):
  Board        data             gate
  PU-xx        unknown?         unknown?        ;older PSX boards
For newer PSX and PSone boards (data/sync):
  Board        data             sync
  PU-23, PM-41 CXD2938Q.Pin42   CXD2938Q.Pin5   ;newer PSX and older PSone
  PM-41(2)     CXD2941R.Pin36   CXD2941R.Pin76  ;newer PSone boards
On the mainboard should be a big SMD capacitor (connected to the "data" pin), and a big testpoint (connected to the "sync" pin); it's easier to connect the signals to that locations than to the tiny CXD-chip pins.
gate and data must be tristate outputs, or open-collector outputs (or normal high/low outputs passed through a diode).

Note on "data" pin (all boards)
Transfers the "SCEx" data. Note that the signal produced by the modchip is looking entirly different than the signal produced by original disks, the real signal would be modulated 22050Hz wobble, while the modchip is simply dragging the signal permanently LOW throughout "1" bits, and leaves it floating for "0" bits. Anyways the "faked" signal seems to be accurate enough to work.

Note on "gate" pin (older PSX boards only)
The "gate" pin needs to be LOW only for use with original licensed disks (reportedly otherwise the SCEx string on that disks would conflict with the SCEx string from the modchip).
At the mainboard side, the "gate" signal is an input, and "data" is an inverted output of the gate signal (so dragging gate to low, would cause data to go high).

Note on "sync" pin (newer PSX and PSone boards only)
The "sync" pin is a testpoint on the mainboard, which does (at single speed) output a frequency of circa 44.1kHz/6 (of which some clock pulses seem to be longer or shorter, probably to indicate adjustments to the rotation speed).
Some modchips are connected directly to "sync" (so they are apparently synchronizing the data output with that signal; which is not implemented in the above source code).
Anyways, other modchips are using a more simplified connection: The modchip itself connects only to the "data" pin, and "sync" is required to be wired to IC723.Pin17.

Note on Multi-Region chips
Modchips that are designed to work in different regions are sending a different string (SCEA, SCEE, SCEI) in each loop cycle. Due to the slow 250bps transfer rate, it may take a while until the PSX has received the correct string, so this multi-region technique may cause a noticeable boot-delay.

Stealth (hidden modchip)
The Stealth connection is required for some newer games with anti-modchip protection, ie. games that refuse to run if they detect a modchip. The detection relies on the fact that the SCEx signal is normally received only when booting the disk, whilst older modchips were sending that signal permanently. Stealth modchips are sending the signal only on power-up (and when inserting a new disk, which can be sensed via SHELL_OPEN signal).
Modchip detection reportedly works like so (not too sure if all commands are required, some seem to be rather offtopic):
  1.  Com 19h,20h   ;Retrieve CDROM Controller timestamp
  2.  Com 01h       ;CdlNop: Get CD status
  3.  Com 07h       ;CdlMotorOn: Make CD-ROM drive ready (blah?)
  4.  Com 02h,1,1,1 ;CdlSetloc(01:01:01) (sector that does NOT have SCEx data)
  5.  Com 0Eh,1     ;CdlSetmode: Turn on CD-DA read mode
  6.  Short Delay
  7.  Com 16h       ;CdlSeekP: Seek to Setloc's parameters (4426)
  8.  Com 0Bh       ;CdlMute: Turn off sound so CdlPlay is inaudible
  9.  Com 03h       ;CdlPlay: Start playing CD-DA.
  10. Com 19h,04h   ;ResetSCExInfo (reset GetSCExInfo response to 0,0)
  11. Long Delay    ;wait until the modchip (if any) has output SCEx data
  12. Com 19h,05h   ;GetSCExInfo (returns total,success counters)
  13. Com 09h       ;CdlPause: Stop command 19h.
If GetSCExInfo returns nonzero values, then the console is equipped with a modchip, and if so, anti-modchip games would refuse to work (no matter if the disk is an illegal copy, or not).

NTSC-Boot BIOS Patch
Typically connects to two or three BIOS address/data lines, apparently watching that signals, and dragging a data line LOW at certain time, to skip software based region checks (eg. allowing to play NTSC games on PAL consoles).
Aside from the modchip connection, that additionally requires to adjust the video signal (in 60Hz NTSC mode, the PSX defaults to generate a NTSC video signal) (whilst most PAL screens can handle 60Hz refresh, they can't handle NTSC colors) (on PSone boards, this can be fixed simply by grounding the /PAL pin; IC502.Pin13) (on older PSX boards it seems to be required to install an external color clock generator).

MODCHIP Connection Example
Connection for 8pin "12C508" mod chip from fatcat.co.nz for a PAL PSone with PM-41 board (ie. with 208pin SPU CXD2938Q, and 52pin IC304 "C 3060, SC430943PB"):
  1 3.5V        (supply)
  2 IC304.Pin44 (unknown?) (XLAT)
  3 BIOS.Pin15  (D2)
  4 BIOS.Pin31  (A18)
  5 SPU.Pin5    ("sync")
  6 SPU.Pin42   ("data")
  7 IC304.Pin19 (SHELL_OPEN)
  8 GND         (supply)
The chip can be used in a Basic connection (with only pin1,5,6,8 connected), or Stealth and NTSC-Boot connection (additionally pin2,3,4,7 connected). Some other modchips (such without internal oscillator) are additionally connected to a 4MHz or 4.3MHz signal on the mainboard. Some early modchips also connected to a bunch of additional pins that were reportedly for power-on timings (whilst newer chips use hardcoded power-on delays).

Nocash BIOS "Modchip" Feature
The nocash PSX bios outputs the "data" signal on the A20 address line, so (aside from the BIOS chip) one only needs to install a 1N4148 diode and two wires to unlock the CDROM:
  SPU.Pin42 "data" -------|>|------ CPU.Pin149 (A20)
  SPU.Pin5  "sync" ---------------- IC723.Pin17
With the "sync" connection, the SCEx signal from the disk is disabled (ie. even original licensed disks are no longer recognized, unless SCEx is output via A20 by software). For more variants, see:
CDROM Protection - Chipless Modchips


CDROM Protection - Chipless Modchips

The nocash kernel clone outputs a SCEX signal via A20 and A21 address lines, (so one won't need a separate modchip/microprocessor):
  A20 = the normal SCEX signal (inverted ASCII, eg. "A" = BEh)   ;all boards
  A21 = uninverted SCEX signal (uninverted ASCII, eg. "A" = 41h) ;PU-7..PU-20
  A21 = always 1 during SCEX output                              ;PU-22 and up
When using the clone bios as internal ROM replacement, A20 can be used with simple wires/diodes. Doing that with external expansion ROMs would cause the console to stop working when unplugging the ROM, hence needing a slightly more complex circuit with transistors/logic chips.

External Expansion ROM version, for older boards (PU-7 through PU-20):
              .--------.-.                 .--------.-.
  GATE--------|C  NPN  |  .    DATA--------|C  NPN  |  .
  A20--[10K]--|B  BC   |  |    A21--[10K]--|B  BC   |  |
  GND---------|E  547  |  '    GND---------|E  547  |  '
              '--------'-'                 '--------'-'

External Expansion ROM version, for newer boards (PU-22):
         .-------------------.
  A21----|OE1,OE2            |
  A20----|IN1   74HC126  OUT1|--- DATA
  WFCK---|IN2            OUT2|--- SYNC
         '-------------------'

Internal Kernel ROM version, for older boards (PU-7 through PU-20):
  GATE---------GND
  DATA---------A20

Internal Kernel ROM version, for newer boards (PU-22 through PM-41(2)):
  SYNC--------WFCK
  DATA---|>|---A20

What pin is where...
  GATE is IC703.Pin2  (?) (8pin chip with marking "082B")   ;PU-7? .. PU-16
  GATE is IC706.Pin7/10   (16pin "118" (uPC5023GR-118)      ;PU-18 .. PU-20
  SYNC is IC723.Pin17(TEO)(20pin "SONY CXA2575N")           ;PU-22 .. PM-41(2)
  DATA is IC???.Pin7 (CG) (8pin chip with marking "2903")   ;PU-7? .. PU-16
  DATA is IC706.Pin1 (CG) (16pin "118" (uPC5023GR-118)      ;PU-18 .. PU-20
  DATA is HC05.Pin17 (CG) (52pin "SONY SC4309xxPB")         ;PU-7 .. EARLY-PU-8
  DATA is HC05.Pin32 (CG) (80pin "SONY E35D, 4246xx 185")   ;LATE-PU-8 .. PU-20
  DATA is SPU.Pin42 (CEI) (208pin "SONY CXD2938Q")          ;PU-22 .. PM-41
  DATA is SPU.Pin36?(CEI) (176pin "SONY CXD2941R")          ;PM-41(2)
  WFCK is SPU.Pin5 (WFCK) (208pin "SONY CXD2938Q")          ;PU-22 .. PM-41
  WFCK is SPU.Pin84(WFCK) (176pin "SONY CXD2941R")          ;PM-41(2)
  A20  is CPU.Pin149(A20) (208-pin CPU CXD8530 or CXD8606)  ;PU-7 .. PM-41(2)
  A20  is EXP.Pin28 (A20) (68-pin Expansion Port)           ;PU-7 .. PU-22
  A21  is CPU.Pin150(A21) (208-pin CPU CXD8530 or CXD8606)  ;PU-7 .. PM-41(2)
  A21  is EXP.Pin62 (A21) (68-pin Expansion Port)           ;PU-7 .. PU-22
GATE on PU-18 is usually IC706.Pin7 (but IC706.Pin10 reportedly works, too).
GATE on PU-20 is usually IC706.Pin10 (but IC706.Pin7 might work, too).


CDROM Protection - LibCrypt

LibCrypt is an additional copy-protection, used by about 100 PSX games. The protection uses a 16bit decryption key, which is stored as bad position data in Subchannel Q. The 16bit key is then used for a simple XOR-decryption on certain 800h-byte sectors.

Protected sectors generation schemas
There are some variants on how the Subchannel Q data is modified:
  1. 2 bits from both MSFs are modified,
     CRC-16 is recalculated and XORed with 0x0080.
     Games: Net Yaroze Demo (E), MediEvil (E).
  2. 2 bits from both MSFs are modified,
     original CRC-16 is XORed with 0x8001.
     Games: CTR: Crash Team Racing (E) (No EDC), CTR: Crash Team Racing (E)
     (EDC), Dino Crisis (E), Eagle One: Harrier Attack (E), Gekido:
     Urban Fighters (E), et al.
  3. Either 2 bits or none from both MSFs are modified,
     CRC-16 is recalculated and XORed with 0x0080.
     Games: Ape Escape (S) et al.
Anyways, the relevant part is that the modified sectors have wrong CRCs (which means that the PSX cdrom controller will ignore them, and the GetlocP command will keep returning position data from the previous sector).

LibCrypt sectors
The modified sectors could be theoretically located anywhere on the disc, however, all known protected games are having them located on the same sectors:
  No.    <------- Minute=03/Normal ------->  <------- Minute=09/Backup ------->
  Bit15  14105 (03:08:05)  14110 (03:08:10)  42045 (09:20:45)  42050 (09:20:50)
  Bit14  14231 (03:09:56)  14236 (03:09:61)  42166 (09:22:16)  42171 (09:22:21)
  Bit13  14485 (03:13:10)  14490 (03:13:15)  42432 (09:25:57)  42437 (09:25:62)
  Bit12  14579 (03:14:29)  14584 (03:14:34)  42580 (09:27:55)  42585 (09:27:60)
  Bit11  14649 (03:15:24)  14654 (03:15:29)  42671 (09:28:71)  42676 (09:29:01)
  Bit10  14899 (03:18:49)  14904 (03:18:54)  42813 (09:30:63)  42818 (09:30:68)
  Bit9   15056 (03:20:56)  15061 (03:20:61)  43012 (09:33:37)  43017 (09:33:42)
  Bit8   15130 (03:21:55)  15135 (03:21:60)  43177 (09:35:52)  43182 (09:35:57)
  Bit7   15242 (03:23:17)  15247 (03:23:22)  43289 (09:37:14)  43294 (09:37:19)
  Bit6   15312 (03:24:12)  15317 (03:24:17)  43354 (09:38:04)  43359 (09:38:09)
  Bit5   15378 (03:25:03)  15383 (03:25:08)  43408 (09:38:58)  43413 (09:38:63)
  Bit4   15628 (03:28:28)  15633 (03:28:33)  43634 (09:41:59)  43639 (09:41:64)
  Bit3   15919 (03:32:19)  15924 (03:32:24)  43963 (09:46:13)  43968 (09:46:18)
  Bit2   16031 (03:33:56)  16036 (03:33:61)  44054 (09:47:29)  44059 (09:47:34)
  Bit1   16101 (03:34:51)  16106 (03:34:56)  44159 (09:48:59)  44164 (09:48:64)
  Bit0   16167 (03:35:42)  16172 (03:35:47)  44312 (09:50:62)  44317 (09:50:67)
A modified sector means a "1" bit, an unmodified sector means a "0" bit. The 16bit keys of the existing games are always having eight "0" bits, and eight "1" bits (meaning that there are a total of 32 modified sectors; assuming that each of the 8 bits is stored on 4 sectors for backup purposes).

LibCrypt anti-scratch backups (five sectors apart)
Each bit is stored twice on Minute=03 (five sectors apart).
Five-Sector-Apart backups exist on all discs, except very old ones (Net Yaroze Demo, and MediEvil).

LibCrypt unused backups (on Minute=09)
For some reason, there is also a "backup copy" on Minute=09 (however, the libcrypt software doesn't actually support using that backup stuff).
Minute=09 backups exist on all discs, except Net Yaroze Demo (either because it is too old, or because Minute=09 would be in Lead-Out). Note: Data Track 1 is rather short in Gekido: Urban Fighters, but the Minute=09 backup does nethertheless exist (in Audio Track 3).

LibCrypt sectors in early Libcrypt (Net Yaroze Demo, SLED-01340)
This old version works a bit different: There are only 6 modified sectors (without any backups), and 6 unmodified sectors.
  No.     <-- Modified -->      No.     <--Unmodified-->
  Bit15   14105 (03:08:05)      Bit14   14104 (03:08:04)
  Bit13   14231 (03:09:56)      Bit12   14230 (03:09:55)
  Bit11,3 14485 (03:13:10)      Bit10,2 14484 (03:13:09)
  Bit9,1  14579 (03:14:29)      Bit8,0  14578 (03:14:28)
  Bit7    14649 (03:15:24)      Bit6    14648 (03:15:23)
  Bit5    14899 (03:18:49)      Bit4    14898 (03:18:48)
The 6 modified sectors are in the same location as Bit10-15 in later libcrypt versions. The 6 unmodified sectors are located 1 sector apart from the modified sectors. Some of the 12 sectors are read twice to obtain a 16bit key.

Example (Legacy of Kain)
Legacy of Kain (PAL) is reading the LibCrypt data during the title screen, and does then display GOT KEY!!! on TTY terminal (this, no matter if the correct 16bit key was received).
The actual protection jumps in a bit later (shortly after learning to glide, the game will hang when the first enemies appear if the key isn't okay). Thereafter, the 16bit key is kept used once and when to decrypt 800h-byte sector data via simple XORing.
The 16bit key (and some other related counters/variables) aren't stored in RAM, but rather in COP0 debug registers (which are mis-used as general-purpose storage in this case), for example, the 16bit key is stored in LSBs of the "cop0r3" register.
In particuar, the encryption is used for some of the BIGFILE.DAT folder headers:
CDROM File Archive BIGFILE.DAT (Soul Reaver)


CDROM Disk Images CCD/IMG/SUB (CloneCD)

File.IMG - 2352 (930h) bytes per sector
Contains the sector data, recorded at 930h bytes per sector. Unknown if other sizes are also used/supported (like 800h bytes/sector, or even images with mixed sizes of 800h and 930h for different tracks).

File.SUB - 96 (60h) bytes per sector (subchannel P..W with 96 bits each)
Contains subchannel data, recorded at 60h bytes per sector.
  00h..0Bh 12 Subchannel P (Pause-bits, usually all set, or all cleared)
  0Ch..17h 12 Subchannel Q (ADR/Control, custom info, CRC-16-CCITT)
  18h..5Fh .. Subchannel R..W (usually zero) (can be used for CD-TEXT)
Optionally, the .SUB file can be omitted (it's needed only for discs with non-standard subchannel data, such like copy-protected games). And, some CloneCD disc images are bundled with an empty 0-byte .SUB file (which is about same as completely omitting the .SUB file).

File.CCD - Lead-in info in text format
Contains Lead-in info in ASCII text format. Lines should be terminated by 0Dh,0Ah. The overall CCD filestructure is:
  [CloneCD]     ;File ID and version
  [Disc]        ;Overall Disc info
  [CDText]      ;CD-TEXT (included only if present)
  [Session N]   ;Session(s) (numbered 1 and up)
  [Entry N]     ;Lead-in entries (numbered 0..."TocEntries-1")
  [TRACK N]     ;Track info (numbered 1 and up)
Read on below for details on the separate sections.

[CloneCD]
  Version=3             ;-version (usually 3) (rarely 2)

[Disc]
  TocEntries=4          ;-number of [Entry N] fields (lead-in info blocks)
  Sessions=1            ;-number of sessions (usually 1)
  DataTracksScrambled=0 ;-unknown purpose (usually 0)
  CDTextLength=0        ;-total size of 18-byte CD-TEXT chunks (usually 0)
  CATALOG=NNNNNNNNNNNNN ;-13-digit EAN-13 barcode (included only if present)

[CDText]
  Entries=N       ;number of following entries (CDTextLength/18) (not /16)
  Entry 0=80 00 NN NN NN NN NN NN NN NN NN NN NN NN NN NN   ;entry 0
  Entry 1=80 NN NN NN NN NN NN NN NN NN NN NN NN NN NN NN   ;entry 1
  ...
  Entry XX=8f NN NN NN NN NN NN NN NN NN NN NN NN NN NN NN  ;entry N-1
  Note: Each entry contains 16 bytes (ie. "18-byte CD-TEXT" with CRC excluded)
  "NN NN NN.." consists of 2-digit lowercase HEX numbers (without leading "0x")

[Session 1]
  PreGapMode=2          ;-unknown purpose (usually 1 or 2) (or 0)
  PreGapSubC=1          ;-unknown purpose (usually 0 or 1)
Above are unknown, PreGapMode might be 0=Audio, 1=Mode1, 2=Mode2 for pregap, though unknown for which pregap(s) of which track(s), presumably for first track?

[Entry 0]
[Entry 0..2] are usually containing Point A0h..A2h info. [Entry 3..N] are usually TOC info for Track 1 and up.
  Session=1             ;-session number that this entry belongs to (usually 1)
  Point=0xa0            ;-point (0..63h=Track, non-BCD!) (A0h..XXh=specials) Q2
  ADR=0x01              ;-lower 4bit of ADR/Control (usually 1)           Q0.lo
  Control=0x04          ;-upper 4bit of ADR/Control (eg. 0=audio, 4=data) Q0.hi
  TrackNo=0             ;-usually/always 0 (as [Entry N]'s are in Lead-in)   Q1
  AMin=0                ;\current MSF address                                Q3
  ASec=0                ; (dummy zero values) (actual content                Q4
  AFrame=0              ; would be current lead-in position)                 Q5
  ALBA=-150             ;/ALBA=((AMin*60+ASec)*75+AFrame)-PreGapSize
  Zero=0                ;-probably reserved byte from Q channel              Q6
  PMin=1                ;\referenced MSF address (non-BCD!), for certain     Q7
  PSec=32               ; Point's, PMin may contain a Track number, and PSec Q8
  PFrame=0              ; the disc type value (that without non-BCD-glitch)  Q9
  PLBA=6750             ;/PLBA=((PMin*60+PSec)*75+PFrame)-PreGapSize

[TRACK 1] ;-track number (non-BCD) (1..99)
  MODE=2                ;-mode (0=Audio, 1=Mode1, 2=Mode2)
  ISRC=XXXXXNNNNNNN     ;-12-letter/digit ISRC code (included only if present)
  INDEX 0=N             ;-1st sector with index 0, missing EVEN if any?
  INDEX 1=N             ;-1st sector with index 1, usually same as track's PLBA
  INDEX 2=N             ;-1st sector with index 2, if any
  etc.

Missing Sectors & Sector Size
The .CCD file doesn't define the "PreGapSize" (the number of missing sectors at begin of first track). It seems to be simply constant "PreGapSize=150". Unless one is supposed to calculate it as "PreGapSize=((PMin*60+PSec)*75+PFrame)-PLBA".
The SectorSize seems to be also constant, "SectorSize=930h".

Non-BCD Caution
All Min/Sec/Frame/Track/Index values are expressed in non-BCD, ie. they must be converted to BCD to get the correct values (as how they are stored on real CDs). Exceptions are cases where those bytes have other meanings: For example, "PSec=32" does normally mean BcdSecond=32h, but for Point A0h it would mean DiscType=20h=CD-ROM-XA).
The Point value is also special, it is expressed in hex (0xNN), but nonetheless it is non-BCD, ie. Point 1..99 are specified as 0x01..0x63, whilst, Point A0h..FFh are specified as such (ie. as 0xA0..0xFF).

Versions
Version=1 doesn't seem to exist (or it is very rare). Version=2 is quite rare, and it seems to lack the [TRACK N] entries (meaning that there is no MODE and INDEX information, except that the INDEX 1 location can be assumed to be same as PLBA). Version=3 is most common, this version includes [TRACK N] entries, but often only with INDEX=1 (and up, if more indices), but without INDEX 0 (on Track 1 it's probably missing due to pregap, on further Tracks it's missing without reason) (so, only ways to reproduce INDEX=0 would be to guess it being located 2 seconds before INDEX=1, or, to use the information from the separate .SUB file, if that file is present; note: presence of index 0 is absolutely required for some games like PSX Tomb Raider 2).

Entry & Points & Sessions
The [Entry N] fields are usually containing Point A0h,A1h,A2h, followed by Point 1..N (for N tracks). For multiple sessions: The session is terminated by Point B0h,C0h. The next session does then contain Point A0h,A1h,A2h, and Point N+1..X (for further tracks). The INDEX values in the [TRACK N] entries are originated at the begin of the corresponding session, whilst PLBA values in [Entry N] entries are always originated at the begin of the disk.


CDROM Disk Images CDI (DiscJuggler)

Overall Format
  Sector Data (sector 00:00:00 and up)          ;-body
  Number of Sessions (1 byte)     <--- located at "Filesize-Footersize"
  Session Block for 1st session (15 bytes)      ;\
  nnn-byte info for 1st track                   ; 1st session
  nnn-byte info for 2nd track (if any)          ;
  etc.                                          ;/
  Session Block for 2nd session (15 bytes)      ;\
  nnn-byte info for 1st track                   ; 2nd session (if any)
  nnn-byte info for 2nd track (if any)          ;
  etc.                                          ;/
  etc.                                          ;-further sessions (if any)
  Session Block for no-more-sessions (15 bytes) ;-end marker
  nnn-byte Disc Info Block                      ;-general disc info
  Entrypoint (4 bytes)            <--- located at "Filesize-4"

Sector Data
Contains Sector Data for sector 00:00:00 and up (ie. all sectors are stored in the file, there are no missing "pregap" sectors).
Sector Size can be 800h..990h bytes/sector (sector size may vary per track).

Number of Sessions (1 byte)
  00h   1   Number of Sessions (usually 1)

Session Block (15-bytes)
  00h   1   Unknown (00h)
  01h   1   Number of Tracks in session (01h..63h) (or 00h=No More Sessions)
  02h   7   Unknown (00h-filled)
  09h   1   Unknown (01h)
  0Ah   3   Unknown (00h-filled)
  0Dh   2   Unknown (FFh,FFh)

Track/Disc Header (30h+F bytes) (used in Track Blocks and Disc Info Block)
  00h   12  Unknown (FFh,FFh,00h,00h,01h,00h,00h,00h,FFh,FFh,FFh,FFh)
  0Ch   3   Unknown (DAh,0Ah,D5h or 64h,05h,2Ah) (random/id/chksum?)
  0Fh   1   Total Number of Tracks on Disc (00h..63h) (non-BCD)
  10h   1   Length of below Path/Filename (F)
  11h   (F) Full Path/Filename (eg. "C:\folder\file.cdi")
  11h+F 11  Unknown (00h-filled)
  1Ch+F 1   Unknown (02h)
  1Dh+F 10  Unknown (00h-filled)
  27h+F 1   Unknown (80h)
  28h+F 4   Unknown (00057E40h) (=360000 decimal) (disc capacity 80 minutes?)
  2Ch+F 2   Unknown (00h,00h)
  2Eh+F 2   Medium Type (0098h=CD-ROM, 0038h=DVD-ROM)

Track Block (E4h+F+I+T bytes)
  00h     30h+F Track/Disc Header (see above)
  30h+F   02h   Number of Indices (usually 0002h) (I=Num*4)
  32h+F   (I)   32bit Lengths (per index) (eg. 00000096h,00007044h)
  32h+FI  04h   Number of CD-Text blocks (usually 0) (T=Num*18+VariableLen's)
  36h+FI  (T)   CD-Text (if any) (see "mirage_parser_cdi_parse_cdtext")
  36h+FIT 02h   Unknown (00h,00h)
  38h+FIT 01h   Track Mode (0=Audio, 1=Mode1, 2=Mode2/Mixed)
  39h+FIT 07h   Unknown (00h,00h,00h,00h,00h,00h,00h)
  40h+FIT 04h   Session Number (starting at 0) (usually 00h)
  44h+FIT 04h   Track Number   (non-BCD, starting at 0) (00h..62h)
  48h+FIT 04h   Track Start Address (eg. 00000000h)
  4Ch+FIT 04h   Track Length        (eg. 000070DAh)
  50h+FIT 0Ch   Unknown (00h-filled)
  5Ch+FIT 04h   Unknown (00000000h or 00000001h)
  60h+FIT 04h   read_mode (0..4)
                  0: Mode1,        800h, 2048
                  1: Mode2,        920h, 2336
                  2: Audio,        930h, 2352
                  3: Raw+PQ,       940h, 2352+16 non-interleaved (P=only 1bit)
                  4: Raw+PQRSTUVW, 990h, 2352+96 interleaved
  64h+FIT 4     Control (Upper 4bit of ADR/Control, eg. 00000004h=Data)
  68h+FIT 1     Unknown (00h)
  69h+FIT 4     Track Length        (eg. 000070DAh) (same as above)
  6Dh+FIT 4     Unknown (00h,00h,00h,00h)
  71h+FIT 12    ISRC Code 12-letter/digit (ASCII?) string (00h-filled if none)
  7Dh+FIT 4     ISRC Valid Flag (0=None, Other?=Yes?)
  81h+FIT 1     Unknown (00h)
  82h+FIT 8     Unknown (FFh,FFh,FFh,FFh,FFh,FFh,FFh,FFh)
  8Ah+FIT 4     Unknown (00000001h)
  8Eh+FIT 4     Unknown (00000080h)
  92h+FIT 4     Unknown (00000002h)     (guess: maybe audio num channels??)
  96h+FIT 4     Unknown (00000010h)      (guess: maybe audio bits/sample??)
  9Ah+FIT 4     Unknown (0000AC44h) (44100 decimal, ie. audio sample rate?)
  9Eh+FIT 2Ah   Unknown (00h-filled)
  C8h+FIT 4     Unknown (FFh,FFh,FFh,FFh)
  CCh+FIT 12    Unknown (00h-filled)
  D8h+FIT 1       session_type  ONLY if last track of a session (else 0)
                   (0=Audio/CD-DA, 1=Mode1/CD-ROM, 2=Mode2/CD-XA)
  D9h+FIT 5     Unknown (00h-filled)
  DEh+FIT 1     Not Last Track of Session Flag (0=Last Track, 1=Not Last)
  DFh+FIT 1     Unknown (00h)
  E0h+FIT 4        address for last track of a session? (otherwise 00,00,FF,FF)

Disc Info Block (5Fh+F+V+T bytes)
  00h     30h+F Track/Disc Header (see above)
  30h+F   4     Disc Size (total number of sectors)
  34h+F   1     Volume ID Length (V) ;\from Primary Volume Descriptor[28h..47h]
  35h+F   (V)   Volume ID String     ;/(ISO Data discs) (unknown for Audio)
  35h+FV  1     Unknown (00h)
  36h+FV  4     Unknown (01h,00h,00h,00h)
  3Ah+FV  4     Unknown (01h,00h,00h,00h)
  3Eh+FV  13    EAN-13 Code 13-digit (ASCII?) string (00h-filled if none)
  4Bh+FV  4     EAN-13 Valid Flag (0=None, Other?=Yes?)
  4Fh+FV  4     CD-Text Length in bytes (T=Num*1)
  53h+FV  (T)   CD-Text (for Lead-in) (probably 18-byte units?)
  53h+FVT 8     Unknown (00h-filled)
  5Bh+FVT 4     Unknown (06h,00h,00h,80h)

Entrypoint (4 bytes) (located at "Filesize-4")
  00h     4     Footer Size in bytes


CDROM Disk Images CUE/BIN/CDT (Cdrwin)

.CUE/.BIN (CDRWIN)
CDRWIN stores disk images in two separate files. The .BIN file contains the raw disk image, starting at sector 00:02:00, with 930h bytes per sector, but without any TOC or subchannel information. The .CUE file contains additional information about the separate track(s) on the disk, in ASCII format, for example:
 FILE "PATH\FILENAME.BIN" BINARY
   TRACK 01 MODE2/2352
     INDEX 01 00:00:00           ;real address = 00:02:00  (+2 seconds)
   TRACK 02 AUDIO
     PREGAP 00:02:00             ;two missing seconds      (NOT stored in .BIN)
     INDEX 01 08:09:29           ;real address = 08:13:29  (+2 seconds +pregap)
   TRACK 03 AUDIO
     INDEX 00 14:00:29           ;real address = 14:04:29  (+2 seconds +pregap)
     INDEX 01 14:02:29           ;real address = 14:06:29  (+2 seconds +pregap)
   TRACK 04 AUDIO
     INDEX 00 18:30:20           ;real address = 18:34:20  (+2 seconds +pregap)
     INDEX 01 18:32:20           ;real address = 18:36:20  (+2 seconds +pregap)
The .BIN file does not contain ALL sectors, as said above, the first 2 seconds are not stored in the .BIN file. Moreover, there may be missing sectors somewhere in the middle of the file (indicated as PREGAP in the .CUE file; PREGAPs are usually found between Data and Audio Tracks).
The MM:SS:FF values in the .CUE file are logical addresses in the .BIN file, rather than physical addresses on real CDROMs. To convert the .CUE values back to real addresses, add 2 seconds to all MM:SS:FF addresses (to compensate the missing first 2 seconds), and, if the .CUE contains a PREGAP, then the pregap value must be additionally added to all following MM:SS:FF addresses.
The end address of the last track is not stored in the .CUE, instead, it can be only calculated by converting the .BIN filesize to MM:SS:FF format and adding 2 seconds (plus any PREGAP values) to it.

FILE <filename> BINARY|MOTOTOLA..or..MOTOROLA?|AIFF|WAVE|MP3
  (must appear before any other commands, except CATALOG)
  (uh, may also appear before further tracks)

FLAGS DCP 4CH PRE SCMS

INDEX NN MM:SS:FF

TRACK NN datatype
  AUDIO          ;930h  ;bytes 000h..92Fh
  CDG            ;?     ;?
  MODE1/2048     ;800h  ;bytes 010h..80Fh
  MODE1/2352     ;930h  ;bytes 000h..92Fh
  MODE2/2336     ;920h  ;bytes 010h..92Fh
  MODE2/2352     ;930h  ;bytes 000h..92Fh
  CDI/2336       ;920h  ;?
  CDI/2352       ;930h  ;bytes 000h..92Fh

PREGAP MM:SS:FF
POSTGAP MM:SS:FF
Duration of silence at the begin (PREGAP) or end (POSTGAP) of a track. Even if it isn't specified, the first track will always have a 2-second pregap.
The gaps are NOT stored in the BIN file.

REM comment
Allows to insert comments/remarks (which are usually ignored). Some third-party tools are mis-using REM to define additional information.

CATALOG 1234567890123
ISRC ABCDE1234567
  (ISRC must be after TRACK, and before INDEX)

PERFORMER "The Band"
SONGWRITER "The Writer"
TITLE "The Title"
These entries allow to define basic CD-Text info directly in the .CUE file.
Some third-party utilites allow to define additional CD-Text info via REM lines, eg. "REM GENRE Rock".
Alternately, more complex CD-Text data can be stored in a separate .CDT file.

CDTEXTFILE "C:\LONG FILENAME.CDT"
Specifies an optional file which may contain CD-TEXT. The .CDT file consists of raw 18-byte CD-TEXT fragments (which may include any type of information, including exotic one's like a "Message" from the producer). For whatever reason, there's a 00h-byte appended at the end of the file. Alternately to the .CDT file, the less exotic types of CD-TEXT can be defined by PERFORMER, TITLE, and SONGWRITER commands in the .CUE file.

Missing
Unknown if newer CUE/BIN versions do also support subchannel data.

Malformed .CUE files
Some .CCD files are bundled with uncommon/corrupted .CUE files, with entries as so:
   TRACK 1 MODE2/2352   ;three spaces indent, and 1-digit track
   INDEX 1 00:00:00     ;three spaces indent, and 1-digit index
Normally, that should look as so:
  TRACK 01 MODE2/2352   ;two spaces indent, and 2-digit track
    INDEX 01 00:00:00   ;four spaces indent, and 2-digit index
The purpose of the malformed .CUE might be unsuccessful compatibility, or tricking people into thinking that .CCD works better than .CUE.


CDROM Disk Images MDS/MDF (Alcohol 120%)

File.MDF - Contains sector data (optionally with sub-channel data)
Contains the sector data, recorded at 800h..930h bytes per sector, optionally followed by 60h bytes subchannel data (appended at the end of each sector). The stuff seems to be start on 00:02:00 (ie. the first 150 sectors are missing; at least it is like so when "Session Start Sector" is -150).
The subchannel data (if present) consists of 8 subchannels, stored in 96 bytes (each byte containing one bit per subchannel).
  Bit7..0 = Subchannel P..W (in that order, eg. Bit6=Subchannel Q)
The 96 bits (per subchannel) can be translated to bytes, as so:
  1st..8th bit  = Bit7..Bit0 of 1st byte (in that order, ie. MSB/Bit7 first)
  9st..16th bit = Bit7..Bit0 of 2nd byte ("")
  17th..        = etc.

File.MDS - Contains disc/lead-in info (in binary format)
An MDS file's structure consists of the following stuff ...
  Header              (58h bytes)
  Session block(s)    (usually one 18h byte entry)
  Data blocks         (N*50h bytes)
  Index blocks        (usually N*8 bytes)
  Filename blocks(s)  (usually one 10h byte entry)
  Filename string(s)  (usually one 6 byte string)
  Read error(s)       (usually none such)

Header (58h bytes)
  00h 16  File ID ("MEDIA DESCRIPTOR")
  10h 2   Unknown (01h,03h or 01h,04h or 01h,05h) (Fileformat version?)
  12h 2   Media Type (0=CD-ROM, 1=CD-R, 2=CD-RW, 10h=DVD-ROM, 12h=DCD-R)
  14h 2   Number of sessions (usually 1)
  16h 4   Unknown (02h,00h,00h,00h)
  1Ah 2   Zero (for DVD: Length of BCA data)
  1Ch 8   Zero
  24h 4   Zero (for DVD: Offset to BCA data)
  28h 18h Zero
  40h 4   Zero (for DVD: Offset to Disc Structures)   (from begin of .MDS file)
  44h 0Ch Zero
  50h 4   Offset to First Session-Block (usually 58h) (from begin of .MDS file)
  54h 4   Offset to Read errors (usually 0=None)      (from begin of .MDS file)

Session-Blocks (18h bytes)
  00h 4   Session Start Sector (starting at FFFFFF6Ah=-150 in first session)
  04h 4   Session End Sector     (XXX plus 150 ?)
  08h 2   Session number (starting at 1) (non-BCD)
  0Ah 1   Number of Data Blocks with any Point value (Total Data Blocks)
  0Bh 1   Number of Data Blocks with Point>=A0h      (Special Lead-In info)
  0Ch 2   First Track Number in Session (01h..63h, non-BCD!)
  0Eh 2   Last Track Number in Session  (01h..63h, non-BCD!)
  10h 4   Zero
  14h 4   Offset to First Data-Block (usually 70h) (from begin of .MDS file)

Data-Blocks (50h bytes)
Block 0..2 are usually containing Point A0h..A2h info. Block 3..N are usually TOC info for Track 1 and up.
  00h 1   Track mode (see below for details)
  01h 1   Number of subchannels in .MDF file (0=None, 8=Sector has +60h bytes)
  02h 1   ADR/Control (but with upper/lower 4bit swapped, ie. MSBs=ADR!)    Q0
  03h 1   TrackNo (usually/always 00h; as this info is in Lead-in area)     Q1
  04h 1   Point  (Non-BCD!) (Track 01h..63h) (or A0h and up=Lead-in info)   Q2
  05h 4   Zero (probably dummy MSF and reserved byte from Q channel)   Q3..Q6?
  09h 1   Minute (Non-BCD!)  ;\MM:SS:FF of Point'ed track                   Q7
  0Ah 1   Second (Non-BCD!)  ; (or disc/lead-out info when Point>=A0h)      Q8
  0Bh 1   Frame  (Non-BCD!)  ;/                                             Q9
For Point>=A0h, below 44h bytes at [0Ch..4Fh] are zero-filled
  0Ch 4   Offset to Index-block for this track    (from begin of .MDS file)
  10h 2   Sector size (800h..930h) (or 860h..990h if with subchannels)
  12h 1   Unknown (02h) (maybe number of indices?)
  13h 11h Zero
  24h 4   Track start sector, PLBA (00000000h=00:02:00)(or 00000096h=00:02:00?)
  28h 8   Track start offset                      (from begin of .MDF file)
  30h 4   Number of Filenames for this track (usually 1)
  34h 4   Offset to Filename Block for this track (from begin of .MDS file)
  38h 18h Zero
Trackmode:
  (upper 4bit seem to be meaningless?)
  00h=None (used for entries with Point=A0h..FF)
  A9h=AUDIO       ;sector size = 2352    930h  ;bytes 000h..92Fh
  AAh=MODE1       ;sector size = 2048    800h  ;bytes 010h..80Fh
  ABh=MODE2       ;sector size = 2336    920h  ;bytes 010h..92Fh
  ACh=MODE2_FORM1 ;sector size = 2048    800h  ;bytes 018h..817h (incomplete!)
  ADh=MODE2_FORM2 ;sector size = 2324+0? 914h  ;bytes 018h..91Bh (incomplete!)
  ADh=MODE2_FORM2 ;sector size = 2324+4? 918h  ;bytes ??..?? (contains what?)
  ECh=MODE2       ;sector size = 2448    990h  ;(930h+60h) (with subchannels)

Index Blocks (usually 8 bytes per track)
  00h 4  Number of sectors with Index 0 (usually 96h or zero)
  04h 4  Number of sectors with Index 1 (usually size of main-track area)
Index blocks are usually/always 8 bytes in size (two indices per track, even when recording a CD with more than 2 indices per track).
The MDS file does usually contain Index blocks for <all> Data Blocks (ie. including unused dummy Index Blocks for Data Blocks with Point>=A0h).

Filename Blocks (10h bytes)
  00h 4  Offset to Filename (from begin of .MDS file)
  04h 1  Filename format (0=8bit, 1=16bit characters)
  05h 11 Zero
Normally all tracks are sharing the same filename block (although theoretically the tracks could use separate filename blocks; with different filenames).

Filename Strings (usually 6 bytes)
  00h 6  Filename, terminated by zero (usually "*.mdf",00h)
Contains the filename of the of the sector data (usually "*.mdf", indicating to use the same name as for the .mds file, but with .mdf extension).

Read errors aka DPM data blocks (present if errors occured during recording)
  00h 4   Unknown (1)
  04h 4   Offset to following stuff
  08h 4   Unknown (2)
  0Ch 4   Unknown (7)
  10h 4   Unknown (1)
  14h 4   Number of read errors (E)
  18h E*4 LBA's for sectors with read errors (0 and up)
Instead of (or additionally to) read errors, there may be also hundreds of Kbytes of unknown stuff appended (text strings in 8bit or 16bit format, binary numbers, and huge zerofilled blocks).

Missing
Unknown if/how this format supports EAN-13, ISRC, CD-TEXT.


CDROM Disk Images NRG (Nero)

.NRG (NERO)
Nero is probably the most bloated and most popular CD recording software. The first part of the file contains the disk image, starting at sector 00:00:00, with 800h..930h bytes per sector. Additional chunk-based information is appended at the end of the file, usually consisting of only 4-5 chunks (if following order):
  CUES,DAOI,END!,NERO             <-- when image was DUMPED with nero
  TINF,RELO,TOCT,END!,NERO        <-- when image was CREATED with nero

Chunk Entrypoint (in last 8/12 bytes of file)
  4   File ID "NERO"/"NER5"
  4/8 Fileoffset of first chunk

Cue Sheet (summary of the Table of Contents, TOC)
  4   Chunk ID "CUES"/"CUEX"
  4   Chunk size (bytes)
below EIGHT bytes repeated for each track/index,
of which, first FOUR bytes are same for both CUES and CUEX,
  1   ADR/Control from TOC (usually LSBs=ADR=1=fixed, MSBs=Control=Variable)
  1   Track  (BCD) (00h=Lead-in, 01h..99h=Track N, AAh=Lead-out)
  1   Index  (BCD) (usually 00h=pregap, 01h=actual track)
  1   Zero
next FOUR bytes for CUES,
  1   Zero
  1   Minute (BCD) ;starting at 00:00:00 = 2 seconds before ISO vol. descr.
  1   Second (BCD)
  1   Sector (BCD)
or, next FOUR four bytes for CUEX,
  4   Logical Sector Number (HEX) ;starting at FFFFFF6Ah (=00:00:00)
Caution: Above may contain two position 00:00:00 entries: one nonsense entry for Track 00 (lead-in), followed by a reasonable entry for Track 01, Index 00.

Disc at Once Information
  4   Chunk ID "DAOI"/"DAOX"
  4   Chunk size (bytes)
  4   Garbage (usually same as above Chunk size)
  13  EAN-13 Catalog Number (13-digit ASCII) (or 00h-filled if none/unknown)
  1   Zero
  1   Disk type (00h=Mode1 or Audio, 20h=XA/Mode2) (and probably 10h=CD-I?)
  1   Unknown (01h)
  1   First track (Non-BCD) (01h..63h)
  1   Last track  (Non-BCD) (01h..63h)
below repeated for each track,
  12  ISRC in ASCII (eg. "USXYZ9912345") (or 00h-filled if none/unknown)
  2   Sector size (usually 800h, 920h, or 930h) (see Mode entry for more info)
  1   Mode:
        0=Mode1/800h ;raw mode1 data (excluding sync+header+edc+errorinfo)
        3=Mode2/920h ;almost full sector (exluding first 16 bytes; sync+header)
        6=Mode2/930h ;full sector (including first 16 bytes; sync+header)
        7=Audio/930h ;full sector (plain audio data)
      Mode values from wikipedia:
        00h for data                                     Mode1/800h
        02h
        03h for Mode 2 Form 1 data   eh? FORM1???        Mode2/920h
        05h for raw data                                 Mode1?/930h
        06h for raw Mode 2/form 1 data                   Mode2/930h
        07h for audio                                    Audio/930h
        0Fh for raw data with sub-channel                Mode1?/930h+WHAT?
        10h for audio with sub-channel                   Audio/930h+WHAT?
        11h for raw Mode 2/form 1 data with sub-channel  Mode2/WHAT?+WHAT?
       Note: Some newer files do actually use different sector sizes for each
       track (eg. 920h for the data track, and 930h for any following audio
       tracks), older files were using the same sector size for all tracks
       (eg. if the disk contained 930-byte Audio tracks, then Data tracks
       were stored at the same size, rather than at 800h or 920h bytes).
  3   Unknown (always 00h,00h,01h)
  4/8 Fileoffset 1 (Start of Track's Pregap) (with Index=00h)
  4/8 Fileoffset 2 (Start of actual Track) (with Index=01h and up)
  4/8 Fileoffset 3 (End of Track) (aka begin of next track's pregap)

End of chain
  4   Chunk ID "END!"
  4   Chunk size (always zero)

Track Information (contained only in Track at Once images)
  4     Chunk ID "TINF"/"ETNF"/"ETN2"
  4     Chunk size (bytes) (0Ch/14h/1Ch*NumTracks)
below repeated for each track,
  4/4/8 Track fileoffset        ;\32bit in TINF/ETNF chunks,
  4/4/8 Track length (bytes)    ;/64bit in ETN2 chunks
  3     Zero
  1     Mode (should be same as in DAO chunks, see there) (implies sector size)
  0/4/4 Start lba on disc       ;\only in ETNF/ETN2 chunks,
  0/4/4 Unknown?                ;/not in TINF chunks

Unknown 1 (contained only in Track at Once images)
  4   Chunk ID "RELO"
  4   Chunk size (bytes)
  4   Zero

Unknown 2 (contained only in Track at Once images)
  4   Chunk ID "TOCT"
  4   Chunk size (bytes)
  1   Disk type (00h=Mode1 or Audio, 20h=XA/Mode2) (and probably 10h=CD-I?)
  1   Zero (00h)

Session Info (begin of a session) (contained only in multi-session images)
  4   Chunk ID "SINF"
  4   Chunk size (bytes)
  4   Number of tracks in session

CD-Text (contained only in whatever images)
  4   Chunk ID None/"CDTX"
  4   Chunk size (bytes) (must be a multiple of 18 bytes)
below repeated for each fragment,
  18  Raw 18-byte CD-text data fragments

Media Type? (contained only in whatever images)
  4   Chunk ID "MTYP"
  4   Chunk size (bytes)
  4   Unknown? (00000001h for CDROM) (maybe other value for DVD)

Optional Filenames (names where the image was generated from?)
  4   Chunk ID "AFNM"
  4   Chunk size (bytes)
  ..  Track Filenames (eg. "Track1.wav",0,"Track2.wav",0)

Optional Volume name
  4   Chunk ID "VOLM"
  4   Chunk size (bytes)
  ..  Name (eg. "Audio CD",00h)

Notes
Newer/older .NRG files may contain 32bit/64bit values (and use "OLD"/"NEW" chunk names) (as indicated by the "/" slashes).
CAUTION: All 16bit/32bit/64bit values are in big endian byte-order.

Missing
Unknown if newer NRG versions do also support subchannel data.


CDROM Disk Image/Containers CDZ

.CDZ is a compressed disk image container format (developed by pSX Author, and used only by the pSX emulator). The disk is split into 64kbyte blocks, which allows fast random access (without needing to decompress all preceeding sectors).
However, the compression ratio is surprisingly bad (despite of being specifically designed for cdrom compression, the format doesn't remove redundant sector headers, error correction information, and EDC checksums).

.CDZ File Structure
  FileID ("CDZ",00h for cdztool v0/v1, or "CDZ",01h for cdztool v2 and up)
  One or two Chunk(s)

.CDZ Chunk Format
Chunk Header in v0 (unreleased prototype):
  4    32bit Decompressed Size (of all blocks) (must be other than "ZLIB")
Chunk Header in v1 (first released version):
  4    ZLIB ID ("ZLIB")
  8    64bit Decompressed Size (of all blocks)
Chunk Header in v2 and up (later versions):
  4    Chunk ID (eg. "CUE",00h)
  8    Chunk Size in bytes (starting at "ZLIB" up to including Footer, if any)
  4    ZLIB ID ("ZLIB")
  8    64bit Decompressed Size (of all blocks)
Chunk Body (same in all versions):
  4    Number of Blocks (N)
  4    Block 1 Compressed Size (CS.1)
  4    Block 1 Decompressed Size (always 00010000h, except last block)
  CS.1 Block 1 Compressed ZLIB Data (starting with 78h,9Ch)
  ...  ...                                     ;\
  4    Block N Compressed Size (CS.N)          ; further block(s)
  4    Block N Decompressed Size               ; (if any)
  CS.N Block N Compressed ZLIB Data            ;/
Chunk Footer in v0 (when above header didn't have the "ZLIB" ID):
  4*N       Directory Entries for N blocks     ;-this ONLY for BIN chunk
Chunk Footer in v1 and up:
  BPD*(N-1) Directory Entries for N-1 blocks   ;\this ONLY for BIN chunk
  1         Bytes per Directory Entry (BPD)    ;/(not for CUE/CCD/MDS)
The "Compressed ZLIB Data" parts contain Deflate'd data (starting with 2-byte ZLIB header, and ending with 4-byte ZLIB/ADLER checksum), for details see:
CDROM File Compression ZIP/GZIP/ZLIB (Inflate/Deflate)

.CDZ Chunks / Content
The chunk(s) have following content:
  noname+noname       --> .CUE+.BIN (cdztool v1 and below)
  "BIN",0             --> .ISO      (cdztool v2? and up)
  "CUE",0+"BIN",0     --> .CUE+.BIN (cdztool v2 and up)
  "CCD",0+"BIN",0     --> .CCD+.IMG (cdztool v2 and up)
  "CCD",0+"BIN",01h   --> .CCD+.IMG+.SUB (930h sectors, plus 60h subchannels)
  "MDS",0+"BIN",0     --> .MDS+.MDF (cdztool v5 only)
Note: cdztool doesn't actually recognize files with .ISO extension (however, one can rename them to .BIN, and then compress them as CUE-less .BIN file).

Cdztool.exe Versions
  cdztool.exe v0, unrelased prototype
  cdztool.exe v1, 22 May 2005, CRC32=620dbb08, 102400 bytes, pSX v1.0-5
  cdztool.exe v2, 02 Jul 2006, CRC32=bcb29c1e, 110592 bytes, pSX v1.6
  cdztool.exe v3, 22 Jul 2006, CRC32=4062ba82, 110592 bytes, pSX v1.7
  cdztool.exe v4, 13 Aug 2006, CRC32=7388dd3d, 118784 bytes, pSX v1.8-11
  cdztool.exe v5, 22 Jul 2007, CRC32=f25c1659, 155648 bytes, pSX v1.12-13
Note: v0 wasn't ever released (it's only noteworthy because later versions do have backwards compatibility for decompressing old v0 files). v1 didn't work with all operating systems (on Win98 it just says "Error: Couldn't create <output>" no matter what one is doing, however, v1 does work on later windows versions like WinXP or so?).


CDROM Disk Image/Containers ECM

ECM (Error Code Modeler by Neill Corlett) is a utility that removes unneccessary ECC error correction and EDC error detection values from CDROM-images. This is making the images a bit smaller, but the real size reduction isn't gained until subsequently compressing the images via tools like ZIP. Accordingly, these files are extremly uncomfortable to use: One most first UNZIP them, and then UNECM them.

.EXT.ECM - Double extension
ECM can be applied to various CDROM-image formats (like .BIN, .CDI, .IMG, .ISO, .MDF, .NRG), as indicated by the double-extension. Most commonly it's applied to .BIN files (hence using extension .BIN.ECM).

Example / File Structure
  45 43 4D 00                                      ;FileID "ECM",00h
  3C                                               ;Type 0, Len=10h (aka 0Fh+1)
  00 FF FF FF FF FF FF FF FF FF FF 00 00 02 00 02  ;16 data bytes
  02                                               ;Type 2, Len=1 (aka 00h+1)
  00 00 08 00 00 00 00 00 00 00 00 ..... 00 00 00  ;804h data bytes
  3C                                               ;Type 0, Len=10h (aka 0Fh+1)
  00 FF FF FF FF FF FF FF FF FF FF 00 00 02 01 02  ;16 data bytes
  02                                               ;Type 2, Len=1 (aka 00h+1)
  00 00 08 00 00 00 00 00 00 00 00 ..... 00 00 00  ;804h data bytes
  ...
  FC FF FF FF 3F                                   ;End Code (Len=FFFFFFFFh+1)
  NN NN NN NN                                      ;EDC (on decompressed data)

Type/Length Byte(s)
Type/Length is encoded in 1..5 byte(s), with "More=1" indicating that further length byte(s) follow:
  1st Byte: Bit7=More, Bit6-2=LengthBit4-0, Bit1-0=Type(0..3)
  2nd Byte: Bit7=More, Bit6-0=LengthBit5-11
  3rd Byte: Bit7=More, Bit6-0=LengthBit12-18
  4th Byte: Bit7=More, Bit6-0=LengthBit19-25
  5th Byte: Bit7-6=Reserved/Zero, Bit5-0=LengthBit26-31
Length=FFFFFFFFh=End Indicator
The actual decompression LEN is: "LEN=Length+1"

ECM Decompression
Below is repeated LEN times (with LEN being the Length value plus 1):
  Type 0: load 1 byte, save 1 byte
  Type 1: load 803h bytes [0Ch..0Eh,10h..80Fh], save 930h bytes [0..92Fh]
  Type 2: load 804h bytes [14h..817h], save 920h bytes [10h..92Fh]
  Type 3: load 918h bytes [14h..91Bh], save 920h bytes [10h..92Fh]
Type 1-3 are reconstructing the missing bytes before saving. Type 2-3 are saving only 920h bytes, so (if the original image contained full 930h byte sectors) the missing 10h bytes must be inserted via Type 0. Type 0 can be also used for copying whole sectors as-is (eg. Audio sectors, or Data sectors with invalid Sync/Header/ECC/EDC values). And, Type 0 can be used to store non-sector data (such like the chunks at the end of .NRG or .CDI files).

Central Mistakes
There's a lot of wrong with the ECM format. The two central problems are that it doesn't support data-compression (and needs external compression tools like zip/rar), and, that it doesn't contain a sector look-up table (meaning that random access isn't possible unless when scanning the whole file until reaching the desired sector).

Worst-case Scenario
As if ECM as such wouldn't be uncomfortable enough, you may expect typical ECM users to get more things messed up. For example:
  A RAR file containing a 7Z file containing a ECM file containing a BIN file.
  The BIN containing only Track 1, other tracks stored in APE files.
  And, of course, the whole mess without including the required CUE file.


CDROM Subchannel Images

.SBI (redump.org)
  000h 4     FileID ("SBI",00h)
  004h ..    Subchannel entries (with 7 or 14 bytes per entry)
 Subchannel entry format:
  000h 3     Real absolute MM:SS:FF address where the sub q data was bad
  003h 1     Format (1, 2 or 3)
  004h 10    Q0..Q9 (complete 10-byte sub q data, excluding CRC) ;<-- Format 1
  004h 3     Q3..Q5 (3-byte wrong relative MM:SS:FF address)     ;<-- Format 2
  004h 3     Q7..Q9 (3-byte wrong absolute MM:SS:FF address)     ;<-- Format 3
Note: The PSX libcrypt protection relies on bad checksums (Q10..Q11), which will cause the PSX cdrom controller to ignore Q0..Q9 (and to keep returning position data from most recent sector with intact checksum).
Ironically, the SBI format cannot store the required Q10..Q11 checksum. The trick for using SBI files with libcrypted PSX discs is to ignore the useless Q0..Q9 data, and to assume that all sectors in the SBI file have wrong Q10..Q11 checksums.

.LSD (redump.org)
  000h N*15  Subchannel entries (with 15 bytes per entry)
 Subchannel entry format:
  000h 3     Real absolute MM:SS:FF address where the sub q data was bad
  003h 12    Q0..Q11 (complete 12-byte sub q data, including CRC)
About same as SBI, but newer and better (it's containing the whole subchannel data including checksum).

.LCK (no$psx v2.3 and up)
  000h 16    ASCII "LibCryptKey=####" (with #### = 16bit uppercase HEX key)
This is a quick way to produce subchannel errors on the corresponding sectors (albeit not suitable for preserving the exact subchannel values).

.M3S (Subchannel Q Data for Minute 3) (ePSXe)
M3S files are containing Subchannel Q data for all sectors on Minute=03 (the region where PSX libcrypt data is located) (there is no support for storing the (unused) libcrypt backup copy on Minute=09). The .M3S filesize is 72000 bytes (60 seconds * 75 sectors * 16 bytes). The 16 bytes per sector are:
  Q0..Q9   Subchannel Q data (normally position data)
  Q10..Q11 Subchannel Q checksum
  Q12..Q15 Dummy/garbage/padding (usually 00000000h or FFFFFFFFh)
Unfortunately, there are at least 3 variants of the format:
  1. With CRC (Q0..Q11 intact) (and Q12..Q15 randomly 00000000h or FFFFFFFFh)
  2. Without CRC (only Q0..Q9 intact, but Q10..Q15 zerofilled)
  3. Without anything (only Q0 intact, but Q1..Q15 zerofilled)
The third variant is definetly corrupt (and one should ignore such zerofilled entries). The second variant is corrupt, too (but one might attempt to repair them by guessing the missing checksum: if it contains normal position values assume correct crc, if it contains uncommon values assume a libcrypted sector with bad crc).
The M3S format is intended for libcrypted PSX games, but, people seem to have also recorded (corrupted) M3S files for unprotected PSX games (in so far, more than often, the M3S files might cause problems, instead of solving them).
Note: The odd 16-byte format with 4-byte padding does somehow resemble the "P and Q Sub-Channel" format 'defined' in MMC-drafts; if the .M3S format was based on the MMC stuff: then the 16th byte might contain a Subchannel P "pause" flag in bit7.

CDROM Images with Subchannel Data
Most CDROM-Image formats can (optionally) contain subchannel recordings. The downsides are: Storing all 8 subchannels for a full CDROM takes up about 20MBytes. And, some entries may contain 'wrong' data (read errors caused by scratches cannot be automatically repaired since subchannels do not contain error correction info).
If present, the subchannel data is usually appended at the end of each sector in the main binary file (one exception is CloneCD, which stores it in a separate .SUB file instead of in the .IMG file).
  CCD/IMG/SUB (CloneCD)  P-W  60h-bytes Non-interleaved (in separate .SUB file)
  CDI (DiscJuggler)      P-Q  10h-bytes Non-interleaved (in .CDI file)
  ""                     P-W  60h-bytes Interleaved     (in .CDI file)
  CUE/BIN/CDT (Cdrwin)        N/A                       (none)
  ISO (single-track)          N/A                       (none)
  MDS/MDF (Alcohol 120%) P-W  60h-bytes Interleaved     (in .MDF file)
  NRG (Nero)             P-W  60h-bytes Interleaved     (in .NRG file)
Interleaved Subchannel format (eg. Alcohol .MDF files):
  00h-07h   80 C0 80 80 80 80 80 C0   ;P=FFh, Q=41h=ADR/Control, R..W=00h
  08h-0Fh   80 80 80 80 80 80 80 C0   ;P=FFh, Q=01h=Track,       R..W=00h
  10h-17h   80 80 80 80 80 80 80 C0   ;P=FFh, Q=01h=Index,       R..W=00h
  18h-1Fh   80 80 80 80 80 80 80 80   ;P=FFh, Q=00h=RelMinute,   R..W=00h
  20h-27h   80 80 80 80 80 80 80 80   ;P=FFh, Q=00h=RelSecond,   R..W=00h
  28h-2Fh   80 80 80 80 80 80 80 80   ;P=FFh, Q=00h=RelSector,   R..W=00h
  30h-37h   80 80 80 80 80 80 80 80   ;P=FFh, Q=00h=Reserved,    R..W=00h
  38h-3Fh   80 80 80 80 80 80 80 80   ;P=FFh, Q=00h=AbsMinute,   R..W=00h
  40h-47h   80 80 80 80 80 80 C0 80   ;P=FFh, Q=02h=AbsSecond,   R..W=00h
  48h-4Fh   80 80 80 80 80 80 80 80   ;P=FFh, Q=00h=AbsSector,   R..W=00h
  50h-57h   80 80 C0 80 C0 80 80 80   ;P=FFh, Q=28h=ChecksumMsb, R..W=00h
  58h-5Fh   80 80 C0 C0 80 80 C0 80   ;P=FFh, Q=32h=ChecksumLsb, R..W=00h
Non-Interleaved Subchannel format (eg. CloneCD .SUB files):
  00h-0Bh   FF FF FF FF FF FF FF FF FF FF FF FF  ;Subchannel P (Pause)
  0Ch-17h   41 01 01 00 00 00 00 00 02 00 28 32  ;Subchannel Q (Position)
  18h-23h   00 00 00 00 00 00 00 00 00 00 00 00  ;Subchannel R
  24h-2Fh   00 00 00 00 00 00 00 00 00 00 00 00  ;Subchannel S
  30h-3Bh   00 00 00 00 00 00 00 00 00 00 00 00  ;Subchannel T
  3Ch-47h   00 00 00 00 00 00 00 00 00 00 00 00  ;Subchannel U
  48h-53h   00 00 00 00 00 00 00 00 00 00 00 00  ;Subchannel V
  54h-5Fh   00 00 00 00 00 00 00 00 00 00 00 00  ;Subchannel W
Non-Interleaved P-Q 10h-byte Subchannel format:
  This is probably based on MMC protocol, which would be as crude as this:
  The 96 pause bits are summarized in 1 bit. Pause/Checksum are optional.
  00h-09h   41 01 01 00 00 00 00 00 02 00        ;Subchannel Q (Position)
  0Ah-0Bh   28 32    ;<-- OPTIONAL, can be zero! ;Subchannel Q (Checksum)
  0Ch-0Eh   00 00 00                             ;Unused padding (zero)
  0F        80       ;<-- OPTIONAL, can be zero! ;Subchannel P (Bit7=Pause)


CDROM Disk Images PBP (Sony)

.PBP
Sony's disc image format used on PSP. Can store multi-disc images in a single file. Supports deflate data compression and ATRAC3 audio compression. A homebrew compressor can compress whole discs with deflate (which works, but it isn't very good to compress audio sectors that way).

PBP Format (rev-engineered from homebrew DBALL.PBP)
  000000h 4    ID (00h,"PBP")
  000004h 4    Version? (10000h) (but, reportedly "always 100h or 1000100h")
  000008h 4    Offset of the file PARAM.SFO (28h)
  00000Ch 4    Offset of the file ICON0.PNG (3D8h)
  000010h 4    Offset of the file ICON1.PMF (3D8h) or ICON1.PNG
  000014h 4    Offset of the file PIC0.PNG  (3D8h) or UNKNOWN.PNG
  000018h 4    Offset of the file PIC1.PNG  (3D8h) or PICT1.PNG
  00001Ch 4    Offset of the file SND0.AT3  (3D8h)
  000020h 4    Offset of the file DATA.PSP  (3D8h)
  000024h 4    Offset of the file DATA.PSAR (10000h)
  000028h ..   PARAM.SFO file (zerofilled in homebrew PBP)
  0003D8h ..   PNG files etc  (zerofilled in homebrew PBP)
  010000h 0Ch  ID "PSISOIMG0000"
  01000Ch 4    PBP Size-10000h              (144740h)
  010010h 4    PBP Size-6420h (???)         (14E320h)
  010014h ..   Zerofilled
  010400h 0Bh  Game ID ("_SCUS_94476" for Hot Shots Golf 2)
  01040Bh ..   Zerofilled
  010800h A00h TOC List    (0Ah-byte per entry) (unused entries are zerofilled)
  011200h 20h  Zerofilled
  011220h 4    PBP Size-D2CFh (???)         (147471h)
  011224h 4    Zero
  011228h 4    Unknown     (7FFh)
  01122Ch 11h  Game Name   ("Hot Shots Golf",C2h,AEh,"2")
  01123Dh ..   Zerofilled
  014000h ..   Sector List (20h-byte per entry) (unused entries are zerofilled)
  ...     ..   Zerofilled
  110000h ..   Deflated sectors (9300h bytes after decompression)
  15467Dh B8h  One extra compression block that is NOT in Sector List ???
  154735h 0Bh  Weird padding with ASCII "00000000000"
  154740h -    End of file
 TOC List (Subchannel Q with ADR=1 during Lead-In):
  000h 1   ADR/Control (eg. 41h=Data Track)
  001h 1   Track       (always 00h=Lead-in for all TOC List entries)
  002h 1   Point       (A0h, A1h, A2h, or Track 01h and up)      (BCD?)
  003h 3   Dummy MSF   (usually 00:00:00 or weirdly 00:02:01)    (BCD?)
  006h 1   Reserved    (00h)
  007h 3   Actual MSF  (or TOC info for Point=A0h,A1h)           (BCD?)
 Example TOC (DBALL.PBP):
  41 00 A0 00 00 00 00 01 20 00   ;First Track (1) and Type (20h=CDROM-XA)
  41 00 A1 00 00 00 00 01 00 00   ;Last Track Number (1)
  41 00 A2 00 00 00 00 27 19 22   ;Lead-Out, uh at 27:19:22 in DBALL.PBP ???
  41 00 01 00 02 01 00 00 02 00   ;Track 1 at 00:02:00
  (remaining entries are zerofilled)
 Example TOC (PSALM69.PBP):
  01 00 01 00 02 00 00 00 00 00   ;Track 1 as audio <-- why that ???
  01 00 02 02 37 44 00 00 00 00   ;Track 2 as audio
  01 00 03 03 25 45 00 00 00 00   ;Track 3 as audio
  41 00 01 00 02 01 00 00 02 00   ;Track 1 as data <-- listed last?
  (remaining entries are zerofilled)
  (weirdly, most MM:SS:FF values are stored in byte[3..5] instead [7..9])
  (there are no point=A0h,A1h,A2h entries)
 Example TOC (GOOGLE_AI_TTS.PBP):
  01 00 01 00 02 00 00 00 00 00   ;Track 1 as audio
  01 00 02 00 02 30 00 00 00 00   ;Track 2 as audio, but without pregap?
  01 00 03 00 02 60 00 00 00 00   ;Track 3 as audio, but without pregap?
  01 00 04 00 03 15 00 00 00 00   ;Track 4 as audio, but without pregap?
  (remaining entries are zerofilled)
 Sector List:
  000h 4   Offset-110000h to Sector(N*10h)
  004h 2   Compressed size of Sector(N*10h+(0..0Fh))   ;9300h=uncompressed?
  006h 2   Zero (but, reportedly "usually 1... and 0 for the last entry")
  008h 10h Zero (but, reportedly "first 10h bytes of SHA1 sum of 10h sectors")
  018h 8   Zero (padding)
Data Compression is using raw Deflate (without any zlib headers or the like), and it's unfortunately just compressing the sectors as-is (without filtering out sector headers and ECC/EDC values).
CDROM File Compression ZIP/GZIP/ZLIB (Inflate/Deflate)
Audio Compression format is ATRAC3:
  ?
Multi-disc format is unknown:
  ?
Retail files have "PGD" encryption:
  ?


CDROM Disk Images CHD (MAME)

All numbers are stored in Motorola (big-endian) byte ordering.

V1/V2 header (hdcomp):
V1/V2 contains harddisk related header entries (and apparently doesn't support cdroms).
  000h 08h  ID "MComprHD" (MAME Compressed Hunks of Data)
  008h 4    Header size    (4Ch=V1, 50h=V2)
  00Ch 4    Header version (probably 01h=V1, 02h=V2)
  010h 4    Flags (bit0=DriveHasParent, bit1=AllowWrites)
  014h 4    Compression type (0=None, 1=ZLIB)
  018h 4    Number of sectors per hunk
  01Ch 4    Total number of hunks represented
  020h 4    Number of cylinders on hard disk
  024h 4    Number of heads on hard disk
  028h 4    Number of sectors on hard disk
  02Ch 10h  MD5 checksum on raw data
  03Ch 10h  MD5 checksum on parent file
  N/A  -    V1: Uses fixed 200h-byte Sector size
  04Ch (4)  V2: Number of bytes per sector
  ...  ?    Supposedly followed by map and/or data at whatever locations

V3/V4 header (chdman):
V3/V4 are inventing new "metadata" for info about harddisks or cdroms.
  000h 08h  ID "MComprHD" (MAME Compressed Hunks of Data)
  008h 4    Header size    (78h=V3, 6Ch=V4)
  00Ch 4    Header version (03h=V3, 04h=V4)
  010h 4    Flags (bit0=DriveHasParent, bit1=AllowWrites)
  014h 4    Compression type (0=None, 1=ZLIB, 2=ZLIB_PLUS) (V4: 3=AV)
  018h 4    Total number of hunks represented    (N)       (92h)
  01Ch 08h  Total size of all uncompressed hunks (N*2640h) (15D080h)
  024h 08h  Offset to the first blob of metadata
  02Ch 10h  V3: MD5 checksum on raw data                ;\
  03Ch 10h  V3: MD5 checksum on parent file             ;
  04Ch 4    V3: Number of bytes per hunk (2640h=990h*4) ; V3
  050h 14h  V3: SHA1 checksum on raw data               ;
  064h 14h  V3: SHA1 checksum on parent file            ;/
  02Ch 4    V4: Number of bytes per hunk (2640h=990h*4) ;\
  030h 14h  V4: SHA1 checksum on raw+meta               ; V4
  044h 14h  V4: SHA1 checksum on raw+meta of parent     ;
  058h 14h  V4: SHA1 checksum on raw data               ;/
  ...  N*10h Map entries (for each hunk)
  ...  10h   Map end marker ("EndOfListCookie",00h)
  ...  ..    Metadata Chunk(s)
  ...  ..    Compressed Sectors (aka hunks)

V5 header (chdman):
  000h 8    ID "MComprHD" (MAME Compressed Hunks of Data)
  008h 4    Header size    (7Ch=V5)
  00Ch 4    Header version (05h=V5)
  010h 4    Compressor 0 (usually "cdlz"=cdrom/lzma)
  014h 4    Compressor 1 (usually "cdzl"=cdrom/zlib)
  018h 4    Compressor 2 (usually "cdfl"=cdrom/flac)
  01Ch 4    Compressor 3 (usually 0=none)
  020h 8    Total size of all uncompressed hunks    (N*4C80h-HunkPadding)
  028h 8    Offset to Map                           (3D797h)
  030h 8    Offset to first Metadata chunk          (7Ch)
  038h 4    Number of bytes per hunk (512k maximum) (990h*8) (4C80h)
  03Ch 4    Number of bytes per sector              (990h)   (30h+60h)
  040h 14h  SHA1 on raw data
  054h 14h  SHA1 on raw+meta
  068h 14h  SHA1 on raw+meta of parent (0=No parent)
  ...  ..   Metadata Chunk(s)
  ...  ..   Padding to BytesPerHunk-boundary    ;\when uncompressed
  ...  ..   Uncompressed Sectors (aka hunks)    ;/
  ...  ..   Compressed Sectors (aka hunks)      ;-when compressed
  ...  ..   Map
 ________________________________ CHD Metadata ________________________________

V3/V4/V5 Metadata
Overall Metadata chunk format:
  000h 4   Chunk ID (aka Blob Tag) (eg. "CHT2" for each CDROM track)
  004h 1   Flags (00h=V3, 01h=V4/V5)  ;maybe some kind of flag/type/version?
  005h 3   Chunk Data Size (24bit)
  008h 8   Offset to next Chunk (or 0=Last chunk)
  010h ..  Chunk Data (eg. "TRACK:1 TYPE:MODE2_RAW ... POSTGAP:0",00h for CHT2)
There can be one or more chunks (eg. CHT2 chunk(s), one for each CDROM track).
  Summary of Chunk IDs and corresponding Data entries:
  ID_______Data_______________________________________________________
  "GDDD"   "CYLS,HEADS,SECS,BPS"         ;-hard disk standard info     ;\
  "IDNT"   ?                             ;-hard disk identify info     ; HDD
  "KEY "   ?                             ;-hard disk key info          ;/
  "CIS "   ?                             ;-pcmcia CIS info             ;-PCMCIA
  "CHCD"   94Ch-byte binary (4+99*24 bytes)                            ;\
  "CHTR"   "TRACK TYPE SUBTYPE FRAMES"                                 ; CD-ROM
  "CHT2"   "TRACK TYPE SUBTYPE FRAMES PREGAP PGTYPE PGSUB POSTGAP"     ;/
  "CHGT"   ?                                                           ;\Sega
  "CHGD"   "TRACK TYPE SUBTYPE FRAMES PAD PREGAP PGTYPE PGSUB POSTGAP" ;/GD-ROM
  "AVAV"   "FPS WIDTH HEIGHT INTERLACED CHANNELS SAMPLERATE"           ;\AV
  "AVLD"   ?   (A/V Laserdisc frame)                                   ;/
  "DVD "   ?   (for PSP's UMD)                                         ;-DVD

V3/V4/V5 Metadata in ASCII format
The ASCII items are separated by spaces as shown above (or commas for GDDD).
The last item in each chunk is terminated by 00h (at least so for CHTR/CHT2).
Most items are followed by a colon and decimal string (eg. TRACK:1), except, TYPE,PGTYPE,SUBTYPE,PGSUB are followed by text strings (eg. TYPE:MODE2_RAW).
  CYLS:#          Hard disc number of cylinders
  HEADS:#         Hard disc number of heads
  SECS:#          Hard disc number of sectors
  BPS:#           Hard disc bytes per sector
  TRACK:#         CDROM current track number (1..99)
  TYPE:string     CDROM sector type/size
  SUBTYPE:string  CDROM subchannel info (usually "NONE")
  FRAMES:#        CDROM number of sectors per track (with/without pregap?)
  PAD:#           Sega GDROM only: whatever pad value?
  PREGAP:#        CDROM ... maybe number of pregap sectors? (can be HUGE !!??)
  PGTYPE:string   CDROM ... whatever type?                  (usually "MODE1"??)
  PGSUB:string    CDROM ... whatever subchannel             (usually "RW"??)
  POSTGAP:#       CDROM ... maybe number of pstgap sectors? (usually 0)
  FPS:#.######    AV Video(?)-frames per second? with 6-digit fraction? (.avi?)
  WIDTH:#         AV Width      (maybe in pixels?)
  HEIGHT:#        AV Height     (maybe in pixels?) (with/without interlace?)
  INTERLACED:#    AV Interlace  (maybe a flag that might be maybe 0 or 1?)
  CHANNELS:#      AV Channels   (maybe audio mono/stereo or so?)
  SAMPLERATE:#    AV Samplerate (maybe audio samplerate, maybe in Hertz?)
 For SUBTYPE and PGSUB:
  "RW"      60h-byte interleaved   ;normal "cooked" 96 bytes per sector
  "RW_RAW"  60h-byte uninterleaved ;raw uninterleaved 96 bytes per sector
  "NONE"    0-byte                 ;no subcode data stored (default)
  (unknown how RAW and RW_RAW differ, one format does probably store 8 bits
  for 8 subchannels per byte... but unknown which format is doing so?)
 For TYPE and PGTYPE (and CHCD numeric type 0..7):
  "MODE1/2048" or "MODE1"                   CHCD=0  800h-byte ;\Data Mode1
  "MODE1/2352" or "MODE1_RAW"               CHCD=1  930h-byte ;/
  "MODE2/2336" or "MODE2"          ;\dupe?  CHCD=2  920h-byte ;\
  "MODE2/2336" or "MODE2_FORM_MIX" ;/       CHCD=5  920h-byte ;
  "MODE2/2048" or "MODE2_FORM1"             CHCD=3  800h-byte ; Data Mode2
  "MODE2/2324" or "MODE2_FORM2"             CHCD=4  914h-byte ;
  "MODE2/2352" or "MODE2_RAW" or "CDI/2352" CHCD=6  930h-byte ;/
  "AUDIO" (stored as big-endian samples!!!) CHCD=7  930h-byte ;-Audio CD-DA
Caution:
AUDIO sectors are conventionally stored as 16bit little-endian samples, but CHD is storing them in big-endian (unlike formats like CUE/BIN).
Caution:
Older CHDMAN versions (eg. v0.146) did use nonsense "PGTYPE:MODE1" for all tracks (including audio tracks), later versions (eg. v0.246) did fix that issue; those newer files include a "V" prefix to indicate that the entry contains "valid" info (eg. "PGTYPE:VAUDIO") (except, Track 1 keeps using "PGTYPE:MODE1" without "V" and it's "MODE1" even on MODE2 discs).

CHCD Metadata (94Ch bytes, plus 10h-byte metadata header)
  000h 4     Number of tracks (N) (1..99)
  004h N*18h Track entries
  ...  ..    Zeropadding to 94Ch-byte size (when less than 99 tracks)
 Track entries:
  000h 4     Track Type       (0..7, CHCD=# in above table) (eg. 6=MODE2_RAW)
  004h 4     Subchannel Type  (0=RW, 1=RW_RAW, 2=None)
  008h 4     Sector Size      (800h, 914h, 920h or 930h)
  00Ch 4     Subchannel Size  (0 or 60h)
  010h 4     Number of Frames (aka number of sectors)
  014h 4     Padding Frames   (0..3) (to make Total Frames a multiple of 4)


 __________________________________ CHD Maps __________________________________

The Maps contain info (offset, size, compression method, etc.) for the separate compression blocks.

V1/V2 map format (64bit entries with 44bit+20bit):
  44bit     Offset to compressed data
  20bit     Size of compressed data (or uncompressed data when size=hunksize)
Unknown if offset is in upper or lower 44bit.

V3/V4 map entries (per hunk):
  000h 8    Offset to compressed data  (64bit big-endian)
  008h 4    CRC32 on uncompressed data (32bit big-endian)
  00Ch 3    Size of compressed data    (24bit mixed-endian: Mid, Low, High)
  00Fh 1    Flags, indicating compression info (=whut? maybe below V34 stuff?)
V34_MAP_ENTRY_FLAG_TYPE_MASK = 0x0f; // what type of hunk
V34_MAP_ENTRY_FLAG_NO_CRC = 0x10; // no CRC is present (which CRC?)
V3-V4 entry types
  V34_MAP_ENTRY_TYPE_INVALID        = 0  invalid type
  V34_MAP_ENTRY_TYPE_COMPRESSED     = 1  standard compression
  V34_MAP_ENTRY_TYPE_UNCOMPRESSED   = 2  uncompressed data
  V34_MAP_ENTRY_TYPE_MINI           = 3  mini: use offset as raw data
  V34_MAP_ENTRY_TYPE_SELF_HUNK      = 4  same as another hunk in this file
  V34_MAP_ENTRY_TYPE_PARENT_HUNK    = 5  same as a hunk in the parent file
  V34_MAP_ENTRY_TYPE_2ND_COMPRESSED = 6  compressed with secondary algorithm
Note: Secondary algorithm is NEVER used (it seems to have been intended for FLAC CDDA, but that was apparently never actually implemented in V3/V4).
Blurp: Secondary algorithm is "usually FLAC CDDA" (unknown where that is defined, and if one could also select other algorithms) ("usually FLAC" might mean "always FLAC" for cdroms, and "not used" elsewhere).

V5 Map Formats
 V5 uncompressed map format (when [filehdr+10h]=00000000h):
  000h N*4  Hunk List (32bit offsets: Offset/BytesPerHunk) (usually 1,2,3..)
 V5 compressed map format (when [filehdr+10h]<>00000000h):
  000h 4    Length of compressed map
  004h 6    Offset of first block (48bit)     (E4h, after meta)
  00Ah 2    CRC16 on decompressed map entries
  00Ch 1    bits used to encode complength
  00Dh 1    bits used to encode self-refs
  00Eh 1    bits used to encode parent unit refs
  00Fh 1    Reserved for future use (probably zero)
  010h ..   Compressed Map entries (bitstream with Huffman/RLE encoding)
 The decompressed map entries should look as shown below (one could store them
 differently, eg. as 32bit little endian values; however, they must be stored
 exactly as shown below when computing the CRC16 on decompressed map entries):
  000h 1    Compression type (0..3=Codec0..3, 4=Uncompressed, 5=Self, 6=Parent)
  001h 3    Compressed length (24bit big-endian)
  004h 6    Offset to compressed data (48bit big-endian)
  00Ah 2    CRC16 on decompressed data (big-endian)
 V5 compression codecs:
  0,0,0,0 = CHD_CODEC_NONE        ;-unused (when using less than 4 codecs)
  "zlib" = CHD_CODEC_ZLIB         ;\
  "lzma" = CHD_CODEC_LZMA         ; general codecs
  "huff" = CHD_CODEC_HUFFMAN      ;
  "flac" = CHD_CODEC_FLAC         ;
  "zstd" = CHD_CODEC_ZSTD         ;/
  "cdzl" = CHD_CODEC_CD_ZLIB      ;\
  "cdlz" = CHD_CODEC_CD_LZMA      ; general codecs with CD frontend
  "cdfl" = CHD_CODEC_CD_FLAC      ;
  "cdzs" = CHD_CODEC_CD_ZSTD      ;/
  "avhu" = CHD_CODEC_AVHUFF       ;-A/V codecs

Uncompressed V5 Map loading (when [filehdr+10h]=00000000h)
  readfile(src,NumberOfHunks*4)                            ;\
  i=0                                                      ; load uncomoressed
  while i<NumberOfHunks                                    ; map (needed only
    ofs=bigendian32bit[src+i*4]*BytesPerHunk               ; for uncompressed
    byte[map+i*0Ch+00h]=04h             ;typ=Uncompressed  ; files, which can
    bigendian24bit[map+i*0Ch+01h]=BytesPerHunk             ; be created via
    bigendian48bit[map+i*0Ch+04h]=ofs                      ; chdman commandline
    bigendian16bit[map+i*0Ch+0Ah]=none  ;no crc            ; options)
    ofs=ofs+len, i=i+1                                     ;/

Compressed V5 Map loading (when [filehdr+10h]<>00000000h)
  readfile(hdr,10h)                                        ;\read map hdr and
  readfile(src,bigendian32bit[hdr+0])                      ; compressed map
  InitBitstream(src,BigEndianMsbFirst)                     ;/
  i=0                                                      ;\
  while i<10h                                              ;
    val=GetBits(4), num=1                                  ;
    if val=01h then                                        ; read huffman tree
      val=GetBits(4)                                       ;
      if val<>01h then num=GetBits(4)+3                    ;
    for j=1 to num, codesizes[i]=val, i=i+1                ;
  nonlzh_explode_tree(codetree,codesizes,10h)              ;/
  i=0, typ=0, num=0                                        ;\
  while i<NumberOfHunks                                    ;
    if num=0                                               ; load huffman coded
      x=GetHuffCode(codetree)                              ; map type values
      if x=07h then      ;COMPRESSION_RLE_SMALL            ;
        num=GetHuffCode(codetree)+03h                      ;
      elseif x=08h then  ;COMPRESSION_RLE_LARGE            ;
        num=GetHuffCode(codetree)*10h                      ;
        num=GetHuffCode(codetree)+num+13h                  ;
      else typ=x, num=1                                    ;
    byte[map+i*0Ch+0]=typ, i=i+1, num=num-1                ;/
  i=0, s=0, p=0             ;index,self,parent             ;\
  o=bigendian48bit[hdr+4]   ;offset                        ; load other
  while i<NumberOfHunks                                    ; map items
    typ=byte[map+i*0Ch+00h], ofs=o, len=0, crc=0           ;
    if typ<04h then len=GetBits([hdr+0Ch]), crc=GetBits(16);  ;Method 0..3
    elseif typ=04h then len=BytesPerHunk, crc=GetBits(16)  ;  ;Uncompressed
    elseif typ=05h then s=GetBits([hdr+0Dh]), ofs=s        ;  ;New Self
    elseif typ=06h then p=GetBits([hdr+0Eh]), ofs=p        ;  ;New Parent
    elseif typ=09h then typ=05h, ofs=s                     ;  ;Old Self
    elseif typ=0Ah then typ=05h, s=s+1, ofs=s              ;  ;Old Self+1
    elseif typ=0Bh then typ=06h, p=i*SectorsPerHunk, ofs=p ;  ;Direct Parent
    elseif typ=0Ch then typ=06h, ofs=p                     ;  ;Old Parent
    elseif typ=0Dh then typ=06h, p=p+SectorsPerHunk, ofs=p ;  ;Old Parent+1
    else goto error                                        ;
    byte[map+i*0Ch+00h]=typ                                ;
    bigendian24bit[map+i*0Ch+01h]=len                      ;
    bigendian48bit[map+i*0Ch+04h]=ofs                      ;
    bigendian16bit[map+i*0Ch+0Ah]=crc                      ;
    o=o+len, i=i+1                                         ;/
  if bigendian16bit[hdr+0Ah]<>noncrc16(map,i*0Ch) then error ;-final crc check
noncrc16: Uses the same polynomial as for CDROM subchannels, but with initial value FFFFh (instead 0) and with final value left un-inverted (instead of inverting it).
nonlzh_explode_tree: Uses the same concept as for LZH/ARJ huffman trees (it's storing only the number of bits per each codes, and the codes are then automatically assigned). But CHD is doing that backwards: It's starting with the biggest codes (instead of smallest codes). For example, if you have three codes with size 1, 2, 2. The traditional standard assignment would be 0, 10, 11. But CHD is instead assigning them as 00, 01, 1.

 ______________________________ CHD Compression _______________________________

Compression V1-V4 format 0 (uncompressed)
Compression V5 0,0,0,0 (uncompressed)
  000h ..   Uncompressed data
Uncompressed format can be selected in CHD Map entries (per hunk), and in CHD file header (per whole file).

Compression V1-V4 format 1 (zlib) (Generic Deflate)
Compression V1-V4 format 2 (zlib+) (Generic Deflate)
Compression V5 "zlib" (Generic Deflate)
  000h ..   Deflate-compressed data

Compression V5 "lzma" (Generic LZMA)
  000h ..   LZMA-compressed data (with lc=3, lp=0, pb=2) (without EOS end code)

Compression V5 "flac" (Generic FLAC)
  000h 1    Output format for 16bit samples ("L"=Little-endian, "B"=Big-endian)
  001h ..   FLAC-compressed data frame(s)

Compression V5 "huff" (Generic Huffman)
  000h ..   Huffman-compressed data (small tree, large tree, plus data)

Compression V5 "cdzl" (CDROM Deflate+Deflate)
  000h ..   ECC Flags, (SectorsPerHunk+7)/8 bytes ;little-endian, bit0=1st flag
  ...  2/3  Size of compressed Data part (SIZ)    ;big-endian, 16bit or 24bit
  ...  SIZ  Deflate compressed Data part          ;uncompressed=930h*N bytes
  ...  ..   Deflate compressed Subchannel part    ;uncompressed=60h*N bytes

Compression V5 "cdlz" (CDROM LZMA+Deflate)
  000h ..   ECC Flags, (SectorsPerHunk+7)/8 bytes ;little-endian, bit0=1st flag
  ...  2/3  Size of compressed Data part (SIZ)    ;big-endian, 16bit or 24bit
  ...  SIZ  LZMA compressed Data part             ;uncompressed=930h*N bytes
  ...  ..   Deflate compressed Subchannel part    ;uncompressed=60h*N bytes

Compression V5 "cdfl" (CDROM FLAC+Deflate)
  000h ..   FLAC-compressed Data Frame(s)         ;uncompressed=930h*N bytes
  ...  ..   Deflate compressed Subchannel part    ;uncompressed=60h*N bytes

Compression V5 "avhu" (A/V mixup with Huffman and FLAC or so)
This isn't used on CDROMs and details are unknown/untested. It does reportedly exist in different versions, and does combine different compression methods for audio and video data.

Compression V4 format 3 (AV)
Unknown, maybe same/similar as "avhu".

Compression V3-V4 secondary compression method (FLAC CDDA)
CHD source code claims that V3-V4 maps support "FLAC CDDA", but it doesn't actually seem to support that (audio discs compressed with chdman v0.145 are merely using Deflate).

 _________________________ CHD Compression for CDROMs _________________________

CDROM "cdzl" and "cdlz"
If the sector's ECC flag is set:
  Fix the 0Ch-byte Sync mark at [000h..00Bh]
  Fix the 114h-byte ECC data at [81Ch..92Fh] in relation to Mode at [00Fh]
  Fixing just means to overwrite those values (there's no XOR-filter or so).
  CHD doesn't filter EDC values, MM:SS:FF:Mode Sector headers, nor Subheaders.
The Size entry is 16bit (when N*990h<10000h) or 24bit (when N*990h>=10000h), the size entry has no real purpose, however, it may be useful for:
  decompressing the subchannel part without decompressing the whole data part,
  and for using libraries that don't return the end of the compressed data part

CDROM "cdfl"
There are no ECC flags (since Audio sectors don't have ECC).
There is no size entry (one must decompress the whole FLAC part to find the begin of the Subchannel part).
The FLAC output is always stored in BIG-ENDIAN format (because CHD likes to use big-endian for audio sectors, unlike formats like CUE/BIN).

CDROM Subchannel data
The Data part and Subchannel part must be interleaved after decompression (to form 990h-byte sectors with 930h+60h bytes). The CHD map's CRC is then computed on that interleaved data.
Most CHD files use metadata SUBTYPE:NONE which means that the 60h-byte subchannel data is simply zerofilled and one must replace it by default Index/Position values (AFTER the above CRC check). The CHD metadata lacks accurate info about Index values; the PREGAP part is supposedly meant to have Index=0 and the remaining sectors Index=1).
Although CHD files can contain subchannel data, CHDMAN has very limited support for creating such files (the most practical way seems to be to convert CCD/IMG/SUB to TOC/BIN and then convert that to CHD format).

 ___________________________ CHD CDROM Sector Sizes ___________________________

Decompressed CHD CDROM Sectors are always 990h bytes tall (930h+60h). However, the Metadata TYPE/SUBTYPE entries may specify smaller sizes (corresponding to the format of the original TOC/BIN or CUE/BIN image). CHD does arrange that data as so:
  000h  Sector Data                    (800h, 914h, 920h or 930h bytes)
  ...   Subchannel Data                (0 or 60h bytes)
  ...   Zeropadding to 990h-byte size  (0..190h bytes)
That is somewhat okay for V3/V4 files, but involves two design mistakes that conflict with the V5 format:
  - The ECC-Filter works only for 930h-byte sectors (920h does also contain
    ECC, but CHD can't filter that, resulting in very bad compression ratio)
  - The last 60h-byte are supposed to be Deflate-compressed Subchannel Data
    (but 800h..920h+60h sectors actually contain Zeropadding in that location)
Note: The CHD Map CRC checks are done on the above arrangement (including zeropadding, and any prior ECC-unfiltering).
After the CRC check, one most relocate the Sector/Subchannel parts to their actual locations (and replace zeropadding by actual Sync marks, header, sub-header, ECC/EDC, and Subchannel data as needed).

 __________________________ CHD Compression Methods ___________________________

Deflate
This is raw Deflate (despite of being called "zlib" in chd headers and source code; there aren't any ZLIB headers nor Adler checksums). V1-V4 does distinguish between "zlib" and "zlib+" (both are using normal Deflate) (V3/V4 are always using "zlib+") (the "+" does probably just mean that file was compressed with improved compression ratio).
CDROM File Compression ZIP/GZIP/ZLIB (Inflate/Deflate)

LZMA
This contains a raw LZMA bitstream (without .lzma or .lz headers). The LZMA bitstream starts with 8 ignored bits, if Normalization occurs after last compression code, then it will also end with 8 ignored bits (those ignored bits aren't CHD-specific, they do also occur in other LZMA-based formats).
CDROM File Compression LZMA

FLAC
The data consists of raw FLAC Frames (without FLAC file header or FLAC metadata blocks), the format is always signed 16bit/stereo (NumChannels=2 SampleDepth=16), the sample rate is don't care for compression purposes (the FLAC Frame headers have it set to 09h=44100Hz).
Each FLAC Frame starts with a 14bit Sync mark (3FFEh), and ends with 16bit CRC. There are usually several FLAC frames per CHD hunk (one must decompress all FLAC frames, until reaching the decompressed hunk size).
Each FLAC Frame contains Left samples, followed by Right samples. After decompression, CHD does store them in interleaved form (L,R,L,R,etc.)
CDROM File Compression FLAC audio

Huffman
This is using some custom CHD-specific Huffman compression.
 decompress_chd_huffman_hunk:
  InitBitstream(src,BigEndianMsbFirst)                               ;-init
  codesizes[0..17h]=00h                     ;initially all unused    ;\
  codesizes[0]=GetBits(3)                   ;get first entry         ;
  i=GetBits(3)+1                            ;leading unused entries  ; small
 @@small_tree_lop:                                                   ; tree
  val=GetBits(3)                                                     ;
  if val=07h then goto @@small_tree_done    ;trailing unused entries ;
  codesizes[i]=val, i=i+1                   ;apply entry             ;
  if i<18h then goto @@small_tree_lop                                ;
 @@small_tree_done:                                                  ;
  nonlzh_explode_tree(codetree,codesizes,18h)                        ;/
  data=00h                                                           ;\
 @@large_tree_lop:                                                   ;
  val=GetHuffCode(codetree)-1               ;using small tree codes  ; large
  if val>=00h then                                                   ; tree
    data=val, codesizes[i]=data, i=i+1                               ;
  else                                                               ;
    len=GetBits(3)+2                                                 ;
    if len=7+2 then len=GetBits(8)+7+2                               ;
    for n=1 to len, codesizes[i]=datal, i=i+1                        ;
  if i<100h then goto @@large_tree_lop                               ;
  nonlzh_explode_tree(codetree,codesizes,100h)                       ;/
  for n=1 to decompressed_size                                       ;\data
    [dst]=GetHuffCode(codetree), dst=dst+1  ;using large tree codes  ;/


 _________________________________ CHD Notes __________________________________

Track/Hunk Padding and Missing Index0 sectors
A normal CDROM contains a series of sectors. The CHD format is violating that in several ways: It's removing Index0/Pregap sectors, and it's instead inserting dummy/padding sectors between tracks.
  Track        <---- Track1---------> <---- Track2---------> <--End-->
  Section      Index0 IndexN TrackPad Index0 IndexN TrackPad HunkPad
  Real Disc    Yes    Yes    -        Yes    Yes    -        -
  CHD Header   -      Yes    Yes      -      Yes    Yes      -
  CHD Data     -      Yes    Yes      -      Yes    Yes      Yes
That is, the critical parts are:
  Index0/pregap:  Metadata PREGAP:sectors isn't stored in compressed data
  Track padding:  Metadata FRAMES:sectors is rounded up to N*4 sectors
  Hunk padding:   The last hunk is additionally rounded up to hunksize
Missing Index0 might be a problem if a disc contains nonzero data between tracks (like audio discs with applause in Index0 periods).
Track padding is total nonsense. The final hunk padding makes sense (but confusingly that extra padding isn't included in the uncompressed size entry in CHD header).

Parent references
Parent files are only used for writeable media like harddisks. The idea is to store the original installation and operating system in a readonly Parent file, and to store changes that file in a writeable Child file.
Unknown what determines which parent belongs to which child, and if parents can be nested with other grandparents. Anyways, Parents aren't needed for CDROMs (except, one could theoretically store CDROM patches in child files).

Self references
This can be used to reference to another identical hunk in the same file (eg. zerofilled sectors or other duplicated data). There are some restrictions for CDROMs: Data sector headers contain increasing sector numbers, so there won't be any identical sectors. However, Audio sectors can be identical (unless they are stored with subchannel info, which does also contain increasing sector numbers).

Mini
Mini is only used in V3/V4 maps. It does apparently store the "data" directly in the 8-byte Map offset field.
  XXX Unknown what kind of "data" that is
  (probably "normal compressed data", that happens to be 8 bytes or smaller).
Mini isn't used in V5 because the compressed V5 map doesn't contain any offset fields (and things like zerofilled sectors could be as well encoded as Self instead of Mini).

CHDMAN versions
CHD files can (cannot) be generated with the CHDMAN.EXE tool:
  chdman hdr meta  features/requirements/bugs/quirks/failures...
  v0.58  -   -     -   ;-CHD didn't exist in older MAME versions
  v0.59  V1  -     -   ;\
  v0.71  V2  -     -   ; supports harddisk CHD files only, not cdrom
  v0.78  V3  xxxx  -   ;/
  v0.81  V3  CHCD  bad ;-crashes after creating the CHD file header
  v0.90  V3  CHCD  ok  ;\
  v0.110 V3  CHCD  ok  ; requires cdrdao TOC/BIN as input (CUE/BIN does crash)
  v0.111 V3  CHTR  ok  ; (warning: BIN filenames may not contain space chars!)
  v0.112 V3  CHTR  bug ;    ;\works, but compression is somewhat bugged (files
  v0.118 V3  CHTR  bug ;    ;/are BIGGER instead of SMALLER after compression)
  v0.120 V3  CHTR  ok  ;
  v0.130 V3  CHTR  ok  ;
  v0.131 V4  CHTR  ok  ;/
  v0.140 V4  CHT2  ok  ;\requires "unicows.dll" (=Quintessential Media Player)
  v0.145 V4  CHT2  ok  ;/
  v0.146 V5  CHT2  bad ;\says output file already exists (crashes on -f force)
  v0.154 V5  CHT2  bad ;/
  v0.155 V5  CHT2  bad ;\crashes instantly (shortly before CreateEventW)
  v0.160 V5  CHT2  bad ;/
  v0.161 V5  CHT2  bad ;\says output file already exists (crashes on -f force)
  v0.169 V5  CHT2  bad ;/
  v0.170 V5  CHT2  bad ;\missing KERNEL32.DLL:AddVectoredExceptionHandler
  v0.217 V5  CHT2  bad ;/
  v0.218 V5  CHT2  bad ;\requires "newer version of windows" (64bit)
  v0.247 V5  CHT2  bad ;/
  v0.265 ?   ?     bad ;-missing KERNEL32.DLL:GetModuleHandleExW
Note: The compression tool was originally called HDCOMP (V1/V2), and later renamed to CHDMAN (V3/V4/V5).

References
CHD source code (see files cdrom.*, chd*.*, etc):
  https://github.com/mamedev/mame/tree/master/src/lib/util
CHDMAN commandline tool for generating chd files:
  https://github.com/mamedev/mame/blob/master/src/tools/chdman.cpp
CHD decompression clone with useful comments:
  https://github.com/SnowflakePowered/chd-rs/tree/master/chd-rs/src
CHD format reverse-engineering thread:
  http://www.psxdev.net/forum/viewtopic.php?f=70&t=3980


CDROM Disk Images Other Formats

.ISO - A raw ISO9660 image (can contain a single data track only)
Contains raw sectors without any sub-channel information (and thus it's restricted to the ISO filesystem region only, and cannot contain extras like additional audio tracks or additional sessions). The image should start at 00:02:00 (although I wouldn't be surprised if some <might> start at 00:00:00 or so).
Obviously, all sectors must have the same size, either 800h or 930h bytes (if the image contains only Mode1 or Mode2/Form1 sectors then 800h bytes would usually enough; if it contains one or more Mode2/Form2 sectors then all sectors should be 930h bytes).
  800h-byte ISO's seem to be most common (for non-PSX images)
  930h-byte ISO's are sometimes used for PSX-images (but lack CDDA tracks)
Filename Extension:
  Raw ISO's for PSX do often have extension .BIN instead of .ISO
  (that's bad because Open File Menues usually don't show .BIN files,
  because .BIN is usually expected to be bundled with .CUE sheet files)
Handling .ISO files does thus require to detect the image's sector size, and to search the sector that contains the first ISO Volume Descriptor. In case of 800h byte sectors it may be additionally required to detect if it is a Mode1 or Mode2/Form1 image; for PSX images (and any CD-XA images) it'd be Mode2.

.C2D
Something. Can contain compressed or uncompressed CDROM-images. Fileformat and compression ratio are unknown. Also unknown if it allows random-access.
Some info on (uncompressed) .C2D files can be found in libmirage source code.

.ISZ - compressed ISO file with 800h-byte sectors (UltraISO)
This contains a compressed ISO filesystem, without supporting any CD-specific features like Tracks, FORM2 sectors, or CD-DA Audio.
  http://www.ezbsystems.com/isz/iszspec.txt
The format might be suitable for PC CDROMs, but it's useless for PSX CDROMs.


.MDX
Reportedly a "compressed" MDS/MDF file, supported by Daemon Tools.
Other info says that MDX is just MDS/MDF merged into a single file, without mentioning any kind of "compression" support.
Basically... Daemon Tools is Adware that can merge MDS+MDF into one MDX file... with additional Advertising?
However, the MDS+MDF format is completely different than MDX format:
  000h 10h  ID ("MEDIA DESCRIPTOR") (weirdly, same as in Alcohol .MDS)
  010h 2    Unknown (02h,01h) (maybe version or so)
  012h 1Ah  Copyright string (A9h," 2000-2015 Disc Soft Ltd.")
  02Ch 4    Unknown (FFFFFFFFh)
  030h 4    Offset to Unknown Footer (322040h) (N*800h+40h)
  034h 4    Unknown (0)
  038h 4    Unknown (B0h)
  03Ch 4    Unknown (0)
  040h N*800h  Sector Data
  322040h 270h Unknown (Advertising IDs? CRCs? Encrypted CUE sheet? Garbage?)


.CU2/.BIN
Custom format used by PSIO (an SD-card based CDROM-drive emulator connected to PSX expansion port). The .CU2 file is somewhat intended to be smaller and easier to parse than normal .CUE files, the drawback is that it's kinda non-standard, and doesn't support INDEX and ADSR information. A sample .CUE file looks as so:
  ntracks 3
  size      39:33:17
  data1     00:02:00
  track02   31:36:46
  track03   36:03:17
  ;(insert 2 blanks lines here, and insert 1 leading space in next line)
  trk end 39:37:17
All track numbers and MM:SS:FF values are decimal. The ASCII strings should be as shown above, but they are simple ignored by the PSIO firmware (eg. using "popcorn666" instead of "size" or "track02" should also work). The first track should be marked "data1", but PSIO ignores that string, too (it does always treat track 1 as data, and track 2-99 as audio; thus not supporting PSX games with multiple data tracks). The "trk end" value should be equal to the "size" value plus 4 seconds (purpose is unknown, PSIO does just ignore the "trk end" value).
CU2 creation seems to require CDROM images in "CUE/BIN redump.org format" (with separate BIN files for each track), the CUE is then converted to a CU3 file (which is used only temporarily), until the whole stuff is finally converted to a CU2 file (and with all tracks in a single BIN file). Tools like RD2PSIO (aka redump2psio) or PSIO's own SYSCON.ZIP might help on doing some of those steps automatically.
Alongsides, PSIO uses a "multidisc.lst" file... for games that require more than one CDROM disc?

CD Image File Format (Xe - Multi System Emulator)
This is a rather crude file format, used only by the Xe Emulator. The files are meant to be generated by a utility called CDR (CD Image Ripper), which, in practice merely displays an "Unable to read TOC." error message.
The overall file structure is, according to "Xe User's Manual":
  header: 200h bytes header (see below)
  data:   990h bytes per sector (2352 Main, 96 Sub), 00:00:00->Lead Out
The header "definition" from the "Xe User's Manual" is as unclear as this:
  000h   00
  001h   00
  002h   First Track
  003h   Last Track
  004h   Track 1 (ADR << 4) | CTRL              ;\
  005h   Track 1 Start Minutes                  ; Track 1
  006h   Track 1 Start Seconds                  ;
  007h   Track 1 Start Frames                   ;/
  ...     ...                                   ;-Probably Further Tracks (?)
  n+0    Last Track Start Minutes               ;\
  n+1    Last Track Start Seconds               ; Last Track
  n+2    Last Track Start Frames                ;
  n+3    Last Track (ADR << 4) | CTRL           ;/
  n+4    Lead-Out Track Start Minutes           ;\
  n+5    Lead-Out Track Start Seconds           ; Lead-Out
  n+6    Lead-Out Track Start Frames            ;
  n+7    Lead-Out Track (ADR << 4) | CTRL       ;/
  ...    00
  1FFh   00
Unknown if MM:SS:FF values and/or First+Last Track numbers are BCD or non-BCD.
Unknown if Last track is separately defined even if there is only ONE track.
Unknown if Track 2 and up include ADR/Control (and if yes: where?).
Unknown if ADR/Control is really meant to be <before> MM:SS:FF on Track 1.
Unknown if ADR/Control is really meant to be <after> MM:SS:FF on Last+Lead-Out.
Unknown if this format does have a file extension (if yes: which?).
Unknown if subchannel data is meant to be interleaved or not.
The format supports only around max 62 tracks (in case each track is 4 bytes).
There is no support for "special" features like multi-sessions, cd-text.


CDROM Patch Files

Playstation Patch File (.PPF)
The .PPF format allows to patch CDROM images (such like removing LibCrypt protections, or applying cheats or translations) and one could then burn the patched image. The older .IPS supported only 24bit offsets (which could only patch the first 16Mbyte of CDROM images). The .PPF patch offsets must match up with sector size of the CDROM image (PPF is apparently expecting 930h-byte sectors).

PPF Header v1.0
  000h 5      PPF Header ID ("PPF10")
  005h 1      Encoding Method (0=v1.0)
  006h 32h    Patch Description (50 chars, space-padded)
  038h ..     Patch entries

PPF Header v2.0
  000h 5      PPF Header ID ("PPF20")
  005h 1      Encoding Method (0=v1.0, 1=v2.0) (usually 1)
  006h 32h    Patch Description (50 chars, space-padded)
  038h 4      Filesize of patched image (usually multiple of 930h)
  03Ch 400h   Validation data (from .BIN offset 9320h)
  43Ch ..     Patch entries
  ...  (12h)  ID "@BEGIN_FILE_ID.DIZ"               ;\
  ...  (LEN)  ASCII text                            ; optional
  ...  (10h)  ID "@END_FILE_ID.DIZ"                 ; (as so in SLES-02080.PPF)
  ...  (4)    Size of ASCII text (LEN, 32bit)       ;/

PPF Header v3.0
  000h 5      PPF Header ID ("PPF30")
  005h 1      Encoding Method (0=v1.0, 1=v2.0, 2=v3.0) (usually 2)
  006h 32h    Patch Description (50 chars, space-padded)
  038h 1      Imagetype                (0=BIN, 1=GI PrimoDVD)
  039h 1      Validation data present  (0=No, 1=Yes)
  03Ah 1      Undo data present        (0=No, 1=Yes)
  03Bh 1      Dummy (not used)         (0)
  03Ch (400h) Validation data (from 9320h or 80A0h) ;-optional (when [039h]=1)
  ...  ..     Patch entries
  ...  (12h)  ID "@BEGIN_FILE_ID.DIZ"               ;\
  ...  (LEN)  ASCII text (max 3072 chars)           ; optional
  ...  (10h)  ID "@END_FILE_ID.DIZ"                 ; (as so in SLES-X2082.PPF)
  ...  (2)    Size of ASCII text (LEN, 16bit)       ;/
Validation is from offset 9320h (for Imagetype=0) or 80A0h (for Imagetype=1)

PPF Patch entries v1.0 and v2.0
  000h 4      Offset (32bit, good for CDROM)
  004h 1      Length
  005h LEN    New Data
Unknown if v1.0 and v2.0 differ somehow. PPF30 can reportedly also use the old v1.0/v2.0 entry format, but unknown if it could append Undo data to such entries).

PPF Patch entries v3.0
  000h 8      Offset (64bit, probably intended for DVD)
  008h 1      Length
  009h LEN    New Data
  ...  (LEN)  Old Data for undo                   ;-optional (when [03Ah]=1)

Notes
PPF10 files do usually include patches for ECC/EDC checksums, but PPF20/PPF30 seem to omit them (so the patching tool or external tools need to fix ECC/EDC after patching).
The FILE_ID.DIZ feature was added because Amiga users would do such things; To find the end of the Patch area, one could look for the "@BEGIN" string, or check if "@END" occurs ar EOF-14h (PPF20) or EOF-12h (PPF30), and then use the Size entry at EOF-4 or EOF-2 to navigate to the "@BEGIN" location.

References
https://raw.githubusercontent.com/meunierd/ppf/master/ppfdev/PPF3.txt v3.0
https://raw.githubusercontent.com/file/file/master/magic/Magdir/console hdr's
https://alex-free.github.io/libcrypt-patcher/changelog.html source with PPF's


CDROM Internal Info on PSX CDROM Controller

PSX software can access the CDROM via Port 1F801800h..1F801803h (as described in the previous chapters). The following chapters describe the inner workings of the PSX CDROM controller - this information is here for curiosity only - normally PSX software cannot gain control of those lower-level stuff (although some low level registers can be manipulated via Test commands, but that will usually conflict with normal operation).

Motorola MC68HC05 (8bit single-chip CPU)
The Playstation CDROM drive is controlled by a MC68HC05 8bit CPU with on-chip I/O ports and on-chip BIOS ROM. There is no way to reprogram that BIOS, nor to tweak it to execute custom code in RAM.
CDROM Internal HC05 Instruction Set
CDROM Internal HC05 On-Chip I/O Ports
CDROM Internal HC05 I/O Port Usage in PSX
CDROM Internal HC05 Motorola Selftest Mode
The PSX can read HC05 I/O Ports and RAM via Test Commands:
CDROM - Test Commands - Read HC05 SUB-CPU RAM and I/O Ports

Decoder/FIFO (CXD1199BQ or CXD1815Q)
This chip handles error correction and ADPCM decoding, and acts as some sort of FIFO interface between main/sub CPUs and incoming cdrom sector data. On the MIPS Main CPU it is controlled via Port 1F801800h..1F801803h.
CDROM Controller I/O Ports
On the HC05 Sub CPU it is controlled via Port A (data in/out), Port E (address/index), and Port D (read/write/select signals); the HC05 doesn't have external address/data bus, so one must manually access the CXD1815Q via those ports.
CDROM Internal CXD1815Q Sub-CPU Configuration Registers
CDROM Internal CXD1815Q Sub-CPU Sector Status Registers
CDROM Internal CXD1815Q Sub-CPU Address Registers
CDROM Internal CXD1815Q Sub-CPU Misc Registers
The PSX can read/write the Decoder I/O Ports and SRAM via Test commands:
CDROM - Test Commands - Read/Write Decoder RAM and I/O Ports
The sector buffer used in the PSX is 32Kx8 SRAM. Old PU-7 boards are using CXD1199BQ chips, later boards are using CXD1815Q, and even later boards have the stuff intergrated in the SPU. Note: The CXD1199BQ/CXD1815Q are about 99% same as described in CXD1199AQ datasheet.

Signal Processor and Servo Amplifier
Older PSX mainboards are using two separate chips:
CDROM Internal Commands CX(0x..3x) - CXA1782BR Servo Amplifier
CDROM Internal Commands CX(4x..Ex) - CXD2510Q Signal Processor
Later PSX mainboards have the above intergrated in a single chip, with some extended features:
CDROM Internal Commands CX(0x..Ex) - CXD2545Q Servo/Signal Combo
Later version is CXD1817R (Servo/Signal/Decoder Combo).
Even later PSX mainboards have it integrated in the Sound Chip: CXD2938Q (SPU+CDROM) with some changed bits and New SCEx transfer:
CDROM Internal Commands CX(0x..Ex) - CXD2938Q Servo/Signal/SPU Combo
Finally, PM-41(2) boards are using a CXD2941R chip (SPU+CDROM+SPU_RAM), unknown if/how far the CDROM part of that chip differs from CXD2938Q.
Some general notes:
CDROM Internal Commands CX(xx) - Notes
CDROM Internal Commands CX(xx) - Summary of Used CX(xx) Commands
The PSX can manipulate the CX(..) registers via some test commands:
CDROM - Test Commands - Test Drive Mechanics
Note: Datasheets for CXD2510Q/CXA1782BR/CXD2545Q do exist.

CDROM Pinouts
Pinouts - DRV Pinouts
Pinouts - HC05 Pinouts


CDROM Internal HC05 Instruction Set

ALU, Load/Store, Jump/Call
  Opcode      Clk HINZC Name Syntax
  x6 ...      2-5 --NZ- LDA  MOV  A,<op>      ;A=op
  xE ...      2-5 --NZ- LDX  MOV  X,<op>      ;X=op
  x7 ...      4-6 --NZ- STA  MOV  <op>,A      ;op=A
  xF ...      4-6 --NZ- STX  MOV  <op>,X      ;op=X
  xC ...      2-4 ----- JMP  JMP  <op>        ;PC=op
  xD ...      5-7 ----- JSR  CALL <op>        ;[SP]=PC, PC=op
  xB ...      2-5 H-NZC ADD  ADD  A,<op>      ;A=A+op
  x9 ...      2-5 H-NZC ADC  ADC  A,<op>      ;A=A+op+C
  x0 ...      2-5 --NZC SUB  SUB  A,<op>      ;A=A-op
  x2 ...      2-5 --NZC SBC  SBC  A,<op>      ;A=A-op-C
  x4 ...      2-5 --NZ- AND  AND  A,<op>      ;A=A AND op
  xA ...      2-5 --NZ- ORA  OR   A,<op>      ;A=A OR op
  x8 ...      2-5 --NZ- EOR  XOR  A,<op>      ;A=A XOR op
  x1 ...      2-5 --NZC CMP  CMP  A,<op>      ;A-op
  x3 ...      2-5 --NZC CPX  CMP  X,<op>      ;X-op
  x5 ...      2-5 --NZ- BIT  TEST A,<op>      ;A AND op
  A7,AF,AC = Reserved (no STA/STX/JMP with immediate operand)
Operands can be...
  Opcode      Clk ALU/LDA/LDX      Clk STA/STX          Clk JMP/CALL
  Ax nn         2 cmd r,nn           - N/A              -/6 call relative (BSR)
  Bx nn         3 cmd r,[nn]         4 mov [nn],r       2/5 cmd nn
  Cx nn mm      4 cmd r,[nnmm]       5 mov [nnmm],r     3/6 cmd nnmm
  Dx nn mm      5 cmd r,[X+nnmm]     6 mov [X+nnmm],r   4/7 cmd X+nnmm
  Ex nn         4 cmd r,[X+nn]       5 mov [X+nn],r     3/6 cmd X+nn
  Fx            3 cmd r,[X]          4 mov [X],r        2/5 cmd X

Read-Modify-Write
  Opcode      Clk HINZC Name Syntax
  xC ...      3-6 --NZ- INC  INC op      ;increment   ;op=op+1
  xA ...      3-6 --NZ- DEC  DEC op      ;decrement   ;op=op-1
  xF ...      3-6 --01- CLR  ??  op,00h  ;clear       ;op=op AND 00h
  x3 ...      3-6 --NZ1 COM  NOT op      ;complement  ;op=op XOR FFh
  x0 ...      3-6 --NZC NEG  NEG op      ;negate      ;op=00h-op
  x9 ...      3-6 --NZC ROL  RCL op      ;rotate left through carry
  x6 ...      3-6 --NZC ROR  RCR op      ;rotate right through carry
  x8 ...      3-6 --NZC LSL  SHL op      ;shift left logical
  x4 ...      3-6 --0ZC LSR  SHR op      ;shift right logical
  x7 ...      3-6 --NZC ASR  SAR op      ;shift right arithmetic
  xD ...      3-5 --NZ- TST  TEST op,FFh ;test for negative or zero (AND FFh?)
  x1,x2,x5,xB,xE = Reserved (except for: 42 = MUL)
Operands can be...
  Opcode      Clk RMW          Clk CLR                Clk TST
  3x nn         5 cmd [nn]       5 MOV [nn],00h         4 TEST [nn],0FFh
  4x            3 cmd A          3 MOV A,00h,slow       3 TEST A,0FFh,slow
  5x            3 cmd X          3 MOV X,00h,slow       3 TEST X,0FFh
  6x nn         6 cmd [X+nn]     6 MOV [X+nn],00h       5 TEST [X+nn],0FFh
  7x            5 cmd [X]        5 MOV [X],00h          4 TEST [X],0FFh
CLR includes a dummy-read-cycle, whilst TST does omit the dummy-write cycle.
The ",slow" RMW opcodes are smaller, but slower than equivalent ALU opcodes.

Bit Manipulation and Bit Test with Relative Jump (to $+3+/-dd)
  Opcode      Clk HINZC Name  Syntax
  00h+i*2 nn dd 5 ----C BRSET JNZ [nn].i,dest  ;C=[nn].i, branch if set
  01h+i*2 nn dd 5 ----C BRCLR JZ  [nn].i,dest  ;C=[nn].i, branch if clear
  10h+i*2 nn    5 ----- BSET  SET [nn].i       ;set [nn].i
  11h+i*2 nn    5 ----- BCLR  RES [nn].i       ;clear [nn].i

Branch (Relative jump to $+2+/-nn)
  Opcode      Clk HINZC Name    Syntax
  20 nn         3 ----- BRA     JR  nn      ;branch always
  21 nn         3 ----- BRN     NUL nn      ;branch never
  22 nn         3 ----- BHI     JA  nn      ;if C=0 and Z=0, higher        ?
  23 nn         3 ----- BLS     JBE nn      ;if C=1 or Z=1, lower or same  ?
  24 nn         3 ----- BCC/BHS JNC/JAE nn  ;if C=0, carry clear, higher.same
  25 nn         3 ----- BCS/BLO JC/JB nn    ;if C=1, carry set, lower
  26 nn         3 ----- BNE     JNZ/JNE nn  ;if Z=0, not equal / not zero
  27 nn         3 ----- BEQ     JZ/JE nn    ;if Z=1, equal / zero
  28 nn         3 ----- BHCC    JNH nn      ;if H=0, half-carry clear
  29 nn         3 ----- BHCS    JH  nn      ;if H=1, half-carry set
  2A nn         3 ----- BPL     JNS nn      ;if S=0, plus / not signed
  2B nn         3 ----- BMI     JS  nn      ;if S=1, minus / signed
  2C nn         3 ----- BMC     JEI nn      ;if I=0, interrupt mask clear
  2D nn         3 ----- BMS     JDI nn      ;if I=1, interrupt mask set
  2E nn         3 ----- BIL     JIL nn      ;if XX=LO, interrupt line low
  2F nn         3 ----- BIH     JIH nn      ;if XX=HI, interrupt line high
  AD nn         6 ----- BSR     CALL relative nn  ;branch to subroutine always

Control/Misc
  Opcode      Clk HINZC Name Syntax
  9D            2 ----- NOP  NOP            ;no operation
  97            2 ----- TAX  MOV X,A        ;transfer A to X
  9F            2 ----- TXA  MOV A,X        ;transfer X to A
  9C            2 ----- RSP  MOV SP,00FFh   ;reset stack pointer (SP=00FFh)
  42           11 0---0 MUL  MUL X,A        ;X:A=X*A (unsigned multiply)
  81            6 ----- RTS  RET            ;return from subroutine
  80            9 xxxxx RTI  RETI           ;return from interrupt
  99            2 ----1 SEC  STC            ;set carry flag
  98            2 ----0 CLC  CLC            ;clear carry flag
  9B            2 -1--- SEI  DI             ;set interrupt mask (disable ints)
  9A            2 -0--- CLI  EI             ;clear interrupt mask (enable ints)
  8E          ..2 -0--- STOP STOP           ;?
  8F          ..2 -0--- WAIT WAIT           ;?
  83           10 -1--- SWI  SWI            ;software interrupt ...? PC=[FFFCh]
  <IRQ>         ? ????? Interrupt           ;?                       PC=[FFFxh]
  <RESET>       ? ????? Reset               ;?                       PC=[FFFEh]
  82,84..8D,90..96,9E = Reserved
MUL isn't supported in original "M146805 CMOS" family (MUL is used/supported in PSX cdrom controller).

Registers
  A   8bit  accumulator
  X   8bit  index register
  SP  6bit  stack pointer (range 00C0h..00FFh)
  PC  16bit program pointer (range 0000h..FFFFh)
  CCR 5bit  condition code register (flags) (111HINZC)

Pushed on IRQ are:
  SP.highest PC.lo
             PC.hi
             X
             A
  SP.lowest  Flags (CCR, 5bit condition code register) (111HINZC)

Addressing Modes
  nn       immediate             ;00h..FFh
  [nn]     direct address        ;[0000h..00FFh]
  [nnmm]   extended address      ;[0000h..FFFFh]
  [X]      indexed, no offset    ;[0000h..00FFh]
  [X+nn]   indexed, 8bit offset  ;[0000h..01FEh]
  [X+nnmm] indexed, 16bit offset ;[0000h..FFFFh]
  [nn].i   bit                   ;[0000h..00FFh].bit0..7
  dd       relative              ;$+2..3+(-80h..+7Fh)
Notes:
  operand "X+nn" performs an unsigned addition, and can address 0000h..01FEh.
  16bit operands (nnmm) are encoded in BIG-ENDIAN format (same for pushed PC).

Exception Vectors
Exception vectors are 16bit BIG-ENDIAN values at FFF0h-FFFFh (or at FFE0h-FFEFh when running in Motorola Bootstrap mode).
  Vector Prio Usage
  FFF0h  7=lo TBI Vector (Timebase)
  FFF2h  6    SSPI Vector (SPI bus)     (SPI1 and SPI2)
  FFF4h  5    Timer 2 Interrupt Vector  (Timer 2 Input/Compare)
  FFF6h  4    Timer 1 Interrupt Vector  (Timer 1 Input/Compare/Overflow)
  FFF8h  3    KWI Vector (Key Wakeup)   (KWI0..7 pins)
  FFFAh  2    External Interrupt Vector (/IRQ1 and /IRQ2 pins)
  FFFCh  none Software Interrupt Vector (SWI opcode)            ;\regardless of
  FFFEh  1=hi Reset Vector              (/RESET signal and COP) ;/CPU's "I"

Directives/Pseudos (used by a22i assembler; in no$psx utility menu)
  .hc05         select HC05 instruction set (default would be .mips)
  .nocash       select nocash syntax (default would be .native opcode names)
  db ...        define 8bit byte(s), or quoted ascii strings
  dw ...        define 16bit word(s) in BIG ENDIAN (for HC05 exception vectors)
  org nnnn      change origin for following opcodes
  end           end of file
  mov c,[nn].i  alias for "jnz [nn].i,$+3" (dummy jump & set carry=[nn].i)


CDROM Internal HC05 On-Chip I/O Ports

HC05 Port 3Eh - MISC - Miscellaneous Register (R/W)
  0    OPTM  Option Map Select (bank-switching for Port 00h..0Fh)
  1    FOSCE Fast (Main) Oscillator Enable (0=Disable OSC, 1=Normal)
  2-3  SYS   System Clock Select (0=OSC/2, 1=OSC/4, 2=OSC/64, 3=XOSC/2)
  4-5  -     Not used (0)
  6    STUP  XOSC Time Up Flag   (R)
  7    FTUP  OSC Time Up Flag    (R)   (0=Busy, 1=Ready/Good/Stable)
Note: For PSX, OSC is 4.0000MHz (PU-7/PU-8), 4.2336MHz (PU-18 and up). SysClk is usually set to OSC/2, ie. around 2MHz.

HC05 Port OPTM=0:00h - PORTA - Port A Data Register (R/W)
HC05 Port OPTM=0:01h - PORTB - Port B Data Register (R)
HC05 Port OPTM=0:02h - PORTC - Port C Data Register (R/W)
HC05 Port OPTM=0:03h - PORTD - Port D Data Register (R/W)
HC05 Port OPTM=0:04h - PORTE - Port E Data Register (R/W)
HC05 Port OPTM=0:05h - PORTF - Port F Data Register (R) (undoc: R/W)
These are general purpose I/O ports (controlling external pins). Some ports are Input-only, and some can be optionally used for special things (like IRQs, SPI-bus, or as Timer input/output).
  PA.0-7  PAn   Port A Bit0..7 Input/Output            (0=Low, 1=High) (R/W)
  PB.0-7  PBn   Port B Bit0..7 Input        /KWI0..7   (0=Low, 1=High) (R)
  PC.0    PC0   Port C Bit0    Input/Output /SDI1 (SPI)(0=Low, 1=High) (R/W)
  PC.1    PC1   Port C Bit1    Input/Output /SDO1 (SPI)(0=Low, 1=High) (R/W)
  PC.2    PC2   Port C Bit2    Input/Output /SCK1 (SPI)(0=Low, 1=High) (R/W)
  PC.3    PC3   Port C Bit3    Input/Output /TCAP (T1) (0=Low, 1=High) (R/W)
  PC.4    PC4   Port C Bit4    Input/Output /EVI  (T2) (0=Low, 1=High) (R/W)
  PC.5    PC5   Port C Bit5    Input/Output /EVO  (T2) (0=Low, 1=High) (R/W)
  PC.6    PC6   Port C Bit6    Input/Output /IRQ2      (0=Low, 1=High) (R/W)
  PC.7    PC7   Port C Bit7    Input/Output /IRQ1      (0=Low, 1=High) (R/W)
  PD.0-7  PDn   Port D Bit0..7 Input/Output            (0=Low, 1=High) (R/W)
  PE.0-7  PEn   Port E Bit0..7 Input/Output            (0=Low, 1=High) (R/W)
  PF.0-7  PFn   Port F Bit0..7 Input/Undoc  A/D-input  (0=Low, 1=High) (R)(R/W)

HC05 Port OPTM=1:00h - DDRA - Port A Data Direction Register (R/W)
HC05 Port OPTM=1:02h - DDRC - Port C Data Direction Register (R/W)
HC05 Port OPTM=1:03h - DDRD - Port D Data Direction Register (R/W)
HC05 Port OPTM=1:04h - DDRE - Port E Data Direction Register (R/W)
HC05 Port OPTM=1:05h - DDRF - Port F Data Direction Register (undoc)
  DDRX.0-7  DDRXn Port X Data Direction Bit0..7 (0=Input, 1=Output) (R/W)
Officially, there are no DDRB and DDRF registers (Port B and F are always Inputs). Although, actually, Motorola's Bootstrap RAM <does> manipulate DDRF.

HC05 Port OPTM=1:08h - RCR1 - Resistor Control Register 1 (R/W)
HC05 Port OPTM=1:09h - RCR2 - Resistor Control Register 2 (R/W)
  RCR1.0    RAL   Port A.Bit0-3 Pullup Resistors (0=Off, 1=On)
  RCR1.1    RAH   Port A.Bit4-7 Pullup Resistors (0=Off, 1=On)
  RCR1.2    RBL   Port B.Bit0-3 Pullup Resistors (0=Off, 1=On)
  RCR1.3    RBH   Port B.Bit4-7 Pullup Resistors (0=Off, 1=On)
  RCR1.4    RGL   Port G.Bit0-3 Pullup Resistors (0=Off, 1=On) ;\
  RCR1.5    RGH   Port G.Bit4-7 Pullup Resistors (0=Off, 1=On) ; on chips
  RCR1.6    RHL   Port H.Bit0-3 Pullup Resistors (0=Off, 1=On) ; with Port G,H
  RCR1.7    RHH   Port H.Bit4-7 Pullup Resistors (0=Off, 1=On) ;/
  RCR2.0-7  RCn   Port C.Bit0-7 Pullup Resistors (0=Off, 1=On)

HC05 Port OPTM=1:0Ah - WOM1 - Open Drain Output Control Register 1 (R/W)
HC05 Port OPTM=1:0Bh - WOM2 - Open Drain Output Control Register 2 (R/W)
  WOM1.0   AWOML Port A.Bit0-3 Open Drain Mode when DDR=1 (0=No, 1=Open Drain)
  WOM1.1   AWOMH Port A.Bit4-5 Open Drain Mode when DDR=1 (0=No, 1=Open Drain)
  WOM1.2   GWOML Port G.Bit0-3 Open Drain Mode when DDR=1 (0=No, 1=Open Drain)
  WOM1.3   GWOMH Port G.Bit4-5 Open Drain Mode when DDR=1 (0=No, 1=Open Drain)
  WOM1.4   HWOML Port H.Bit0-3 Open Drain Mode when DDR=1 (0=No, 1=Open Drain)
  WOM1.5   HWOMH Port H.Bit4-5 Open Drain Mode when DDR=1 (0=No, 1=Open Drain)
  WOM1.6-7 -     Not used (0)
  WOM2.0-5 CWOMn Port C.Bit0..5 Open Drain Mode when DDR=1 (0=No, 1=Open Drain)
  WOM2.6-7 -     Not used (always both bits set)

==== Interrupts =====

HC05 Port OPTM=0:08h - INTCR - Interrupt Control Register (R/W)
  0-1  -     Not used (0)
  2    IRQ2S IRQ2 Select Edge-Sensitive Only (0=LowLevelAndNegEdge, 1=NegEdge)
  3    IRQ1S IRQ1 Select Edge-Sensitive Only (0=LowLevelAndNegEdge, 1=NegEdge)
  4    KWIE  Key Wakeup Interrupt Enable (0=Disable, 1=Enable)
  5    -     Not used (0)
  6    IRQ2E IRQ2 Interrupt Enable (0=Disable, 1=Enable)
  7    IRQ1E IRQ1 Interrupt Enable (0=Disable, 1=Enable)

HC05 Port OPTM=0:09h - INTSR - Interrupt Status Register (R and W)
  0    RKWIF Reset Key Wakeup Interrupt Flag (0=No Change, 1=Reset) (W)
  1    -     Not used (0)
  2    RIRQ2 Reset IRQ2 Interrupt Flag       (0=No Change, 1=Reset) (W)
  3    RIRQ1 Reset IRQ1 Interrupt Flag       (0=No Change, 1=Reset) (W)
  4    KWIF  Key Wakeup Interrupt Flag (PB/KWI)       (0=No, 1=IRQ) (R)
  5    -     Not used (0)
  6    IRQ2F IRQ2 Interrupt Flag (PC6)                (0=No, 1=IRQ) (R)
  7    IRQ1F IRQ1 Interrupt Flag (PC7)                (0=No, 1=IRQ) (R)

HC05 Port OPTM=1:0Eh - KWIE - Key Wakeup Interrupt Enable Register (R/W)
  0-7  KWIEn Port B.Bit0..7 Key Wakeup Interrupt Enable (0=Disable, 1=Enable)

==== SPI Bus ====

HC05 Port OPTM=0:0Ah - SPCR1 - Serial Peripheral Control Register 1 (R/W)
  0    SPRn  SPI Clock Rate (0=ProcessorClock/2, 1=ProcessorClock/16)
  1-3  -     Not used (0)
  4    MSTRn SPI Master Mode Select      (0=Slave/SCK.In, 1=Master/SCK.Out)
  5    DORDn SPI Data Transmission Order         (0=MSB First, 1=LSB First)
  6    SPEn  SPI Enable (SPI1:PortC, SPI2:PortG) (0=Disable, 1=Enable)
  7    SPIEn SPI Interrupt Enable (... ack HOW?) (0=Disable, 1=Enable)

HC05 Port OPTM=0:0Bh - SPSR1 - Serial Peripheral Status Register 1 (R)
  0-5  -     Not used (0)
  6    DCOLn SPI Data Collision Occurred         (0=No, 1=Collision)
  7    SPIFn SPI Transfer Complete Flag          (0=Busy, 1=Complete) (R)
Note: SPSR1.7 appears to be reset after reading SPSR1 (probably same for SPSR1.6, and maybe also same for whatever SPI IRQ signal).

HC05 Port OPTM=0:0Ch - SPDR1 - Serial Peripheral Data Register 1 (R/W)
  0-7  BITn  Data to be sent / being received

==== Time Base / Config ====

HC05 Port 10h - TBCR1 - Time Base Control Register 1 (R/W)
  0-1  T2R   Timer2 Prescaler (0=SysClk, 1=SysClk/4, 2=SysClk/32, 3=SysClk/256)
  2-3  T3R   PWM Prescaler    (0=CLK3, 1=CLK3/2, 2=CLK3/8, 3=Timer2compare)
  4-6  -     Not used (0)
  7    TBCLK Time Base Clock (0=XOSC, 1=OSC/128) ;<-- write-able only ONCE

HC05 Port 11h - TBCR2 - Time Base Control Register 2 (R/W, some bits R or W)
  0    COPC  COP Clear 2bit COP timeout divider (0=No Change, 1=Clear) (W)
  1    COPE  COP Enable                          ;<-- write-able only ONCE
  2    -     Not used (0)
  3    RTBIF Reset Time Base Interrupt Flag (0=No Change, 1=Clear TBIF) (W)
  4-5  TBR   Time Base Interrupt Rate (0=TBCLK/128, 1=/4096, 2=/8192, 3=/16384)
  6    TBIE  Time Base Interrupt Enable (0=Disable, 1=Enable)
  7    TBIF  Time Base Interrupt Flag   (0=No, 1=IRQ)        (R)

HC05 Port OPTM=1:0Fh - MOSR - Mask Option Status Register (R)
  0-4  -     Not used (0)
  5    XOSCR XOSC Feedback Resistor (0=None, 1=Implemented)
  6    OSCR  OSC Feedback Resistor  (0=None, 1=Implemented)
  7    RSTR  /RESET Pullup Resistor (0=None, 1=Implemented)
Reading this register returns A0h (on PSX/PSone with 52pin chips).

==== Timer 1 ====

HC05 Port 12h - TCR - Timer 1 Control Register (R/W)
  0    OLVL  Output Level on TCMP pin on Compare Match? (0=Low, 1=High)
  1    IEDG  Input Edge on TCAP pin (0=NegativeEdge, 1=PositiveEdge)
  2-4  -     Not used (0)
  5    TOIE  Timer Overflow Interrupt Enable (0=Disable, 1=Enable)
  6    OC1IE Output Compare Interrupt Enable (0=Disable, 1=Enable)
  7    ICIE  Input Capture Interrupt Enable  (0=Disable, 1=Enable)

HC05 Port 13h - TSR - Timer 1 Status Register (R)
  0-4  -     Not used (0)
  5    TOF   Timer Overflow Flag (0=No, 1=Yes) (R) ;clear by Port 19h access
  6    OC1F  Output Compare Flag (0=No, 1=Yes) (R) ;clear by Port 17h access
  7    ICF   Input Capture Flag  (0=No, 1=Yes) (R) ;clear by Port 15h access

HC05 Port 14h - ICH - Timer 1 Input Capture High (undoc)
HC05 Port 15h - ICL - Timer 1 Input Capture Low (undoc)
  0-15 Capture Value

HC05 Port 16h - OC1H - Timer 1 Output Compare 1 High (undoc)
HC05 Port 17h - OC1H - Timer 1 Output Compare 1 Low (undoc)
  0-15 Compare Value

HC05 Port 18h - TCNTH - Timer 1 Counter 1 High (undoc)
HC05 Port 19h - TCNTL - Timer 1 Counter 1 Low (undoc)
  0-15 Counter

HC05 Port 1Ah - ACNTH - Alternate Counter High (undoc)
HC05 Port 1Bh - ACNTL - Alternate Counter Low (undoc)
  0-15 Alternate Counter (uh, what?)

==== Timer 2 ====

HC05 Port 1Ch - TCR2 - Timer 2 Control Register (R/W)
  0    OL2   Timer Output 2 Edge (0=Falling, 1=Rising)
  1    OE2   Timer Output 2 Enable (EVO) (0=Disable, 1=Enable)
  2    IL2   Timer Input 2 Edge/Level (0=Low/Falling, 1=High/Rising)
  3    IM2   Timer Input 2 Mode Select for EVI (0=EventMode, 1=GatedByCLK2)
  4    T2CLK Timer 2 Clock Select (0=CLK2 from Prescaler, 1=EXCLK from EVI)
  5    -     Not used (0)
  6    OC2IE Output Compare 2 Interrupt Enable    (0=Disable, 1=Enable)
  7    TI2IE Timer Input 2 Interrupt Enable (EVI) (0=Disable, 1=Enable)

HC05 Port 1Dh - TSR2 - Timer 2 Status Register (R/W)
  0-1  -     Not used (0)
  2    ROC2F Reset Output Compare 2 Interrupt Flag (0=No Change, 1=Clear) (W)
  3    RTI2F Reset Timer Input 2 Interrupt Flag    (0=No Change, 1=Clear) (W)
  4-5  -     Not used (0)
  6    OC2F  Output Compare 2 Interrupt Flag    (0=No, 1=Yes) (R)
  7    TI2F  Timer Input 2 Interrupt Flag (EVI) (0=No, 1=Yes) (R)

HC05 Port 1Eh - OC2 - Timer 2 Output Compare Register (R/W)
  0-7  Compare Value ("Transferred to buffer on certain events?")

HC05 Port 1Fh - TCNT2 - Timer 2 Counter Register (R) (W=Set Counter to 01h)
  0-7  Counter Value, incremented at T2R (set to 01h on Compare Matches)

==== Reserved ====

HC05 Port 3Fh - Unknown/Unused
Reading this port via Sony's test command returns 20h (same as openbus), but reading it via Motorola's selftest function returns 00h (unlike openbus), so it seems to have some unknown/undocumented function; bit5 might indicate selftest mode, or it might reflect initialization of whatever other ports.

HC05 Port OPTM=0:06h..07h,0Dh..0Fh - Reserved
HC05 Port OPTM=1:01h,06h..07h,0Ch..0Dh - Reserved
HC05 Port 20h..3Dh - Reserved
These ports are unused/reserved. Trying to read them on a PSone does return 20h (possibly the prefetched next opcode value from the RAM test command). Other HC05 variants contain some extra features in these ports:
CDROM Internal HC05 On-Chip I/O Ports - Extras
The PSX CDROM BIOS doesn't use any of these ports - execpt, it is writing [20h]=2Eh (possibly to disable unused LCD hardware; which might be actually present in the huge 80pin HC05 chips on old PU-7 mainboards).

HC05 Openbus
Openbus values can be read from invalid memory locations, on PSX with 52pin chips:
  I/O bank 0:    0:06h..07h, 0:0Dh..0Fh
  I/O bank 1:    1:01h, 1:06h..07h, 1:0Ch..0Dh, and upper 4bit of 1:05h
  Unbanked I/O:  20h..3Dh
  Unused Memory: 0240h..0FFFh, 5000h..FDFFh
The returned openbus value depends on the opcode's memory operand:
  [nn],[mmnn],[nn+x],[mmnn+x] --> returns LAST byte of current opcode (=nn)
  [x]                         --> returns FIRST byte of following opcode


CDROM Internal HC05 On-Chip I/O Ports - Extras

HC05 Port OPTM=0:0Dh - SPCR2 - Serial Peripheral Control Register 2 (R/W)
HC05 Port OPTM=0:0Eh - SPSR2 - Serial Peripheral Status Register 2 (R)
HC05 Port OPTM=0:0Fh - SPDR2 - Serial Peripheral Data Register 2 (R/W)
This is a second SPI channel, works same as first SPI channel, but using the lower 3bits of Port G (instead of Port C) for the SPI signals.

HC05 Port OPTM=0:06h - PORTG - Port G Data Register (R/W)
HC05 Port OPTM=0:07h - PORTH - Port H Data Register (R/W)
HC05 Port 3Ch - PORTJ - Port J Data Register (R/W)
  PG.0    PG0   Port G Bit0    Input/Output /SDI2      (0=Low, 1=High) (R/W)
  PG.1    PG1   Port G Bit1    Input/Output /SDO2      (0=Low, 1=High) (R/W)
  PG.2    PG2   Port G Bit2    Input/Output /SCK2      (0=Low, 1=High) (R/W)
  PG.3    PG3   Port G Bit3    Input/Output /TCMP      (0=Low, 1=High) (R/W)
  PG.4    PG4   Port G Bit4    Input/Output /PWM0      (0=Low, 1=High) (R/W)
  PG.5    PG5   Port G Bit5    Input/Output /PWM1      (0=Low, 1=High) (R/W)
  PG.6    PG6   Port G Bit6    Input/Output /PWM2      (0=Low, 1=High) (R/W)
  PG.7    PG7   Port G Bit7    Input/Output /PWM3      (0=Low, 1=High) (R/W)
  PH.0-7  PHn   Port H Bit0..7 Input/Output            (0=Low, 1=High) (R/W)
  PJ.0-3  PJn   Port J Bit0..3 Output                  (0=Low, 1=High) (R/W)
  PJ.4-7  -     Not used (0)

HC05 Port OPTM=1:06h - DDRG - Port G Data Direction Register (R/W)
HC05 Port OPTM=1:07h - DDRH - Port H Data Direction Register (R/W)
  0-7  DDRXn Port X Data Direction Bit0..7 (0=Input, 1=Output) (R/W)

HC05 Port 20h - LCDCR - LCD Control Register (R/W)
  0    -     Not used (0)
  1    PDH   Select Port D (H) (0=FP35-FP38 pins, 1=PD7-PD4 pins)
  2    PEL   Select Port E (L) (0=FP31-FP34 pins, 1=PE3-PE0 pins)
  3    PEH   Select Port E (H) (0=FP27-FP30 pins, 1=PE7-PE4 pins)
  4    -     Not used (0)
  5-6  DUTY  LCD Duty Select (...)
  7    LCDE  LCD Output Enable BP and FP pins (0=Disable, 1=Enable)

HC05 Port 21h..34h - LCDDR1..20 - LCD Data Register 1..20 (R/W)
  0-3  First Data Unit  ;\Fourty 4bit LCD values (in the twenty registers)
  4-7  Second Data Unit ;/(some duties use only the LSBs of that 4bit values)

HC05 Port 34h - PWMCR - PWM Pulse Width Modulation Control Register (R/W)
  0-3  CH0-3 PWM Channel 0..3 on Port G.Bit4-7 Enable (0=Disable, 1=Enable)
  4-7  -     Not used (0)

HC05 Port 35h - PWMCNT - PWM Counter Register (R) (W=Set Counter to FFh)
  0-7  PWM Counter, incremented at PHI2 (range 01h..FFh)

HC05 Port 36h - PWMDR0 - PWM Duty Register 0 (R/W)
HC05 Port 37h - PWMDR1 - PWM Duty Register 1 (R/W)
HC05 Port 38h - PWMDR2 - PWM Duty Register 2 (R/W)
HC05 Port 39h - PWMDR3 - PWM Duty Register 3 (R/W)
  0-7  Duty (N cycles High, 255-N cycles Low)

HC05 Port 3Ah - ADR - A/D Data Register (R)
  0-3  A/D Conversion result (probably unsigned, 00h=Lowest, FFh=Max voltage?)

HC05 Port 3Bh - ADSCR - A/D Status and Control Register (R/W)
  0-3  CH0-3 A/D Channel (0..7=PortF.Bit0-7, 8..0Fh=Reserved/Vref/FactorTest)
  4    -     Not used (0)
  5    ADON  A/D Charge Pump enable (0=Disable, 1=Enable)
  6    ADRC  A/D RC Oscillator On (0=Normal/Use CPU Clock, 1=Use RC Clock)
  7    COCO  A/D Conversion Complete (0=Busy, 1=Complete) (R)

HC05 Port 3Dh - PCR - Program Control Register (R/W) (for EPROM version)
  0    PGM   EPROM Program Command (0=Normal, 1=Apply Programming Power)
  1    ELAT  EPROM Latch Control (0=Normal/Read, 1=Latch/Write)
  2-7  RES   Reserved for Factory Testing (always 0 in user mode)


CDROM Internal HC05 I/O Port Usage in PSX

Port A - Data (indexed via Port E)
  porta.0-7 i/o  CXD1815Q.Data (indexed via Port E)
  porta.0   in   debug.dta.serial.in  ;\normally unused (exists in early bios)
  porta.1   out  debug.dta.serial.out ; (prototype/debug_status stuff)
  porta.2   out  debug.clk.serial.out ;/(with portc.5 = debug.select)

Port B - Inputs
  portb.0   in   F-BIAS  ;unused
  portb.1   in   SCEx input (serial 250 baud, received via 1000Hz timer2 irq)
  portb.2   in   LMTSW  aka /POS0        ;\pos0 and door switches
  portb.3   in   DOOR   aka SHELL_OPEN   ;/
  portb.4   in   TEST2
  portb.5   in   TEST1 (CL316) enter test mode (instead of mainloop)
  portb.6   in   COUT   ;<-- unused, extra pin, not "SENSE=COUT"
  portb.7   in   CXD2510Q.SENSE ;-from CXD2510Q (and forwarded from CXA1782BR)

Port C - Inputs/Outputs
  portc.0   in   CXD2510Q.SUBQ  ;\
  portc.1   in?  NC (SPI.OUT)   ; used via SPDR1 to receive SPI bus SUBQ data
  portc.2   out  CXD2510Q.SQCK  ;/
  portc.3   out  SPEED
  portc.4   out    ="SPEED XOR 1"  ... AL/TE ... or CG ... or MIRR ?
  portc.5   out  ROMSEL: debug.select   (or "SCLK" on later boards???)
  portc.6   in   CXD1815Q.XINT/IRQ2 ;unused (instead INTSTS bits are polled)
  portc.7   in   CXD2510Q.SCOR/IRQ1 ;used via polling INTSR.7 (not as irq)

Port D - Outputs
  portd.0   out  NC             ;-unused (always 1)
  portd.1   out  CXD2510Q.DATA  ;\serial bus for CXD2510Q
  portd.2   out  CXD2510Q.XLAT  ; (and also forwarded to CXA1782BR)
  portd.3   out  CXD2510Q.CLOK  ;/
  portd.4   out  CXD1815Q.DECCS ;\
  portd.5   out  CXD1815Q.DECWR ; control for data/index on Port A/E
  portd.6   out  CXD1815Q.DECRD ;/
  portd.7   out  LDON  ... IC723.Pin11 ... maybe "laser on" ?

Port E - Index (for data on Port A)
  porte.0-4 out  CXD1815Q.Index (for data on Port A)
  porte.5   out  NC, not used
  porte.6   out  NC, see "idx_4xh" maybe test signal ???
  porte.7   out? NC, TEST? configured as OUTPUT... but used as INPUT?

Port F - Motorola Bootstrap Serial I/O (not used in cdrom bios)
  portf.0   out  NC, TX         ;\
  portf.1   in   NC, RX         ; not used by sony's cdrom bios
  portf.2   out  NC, RTS        ; (but used by motorola's bootstrap rom)
  portf.3   out  NC, DTR        ;/
  portf.0   in   Serial Data In  (from daughterboard)  ;\
  portf.1   out  Serial Data Out   (to daughterboard)  ; usage in SCPH-5903
  portf.2   out  Serial Clock Out  (to daughterboard)  ; (PSX with Video CD)
  portf.3   out  Audio/Video Select (0=Normal, 1=VCD)  ;/
  portf.4-7 -    NC, not used (probably pins don't even exist)

Other HC05 I/O Ports
  SPI 1   - used for receiving SUBQ (via Port C)
  IRQ 1   - used for latching/polling SUBQ's "SCOR" (not used as interrupt)
  IRQ 2   - connects to CXD1815Q.XINT, but isn't actually used at all
  Timer 1 - unused
  Timer 2 - generates 1000Hz interrupts (for 250 baud "SCEx" string transfers)
  DDRx    - data directions for Port A-F (as listed above)
Note: The PSX has the HC05 clocked via 4.00MHz oscillator (older boards), or via 4.3MHz signal from SPU (newer boards); internally, the HC05 is clocked at half of those frequencies (ie. around 2 MHz).


CDROM Internal HC05 Motorola Selftest Mode

52-pin HC05 chips (newer psx cdrom controllers)
52-pin chips are used on LATE-PU-8 boards, and on later boards ranging from PU-18 up to PM-41(2).
CDROM Internal HC05 Motorola Selftest Mode (52pin chips)

80-pin HC05 chips (older psx cdrom controllers)
80-pin chips are used PU-7, EARLY-PU-8, and PU-9 boards.
CDROM Internal HC05 Motorola Selftest Mode (80pin chips)

32-pin HC05 chips (joypad/mouse)
Sony's Digital Joypad and Mouse are using 32pin chips (with TQFP-32 package), which are probably containing Motorola HC05 CPUs, too. Unknown if/how those chips can be switched into bootstrap/dumping modes.

Pinouts
Pinouts - HC05 Pinouts


CDROM Internal HC05 Motorola Selftest Mode (52pin chips)

Motorola Bootstrap ROM
The Motorola MC68HC05 chips are including a small bootstrap ROM which gets activated upon /RESET when having two pins strapped to following levels:
  Pin30 PortC.6 (/IRQ2) (/XINT) ----> wire to 3.5V (VCC)
  Pin31 PortC.7 (/IRQ1) (SCOR)  ----> wire to 7V (2xVCC)
Moreover, two pins are needed on /RESET for selecting a specific test mode:
  Pin16 PortB.0 ----> ModeSelectBit0 (0=GND, 1=3.5V)
  Pin17 PortB.1 ----> ModeSelectBit1 (0=GND, 1=3.5V)
The selectable four modes are:
  Mode0: Jump to RAM Address 0040h (useless when RAM is empty)
  Mode1: Semifunctional Selftest (useless)
  Mode2: Upload 200h bytes to RAM & jump to 0040h (allows fast/custom dumping)
  Mode3: Download ROM as ASCII hexdump (nice, but very slow)
The upload/download functions are using following additional pins:
  Pin50 PortF.0 ----> TX output (11bytes: 0Dh,0Ah," AAAA DD ")
  Pin51 PortF.1 <---- RX input  (1byte: "!" to request next 11 bytes)
  Pin52 PortF.2 ----> RTS output or so (not needed)
  Pin1  PortF.3 ----> DTR output or so (not needed)
  Ground ------------ GND for RX/TX
RX/TX are RS232-like serial signals (but using other voltages, 0=0V and 1=3.5V). Transfer format is 8-N-1, ie. one startbit(0), 8 databits LSB first, no parity, one stopbit(1). Baudrate is OSC/2/208 (ie. 9616 bps for 4.000MHz, or 10176 bps for 4.2336MHz clock derived from CXD2545Q/CXD2938Q).
Note: Above pins may vary on some chips (namely on chips that don't have PortF). The pins for entering bootstrap mode (PortC in this case) should be described in datasheets; but transfer protocol and mode selection (PortB) and transmission (PortF) aren't officially documented.

Mode2: Upload 200h bytes to RAM & jump to 0040h
This mode is very simple and powerful: After /RESET, you send 200h bytes to the RX input (without any response on TX output), the bytes are stored at 0040h..023Fh in RAM, and the chip jumps to 0040h after transferring the last byte. The uploaded program can contain a custum highspeed dumping function, or perform hardware tests, etc. A custom dumping function for PSX/PSone can be found at:
  http://www.psxdev.net/forum/viewtopic.php?f=70&t=557
After uploading the 200h-byte dumping function it will respond by send 4540h bytes (containing some ASCII string, the 16.5Kbyte ROM image, plus dumps for RAM and (banked) I/O port region, plus openbus tests for unused memory and I/O regions.

Wiring for Mode2 on PSX/PSone consoles with 52-pin HC05 chips
                            .------------ pin31, PC7, SCOR, cut the connection
                   39       |   27               to Signal Processor,
                 .-----------------.             then wire Pin31 to 7.5V
              40 |                 | 26
                 |  C nnnn         |
                 |  SC4309nnPB     |
                 |  G63C 185       |
  pin50, TX <--- |                 | ---- pin17, PB1, SCEX, wire to 3.5V,
  pin51, RX ---> |                 |                  for Mode2 Selection
              52 | O               | 14
                 '-----------------'
                   1            13
Good places to pick 3.5V and 7.5V from nice solder pads are:
  CN602.Pin1  = 7.5V     ;\on PSX boards (with either 5pin or
  CN602.Pin3  = 3.5V     ;/               7pin CN602 connectors)
  IC601.Pin1  = 7.5V     ;-on PSone boards (3pin 78M05 voltage regulator)
  IC102.Pin32 = 3.5V     ;-on PSone boards (32pin Main BIOS ROM chip)
The SCOR trace on Pin31, connects to Signal Processor...
  CXD2510Q.Pin63  (eg. on PU-8 boards)   ;\
  CXD2545Q.Pin74  (eg. on PU-18 boards)  ; either one of these, depending
  CXD1817R.Pin49  (eg. on PU-20 boards)  ; on which chipset you have
  CXD2938Q.Pin77  (eg. on PM-41 boards)  ;
  CXD2941R.Pin85  (eg. PM-41(2) boards)  ;/
cut that trace (preferably on the PCB between two vias or test points, so you can later repair it easily) (better don't try to lift Pin31, it breaks off easily)
Note: Mode2 also requires Pin16=Low, and Pin30=High (but PSX/PSone boards should have those pins at that voltages anyways).

Mode3: Download ROM as ASCII hexdump
This mode is very slow and not too powerful. But it may useful if you can't get Mode2 working for whatever reason. Wiring for Mode3 is same as above, plus PortB.0=3.5V. In this mode, the chip will send one 0Dh,0Ah," AAAA DD " string immediately after /RESET (with 16bit address "AAAA" (initially 1000h), and 8bit data "DD"). Thereafter the chip will wait for incoming commands:
  4-digit ASCII HEX address --> change address, and return 0Dh,0Ah," AAAA DD "
  chr(00h) --> increment address, and return 0Dh,0Ah," AAAA DD "
  chr(07h) --> jump to current address (not so useful)
  other characters --> same as chr(00h)
  All digits/characters sent to RX input will produce an echo on TX output.
Basic setup would be wiring RX to GND (the chip will treat that as infinite stream of start bits with chr(00h), so it will respond by sending data from increasing addresses automatically; the increment wraps from 4FFFh to FE00h (skipping the gap between Main ROM and Bootstrap ROM), and also wraps from FFFFh to 0000h; transfer is ultraslow: 13 characters needed per dumped byte: chr(00h) to chip, chr(00h) echo from chip, and 0Dh,0Ah," AAAA DD " from chip.


CDROM Internal HC05 Motorola Selftest Mode (80pin chips)

80pin Sony 4246xx chips
And for anyone else planning to try this, these are the connections:
  Pin PortC
  46  PC7/IRQ1 (SCOR) disconnect from PCB, then wire the pin to Vtst (7.6V)
  45  PC6/IRQ2 (/XINT) wire to Vdd (3.5V) (you have to solder to the pin)
In bootstrap mode, Port A is used as follows:
  Pin PortA DDRA Usage
  23  PA0   in   RXD
  24  PA1   out  TXD
  25  PA2   in   -
  26  PA3   in   Testmode.bit0 (GND=0, 3.5V=1)
  27  PA4   in   Testmode.bit1 (GND=0, 3.5V=1)
  28  PA5   in   Testmode.bit2 (GND=0, 3.5V=1)
  29  PA6   out  RTS (don't care)
  30  PA7   out  -
The selectable testmodes are:
  PA5 PA4 PA3  Effect
  0   x   x    Jump to 0040h      ;\
  1   0   0    Test (complex)     ; not so useful
  1   0   1    Test (simple loop) ;/
  1   1   0    ROM Dump 4200h bytes (plain binary, non-ASCII)
  1   1   1    RAM Upload 100h bytes to 0040h..013Fh, then jump to 0040h
RX/TX are plain binary (non-ASCII), baudrate is 9600 (when using 4.000MHz oscillator), transfer format is 8,N,2 (aka 8,N,1 with an extra pause bit).

Wiring for Upload/Download on PSX consoles with 80-pin HC05 chips
                  .------------ pin46, PC7/IRQ1, SCOR, cut & wire to 7.5V
                  |.----------- pin45, PC6/IRQ2, wire to 3.5V
         60       ||  41
       .-----------------.
    61 |               o | 40
       |  Sony Computer  |           ,----- pin28, PA5, wire to 3.5V
       |  Entertainment  | _________/  ,--- pin27, PA4, wire to 3.5V
       |  Inc. (C) E35D  | ==========='---- pin26, PA3, mode select
       |     4246xx 185  | ----> pin24, PA1, TXD (for ROM dump)
       |                 | <---- pin23, PA0, RXD (for RAM upload)
    80 | O               | 21
       '-----------------'
         1            20
Good places to pick 3.5V and 7.5V from nice solder pads are:
  CN602.Pin1  = 7.5V     ;\on PSX boards (with 7pin CN602 connectors)
  CN602.Pin3  = 3.5V     ;/
Credits to TriMesh for finding the 80pin chip's bootstrap signals.

Other 80pin chips
DTL-H100x uses 80pin chip with onchip PROM (chip text "(M) MC68HC705L15", instead of "Sony [...] 4246xx"), wiring for serial dumping on that is unknown (the bootstrap ROM may be a little different because it should contain PROM burning functions). PU-9 boards boards seem to use a similar PROM (with some sticker on it).
DTL-H2000 uses 80pin CXP82300 chip with socketed piggyback 32pin EPROM - that chip is a Sony SPC700 CPU, not a Motorola HC05 CPU. Accordingly there's no Motorola Bootstrap mode in it, but of course one can simply dump the EPROM with standard eprom utilities, as done by TriMesh).


CDROM Internal CXD1815Q Sub-CPU Configuration Registers

00h - DRVIF - Drive Interface (W)
  0-1 "L"     Reserved (should be 0)
  2   LSB 1st CD DSP DATA order               (0=MSB first, 1=LSB first)
  3-4 BCK MD  CD DSP Number of BCLKs per WCLK (0=16, 1=24, 2=32, 3=Reserved)
  5   BCK RED Strobe DATA on BLCK Edge        (0=Falling Edge, 1=Rising Edge)
  6   LCH LOW Channel on LRCK=Low             (0=Right, 1=Left)
  7   C2PL1st      ... C2PO lower byte 1st

01h - CONFIG 1 - Configuration 1 (W)
  0   HCLKDIS  HCLK Pin Output (0=8.4672MHz, 1=Disable; Fixed Low)
  1   CLKDIS   CLK Pin Output (0=16.9344MHz, 1=Disable; Fixed Low)
  2   9BITRAM  SRAM Databus width (0=8bit/normal, 1=9bit)
  3-4 RAM SZ   SRMA Address bus (0=32K, 1=64K, 2=128K, 3=Reserved)
  5   PRTYCTL      ... Priority Control
  6   XSLOW    Number of clock cycles per DMA cycle (0=12, 1=4) (for SRAM)
  7   "L"      Reserved (should be 0)

02h - CONFIG 2 - Configuration 2 (W)
  0   "L"      Reserved (should be 0)
  1   DACODIS        .... DAC Out Disable
  2   DAMIXEN  Digital Audio Mixer Enable (0=Attentuator/Mixer for CD-DA, 1=No)
  3   SMBF2    Number of Sound Map Buffer Surfaces (0=Three, 1=Two)
  4   SPMCTL   Sound Parameter Majority Control (0=?)  ;\for ADPCM params
  5   SPECTL   Sound Parameter Error Control    (0=?)  ;/
  6-7 "L"      Reserved (should be 0)

03h - DECCTL - Decoder Control (W)
  0-2 DECMD    Decoder Mode (0-7)
                 0 or 1  Decoder Disable            ;-disable sector reading
                 2 or 3  Monitor-only Mode          ;\no error correction
                 4       Write-only Mode            ;/
                 5       Real-time Correction Mode  ;\with error correction
                 6       Repeat Correction Mode     ;/
                 7       CD-DA Mode                 ;-audio
  3   AUTODIST Auto Distinction (0=Use MODESEL/FORMSEL bits, 1=Use Sector Hdr)
               (Error Correction is done according to above MODE/FORM values)
  4   FORMSEL  Form Select (0=FORM1, 1=FORM2) (must be 0 for MODE1)
  5   MODESEL  Mode Select (0=MODE1, 1=MODE2)
  6   ECCSTR   ECC Strategy (0=Normal, 1=Use Error Flags; requires 9bit SRAM)
  7   ENDLADR  Enable Drive Last Address    ...

07h - CHPCTL - Chip Control (W)
  0   "L"      Reserved (should be 0)
  1   DBLSPD   Double Speed Mode (0=Normal, 1=Double) (init CD DSP first)
  2   RPSTART  Repeat Correction Start (0=No, 1=Start) (automatically cleared)
  3   SWOPEN   Sync Window Open (0=SyncControlledByIC, 1=OpenDetectionWindow)
  4   CD-DA    CD-DA Play     (0=No, 1=Playback CD-DA as audio)
  5   CDDAMUTE CD-DA Mute     (0=Normal, 1=Mute CD-DA Audio)
  6   RTMUTE   Real-time Mute (0=Normal, 1=Mute CDROM ADPCM)
  7   SMMUTE   Sound Map Mute (0=Normal, 1=Mute Sound Map ADPCM)


CDROM Internal CXD1815Q Sub-CPU Sector Status Registers

00h - ECCSTS - ECC Status (R)
  0 CFORM   FORM assumed by Error Correction (0=FORM1, 1=FORM2)
  1 CMODE   MODE assumed by Error Correction (0=MODE1, 1=MODE2)
  2 ECCOK   ECC Okay (0=Bad, 1=Okay)
  3 EDCOK   EDC Okay (0=Bad, 1=Okay)
  4 CORDONE Correction Done (0=None, 1=Error occurred and was corrected)
  5 CORINH  Correction Inhibit (0=Okay,1=AUTODIST couldn't determine MODE/FORM)
  6 ERINBLK Erasure in Block (0=Okay, 1=At least 1 byte is wrong & uncorrected)
  7 EDCALL0 EDC all-zero  (0=No/EDC Exists, 1=Yes/All four EDC bytes are 00h)

01h - DECSTS - Decoder Status (R)
  0   NOSYNC   No Sync       (0=Okay, 1=Sector Sync Mark Missing)
  1   SHRTSCT  Short Sector  (0=Okay, 1=Sector Sync Mark within Sector Data)
  2-4 -        Reserved (undefined)
  5   RTADPBSY Real-time ADPCM Busy (0=No, 1=Busy/playback)
  6-7 -        Reserved (undefined)

02h - HDRFLG - Header/Subheader Error Flags for HDR/SHDR registers (R)
  0 CI      Error in 4th Subheader byte (Coding Info) (0=Okay, 1=Error)
  1 SUBMODE Error in 3rd Subheader byte (Submode)     (0=Okay, 1=Error)
  2 CHANNEL Error in 2nd Subheader byte (Channel)     (0=Okay, 1=Error)
  3 FILE    Error in 1st Subheader byte (File)        (0=Okay, 1=Error)
  4 MODE    Error in 4th Header byte (MODE)           (0=Okay, 1=Error)
  5 BLOCK   Error in 3rd Header byte (FF)             (0=Okay, 1=Error)
  6 SEC     Error in 2nd Header byte (SS)             (0=Okay, 1=Error)
  7 MIN     Error in 1st Header byte (MM)             (0=Okay, 1=Error)
Error flags for current sector are probably stored straight in this register (ie. these flags are probably available even without using 9bit SRAM).
Or maybe not... if the chip supports receiving newer sectors during time-consuming error corrections... then those newer would need to be stored in SRAM, and would thus require 9bit SRAM for the error flags?

03h - HDR - Header Bytes (R)
  1st read: 1st Header byte (MM)
  2nd read: 2nd Header byte (SS)
  3rd read: 3rd Header byte (FF)
  4th read: 4th Header byte (MODE)

04h - SHDR - Subheader Bytes (R)
  1st read: 1st Subheader byte (File)
  2nd read: 2nd Subheader byte (Channel)
  3rd read: 3rd Subheader byte (Submode) (SM)
  4th read: 4th Subheader byte (Coding Info) (CI)
The contents of the HDRFLG, HDR, SHDR registers indicate:
      (1) The corrected value in the real-time correction or
          repeat correction mode
      (2) Value of the raw data from the drive in the monitor-only
          or write-only mode
    The CMOME? and CMODE bits (bits 1, 0) of ECCSTS indicate the FORM and MODE
    of the sector the decoder has discriminated by the raw data from the drive.
    Due to erroneous correction, the values of these bits may be at variance
    with those of the HDR register MODE byte and SHDR register submode byte
    bit5.

Unknown when 1st..4th read indices are reset for HDR and SHDR (maybe on access to certain I/O ports, or maybe anytime when receiving a new sector), also unknown what happens on 5th read and up.


CDROM Internal CXD1815Q Sub-CPU Address Registers

Drive Address -- used for storing incoming CDROM sectors in Buffer RAM
Host Address -- used for transferring Buffer RAM to (or from) Main CPU
ADPCM Address -- used for Real-time ADPCM audio output from Buffer RAM

05h - CMADR - Drive Current Minute Address (R)
  0-6   CMADR    Address bit10-16 (in 1Kbyte steps)
  7     -        Reserved (undefined)
Indicates the start address of the most recently decoded sector (called "Minute Address" because it points to the MM byte of the MM:SS:FF:MODE sector header). Normally, CMADR should be forwarded to Host:
  HADR = (CMADR AND 7Fh)*400h+offset
  HXFR = length OR 4000h
Whereas, offset would be usually 00h, 04h, or 0Ch (to start reading from the begin of the sector, or to skip 4-byte MODE1 header, or 12-byte MODE2 header). And length would be usually 800h (normal data sector), or 924h (entire sector, excluding the leading 12 sync-bytes). Length bit14 is undocumented/reserved, but the PSX CDROM BIOS does set that bit for whatever reason.
Alternately, the sector can be forwarded to the Real-time ADPCM decoder:
  ADPMNT = (CMADR AND 7Fh) OR 80h

19h - ADPMNT - ADPCM "MNT" Address (W)
  0-6   ADPxxx  ADPCM source Address bit10-16 (in 1Kbyte-steps)
  7     RTADPEN Real-time ADPCM Enable (0=Disable, 1=Enable Real-time ADPCM)

04h - DLADR-L, Drive Last Address, bit0-7 (W)
05h - DLADR-M, Drive Last Address, bit8-15 (W)
06h - DLADR-H, Drive Last Address, bit16 (W)
  0-16  DLADR  Addr. bit0-16     ...
  17-23 "L"    Reserved (should be 0)

10h - DADRC-L - Drive Address Counter, bit0-7 (W)
11h - DADRC-M - Drive Address Counter, bit8-15 (W)
12h - DADRC-H - Drive Address Counter, bit16 (W)
  0-16  DADRC    Incrementing Drive-to-Buffer Write Address, bit0-16
  17-23 "L"      Reserved (should be 0)

0Eh - DADRC-L - Drive Address Counter, Bit0-7 (R)
0Fh - DADRC-M - Drive Address Counter, Bit8-15 (R)
  0-15  DADRC Address bit0-15  ;bit16 is in Port 0Bh            ...

0Ch - HXFR-L - Host Transfer Length, bit0-7 (W)
0Dh - HXFR-H - Host Transfer Length, bit8-11 and stuff (W)
  0-11  HXFR     number of data bytes, bit0-11 (0..FFFh)       ...
  12    HADR.16  HADR  bit16
  13    "L"      Reserved (should be 0)
  14    "L" ??   Reserved (should be 0)   ;<-- XXX but on PSX: Always 1 !?!
                                          ;    seems to Disable INT8 ?!!!
  15    DISHXFRC Disable HXFRC (0=Use HXFRC, 1=Disable, Infinite-or-Zero Len?)

0Eh - HADR-L - Host Transfer Address, bit0-7 (W)
0Fh - HADR-M - Host Transfer Address, bit8-15 (W)
  0-15  HADR     Addr. bit0-15  ;bit16 in Port 0Dh    ...

0Ah - HXFRC-L - Host Transfer Remain Counter, bit0-7 (R)
0Bh - HXFRC-H - Host Transfer Remain Counter, bit8-11, and other bits (R)
  0-11  HXFRC Host Transfer Counter bit0-11 (number of remaining bytes)
  12    HADRC bit16  ;MSB of Port 0Ch/0Dh
  13    DADRC bit16  ;MSB of Port 0Eh/0Fh
  14-15 -     Reserved (undefined) (usually both bits set)

0Ch - HADRC-L - Host Transfer Address Counter, bit0-7 (R)
0Dh - HADRC-M - Host Transfer Address Counter, bit8-15 (R)
  0-15  HADRC Address bit0-15  ;bit16 is in Port 0Bh
"This counter keeps the addresses which write or read the data with host into/from the buffer.
When data from the host is written into the buffer or data to the host is read from the buffer, the HADRC value is output from MA0 to 16. HADRC is incremented each time one byte of data from the drive is read from the buffer (BFRD is high) or written into the buffer (BFWR is high)."

Note
When reading from SRAM, data seems to go through a 8-byte data fifo, the HXFRC (remain) and HADRC (addr) values aren't aware of that FIFO (ie. if there's data in the fifo, then addr will be 8 bigger and remain 8 smaller than what has arrived at the host).

Unclear Notes
"If sound map data is to be transferred before the data is transferred (immediately after the host has set the BFRD and BFWR bits (bits 7 and 6) of the HCHPCTL register high)":
  900h is loaded into HXFRC
  and 600Ch, 6A0Ch, or 740Ch is loaded into HADRC
  (at least, supposedly, above addresses , for cases when using 32K SRAM)
"At any other time":
  HADR and HXFR are loaded into HADRC and HXFRC
Unknown what the above crap is trying to say exactly.
"At any other time" does apparently refer to cases when transfers get started (whilst during transfer, the address/remain values are obviously increasing/decreasing).
For sound map, theoretically, the SMEN bit should be set, but above does somewhat suggest that BFRD or BFWR (or actually: both BFRD and BFWR) need to be set...?

Sector Buffer Memory Map (32Kx8 SRAM)
  0000h 1st Sector (at 0000h..0923h) (unused gap at 0924h..0BFFh)
  0C00h 2nd Sector (at 0C00h..1523h) (unused gap at 1524h..17FFh)
  1800h 3rd Sector (at 1800h..2123h) (unused gap at 2124h..23FFh)
  2400h 4th Sector (at 2400h..2D23h) (unused gap at 2D24h..2FFFh)
  3000h 5th Sector (at 3000h..3923h) (unused gap at 3924h..3BFFh)
  3C00h 6th Sector (at 3C00h..4523h) (unused gap at 4524h..47FFh)
  4800h 7th Sector (at 4800h..5123h) (unused gap at 5124h..53FFh)
  5400h 8th Sector (at 5400h..5D23h) (unused gap at 5D24h..5FFFh)
  6000h Soundmap ADPCM Buffer (at 600Ch..690Bh) (gaps at 6000h and 690Ch)
  6A00h Soundmap ADPCM Buffer (at 6A0Ch..730Bh) (gaps at 6A00h and 730Ch)
  7400h Soundmap ADPCM Buffer (at 740Ch..7D0Bh) (gaps at 7400h and 7D0Ch)
  7E00h Unknown/Unused


CDROM Internal CXD1815Q Sub-CPU Misc Registers

16h - HIFCTL - Host Interface Control (W)
  0-2  HINT    Request Host Interrupt (INT1..INT7, or 0=None/No change)
  3-7  "L"     Reserved (should be 0)

11h - HIFSTS - Host Interface Status (R)
  0-2 HINTSTS  Pending Host Interrupt (INT1..INT7, or 0=None/All acknowledged)
  3   DMABUSY  DMA Busy (0=Data FIFO Empty and HXFRC=0, 1=Data Transfer Busy)
  4   PRMRRDY  Parameter Read Ready (0=Parameter FIFO Empty, 1=Ready/Not Empty)
  5   RSLEMPT  Result Empty         (0=Response FIFO Not Empty, 1=Empty)
  6   RSLWRDY  Result Write Ready   (0=Response FIFO Full, 1=Ready/Not Full)
  7   BUSYSTS  Command Busy Status  (0=Command Not Empty, 1=Ack'ed by CLRBUSY)

0Ah - CLRCTL - Clear Control (W)
  0   RESYNC   Sync with CD DSP (0=No change, 1=Resync, eg. after speed change)
  1-3 "L"      Reserved (should be 0)
  4   RTADPCLR Abort Real-time ADPCM (0=No Change, 1=Abort; when ADPMNT.7=0)
  5   CLRRSLT  Clear Reply FIFO     (0=No change, 1=Acknowledge; clear FIFO)
  6   CLRBUSY  Acknowledge Command  (0=No change, 1=Acknowledge; clear BUSYSTS)
  7   CHPRST   Chip Reset           (0=No change, 1=Do Chip Initialization)

07h - INTSTS - Interrupt Status (R) - (0=No, 1=IRQ)
09h - INTMSK - Interrupt Mask (W) - (0=Disable, 1=Enable)
0Bh - CLRINT - Clear Interrupt Status (W) - (0=No change, 1=Clear/Ack)
  0   HCRISD   Host Chip Reset Issued
  1   HSTCMND  Host Command                ...
  2   DECINT   Decoder Interrupt           ..
  3   HDMACMP  Host DMA Complete           .   <-- PSX: used for retry ?!?!!!
  4   RTADPEND Real-time ADPCM end
  5   RSLTEMPT Result Empty
  6   DECTOUT  Decoder Time Out
  7   DRVOVRN  Drive Overrun

12h - HSTPRM - Host Parameter (R)
  0-7  Param FIFO (check HIFSTS.4 to see if the FIFO is empty)
HIFSTS.4 goes off when all bytes read.
Said to have 8-byte FIFO in CXD1199AQ datasheet.
But, PSX has 16-byte Parameter FIFO...!?!

13h - HSTCMD - Host Command (R)
  0-7  Command (check INTSTS.1 or HIFSTS.7 to see if a command was sent)
Command should be ack'ed via CLRINT.1 and CLRCTL.6.

17h - RESULT - Response FIFO (W)
  0-7  Data (has 8-byte FIFO)
Said to have 8-byte FIFO in CXD1199AQ datasheet.
But, PSX has 16-byte Response FIFO...!?!

08h - ADPCI - ADPCM Coding Information (R)
  0   S/M      ADPCM Stereo/Mono        (0=Mono, 1=Stereo)
  1   -        Reserved (undefined)
  2   FS       ADPCM Sampling Frequency (0=37.8kHz, 1=18.9kHz)
  3   -        Reserved (undefined)
  4   BITLNGTH ADPCM Sample Bit Length  (0=Normal/4bit, 1=8bit)
  5   ADPBUSY  ADPCM Decoding           (0=No, 1=Yes/Busy)
  6   EMPHASIS ADPCM Emphasis           (0=Normal/Off, 1=On)
  7   MUTE     DA Data is Muted (uh?)   (0=No, 1=Yes/Muted)
Unknown if ADPCI is affected by configurations by Main-CPU's Sound Map ADPCM or by Sub-CPU's Real-time ADPCM (or by both)?
Note: Bit5,7 are semi-undocumented in the datasheet (mentioned in the ADPCI description, but missing in overall register summary).

1Bh - RTCI - Real-time ADPCM Coding Information (W)
  0    S/M      ADPCM Stereo/Mono        (0=Mono, 1=Stereo)
  1    "L"      Reserved (should be 0)
  2    FS       ADPCM Sampling Frequency (0=37.8kHz, 1=18.9kHz)
  3    "L"      Reserved (should be 0)
  4    BITLNGTH ADPCM Sample Bit Length  (0=Normal/4bit, 1=8bit)
  5    "L"      Reserved (should be 0)
  6    EMPHASIS ADPCM Emphasis           (0=Normal/Off, 1=On)
  7    "L"      Reserved (should be 0)

06h,09h,10h,14h..1Fh - Reserved (R)
  0-7  Reserved (undefined)
Of these, 09h and 10h are officially unused/reserved. And addresses 06h and 14h..1Fh aren't officially mentioned to exist at all.
Trying to read these registers on a PSone returns Data=C0h for 06h, 09h, 10h, 15h-16h, 18h-1Fh, and Data=FFh for 14h, and Data=DEh for 17h.

08h,13h-15h,18h,1Ah,1Ch-1Fh - Reserved (W)
  0-7  Reserved (should be 00h) (or don't write at all)
Of these, 09h,13h-15h,18h,1Ah are officially unused/reserved. And addresses 1Ch-1Fh aren't officially mentioned to exist at all.


CDROM Internal Commands CX(0x..3x) - CXA1782BR Servo Amplifier

CXA1782BR - CX(0x) - Focus Servo Control - "FZC" FocusZeroCross at SENS pin
  23-20 4bit  Command (00h)
  19    1bit  FS4 Focus Servo (0=Off, 1=On)
  18    1bit  FS3 DEFECT
  17    1bit  FS2 Enable Focus Search Voltage (0=Off, 1=On)
  16    1bit  FS1 Select Focus Search Voltage (0=Falling, 1=Rising)
  15-0  16bit Unused (don't care)
For Focus Search: Keep FS1=on, and toggle FS2 on and off (this will generate a waveform, and SENS will indicate when reaching a good focus voltage).

CXA1782BR - CX(1x) - Tracking/Brake/Sled - "DEFECT" at SENS pin
  23-20 4bit  Command (01h)
  19    1bit  TG1,TG2 ON/OFF Tracking Servo Gain Up/Normal (hmmm?)
  18    1bit  Brake Circuit ON/OFF
  17-16 2bit  PS Sled Kick Height (0=+/-1, 1=+/-2, 2=Undoc, 3="Don't use"?)
  15-0  16bit Unused (don't care)
Note: The PSX CDROM BIOS does use the "Undoc" setting (ie. bit17=1), but the effect is undoc/unknown?
Note: CX(1x) works different on CXD2545Q (some bits are moved around, and the "SledKickHeight" bits are renamed to "SledKickLevel" and moved to different/new CX(3X) commands.

CXA1782BR - CX(2x) - Tracking and Sled Servo Control - "TZC" at SENS pin
  23-20 4bit  Command (02h)
  19-18 2bit  Tracking Control (0=Off, 1=Servo On, 2=F-Jump, 3=R-Jump) ;TM1,3,4
  17-16 2bit  Sled Control     (0=Off, 1=Servo On, 2=F-Fast, 3=R-Fast) ;TM2,5,6
  15-0  16bit Unused (don't care)

CXA1782BR - CX(3x) - "Automatic Adjustment Comparator Output" at SENS pin
  23-20 4bit  Command (03h)
  19    1bit  Value to be adjusted (0=Balance, 1=Gain)
  18-16 3bit  New Balance or Gain value (depending on above bit)
  15-0  16bit Unused (don't care)
Note: CX(3x) is extended and works very different on CXD2545Q.

CXA1782BR Command 4x..7x - "HIGH-Z" at SENS pin
  N-N   4bit  Command (04h..07h)

CXA1782BR Command 8x..Fx - "UNSPECIFIED???" at SENS pin
  N-N   4bit  Command (08h..0Fh)

Note
The Servo Amplifier isn't directly connected to the CPU. Instead, it's connected as a slave device to the Signal Processor. There are two ways to access the Servo Amplifier:
1) The CPU can send CX(0X..3X) commands to the Signal Processor (which will then forward them to the Servo Amplifier).
2) The Signal Processor can send CX(0X..3X) commands to the Servo Amplifier (this happens during CX(4xxx) Auto Sequence command).


CDROM Internal Commands CX(4x..Ex) - CXD2510Q Signal Processor

CXD2510Q - CX(4xxx) - Auto Sequence
  23-20 4bit  Command (4)
  19-16 4bit  AS3-0 Auto Sequence Command (see below)
  15-12 4bit  MT3-0 Max Timer Value (N timer units, or 0=Invalidate Timer)
  11    1bit  LSSL  Timer Units     (0=2.9ms, 1=186ms) (for above MT value)
  10-8  3bit  Unused (zero)
  7-0   8bit  Unused (don't care)
Values for AS (Auto Sequence Command):
  00h     Cancel
  04h/05h Forward/Reverse Fine Search   ;<--sends CX(25h) ;\these do internally
  07h     Focus-On                      ;<--sends CX(02h) ; send commands to
  08h/09h Forward/Reverse 1 Track Jump  ;\                ; CXA1782BR
  0Ah/0Bh Forward/Reverse 10 Track Jump ;   sends CX(25h) ; and, auto sequence
  0Ch/0Dh Forward/Reverse 2N Track Jump ;/                ;/is interrupted?
  0Eh/0Fh Forward/Reverse 1N Track Move ;<--CXD2545Q only(Reserved on CXD2510Q)
  01h..03h,06h = Reserved

CXD2510Q - CX(5x) - Blind,Brake,Overflow Timer
  23-20 4bit  Command (5)
  19-16 4bit  TR3-0 Timer (N*0.022ms for Blind/Overflow, N*0.045ms for Brake)
  15-8  8bit  Unused (don't care on CXD2510Q, zero on CXD2545Q)
  7-0   8bit  Unused (don't care)

CXD2510Q - CX(6xx) - SledKick,Brake,Kick Timer
  23-20 4bit  Command (6)
  19-16 4bit  SD3-0 Timer KICK.D (N*2.9ms for Fine Search? else N*1.45ms?)
  15-12 4bit  KF3-0 Timer KICK.F (N*0.09ms)
  11-8  4bit  Unused (don't care on CXD2510Q, zero on CXD2545Q)
  7-0   8bit  Unused (don't care)

CXD2510Q - CX(7xxxx) - Track jump count setting (for Auto Sequence Command)
  23-20 4bit  Command (7)
  19-4  16bit Track Jump Count Setting (0..65535) for Command 4x
  3-0   4bit  Unused (don't care)

CXD2510Q - CX(8xx) - MODE Specification
  23-20 4bit  Command (8)
  19    1bit  CDROM        (0=Audio, 1=CDROM; no average and pre-value stuff)
  18    1bit  DOUT Mute    (0=Not muted, 1=Mute DOUT)
  17    1bit  D.out Mute-F (0=Not muted, 1=Mute DA)
  16    1bit  WSEL         (0=Enhanced Sync Window, 1=Enhanced Anti-Rolling)
  15    1bit  VCO SEL      (0=Double Correction, 1=Quadruple Correction)
  14    1bit  ASHS         (0=Double Correction, 1=Quadruple Correction)
  13    1bit  SOCT         (0=Output SubQ to SQSO, 1=Output Each? to SQSO)
  12    1bit  Unused (zero)
  11-8  4bit  Unused (don't care on CXD2510Q, zero on CXD2545Q)
  7-0   8bit  Unused (don't care)

CXD2510Q - CX(9xx) - Function Specification
  23-20 4bit  Command (9)
  19    1bit  DCLV ON-OFF (complex stuff, related to gain and frequencies)
  18    1bit  DSPB ON-OFF (0=Normal Speed, 1=Double Speed; fixed pitch)
  17    1bit  ASEQ ON-OFF (select output on SENS pin)
  16    1bit  DPLL ON-OFF (0=Analog RFPLL, 1=Digital RFPLL)
  15-14 1bit  Bilingual Audio (0=Stereo, 1=RightOnly, 2=LeftOnly, 3=Mute)
  13    1bit  FLFC (normally 0)
  12    1bit  Unused (zero)
  11-8  4bit  Unused (don't care on CXD2510Q, zero on CXD2545Q)
  7-0   8bit  Unused (don't care)

CXD2510Q - CX(Axx) - Audio Control
  23-20 4bit  Command (0Ah)
  19    1bit  Vari Up   (write 1-then-0 to increase pitch by +0.1%)
  18    1bit  Vari Down (write 1-then-0 to decrease pitch by -0.1%)
  17    1bit  Mute (0=Not muted; unless muted elsewhere, 1=Mute & Peak=0)
  16    1bit  ATT  (0=Attentuation off, 1=Minus 12 dB)
  15-14 2bit  PCT  (0=Normal, 1=LevelMeter, 2=PeakMeter, 3=Normal) (0-1=QuadC2)
  13-12 2bit  Unused (zero)
  11-8  4bit  Unused (don't care on CXD2510Q, zero on CXD2545Q)
  7-0   8bit  Unused (don't care)
Normal: SQSO outputs... WHAT?
PeakMeter: SQSO outputs highest peak ever on any channel (bit15: usually 0)
LevelMeter: SQSO outputs recent peak (with bit15 toggled: 0=Right, 1=Left)

CXD2510Q - CX(Bxxxx) - Traverse Monitor Counter Setting
  23-20 4bit  Command (0Bh)
  19-4  16bit Traverse Monitor Count (used when monitored by COMP and COUT) (?)
  3-0   4bit  Unused (don't care)

CXD2510Q - CX(Cxx) - Spindle Servo Coefficient Setting
  23-20 4bit  Command (0Ch)
  19-18 2bit  Gain MDP for CLVP mode (0=-6db, 1=0dB, 1=+6dB, 3=Reserved)
  17-16 2bit  Gain MDS for CLVS/CLVP (0=-12dB, 1=-6dB, 2=0dB, 3=Reserved)
  15    1bit  Zero (zero)
  14    1bit  Gain DCLV0 overall gain (0=0dB, 1=+6dB
  13-12 2bit  Unused (zero)
  11-8  4bit  Unused (don't care on CXD2510Q, zero on CXD2545Q)
  7-0   8bit  Unused (don't care)

CXD2510Q - CX(Dx) - CLV Control
  23-20 4bit  Command (0Dh)
  19    1bit  DCLV PWM MD Digital CLV PWM mode  (0=Use MDS+MDP, 1=Ternary MDP)
  18    1bit  TB Bottom Hold in CLVS/CLVH modes (0=At cycle RFCK/32, 1=RFCK/16)
  17    1bit  TP Peak Hold in CLVS mode         (0=At cycle RFCK/4, 1=RFCK/2)
  16    1bit  Gain CLVS for CLVS mode (0=0dB, 1=+6dB)(always +6dB in CLVP mode)
  15-8  8bit  Unused (don't care on CXD2510Q, zero on CXD2545Q)
  7-0   8bit  Unused (don't care)

CXD2510Q - CX(Ex) - CLV Mode
  23-20 4bit  Command (0Eh)
  19-16 4bit  CM3-0
  15-8  8bit  Unused (don't care on CXD2510Q, zero on CXD2545Q)
  7-0   8bit  Unused (don't care)
Values for CM (CLV Mode):
  00h Stop  Spindle Motor Stop mode
  06h CLVA  Automatic CLVS/CLVP switching mode, normally used for playback
  08h Kick  Spindle Motor Forward rotation mode
  0Ah Brake Spindle Motor Reverse rotation mode
  0Ch CLVH  Peak hold at 34kHz
  0Eh CLVS  Rough Servo Mode, RF-PLL related
  0Fh CLVP  PLL Servo mode

N/A - CX(F) - Reserved
  23-0  N/A  Don't use

SUBQ Output
 80bit subq
 15bit peak level (lsb first) (absolute/unsigned value)
 1bit  peak l/r flag (aka appears as "MSB" of peak level)
L/R is toggled after each SUBQ reading, however the PSX Report mode does usually forward SUBQ only every 10 frames, so it stays stuck in one setting (but may toggle after one second; ie. every 75 frames). And, peak is reset after each read, so 9 of the 10 frames are lost.

CXD2510Q - SENS output
  Index         ASEQ=0  ASEQ=1   ;<-- ASEQ can be set via CX(9xx)
  0X            HighZ   SEIN (FZC)                     ;\aka SENS output
  1X            HighZ   SEIN (A.S)    ... aka DEFECT   ; from CXA1782BR
  2X            HighZ   SEIN (T.Z.C)  ... aka TZC      ; forwarded through
  3X            HighZ   SEIN (SSTOP)  ... aka Gain/Bal ;/CXD2510Q
  4X            HighZ   XBUSY
  5X            HighZ   FOK
  6X            HighZ   SEIN (HighZ)
  AX            GFS     GFS
  BX            COMP    COMP
  CX            COUT    COUT
  EX            /OV64   /OV64
  7X-9X,DX,FX   HighZ   0
Whereas,
 FZC    Focus Zero Cross
 DEFECT Defect?
 TZC    Tracking Zero Cross
 SSTOP  Gain or Balance adjust reached wanted level
 XBUSY  Low while the auto sequencer operation is busy
 FOK    High for "focus OK" (same as FOK pin)
 GFS    High when the played back frame sync is obtained with correct timing
 COMP   Measures the number of tracks set with Reg B. High when Reg B is
          latched, low when the initial Reg B number is input by CNIN
 COUT   Measures the number of tracks set with Reg B. High when Reg B is
          latched, toggles each time the Reg B number is input by CNIN. While
          $44 and $45 are being executed, toggles with each CNIN 8-count
          instead of the Reg B number
 OV64   Low when filtered EFM signal is lengthened by 64 channel clock
          pulses or more


CDROM Internal Commands CX(0x..Ex) - CXD2545Q Servo/Signal Combo

CXD2545Q - CX(0x) and CX(2x) - same as CXA1782BR Servo Amplifier
CDROM Internal Commands CX(0x..3x) - CXA1782BR Servo Amplifier

CXD2545Q - CX(4x..Ex) - same as CXD2510Q Signal Processor
CDROM Internal Commands CX(4x..Ex) - CXD2510Q Signal Processor
One small difference is that the CXD2545Q supports a new "M Track Move" function as part of the CX(4xxx) command. And, some "don't care" bits are now reserved (ie. some commands need to be padded with additional leading "0" bits).

CXD2545Q - CX(1x) - Anti Shock/Brake/Tracking Gain/Filter
  23-20 4bit  Command (01h)
  19    1bit  Anti Shock (0=Off, 1=On)
  18    1bit  Brake      (0=Off, 1=On)
  17    1bit  Tracking Gain (0=Normal, 1=Up)
  16    1bit  Tracking Gain Filter (0=Select 1, 1=Select 2)
  15-0  16bit Unused (don't care)

CXD2545Q - CX(30..33) - Sled Kick Level
  23-20 4bit  Command (03h)
  19-18 2bit  Subcommand (0)
  17-16 2bit  Sled Kick Level (0=+/-1, 1=+/-2, 2=+/-3, 3=+/-4)
  15-0  16bit Unused (don't care)

CXD2545Q - CX(34xxxx) - Write to Coefficient RAM
  23-16 8bit  Command (34h)
  15    1bit  Zero (0)
  14-8  7bit  Address (00h..4Fh = Select Coefficient K00..K4F)
  7-0   8bit  Data    (00h..FFh = New value)
  PLUS  8bit  Eight more bits on PSone (!)
Allows to change the default preset coefficient values,
CDROM Internal Coefficients (for CXD2545Q)

CXD2545Q - CX(34Fxxx) - Write to Special Register
  23-12 12bit Command (34Fh)
  11-10 2bit  Index (0=TRVSC, 1=FBIAS, 2=?, 3=?)
  9-0   10bit Data (for FBIAS: bit0=don't care)

CXD2545Q - CX(35xxxx) - FOCUS SEARCH SPEED/VOLTAGE/AUTO GAIN
  23-16 8bit  Command (35h)
  15-14 2bit  FT  Focus Search-up speed 1
  13-8  6bit  FS  Focus Search limit voltage (default 011000b) (+/-1.875V)
  7     1bit  FTZ Focus Search-up speed 2
  6-0   7bit  FG  AGF Convergence Gain Setting (default 0101101b)

CXD2545Q - CX(36xxxx) - DTZC/TRACK JUMP VOLTAGE/AUTO GAIN
  23-16 8bit  Command (36h)
  15    1bit  Zero (0)
  14    1bit  DTZC DTZC Delay (0=4.25us/Default, 1=8.5us)
  13-8  6bit  TJ   Track Jump voltage (default 001110b) (+/-1.09V)
  7     1bit  Zero (0)
  6-0   7bit  TG   AGT Convergence Gain Setting (default 0101110b)

CXD2545Q - CX(37xxxx) - FZSL/SLED MOVE/Voltage/AUTO GAIN
  23-16 8bit  Command (37h)
  15-14 2bit  FZS              XXX pg. 84
  13-8  6bit  SM    Sled Move Voltage
  7     1bit  AGS
  6     1bit  AGJ
  5     1bit  AGGF
  4     1bit  AGGT
  3     1bit  AGV1
  2     1bit  AGV2
  1     1bit  AGHS
  0     1bit  AGHT

CXD2545Q - CX(38xxxx) - Level/Auto Gain/DFSW (Initialize)
  23-16 8bit  Command (38h)
  15    1bit  VCLM VC level measurement on/off
  14    1bit  VCLC VC level compensation for FCS_In Register on/off
  13    1bit  FLM  Focus zero level measurement on/off
  12    1bit  FLC0 Focus zero level compensation for FZC Register on/off
  11    1bit  RFLM RF zero level measurement on/off
  10    1bit  RFLC RF zero level compensation on/off
  9     1bit  AGF  Focus automatic gain adjustment on/off
  8     1bit  AGT  Tracking automatic gain adjustment on/off
  7     1bit  DFSW Defect switch disable (1=disable defect measurement)
  6     1bit  LKSW Lock switch (1=disable sled free-running prevention)
  5     1bit  TBLM Traverse center measurement on/off
  4     1bit  TCLM Tracking zero level measurement on/off
  3     1bit  FLC1 Focus zero level compensation for FCS_In Register on/off
  2     1bit  TLC2 Traverse center compensation on/off
  1     1bit  TLC1 Tracking zero level compensation on/off
  0     1bit  TLC0 VC level compensation for TRK/SLD_In register on/off
VCLM,FLM,RFLM,TCLM are accepted every 2.9ms.

CXD2545Q - CX(39xx) - Select internal RAM/Registers for serial readout
  23-16 8bit  Command (39h)
  15    1bit  DAC Serial data readout DAC mode on/off
  14-8  7bit  SD  Serial readout data select (see below)
  7-0   8bit  Unused (don't care)
Serial Readout Addresses:
  Addr    Data  Content
  00h     8bit  VC input signal
  01h     8bit  SE input signal
  02h     8bit  TE input signal
  03h     8bit  FE input signal
  04h-07h 9bit  TE AVRG register (mirrored to 04h-07h)
  08h-0Bh 9bit  FE AVRG register (mirrored to 08h-0Bh)
  0Ch-0Fh 9bit  VC AVRG register (mirrored to 0Ch-0Fh)
  12h     8bit  RFDC envelope (peak)
  13h     8bit  RFDC envelope (bottom)
  1Ch     9bit  TRVSC register
  1Dh     9bit  FBIAS register
  1Eh     8bit  RFDC input signal
  1Fh     8bit  RF AVRG register
  20h-3Fh 16bit Data RAM        (M00-M1F)
  40h-7Fh 8bit  Coefficient RAM (K00-K3F) (note: K40-K4F cannot be read out)

CXD2545Q - CX(3Ax000) - Focus BIAS addition enable
  23-16 8bit  Command (3Ah)
  15    1bit  Zero (0)
  14    1bit  FBON: FBIAS register addition (0=off, 1=Add FBIAS to FCS)
  13-0  14bit Zero (0)

CXD2545Q - CX(3Bxxxx) - Operation for MIRR/DFCT/FOK
  23-16 8bit  Command (3Bh)
  15-14 2bit  SFO  FOK Slice Level (...depends on SFOX)
  13-12 2bit  SDF  DFCT Slice Level (0=89mV, 1=134mV, 2=179mV, 3=224mV)
  11-10 2bit  MAX  DFCT Maximum Time (0=No Limit, 1=2ms, 2=2.36ms, 3=2.72ms)
  9     1bit  SFOX FOK Slice Level (...depends on SFO)
  8     1bit  BTF  Bottom Hold Double-Speed Count-Up mode for MIRR (0=off)
  7-6   2bit  D2V  Peak Hold 2 for DFCT (0=22.05kHz, 1=44.1, 2=88.2, 3=176.4)
  5-4   2bit  D1V  Peak Hold 1 for DFCT (0=176.4kHz, 1=352.8, 2=705.6, 3=1411)
  3-0   4bit  Zero (0)

CXD2545Q - CX(3Cxxxx) - TZC for COUT SLCT HPTZC (Default)
  23-16 8bit  Command (3Ch)
  15-0  16bit Unused (don't care)

CXD2545Q - CX(3Dxxxx) - TZC for COUT SLCT DTZC
  23-16 8bit  Command (3Dh)
  15-0  16bit Unused (don't care)

CXD2545Q - CX(3Exxxx) - Filter
  23-16 8bit  Command (3Eh)
  15-14 2bit  F1NDM FCS servo filter 1st stage (1=normal, 2=down)
  13-12 2bit  F3NUM FCS servo filter 3rd stage (1=normal, 2=up)
  11-10 2bit  T1NDM TRK servo filter 1st stage (1=normal, 2=down)
  9-8   2bit  T3NUM TRK servo filter 3rd stage (1=normal, 2=up)
  7     1bit  DFIS  FCS hold filter input extraction node (0=M05, 1=M04)
  6     1bit  TLCD  Mask TLC2 set by D2 of CX(38) only when FOK low
  5     1bit  RFLP  Pass signal from RFDC pin through low-pass-filter
  4-0   5bit  Zero (0)

CXD2545Q - CX(3Fxxxx) - Others
  23-16 8bit  Command (3Fh)          ... XXX pg. 89
  15-14 2bit  Unused (0)
  13-12 2bit  XTD
  11    1bit  Unused (0)
  10-8  3bit  DRR
  7     1bit  Unused (0)
  6     1bit  ASFG
  5     1bit  Unused (0)
  4     1bit  LPAS
  3-2   2bit  SRO
  1-0   2bit  Unused (0)

CXD2545Q feedback on 39xx: see pg. 77 (eg. 390C = VC AVRG)
XXX

CXD2545Q - SENS output
  Index          ASEQ=0  ASEQ=1           Length
  $0X            Z       FZC              -
  $1X            Z       AS               -
  $2X            Z       TZC              -
  $38            Z       AGOK*1           -
  $38            Z       XAVEBSY*1        -
  $30-37,$3A-3F  Z       SSTP             -
  $3904          Z       TE Avrg Reg.     9 bit
  $3908          Z       FE Avrg Reg.     9 bit
  $390C          Z       VC Avrg Reg.     9 bit
  $391C          Z       TRVSC Reg.       9 bit
  $391D          Z       FB Reg.          9 bit
  $391F          Z       RFDC Avrg Reg.   8 bit
  $4X            Z       XBUSY            -
  $5X            Z       FOK              -
  $6X            Z       0                -
  $AX            GFS     GFS              -
  $BX            COMP    COMP             -
  $CX            COUT    COUT             -
  $EX            OV64    OV64             -
  $7X-9X,DX,FX   Z       0                -
*1 $38 outputs AGOK during AGT and AGF command settings, and XAVEBSY during AVRG measurement.
SSTP is output in all other cases.


CDROM Internal Commands CX(0x..Ex) - CXD2938Q Servo/Signal/SPU Combo

Most commands are same as on CXD2545Q. New/changed commands are:

CXD2938Q - CX(349xxxxx) - New SCEx
Older PSX consoles have received the "SCEx" string at 250 baud via HC05 PortB.bit1, which allowed modchips to injected faked "SCEx" signals to that pin. To prevent that, the CXD2938Q contains some new 32bit commands that allow to receive somewhat encrypted "SCEx" strings via SPI bus. The used commands are:
  CX(34910000) NewScexStopReading
  CX(3491xy80) NewScexRandomKey(xy)
  CX(34920000) NewScexFlushResyncOrSo
  CX(34944A00) NewScexInitValue1
  CX(3498C000) NewScexInitValue2
  CX(349C1000) NewScexThis   ;\inverse  ;\use CX(3C2080) for COUT selection
  CX(349D1000) NewScexThat   ;/of COUT  ;/
The relevant command is NewScexRandomKey(xy) which does send a random value (x=01h..0Fh, and y=01h), and does then receive a 12-byte response via SPI bus (which is normally used to receive SUB-Q data).
  1st byte: Unknown/unused (normally ADR/Control) ;\these should be probably
  2nd byte: Unknown/unused (normally Track)       ; set to some invalid values
  3rd byte: Unknown/unused (normally Index/Point) ;/to avoid SUB-Q confusion
  4th..10th byte: SCEx data or Dummy bytes (depending on xy.bit7..1)
  11th..12th byte: Unknown/unused (normally Audio Peak level)
The 12-byte packet does contain one SCEx character encoded in 4th..10th byte corresponding to Flags in "xy" bit 7..1 (in that order):
All bytes with Flag=1 are ORed together to compute a Character byte (those bytes could be all set to 53h for "S", or if more than one flag is set, it could be theoretically split to something like 41h and 12h).
All bytes with Flag=0 are ORed together to compute a Dummy byte. If the Character byte is same as the Dummy byte, then it gets destroyed by setting Character=00h (to avoid that, one could set all dummies to 00h, or set one or more dummies to FFh, for example).
Finally, "xy" bit0=0 indicates that the resulting character byte is inverted (XORed by FFh), however, the CDROM BIOS does always use bit0=1, so the inversion feature is never used.
For the whole SCEx string, there must be at least one 00h byte inserted between each character (or some Char=Dummy mismatch, which results in Char=00h either), and there should be a few more 00h bytes preceeding the first character ("S").
Note: Modchips didn't bother to reproduce that new SCEx transfers, instead they have simply bypassed it by injecting the 250 baud SCEx string to some analog lower level signal.

CXD2938Q - CX(3Bxxxx) - Some Changed Bits
Same as in older version, but initialized slightly differently: CXD2545Q used CX(3B2250) whilst CXD2938Q is using CX(3B7250).

CXD2938Q - CX(3Cxxxx) - TzcCoutSelect with New/Changed Extra Bits
The CXD2545Q used two 8bit commands, CX(3C) and CX(3D), for TzcOut selection, which are now replaced by a single 24bit command, CX(3Cxxxx), and which do include a new mode related to New SCEx.
  CXD2545Q   CXD2938Q
  CX(3C)     CX(3C0080) TzcCoutSelectHPTZC;\ <--formerly CX(3C)
  -          CX(3C2080) TzcCoutSelectSCEX ;  <--special NewScex mode
  CX(3D)     CX(3C4080) TzcCoutSelectDTZC ;/ <--formerly CX(3D)

CXD2938Q - CX(8xxxxx) - Disc Mode with New/Changed Extra Bits
Command CX(8xx) has been 12bit wide on CXD2545Q, and is now expanded 24bit width (with some changed/unknown bits).
  CXD2545Q   CXD2938Q
  CX(8180)   CX(810408) MODE = Audio (CD-DA)
  CX(8120)   CX(812400) MODE = Audio (CD-DA) (manual SPI bus access)
  CX(8980)   CX(890408) MODE = CDROM (Data)
  -          CX(898000) MODE = CDROM (Data) (used on RESET)

CXD2938Q - CX(9xx000) - Normal/Double Speed with New Extra Bits
Command CX(9xx) has been 12bit wide on CXD2545Q (with bit12=reserved/zero), and is now expanded 24bit width (with bit12=unknown/one and bit11-0=unknown/zero).

CXD2938Q - CX(Dx0000) and CX(Ex0000) - New Zero Padding
Commands CX(Dx) and CX(Ex) have been 8bit wide on CXD2545Q, and are now zeropadded to 24bit width, ie. CX(Dx0000) and CX(Ex0000). Unknown if the extra bits are hiding any extra features. In practice, the CDROM BIOS is always setting them zero (except in some test commands which are accidently still using the old 8bit form, resulting in garbage in lower 16bits).


CDROM Internal Commands CX(xx) - Notes

Serial Command Transmission (for Signal Processor and Servo Amplifier)
Commands are sent serially LSB first via DATA,CLOK,XLAT pins: DATA+CLOK are used to send commands to the chip, command execution is then applied by dragging XLAT low for a moment.
Commands can be up to 24bits in length, but unused LSBs (the "don't care" bits) can be omitted; the PSX BIOS clips the length to 8bit/16bit where possible (due to the LSB-first transfer order, the chip does treat the most recently transferred bit as MSB=bit23, and there's no need to transfer the LSBs if they aren't used).
Aside from being used as command number, the four most recently transferred bits are also used to select SENS status feedback (for the SENS selection it doesn't matter if the four bits were terminated by XLAT or not).

Sled Motor / Track Jumps / Tracking
The Sled motor moves the drive head to the current read position. On a Compact Disc, the term "Track" does normally refer to Audio tracks (songs). But the drive hardware uses the terms "Track" and "Tracking" for different purposes:
Tracking appears to refer to moving the Optics via magnets (ie. moving only the laser/lens, without actually moving the whole sled) (this is done for fine adjustments, and it seems to happen more or less automatically; emulators can just return increasing sectors without needing to handle special tracking commands).
Track jumps refer to moving the entire Sled, one "track" is equal to one spiral winding (1.6 micrometers). One winding contains between 9 sectors on innermost windings, and 22.5 sectors on outermost windings (the PSX cdrom bios is translating the sector-distance to non-linear track-distance, and emulators must undo that translation; otherwise the sled doesn't arrive at the intended location; the cdrom bios will retry seeking a couple of times and eventually settle down at the desired location - but it will timeout if the sled emulation is too inaccurate).
The PSX hardware uses two mechanisms for moving the Sled:
Command CX(4xxx) Forward/Reverse Track Jump: allows to move the sled by 1..131070 tracks (ie. max 210 millimeters), and the hardware does stop automatically after reaching the desired distance.
Command CX(2x) Forward/Reverse Fast Sled: moves the sled continously until it gets stopped by another command (in this mode, software can watch the COUT signal, which gets toggled each "N" tracks; whereas "N" can be selected via Command CX(Bxxxx), which is configured to N=100h in PSX).
The PSX cdrom bios is issuing another Fast Sled command (in opposite direction) after Fast Sled commands, emulators must somehow interprete this as "sled slowdown" (rather than as actually moving the sled in opposite direction, which could move the sled miles away from the target). For some reason vC1 BIOS is using a relative short slowdown period, whilst vC2/vC3 are using much longer slowdown periods (probably related to different SledKickHeight aka SledKickLevel settings and/or to different Sled Move Voltage settings).

Focus / Gain / Balance
The hardware includes commands for adjusting & measuring focus/gain/balance. Emulators can just omit that stuff, and can always signalize good operation (except that one should emulate failures for Disc Missing; and eventually also for cases like Laser=Off, or Spindle=Stopped).
Focus does obviously refer to moving the lens up/down. Gain does probably refer to reflection level/laser intensity. Balance might refer to tracking adjustments or so.


CDROM Internal Commands CX(xx) - Summary of Used CX(xx) Commands

The PSX CDROM BIOS versions vC1, vC2, and vC3 are using following CX() commands:
  <--vC1-->  <--vC2-->  <--vC3-->
  CXD2510Q   CXD2545Q   CXD2938Q
  CX(00)     CX(00)     CX(00)     AllFocusSwitchesOff
  CX(02)     CX(02)     CX(02)     FocusSearchVoltageFalling
  CX(03)     CX(03)     CX(03)     FocusSearchVoltageRising ;ForTestOnly
  CX(08)     CX(08)     CX(08)     FocusServoOn
  CX(0C)     CX(0C)     CX(0C)     FocusServoOnAndDefectOn ;diff.usage vC# ?
  -----
  CX(11)     -          -          SledKickHeight2
  CX(12)     -          -          SledKickHeightInvalid
  CX(19)     -          -          TrackingGainAndSledKickHeight2
  CX(1D)     -          -          TrackingGainBrakeAndSledKickHeight2
  CX(1E)     -          -          TrackingGainBrakeAndSledKickHeightInvalid
  -----
  -          CX(11)     CX(11)     AntiShockOff            ;\
  -          CX(13)     CX(13)     AntiShockOffGainUp      ;
  -          CX(17)     CX(17)     AntiShockOffGainUpBrake ;/
  -----
  CX(20)     CX(20)     CX(20)     SledAndTrackingOff
  CX(21)     CX(21)     CX(21)     SledServoOn          ;ForTestOnly
  CX(22)     CX(22)     CX(22)     SledFastForward
  CX(23)     CX(23)     CX(23)     SledFastReverse
  CX(24)     -          -          TrackingServoOn
  CX(25)     CX(25)     CX(25)     SledAndTrackingServoOn
  -          CX(26)     CX(26)     SledFastForwardAndTrackingServoOn
  CX(28)     CX(28)     CX(28)     TrackingForwardJump  ;ForTestOnly
  CX(2C)     CX(2C)     CX(2C)     TrackingReverseJump  ;ForTestOnly
  -----
  CX(30+n)   -          -          BalanceAdjust(0..7)
  CX(38+n)   -          -          GainAdjust(0..7)
  -----
  -          CX(30)     CX(30)     SetSledKickLevel1       ;\
  -          CX(31)     CX(31)     SetSledKickLevel2       ;
  -          CX(32)     CX(32)     SetSledKickLevel3       ;/
  -----
  -          CX(3400E6) CX(3400E6) SetK00toE6hSledInputGain            ;def=E0h
  -          CX(340730) CX(340730) SetK07to30hSledAutoGain       ;blah ;def=30h
  -          CX(34114A) CX(34114A) SetK11to4AhFocusOutputGain          ;def=32h
  -          CX(341330) CX(341330) SetK13to30hFocusAutoGain      ;blah ;def=30h
  -          CX(341D6F) CX(341D6F) SetK1Dto6FhTrackingLowBoostFilterAL ;def=44h
  -          CX(341F64) CX(341F64) SetK1Fto64hTrackingLowBoostFilterBL ;def=5Eh
  -          CX(342220) CX(342220) SetK22to20hTrackingOutputGain       ;def=18h
  -          CX(342330) CX(342330) SetK23to30hTrackingAutoGain   ;blah ;def=30h
  -          CX(342D28) CX(342D28) SetK2Dto28hFocusGainDownOutputGain  ;def=1Bh
  -          CX(343E70) CX(343E70) SetK3Eto70hTrackingGainUpOutputGain ;def=57h
  -          -          CX(34910000) NewScexStopReading      ;\
  -          -          CX(3491x180) NewScexRandomKey(x)     ;
  -          -          CX(34920000) NewScexFlushResyncOrSo  ; SCEX SPECIAL
  -          -          CX(34944A00) NewScexInitValue1       ; see also:
  -          -          CX(3498C000) NewScexInitValue2       ; CX(3C2080)
  -          -          CX(349C1000) NewScexThis   ;\inverse ;
  -          -          CX(349D1000) NewScexThat   ;/of COUT ;/
  -          CX(34F000) CX(34F000) SetTRVSCto000h
  -          CX(34Fxxx) CX(34Fxxx) SetFBIAStoNNNh
  -----
  -          CX(3740AA) CX(3740AA) SetSMto00h      ;\set SM to 0,6,7,9
  -          CX(3746AA) CX(3746AA) SetSMto06h      ; (sled move voltage)
  -          CX(3747AA) CX(3747AA) SetSMto07h      ; (and init several
  -          CX(3749AA) CX(3749AA) SetSMto09h      ;/fixed settings)
  -----
  -          CX(380010) CX(380010) ModeMeasureTrackingZeroLevel ;\Measure modes
  -          CX(380800) CX(380800) ModeMeasureRfZeroLevel       ; (accepted
  -          CX(382000) CX(382000) ModeMeasureFocusZeroLevel    ; every 2.9ms)
  -          CX(388000) CX(388000) ModeMeasureVcLevel           ;/
  -          CX(38140A) CX(38140A) ModeCompensate
  -          CX(38140E) CX(38140E) ModeCompensateAndTraverseCenter
  -          CX(38148A) CX(38148A) ModeCompensateAndDefectOff
  -          CX(38148E) CX(38148E) ModeCompensateAndDefectOffTraverseCenter
  -          CX(3814AA) CX(3814AA) ModeCompensateAndStuffAndMeasureTraverse ;!
  -          CX(38150A) CX(38150A) ModeCompensateAndTrackingAutoGain
  -          CX(38150E) CX(38150E) ModeCompensateAndTrackingAutoGain
  -          CX(38160A) CX(38160A) ModeCompensateAndFocusAutoGain
  -----
  -          CX(391E)   -          SenseRFDCinputSignalWithoutDAC  ;\rather
  -          CX(3983)   -          SenseFEinputSignalWithDAC       ;/unused
  -          CX(399C)   -          SenseTRVSCregisterWithDAC       ;\only if
  -          CX(399D)   -          SenseFBIASregisterWithDAC       ;/TEST1=LOW
  -----
  -          CX(3A0000) CX(3A0000) FocusBiasAdditionOff            ;\
  -          CX(3A4000) CX(3A4000) FocusBiasAdditionOn             ;/
  -          CX(3B2250)!CX(3B7250)!InitOperationForMirrDfctFok <-- vC2/vC3 DIFF
  -          CX(3C)  !!!CX(3C0080) TzcCoutSelectHPTZC;\ <--formerly CX(3C)
  -          -       !!!CX(3C2080) TzcCoutSelectSCEX ;  <--special NewScex mode
  -          CX(3D)  !!!CX(3C4080) TzcCoutSelectDTZC ;/ <--formerly CX(3D)
  -          CX(3E0000) CX(3E0000) InitFilterBits                  ;\
  -          CX(3E0008) CX(3E0008) InitFilterBitsInvalid           ;/
  -          CX(3F0008) CX(3F0008) InitOtherStuff                  ;-
  -----
  CX(4000)   CX(4000)   CX(4000)   AutoSeqCancel
  CX(4700)   CX(4700)   CX(4700)   AutoSeqFocusOn
  CX(4800)   CX(4800)   CX(4800)   Forward1track
  CX(4900)   CX(4900)   CX(4900)   Reverse1track
  CX(4C00)   CX(4C00)   CX(4C00)   Forward2Ntrack
  CX(4D00)   CX(4D00)   CX(4D00)   Reverse2Ntrack
  -----
  CX(54)     CX(54)     CX(54)     BlindBrakeOverflowTimer=4
  CX(5A)     CX(5A)     CX(5A)     BlindBrakeOverflowTimer=A
  CX(6100)   CX(6100)   CX(6100)   SledKickBrakeKickTimer
  CX(70xxx0) CX(70xxx0) CX(70xxx0) TrackJumpCountSetting
  CX(8180)   CX(8180)!!!CX(810408) MODE = Audio (CD-DA)
  -          CX(8120)!!!CX(812400) MODE = Audio (CD-DA) (manual SPI bus access)
  -          -          CX(810000/UNUSED)
  -          -          CX(812000/UNUSED)
  CX(8980)   CX(8980)   CX(890408) MODE = CDROM (Data)
  -          -          CX(898000) MODE = CDROM (Data) (used on RESET)
  CX(9B00)   CX(9B00)!!!CX(9B1000) NormalSpeed
  CX(9F00)   CX(9F00)!!!CX(9F1000) DoubleSpeed
  CX(A040)   CX(A040)   CX(A040)   Attentuation Off
  CX(A140)   CX(A140)   CX(A140)   Attentuation -12 dB
  CX(B01000) CX(B01000) CX(B01000) TraverseMonitorCounterSetting
  CX(C600)   CX(C600)   CX(C600)   SpindleServoCoefficientSetting
  CX(D7)     CX(D7)     CX(D70000) ClvControl (fixed)
  CX(E0)     CX(E0)     CX(E00000) SpindleMotorStop
  -          -          CX(E02000) <-- aka bugged CX(E0) with CRAP=2000h
  CX(E6)     CX(E6)     CX(E60000) AutomaticNormal
  CX(E8)     CX(E8)     CX(E80000) SpindleMotorForward
  -          -          CX(E8crap) <-- aka bugged CX(E8) with CRAP=xxxxh
  CX(EA)     CX(EA)     CX(EA0000) SpindleMotorReverse
  -          -          CX(EAcrap) <-- aka bugged CX(EA) with CRAP=xxxxh
  CX(EE)     CX(EE)     CX(EE0000) RoughServo
  -----
  CX(F)      CX(F)      CX(F)      Unused (N/A)
  -----
  CX(Xx)     CX(Xx)     CX(Xx)       ;\
  CX(Xxxx)   CX(Xxxx)   CX(Xxxx)     ; TestCommand (cmd_19h_50h)
  CX(Xxxxxx) CX(Xxxxxx) CX(Xxxxxx)   ;
  -          -          CX(Xxxxxxxx) ;/
  -          CX(Xxxxxx) CX(Xxxxxx) SerialSense, CX(Xxxx) with extra 8bit junk
Note: for vC2, some CX(38xxxx) values may differ depending on "set_mid_lsb_to_140Eh".
For vC2, CX(Dx) and CX(Ex) should be officially zero-padded to CX(Dx00) and CX(Ex00), but the vC2 BIOS doesn't do that, it still uses short 8bit form.
For vC2, CX(Dx) and CX(Ex) should be apparently zero-padded to CX(Dx0000) and CX(Ex0000), at least, the vC3 BIOS is doing so (except on some test comannds that do still use the CX(Ex) short form).

Used Sense Values
  sense(30)  SEIN.BAL       ;vC2: SSTP
  sense(38)  SEIN.GAIN      ;vC2: AGOK(AGT/AGF) or XAVEBSY(AVRG) or SSTP(else?)
  sense(40)  XBUSY (low=AutoSeqBusy)
  sense(50)  FOK   (high=FokusOkay)
  sense(A0)  GFS   (high=GoodFrameSync, ie. CorrectPlaybackSpeed)
  sense(C5)  COUT  (toggles each 100h 'tracks') (100h=selected via CX(B01000))
  sense(EA)  /OV64 (low=EFM too long?)


CDROM Internal Coefficients (for CXD2545Q)

The CXD2545Q contains Preset Coefficients in internal ROM, which are copied to internal Coefficient RAM shortly after Reset. CX(34xxxx) allows to change those RAM settings, and CX(39xxxx) allows to readout some of those values serially.

CXD2545Q - Coefficient Preset Values
  Addr Val Expl.
  K00  E0  Sled input gain
  K01  81  Sled low boost filter A-H
  K02  23  Sled low boost filter A-L
  K03  7F  Sled low boost filter B-H
  K04  6A  Sled low boost filter B-L
  K05  10  Sled output gain
  K06  14  Focus input gain
  K07  30  Sled auto gain
  K08  7F  Focus high cut filter A
  K09  46  Focus high cut filter B
  K0A  81  Focus low boost filter A-H
  K0B  1C  Focus low boost filter A-L
  K0C  7F  Focus low boost filter B-H
  K0D  58  Focus low boost filter B-L
  K0E  82  Focus phase compensate filter A
  K0F  7F  Focus defect hold gain
  K10  4E  Focus phase compensate filter B
  K11  32  Focus output gain
  K12  20  Anti shock input gain
  K13  30  Focus auto gain
  K14  80  HPTZC / Auto Gain High pass filter A
  K15  77  HPTZC / Auto Gain High pass filter B
  K16  80  Anti shock high pass filter A
  K17  77  HPTZC / Auto Gain low pass filter B
  K18  00  Fix (should not change this preset value)
  K19  F1  Tracking input gain
  K1A  7F  Tracking high cut filter A
  K1B  3B  Tracking high cut filter B
  K1C  81  Tracking low boost filter A-H
  K1D  44  Tracking low boost filter A-L
  K1E  7F  Tracking low boost filter B-H
  K1F  5E  Tracking low boost filter B-L
  K20  82  Tracking phase compensate filter A
  K21  44  Tracking phase compensate filter B
  K22  18  Tracking output gain
  K23  30  Tracking auto gain
  K24  7F  Focus gain down high cut filter A
  K25  46  Focus gain down high cut filter B
  K26  81  Focus gain down low boost filter A-H
  K27  3A  Focus gain down low boost filter A-L
  K28  7F  Focus gain down low boost filter B-H
  K29  66  Focus gain down low boost filter B-L
  K2A  82  Focus gain down phase compensate filter A
  K2B  44  Focus gain down defect hold gain
  K2C  4E  Focus gain down phase compensate filter B
  K2D  1B  Focus gain down output gain
  K2E  00  Not used
  K2F  00  Not used
  K30  80  Fix (should not change this preset value)
  K31  66  Anti shock low pass filter B
  K32  00  Not used
  K33  7F  Anti shock high pass filter B-H
  K34  6E  Anti shock high pass filter B-L
  K35  20  Anti shock filter comparate gain
  K36  7F  Tracking gain up2 high cut filter A
  K37  3B  Tracking gain up2 high cut filter B
  K38  80  Tracking gain up2 low boost filter A-H
  K39  44  Tracking gain up2 low boost filter A-L
  K3A  7F  Tracking gain up2 low boost filter B-H
  K3B  77  Tracking gain up2 low boost filter B-L
  K3C  86  Tracking gain up phase compensate filter A
  K3D  0D  Tracking gain up phase compensate filter B
  K3E  57  Tracking gain up output gain
  K3F  00  Not used
  K40  04  Tracking hold filter input gain
  K41  7F  Tracking hold filter A-H
  K42  7F  Tracking hold filter A-L
  K43  79  Tracking hold filter B-H
  K44  17  Tracking hold filter B-L
  K45  6D  Tracking hold filter output gain
  K46  00  Not used
  K47  00  Not used
  K48  02  Focus hold filter input gain
  K49  7F  Focus hold filter A-H
  K4A  7F  Focus hold filter A-L
  K4B  79  Focus hold filter B-H
  K4C  17  Focus hold filter B-L
  K4D  54  Focus hold filter output gain
  K4E  00  Not used
  K4F  00  Not used


CDROM Video CDs (VCD)

VCDs are Video CDs with MPEG compression, yielding a playtime of about 74 minutes per disc (whole movies usually being stored on two CDs). VCDs are popular in asia (as opposed to VHS tapes used in western world).

VCDs on Playstation
For the Playstation, the asian SCPH-5903 model includes a special daughterboard with MPEG decoding hardware for playing VCDs.
CDROM - Video CD Commands
Pinouts - VCD Pinouts
Without that hardware it has been widely believed to be impossible to play VCDs on Playstations, although, as of 2017, it turned out that the Playstation's CPU and MDEC decoder are fast enough for that purpose (when skipping B-frames, rendering the movie in monochrome without colors, and reducing audio output to 11kHz/mono).

ISO Filesystem (Track 1)
VCD ISO Basic Files (INFO, ENTRIES, AVSEQnn, ISO Filesystem)
VCD ISO Playback Control PBC Files (PSD, LOT, ITEMnnnn)
VCD ISO Search Files (SCANDATA, SEARCH, TRACKS, SPICONTX)
VCD ISO Misc files (CAPTnn, AUDIOnn, KARINFO, PICTURES, CDI)

MPEG Streams (Track 2 and up)
VCD MPEG-1 Multiplex Stream
VCD MPEG-1 Video Stream
XXX MPEG-1 Macroblocks
VCD MP2 Audio Stream

VCD Versions & Variants
XXX


VCD ISO Basic Files (INFO, ENTRIES, AVSEQnn, ISO Filesystem)

Primary Volume Descriptor (00:02:16)
VCDs are having a standard ISO Primary Volume Descriptor, with some VCD specific entries:
  008h 32  System Identifier (always "CD-RTOS CD-BRIDGE" for VCDs)
  028h 32  Volume Identifier (often nonsense, eg. "" or "__" or "VolumeLabel")
  23Eh 128 Application Identifier ("CDI/CDI_APPL.VCD;1" or "CDI/CDI_VCD.APP;1")
  400h 8   CD-XA Identifying Signature ("CD-XA001" for PSX and VCD)
There are some more differences to normal CDROMs:
  VCDs are using MODE2 (with 800h-byte and 914h-byte sectors)
  MPEG videos are on extra data tracks (outside of the ISO area on Track 1)
  Files in VCD or SVCD folders use fixed sectors numbers (00:04:00 and up)
  All 16bit/32bit values in files in VCD,SVCD,EXT,etc are BIG-ENDIAN
Due to the fixed sector numbers, VCDs players can completely ignore the ISO filesystem with filenames and folders, and just address everything via sector numbers (though accessing files in EXT and CDI folders seem to require using the filesystem).

VCD\INFO.VCD or SVCD\INFO.SVD (00:04:00) (800h bytes, one sector)
  000h 8    ID "VIDEO_CD" for VCD (or "SUPERVCD"/"HQ-VCD  " for SVCD)
  008h 1    Version             ;Version Major (01h) (or 02h for VCD 2.0)
  009h 1    System Profile Tag  ;Version Minor (00h) (or 01h for VCD 1.1 or HQ)
  00Ah 16   Album ID/Desc (name in ASCII, padded with SPC) (usually empty)
  01Ah 2    Total Number of CDs in Album (1..N) ;\usually always 1,1 (even
  01Ch 2    Number of this CD in Album   (1..N) ;/for movies with 2 discs)
  01Eh 13   PAL Flags, 98x1bit, for each Track? (0=NTSC, 1=PAL)
  02Bh 1    InfoStatusFlags (see below)
 Below is usually zero-filled when not using PBC
  02Ch 4    Size of PSD.VCD file (or PSD.SVD?) (0=None)
  030h 3    First segment addr MM:SS:00 in BCD    (00:02:00 ???)
  033h 1    Offset Multiplier for "PsdOffset" values in PSD.VCD (must be 8)
  034h 2    Number of ListIDs in LOT.VCD file (1..7FFFh, plus 1 in some discs)
  036h 2    Number of ITEMnnnn.DAT files (plus nonsense in some discs?)
 Below is usually zero-filled (maybe exists on SVCD only?)
  038h 1980 SegmentContent[1..1980] (b0-1=Audio, b2-4=Video, b5=Cont, b6-7=OGT)
  7F4h 5*2  volume start time[0]: 5x16bit  ;aka playing_time[5] in seconds (?)
  7FEh 2    Reserved (0)
InfoStatusFlags at [02Bh] describes certain characteristics of the disc:
  bit0   Reserved, must be zero
  bit1-2 Restriction (0=No, 1..3=Restricted category 1..3) (eg. "not for kids")
  bit3   Special Information is encoded in the pictures, uh?
  bit4   MPEG User Data is used for Closed Caption (user_data_cc) (0=No, 1=Yes)
  bit5   Next Disc with PBC     (0=Start at ListID#1, 1=Start at ListID#2)
  bit6   Next Disc without PBC  (0=Start at Track #2, 1=Start at Track #3)
  bit7   Extended PBC available (0=No, 1=Yes... aka EXT\PSD_X exists?)
Note: Bit5/6 are used only if the next disc has the same Album ID (eg. the feature allows to skip copyright messages if the same message was already shown on another disc).
First_segment_addr: The location of the first sector of the Segment Play Item Area [that is... the first ITEMnnnn.DAT file?], in the form mm:ss:00. Must be 00:00:00 if PSD size is zero. If PSD size is nonzero, but no segments used: Usually set to 00:02:00.

VCD\ENTRIES.VCD or SVCD\ENTRIES.SVD (00:04:01) (800h bytes, one sector)
  000h 8     ID "ENTRYVCD" for VCD and SVCD (or "ENTRYSVD" for VCD30)
  008h 1     Version               ;\same as in INFO.VCD/SVD
  009h 1     System Profile Tag    ;/
  00Ah 2     Number of Entries/Chapters (1..500)
  00Ch 4*500 Entry[N] (Track 02h..99h, and MM:SS:FF) (all 4 bytes in BCD)
  7DCh 36    Reserved (0)
Version;
  0x02 --- VCD2.0
  0x01 --- SVCD, should be same as version in INFO.SVD
Sys_prof_tag;
  0x01 if VCD1.1
  0x00 else

MPEGAV\AVSEQnn.DAT (pointers to max 98 MPEG-1 Tracks, nn=01..98) (for VCDs)
MPEG2\AVSEQnn.MPG (pointers to max 98 MPEG-2 Tracks, nn=01..98) (for SVCDs)
MPEGAV\AVSEQnn.MPG (pointers to WHATEVER) (as so on some SVCDs or VCD30?)
These filesystem entries contain pointers to the video tracks (that is, outside of the ISO area on Track 1).
Commercially made SVCDs can reportedly contain 7 folders: Autorun, Data, Ext, Mpegav, Segment, Svcd and Vmp (ie. there's no MPEG2 folder on all SVCDs? though that MPEGAV folder is said to contain a .MPG file instead of .DAT file).


VCD ISO Playback Control PBC Files (PSD, LOT, ITEMnnnn)

Playback Control (PBC) is an optional feature that allows to define menues, pictures or text pages (whereas all those is internally just consisting of MPEG compressed bitmaps; rather than of text characters).
Presence of the PBC feature is indicated by PSD.VCD filesize entry (in INFO.VCD) being nonzero. PBC seems to be supported by most VCDs (except older discs from around 1997), however, many VCDs are merely including a single PlayList entry for the movie track, without any further menues/extras.

VCD\PSD.VCD or SVCD\PSD.SVD (00:04:34 and up) (max 256 sectors)
The Descriptors in this file can be considered as being "program code". The program is usually stuck on "executing" the current descriptor (eg. playing a movie, or showing a selection menu) without automatically increasing the program counter. Actual program flow occurs only if the user presses a button (or upon selection timeouts), causing the program to "goto" to a new PsdOffset. And, something does probably happen upon end-of-track/item... maybe that does automatically trigger the Next button handler?
 PsdPlayListDescriptor (14+2*N bytes):
  00h 1   Type (10h=PlayList)
  01h 1   Number of Items (noi)     ;for Start-of-Movie and Numeric-Input?
  02h 2   ListID for this Descriptor (1..7FFFh)
  04h 2   PsdOffset for Prev button                 (FFFFh=Disable)
  06h 2   PsdOffset for Next button                 (FFFFh=Disable)
  08h 2   PsdOffset for Return/back button          (FFFFh=Disable)
  0Ah 2   Play time in 1/15s (=max 72.8 minutes) (or 0000h=full item)
  0Ch 1   Delay time in "1s/10s" units after ;<-- uh, after? after what?
  0Dh 1   Auto pause time in "1s/10s" units (used for each item in list if
          the auto pause flag in a sector is true) [WHAT is that? Trigger bit?]
  0Eh 2*N ItemID[N]  ;item number (0..599 or 1000..2979)
          Entry 0 is for "start of movie" (usually 0002h=Track 2)
          Entry 1..N-1 is for numeric input ?
 PsdSelectionListDescriptor (20+2*N bytes, or 36+6*N bytes):
  00h      1   Type (18h=SELECTION_LIST, or 1Ah=EXT_SELECTION_LIST)
  01h      1   Flags (bit0=SelectionArea, bit1=CommandList, bit2-7=Reserved)
  02h      1   nos     <-- aka Number of Numeric-input selections ?
  03h      1   bsn     <-- ?
  04h      2   ListID for this Descriptor (1..7FFFh)
  06h      2   PsdOffset for Prev button
  08h      2   PsdOffset for Next button
  0Ah      2   PsdOffset for Return/back button
  0Ch      2   PsdOffset for Default button (uh, what is that?)
  0Eh      2   PsdOffset for Timeout
  10h      1   totime  <-- aka Timeout Time maybe? in WHAT units?
  11h      1   loop    <-- aka ?
  12h      2   itemid  <-- aka Item to be displayed during the selection?
  14h      2*N PsdOffset[N] for Numeric-input ?
 Below only for SVCDs (with Type=18h), or for Extended VCDs (with Type=1Ah):
 (14h+2*N) 4   Area for Prev    (x1,y1,x2,y2)  ;\these extra entries exist for
 (18h+2*N) 4   Area for Next    (x1,y1,x2,y2)  ; SVCDs with Type=18h, and
 (1Ch+2*N) 4   Area for Return  (x1,y1,x2,y2)  ; Extended VCDs with Type=1Ah
 (20h+2*N) 4   Area for Default (x1,y1,x2,y2)  ; (but do NOT exist for
 (24h+2*N) 4*N Area[N]          (x1,y1,x2,y2)  ;/older VCDs with Type=18h)
 PsdEndListDescriptor (8 bytes)
  00h 1     Type (1Fh=EndList)
  01h 1     Next_disc   ;00h to stop PBC or NNh to switch to disc no NN (BCD!?)
  02h 2     Item (0 or 1000..2979, should be still image, eg. Change Disc pic)
  04h 4     Reserved (0)
  N/A -     This descriptor doesn't have a ListID (unlike as other descriptors)
 PsdCommandListDescriptor (5+2*N bytes)
  00h 1     Type (20h=CommandList)
  01h 2     Command_count
  03h 2     ListID for this Descriptor (1..7FFFh)
  05h 2*N   command[EMPTY_ARRAY_SIZE]  ;uh, WHAT is a command?
 PsdAlignmentPadding (after each list entry)
  00h 0..7  Padding to next 8-byte PsdOffset boundary (00h-filled)
Delay values in "1s/10s" units (for PlayList[0Ch,0Dh]):
  1..60   --> wait "N" seconds
  61..254 --> wait "(N-60)*10+60" seconds
  255     --> wait infinite
Item numbers (0..599 or 1000..2979) can be:
  0..1        - Play nothing
  2..99       - Play Track 2..99 (TOC tracks, for AVSEQnn.DAT and AUDIOnn.DAT?)
  100..599    - Play Entry 1..500 from table in ENTRIES file up to end of track
  600..999    - Reserved
  1000..2979  - Play SPI Segment Play Item 1..1980 (ITEMnnnn.DAT file)
  2980..65535 - Reserved
PsdOffset values can be:
  0..N   Offset within PSD.VCD file, in 8-byte units
  FFFDh  PSD_OFS_MULTI_DEF_NO_NUM ;\uh, what is that?
  FFFEh  PSD_OFS_MULTI_DEF        ;/
  FFFFh  PSD_OFS_DISABLED         ;-no function assigned to the button
For whatever reason, some PsdOffsets are specified as ListID (lid), these ListID values must be translated to actual PsdOffset via the ListID Offset Table (aka LOT.VCD/LOT.SVD file).

VCD\LOT.VCD or SVCD\LOT.SVD (00:04:02..33) (64Kbyte, 32 sectors)
The ListID Offset Table (LOT) allows to translate ListIDs to PsdOffsets. The file is always 64Kbyte in size (unused entries should be set to FFFFh).
The PSD.VCD file does also assign ListIDs to each descriptor (ie. instead of using the LOT.VCD file, one could also scan all descriptors in PSD.VCD when searching a specific ListID).
  0000h 2       Reserved (0)
  0002h 2*7FFFh PsdOffset[1..7FFFh]  ;for ListID 1..7FFFh
Note: ListID#1 is used as entrypoint to PSD.VCD when inserting a new disc (or when inserting another disc of the SAME movie, the entrypoint can be ListID#2, depending on the Next Disc flag in INFO.VCD).

SEGMENT\ITEMnnnn.DAT (Pictures, Menu screens) (nnnn=0001..1980)
These files contain Pictures/Menu screens referenced from PSD.VCD. The files seem to be stored in FORM2 sectors (not FORM1). Unknown if the files are located on Track 1.
The content of the files seems to resemble short MPEG video clips (with only one picture frame for still images, or with a few frames for short animations, including audio in some cases). Still images are said to be allowed to use twice the resolution of MPEG videos.

EXT\PSD_X.VCD or EXT\PSD_X.SVD (extended version of PSD.VCD)
EXT\LOT_X.VCD or EXT\LOT_X.SVD (extended version of LOT.VCD)
The "extended" files are often identical to the normal PSD/LOT files. The difference is that, if disc uses SelectionLists, then PSD should use the normal descriptor (18h), and PSD_X should use the extended descriptor (1Ah), the latter one seems to be intended to allow to highlight the current menu selection (particulary useful when using +/- buttons instead of Numeric Keypad input). Note: Nethertheless, Muppets from Space uses descriptor 18h in PSD_X.
Unknown if SVCDs do really have "extended" files, too (theoretically the VCD extension should be a default feature for SVCDs).

Playback Control Issues
Although PBC was intended as "nice extra feature", many VCDs are containing faulty PSD files. In general, VCD players should either leave PBC unsupported (or at the very least, provide an option for disabling it).
Red Dragon from 2003 uses extended selection lists, but crops PSD_X.VCD to the same filesize as PSD.VCD.
Muppets from Space from 1999 assigns weird functions to Prev/Next buttons (Next wraps from Last Track to First Track, but Prev doesn't wrap from First to Last; default Non-PBC Prev/Next functions are more user friendly).
Sony's SCPH-5903 console refuses to display the HH:MM:SS playback time when using PBC (instead it does only display a "PBC" logo).


VCD ISO Search Files (SCANDATA, SEARCH, TRACKS, SPICONTX)

Below files can help searching I-frames, and provide some info about the content of Tracks and Segments.
Essentially, searching I-frames is possible without these files - however, if present, then the files may be useful in two cases: For discs with variable bitrates (which isn't allowed on VCDs though), and, for CDROM firmwares that don't support "inaccurate" seeking (like telling it to start reading anywhere NEAR some MM:SS:FF value, so one could skip sectors till reaching an I-frame) (ie. if the firmware insists on a "accurate" seek position, then it's best to give it a known I-frame address).

Caution: Overlapping Sectors (!?!)
Reportedly the new SVCD files TRACKS.SVD and SEARCH.DAT are on these sectors:
  TRACKS_SVD_SECTOR = (PSD_VCD_SECTOR+1)    ;aka 2nd sector in PSD.SVD?
  SEARCH_DAT_SECTOR = (TRACKS_SVD_SECTOR+1) ;aka 3rd..Nth sector in PSD.SVD?
If that's correct, then the files would overlap with PSD.SVD (when PSD.SVD is bigger than one sector), that would be weird, but possible (ie. the "PsdOffset" in PSD.SVD would need to "skip" the region used by those two files).

EXT\SCANDATA.DAT (12+3*N bytes for VCD 2.0) (or 16+3*N+2*X+3*Y+3*Z for SVCD)
This file fulfills much the same purpose of the SEARCH.DAT file except that this file is mandatory only if the System Profile Tag of the INFO.SVD file is 0x01 (HQ-VCD) and also that it contains sector addresses also for each video Segment Play Items in addition to the regular MPEG tracks.
 SCANDATA.DAT Format for VCD 2.0 (12+3*N bytes):
  000h 8    ID "SCAN_VCD"
  008h 1    Version (02h for VCD 2.0)
  009h 1    Reserved (0)
  00Ah 2    Number of scan points (in 0.5s units) (max FFFFh = ca. 9.1 hours)
  00Ch 3*N  Scan Point[0..N-1]  ;MM:SS:FF of closest I-frame
 SCANDATA.DAT Format for SVCD (16+3*N+2*X+3*Y+3*Z bytes):
  000h 8    ID "SCAN_VCD"
  008h 1    Version (01h for SVCD)
  009h 1    Reserved (0)
  00Ah 2    scandata_count ;number of 3-byte entries in the table
  00Ch 2    track_count    ;number of MPEG tracks on disc
  00Eh 2    spi_count      ;number of consecutively recorded play item segments
                           ; (as opposed to the number of segment play items).
  010h 3*N  msf_t cum_playtimes[N]  ;cumulative playing time up to track N.
                                    ; (track time just wraps at 99:59:74)
  xxxh 2*X  spi_indexes[X]          ;Indexes into the following scandata table
  xxxh 2    mpegtrack_start_index   ;Index into the following scandata table
                                    ; (where the MPEG track scan points start)
  xxxh 3*Y  The scandata table... [Y]  ;8bit Track Number and 16bit Index
                uint8_t  track_num       ;Track number as in TOC
                uint16_t table_offset    ;Index into scandata table
  xxxh 3*Z  msf_t scandata_table[Z]  ;MM:SS:FF

SVCD\SEARCH.DAT (13+3*N bytes)
This file defines where the scan points are. It covers all mpeg tracks together. A scan point at time T is the nearest I-picture in the MPEG stream to the given time T. Scan points are given at every half-second for the entire duration of the disc.
  000h 8    ID "SEARCHSV"
  008h 1    Version (01h)
  009h 1    Reserved (0)
  00Ah 2    Number of scan points
  00Ch 1    Time_interval (in units of 0.5 seconds) (must be 01h)
  00Dh 3*N  Scan Point[0..N-1]  ;MM:SS:FF of closest I-frame
Note: This SVCD file is about same as the old EXT\SCANDATA.DAT file on VCDs (with one extra entry for Time Interval). Whilst, SVCDs are storing some different stuff in EXT\SCANDATA.DAT (despite of the identical filename).

SVCD\TRACKS.SVD (11+4*N bytes) (or rarely:11+5*N bytes)
The TRACKS.SVD file contains a series of structures, one for each track, which indicates the track's playing time (in sectors, not actually real time) and contents.
SVCD\TRACKS.SVD is a mandatory file which describes the numbers and types of MPEG tracks on the disc.
 SVCD\TRACKS.SVD Format for SVCD (11+4*N bytes):
  000h 8   ID "TRACKSVD"
  008h 1   Version (01h)
  009h 1   Reserved (0)
  00Ah 1   Number of MPEG tracks (N)
  00Bh 3*N Track playing_time[N]  (MM:SS:FF, in BCD)(in sectors, not real time)
  0xxh 1*N TrackContent[N]  ;bit0-1=Audio,bit2-4=Video,bit5=Reserved,bit6-7=OGT
 SVCD\TRACKS.SVD Format for VCD30 (11+5*N bytes) (some sort of SVCD-prototype):
  000h 8   ID "TRACKSVD"
  008h 1   Version (01h)
  009h 1   Reserved (0)
  00Ah 1   Number of MPEG tracks (N)
  00Bh 5*N Cum_Playing_time and Content (MM:SS:FF in BCD, and OGT, Audio)

SVCD\SPICONTX.SVD (1000h bytes, two sectors)
Unknown if/when/where/why this file exists, possibly only on VCD30?
Note: The same info can be stored in INFO.SVD at offsets [038h..7F3h].
  0000h 8       ID "SPICONSV"
  0008h 1       Version (01h)
  0009h 1       Reserved (0)
  000Ah 2*1980  Segment Content[1..1980] (1st byte=OGT, 2nd byte=Audio)
  0F82h 126     Reserved (0)

Content Flags for Segments and Tracks
For SVCD\INFO.SVD and SVCD\TRACKS.SVD (on SVCD) these are encoded in 1 byte:
  bit0-1  Audio characteristics:
            0 = No MPEG audio stream
            1 = One MPEG1 or MPEG2 audio stream without extension
            2 = Two MPEG1 or MPEG2 audio streams without extension
            3 = One MPEG2 multi-channel audio stream with extension
  bit2-4  Video characteristics:
            In TRACKS.SVD this must be 0,3,7 (no still pictures)
            0 = No MPEG video data
            1 = NTSC still picture
            2 = NTSC Reserved (NTSC still pic hires?)
            3 = NTSC motion picture
            4 = Reserved
            5 = PAL still picture
            6 = PAL Reserved (PAL still pic hires?)
            7 = PAL motion picture
  bit5    Indicates segment is continuation of an item
            In TRACKS.SVD this must be 0 (reserved)
            0 = First or only segment of item
            1 = Second or later segment of item
  bit6-7  Overlay Graphics/Text (OGT):
            0 = No OGT substream
            1 = Sub-stream 0 available
            2 = Sub-stream 0 & 1 available
            3 = All OGT sub-substreams available
For SPICONTX.SVD and SVCD\TRACKS.SVD (on VCD30) these are encoded in 2 bytes:
  1st byte = Audio characteristics        ;\probably same values as
  2nd byte = Overlay Graphics/Text (OGT)  ;/in above bitfields?


VCD ISO Misc files (CAPTnn, AUDIOnn, KARINFO, PICTURES, CDI)

EXT\CAPTnn.DAT (Closed Caption data, aka subtitles) (SVCD only?)
VCDs with subtitles are usually/always having the subtitles encoded directly in the picture frames (ie. in the MPEG macroblocks, rather than using the Closed Caption feature).
These CAPTnn.DAT files are intended for Closed Captions (eg. subtitles in different languages and/or for deaf people).
Alternately, the "user_data_cc" flag in INFO.VCD?/INFO.SVD can indicate to store Closed Captions in MPEG User Data (with START_CODE=000001B2h=User Data) instead of in EXT\CAPTnn.DAT. Either way, the format of those Closed Captions is unknown.
Moreover, Content can be flagged to have Overlay Graphics/Text (OGT), whatever that is: it might be related to Closed Captions.
Note: Reportedly CAPTnn.DAT can exist on VCDs and SVCDs (although the same person reported that VCDs do not support subtitles, so that info sounds wrong).

CDDA\AUDIOnn.DAT (pointers to uncompressed CD Audio Tracks)
These filesystem entries contain pointers to uncompressed audio tracks tracks (that is, outside of the ISO area on Track 1).
Most VCDs don't have audio tracks (though some VCDs do contain empty CDDA folders).
Maybe the feature is occassionally used the other way around: Music discs containing VCD clips as bonus feature?

KARAOKE\KARINFO.xxx (whatever)
The KARAOKE folder exists on many VCDs (about 50%), but it's usually/always empty on all discs.
Reportedly the folder can contain "KARINFO.xxx" files, but the purpose/format of that files is unknown.
Reportedly there are Midi VCDs (MVCDs) for karaoke, maybe those discs have "KARINFO.xxx" files(?)

PICTURES\*.* (whatever)
Unknown purpose. The PICTURES folder has been spotted on one VCD (Wallace and Gromit), but the folder was just empty.

CDI\*.* (some kind of GUI/driver for Philips CDI Players)
The CDI folder is some relict for Philips CDI Players, it isn't used by normal VCD players, however, the CDI folder & files are included on most or all VCDs.
The path/name for the CDI executable is stored at offset 23Eh in the ISO Primary Volume Descriptor (usually "CDI/CDI_APPL.VCD;1" or "CDI/CDI_VCD.APP;1") (or accidentally "CDI_CDI_VCD.APP;1" on homebrew Nero discs).
The files in the CDI folder are usually just some standard files (without any customizations), however, there are some different revisions of these files:
 Revision A (spotted on two discs from 1997 and 1999):
  CDI_APPL.VCD   80702 bytes, 04-Mar-1996, CRC32=AE8FC5D0h  ;executable
  VCD_BACK.DYV   92572 bytes, 18-Jul-1995, CRC32=00693E5Eh  ;whatever?
  VCD_BTN.C8     93719 bytes, 18-Jul-1995, CRC32=FF0A636Ah  ;whatever?
 Revision B (spotted on a disc from 2003):
  CDI_VCD.APP    20648 bytes, 00-Nul-0000  CRC32=DC885F70h  ;executable
  CDI_FONT.FNT  145388 bytes, 00-Nul-0000  CRC32=FB4D63F4h  ;font?
  CDI_ALL.RTF        ? bytes,              CRC32=?          ;realtimefile?
  CDI_BUM.RTF        ? bytes,              CRC32=?          ;realtimefile?
 Revision C (spotted on a disc from 2006, and homebrews from 2001 and 2017):
  CDI_VCD.APP   102400 bytes, 00-Nul-0000  CRC32=E91E128Dh  ;executable
  CDI_VCD.CFG      193 bytes, 00-Nul-0000  CRC32=D1C6F7ADh  ;config/ascii
  CDI_TEXT.FNT   13616 bytes, 00-Nul-0000  CRC32=BDC55E86h  ;font?
  CDI_IMAG.RTF 1510028 bytes, 00-Nul-0000  CRC32=(RIFF)     ;realtimefile?
CDI_VCD.CFG is some ASCII text file (with uncommon 0Dh,0Dh,0Ah line breaks), the file could be customized to change things like GUI colors, but most or all discs seem to contain the same file with CRC32=D1C6F7ADh. Note: The CFG file is missing on the homebrew DemoVCD.
CDI_IMAG.RTF is seen as 1510028 byte file under windows (that is, with a windows RIFF header, and with data area containing the whole 930h bytes from each sector; this includes the MM:SS:FF values from the sector header, so the RTF file may look slightly different depending on which sectors it has been stored on, although the files are usually exactly same apart from those MM:SS:FF values). Note: The RTF file is cropped to 1324220 bytes (instead of 1510028) on the homebrew DemoVCD (apart from that, the file is same as normal).
CDI_ALL.RTF and CDI_BUM.RTF cannot be read/copied under Windows 7 (which is weirdly reporting them to use an "invalid MS-DOS function"; some people also reported having CDI_IMAG.RTF files with similar problems). The reason is unknown, maybe windows doesn't fully support the CD filesystem, or some VCDs are violating the filesystem specs, or whatever... maybe windows is mis-identifying certain RTF files as Rich Text Format files and tries to prevent virus-infections by throwing a faked "MS-DOS" error message.


VCD MPEG-1 Multiplex Stream

Multiplex Stream & Sector Boundaries
The Multiplex stream is some higher level stream, intended to help to distinguish between Audio- and Video-streams (which are enclosed in the Multiplex stream). MPEG's are somewhat organized in "sectors", with sector size varying for normal .mpg files and VCDs:
  VCD discs   --> Sector Size = 914h bytes (the discs MODE2/FORM2 sector size)
  .mpg files  --> Sector Size = 800h bytes (regardless of physical sector size)
Sectors are always beginning with a Multiplex Packet (and Multiplex Packets are never crossing sector boundaries). If the amount of video data exceeds the sector size, then it's split into several Multiplex packets, whereas, that may happen anywhere in the video stream (ie. there can be Multiplex Headers occurring even in the middle of Video packet).

MPEG-1 Multiplex Pack (sector header) (12 bytes)
The Pack Header is found at the begin of the stream (on VCDs, it's also found at the begin of each sector). The SCR values might help on identifying the current playback position, and, with the bitrate value, this could be also used to compute the distance to another position (though there are other ways to determine the position/bitrate, so the Pack is kinda useless).
 32bit PACK_START_CODE (000001BAh)                                      ;-4byte
  2bit Fixed (00b for MPEG-1) (would be 01b for MPEG-2)                 ;\
  2bit Fixed (10b)                                                      ;
  3bit System Clock Reference, bit32-30  ;\                             ;
  1bit Marker (1)                        ; System Clock Reference (SCR) ;
 15bit System Clock Reference, bit29-15  ; (intended Time,              ; 5byte
  1bit Marker (1)                        ; in 90kHz clock cycles)       ;
 15bit System Clock Reference, bit14-0   ;/                             ;
  1bit Marker (1)                                                       ;/
  1bit Marker (1)                                                       ;\
 22bit Multiplex Rate (total bitrate of the stream, in 400bit/s units)  ; 3byte
  1bit Marker (1)                                                       ;/

MPEG-1 Multiplex System Header (12+N*3 bytes)(optionally)(at start of stream)
The System Header is usally found after the first Pack at the begin of the stream.
 32bit SYSTEM_HEADER_START_CODE (000001BBh)                             ;\6byte
 16bit Header Length minus 6 (in bytes) (0006h+N*3)                     ;/
  1bit Marker (1)                                                       ;\
 22bit Rate bound (max multiplex rate of all packs in the stream,       ; 3byte
  1bit Marker (1)                              in 400bit/s units)       ;/
  6bit Audio Bound (max number of audio streams in this ISO stream)     ;\
  1bit Fixed Flag (1=Fixed bitrate)                                     ; 1byte
  1bit CSPS Flag  (1=Constrained)                                       ;/
  1bit System Audio Lock Flag  XXX                                      ;\
  1bit System Video Lock Flag  XXX                                      ; 1byte
  1bit Marker (1)                                                       ;
  5bit Video Bound (max number of video streams in this ISO stream)     ;/
  8bit Reserved (FFh)                                                   ;-1byte
Followed by N*3 bytes for the streams (each with first bit=set):
  8bit Stream ID (C0h..DFh=Audio, E0h..EFh=Video)                       ;\
  2bit Fixed (11b)                                                      ; 3byte
  1bit STD buffer scale (0=Mul128/audio, 1=Mul1024/video)               ;
 13bit STD buffer size  (largest required buffer over all packets)      ;/
Terminated by a value with first bit=cleared (eg. next 000001xxh value).

MPEG-1 Multiplex Video/Audio/Special Packets (7..24 bytes, plus data)
These packets are encapsulating the lower-level Video/Audio streams.
  32bit  START (000001xxh BDh-BFh=Special, C0h-DFh=Audio, E0h-EFh=Video);\6byte
  16bit  Packet Length minus 6 (in bytes) (1..18, plus data)            ;/
If (and while) next two bits are 11b (0..16 padding bytes):
  (2bit) Fixed (11b, indicates presence of stuffing)       ;\optional 0..16byte
  (6bit) Fixed (111111b)                                   ;/
If next two bits are 01b (buffer size info):
  (2bit) Fixed (01b, indicates presence of buffer size)        ;\
  (1bit) STD Buffer Scale (0=Mul128/audio, 1=Mul1024/video)    ; optional 2byte
 (13bit) STD Buffer Size (for decoding, in above scale units)  ;/
Always:
   2bit  Fixed (00b, indicates no further stuffing/buffer info);\
   1bit  PTS Flag (Presentation Time Stamp)                    ; 0.5 bytes
   1bit  DTS Flag (Decoding Time Stamp)                        ;/
If PTS Flag set:
  (3bit) Presentation Time Stamp, bit32-30       ;\
  (1bit) Marker (1)                              ; optional 4.5 bytes
 (15bit) Presentation Time Stamp, bit29-15       ; (time when to output the
  (1bit) Marker (1)                              ; the packet to audio/video
 (15bit) Presentation Time Stamp, bit14-0        ; hardware, in 90kHz cycles)
  (1bit) Marker (1)                              ;/
If DTS Flag set (in this case PTS Flag must be also set):
  (4bit) Fixed (0001b)                           ;\
  (3bit) Decoding Time Stamp, bit32-30           ; optional 5 bytes
  (1bit) Marker (1)                              ; (recommended time when
 (15bit) Decoding Time Stamp, bit29-15           ; to decode the block,
  (1bit) Marker (1)                              ; in 90kHz cycles)
 (15bit) Decoding Time Stamp, bit14-0            ;
  (1bit) Marker (1)                              ;/
If PTS and DTS Flags are both zero:
  (4bit) Fixed (1111b)                           ;-optional 0.5 bytes
Always:
  ...  packet data bytes                         ;-data...(not crossing sector)
Note: The first Multiplex Video Packet would usually start with a Sequence Header Code (000001B3h), and the first Multiplex Audio Packet should always start with an Audio Sync Word (FFFh).
However, the size of the Multiplex packets does usually differ from the size of the packets in the audio/video stream, so new Multiplex Packets may occur anywhere in the middle of those streams (eg. in the middle of a video slice, the next Multiplex Video packet would then begin with the remaining slice bytes, rather than with a 000001xxh code; it's also possible that a Multiplex Audio packet gets inserted in the middle of the video slice).
The best (or easiest) way to get continous data for the lower level streams might be to memcopy the data from Multiplex packets to separate Audio & Video buffers.

MPEG-1 Multiplex End Code (4 bytes)
 32bit END_CODE (000001B9h)                                             ;-4byte
This should occur at the end of the video. On a VCD it does also occur at the end of each video track.


VCD MPEG-1 Video Stream

The Video stream is part of the Multiplex stream, meaning that the Video packets preceeded (and interrupted) by Multiplex headers. Ie. before processing the Video packets, one must first extract the video snippets from the Multiplex stream (see previous chapter).
Raw vides (without audio) may directly start with Video Sequence Header (without any Multiplex headers).

MPEG-1 Video Sequence Header (12, 76, or 140 bytes, ie. 12+N*64)
  32bit SEQUENCE_HEADER_CODE (000001B3h)                        ;-4byte
  12bit Width in pixels  (1..4095)                              ;\3byte
  12bit Height in pixels (1..2800, for max AFh slices)          ;/
   4bit Aspect Ratio (01h..0Eh, see below)                      ;\1byte
   4bit Framerate    (01h..08h, see below)                      ;/
  18bit Bitrate (in 400bit/s units, 3FFFFh=variable rate)       ;\
   1bit Marker (1)                                              ; 3byte
  10bit VBV (required decoding memory size, in "16 kB" units)   ; +6bit
   1bit Constrained Parameter Flag                              ;/
   1bit Load Intra Q Matrix      (0=No, use Standard Matrix, 1=Yes, Custom)
Next 64byte only when above bit was set:
 (64byte) Intra Quantizer Matrix (64 x 8bit, unsigned) (in zigzag order)
   1bit Load Non-Intra Q Matrix  (0=No, use Standard Matrix, 1=Yes, Custom)
Next 64byte only when above bit was set:
 (64byte) Non-Intra Quantizer Matrix (64 x 8bit, unsigned) (in zigzag order)
Aspect Ratio values:
  0     -       ;forbidden
  1     1.0     ;square pixels
  2     0.6735  ;0.6735
  3     0.7031  ;16:9, 625 line, PAL
  4     0.7615  ;0.7615
  5     0.8055  ;0.8055
  6     0.8437  ;16:9, 525 line, NTSC
  7     0.8935  ;0.8935
  8     0.9157  ;4:3, 625 line, PAL, CCIR601
  9     0.9815  ;0.9815
  10    1.0255  ;1.0255
  11    1.0695  ;1.0695
  12    1.0950  ;4:3, 525 line, NTSC, CCIR601
  13    1.1575  ;1.1575
  14    1.2015  ;1.2015
  15    -       ;reserved
Frame Rate values:
  0     -                     ;forbidden
  1     23.976 (24000/1001)   ;NTSC encapsulated film rate
  2     24.0                  ;Standard international cinema film rate
  3     25.0                  ;PAL  video frame rate (625/50)
  4     29.97  (30000/1001)   ;NTSC video frame rate
  5     30.0                  ;NTSC video frame rate drop-frame (525/60)
  6     50.0                  ;PAL  double frame rate/progressive
  7     59.94  (60000/1001)   ;NTSC double frame rate
  8     60.0                  ;NTSC double frame rate drop-frame
  9-15  -                     ;reserved

MPEG-1 Video Group of Pictures (GOP) (8 bytes) XXX...
 32bit GROUP_START_CODE (000001B8h)
  1bit Drop Frame (1=drop this frame; for reducing 30 fps to 29.97 fps)
  5bit Time Code Hours   (0..23)
  6bit Time Code Minutes (0..59)
  1bit Marker (1)
  6bit Time Code Seconds (0..59)
  6bit Time Code Picture (0..59)
  1bit Closed GOP
  1bit Broken Link

MPEG-1 Video Picture Header XXX...
  32bit  PICTURE_START_CODE (00000100h)                           ;\
  10bit  Temporal Reference (display order, 0..3FFh)              ; 61bit
   3bit  Coding Type (0=Invalid, 1=I, 2=P, 3=B, 4=D, 5-7=Reserved);
  16bit  VBV Delay (in 90kHz cycles, FFFFh=variable bitrate)      ;/
If Coding Type is 2 or 3 (P-Frame or B-Frame):
  (1bit) full fel forward vector   (0=half pix, 1=full pix)     ;\optional 4bit
  (3bit) forward f code            (0=invalid, 1..7=0..6bits)   ;/
If Coding Type is 3 (B-Frame):
  (1bit) full backward vector                                   ;\optional 4bit
  (3bit) backward f code                                        ;/
If (and while) next bit is set:
  (1bit) Fixed (1, indicates presence of Extra Info)            ;\opt. N*9bit
  (8bit) Extra Information                                      ;/
End of Extra:
   1bit  Fixed (0, indicates no further Extra Info)             ;-1bit
 0-7bit  Padding to byte boundary (0)                           ;-0..7bit
Coding Type values:
  0  Forbidden
  1  I - Intra Coded                      (full image)
  2  P - Predictive Coded                 (based on prev I or P frame)
  3  B - Bidirectionally Predictive Coded (based on prev+next I or P frame)
  4  D - DC Intra Coded                   (don't care, lowres thumbnail)
  5  Reserved
  6  Reserved
  7  Reserved

Frame Order
  DISPLAY ORDER:
  I B B B P B B B P B B B P B B B I B B B P B B B P B B B P B B B ...
  |       |_______|_______|       |       |_______|_______|
  |               |               |               |
  I-Frame         P-frames        I-Frame         P-frames
The B-fames require to know the next P- (or I-) frame in advance, for that reason, the frames are stored as "PBBB" (although being played as "BBBP"):
  STORAGE ORDER:
  I P B B B P B B B P B B B I B B B P B B B P B B B P B B B ...
  | |_______|_______|       |       |_______|_______|
  |         |               |               |
  I-Frame   P-frames        I-Frame         P-frames

MPEG-1 Video Slice
Slices are containing the actual 16x16 pixel Macro Blocks. Usually a Slice contains one horizontal line - although, theoretically, it could be longer or shorter, ie. a slice could wrap to next line, or a line could be split into several slices (with the leading "MBA Increment" value greater than 1 to define the horizontal start offset).
  32bit  PACK_START_CODE (000001xxh; xx=01h..AFh; vertical index) ;-4byte
   5bit  Quantizer Scale (1..31) (may be later changed by blocks) ;-5bit
If (and while) next bit is set:
  (1bit) Fixed (1, indicates presence of Extra Info)              ;\opt. N*9bit
  (8bit) Extra Information                                        ;/
End of Extra:
   1bit  Fixed (0, indicates no further Extra Info)               ;-1bit
If (and while) next 23bit are nonzero (ie. until next 000001xxh):
   ...   Macroblock (within horizontal line)                      ;...
Final padding:
 0-7bit  Padding to byte boundary (0)                             ;-0..7bit

MPEG-1 Video Group/Sequence Extension Data (reserved)
MPEG-1 Video User Data (optional)
 32bit START_CODE (000001B2h=User Data, 000001B5h=Extension Data)       ;-4byte
   ... data (end is signaled by presence of next 000001xxh code)        ;-data
User Data can contain Closed Captions (see flag in VCD\INFO.VCD or SVCD\INFO.SVD).
User Data contains 11h-byte "Created with Nero" in some homebrew discs.

MPEG-1 Video Sequence End Code (4 bytes)
  32bit SEQUENCE_END_CODE (000001B7h)                                   ;-4byte




MPEG-1 Video 4:2:0 Macroblock
         N*11bit  Macroblock_address_increase escape/stuffing codes (if any)
         1..11bit Macroblock_address_increase
         1-6bit   Macroblock_type
         5bit     Quantizer_scale
         ...      Motion_vector
         3-9bit   Coded_block_pattern
         ...      Block(i)
Aka...
  Addr Incr
  Type
  Motion Vector
  QScale
  CBP
  Block b0 (Y1)
  Block b1 (Y2)
  Block b2 (Y3)
  Block b3 (Y4)
  Block b4 (Cb)
  Block b5 (Cr)



VCD MP2 Audio Stream

VCD video discs and .mpg movie files are having the MP2 Audio Stream enclosed in the Multiplex stream (whilst .mp2 audio files may contain raw MP2 data without Multiplex stream).

Each MP2 frame is starting with a FFFh syncword (which is always located on a byte boundary). Unfortunately, the value FFFh can also occur anywhere in the audio data (eg. a 16bit sample with value 3FFCh).
So, when starting mid-stream, one will need some guessing when searching a valid syncword. The best method is to compute the frame size (based on the supposed frame header), and then to check if supposed frame begins AND ends with a sync word. Moreover, one could check for invalid sample rate values in the frame header, or invalid "groupings" in the frame's data part.
VCDs are conventionally having three audio frames encoded in one CDROM sector, so the first syncword can be simply found right after the multiplex packet header (though that might differ in some cases: VCD2.0 allows different audio bitrates, and a CDROM sector could be theoretically shared for Audio and Video data).

Overall MP2 Frame Format
  Header (32bit)
  Optional CRC (16bit) (or 0bit if none)
  Allocation Information
  Scale Factor Selector Information
  Scale Factors
  Data

MP2 Header
  12bit Syncword (FFFh)                                         ;\
  1bit  Revision (0=MPEG-2, 1=MPEG-1)                           ; 2 bytes
  2bit  Layer (2=Audio LayerII)                   ;for VCDs     ;
              (3=LayerI, 1=LayerIII, 0=reserved)  ;not on VCDs  ;
  1bit  Protection_bit (1=no crc)                               ;/
  4bit  Bitrate_index (1..14)                                   ;\
          (0=free format, 15=reserved)                          ;
  2bit  Sampling_frequency                                      ; 1 byte
  1bit  Padding_bit                                             ;
  1bit  Private_bit                                             ;/
  2bit  Mode                                                    ;\
  2bit  Mode_extension (aka bound)                              ;
  1bit  Copyright                                               ; 1 byte
  1bit  Original/home                                           ;
  2bit  Emphasis                                                ;/

MP2 Checksum (optional)
  16bit CRC

Allocation Information
Scale Factor Selector Information
Scale Factors
Data
  XXX...


Controllers and Memory Cards

Controllers/Memory Cards
Controller and Memory Card I/O Ports
Controller and Memory Card Misc
Controller and Memory Card Signals
Controller and Memory Card Multitap Adaptor

Controllers
Controllers - Communication Sequence
Controllers - Standard Digital/Analog Controllers
Controllers - Mouse
Controllers - Racing Controllers
Controllers - Lightguns
Controllers - Configuration Commands
Controllers - Vibration/Rumble Control
Controllers - Analog Buttons (Dualshock2)
Controllers - Dance Mats
Controllers - Fishing Controllers
Controllers - Mahjong and Card Game Controllers
Controllers - I-Mode Adaptor (Mobile Internet)
Controllers - Keyboards
Controllers - Additional Inputs
Controllers - Misc

Memory Cards
Memory Card Read/Write Commands
Memory Card Data Format
Memory Card Images
Memory Card Notes

Pocketstation (Memory Card with built-in LCD screen and buttons)
Pocketstation

Pinouts
Pinouts - Controller Ports and Memory-Card Ports


Controller and Memory Card I/O Ports

1F801040h JOY_TX_DATA (W)
  0-7   Data to be sent
  8-31  Not used
Writing to this register starts the transfer (if, or as soon as TXEN=1 and JOY_STAT.2=Ready), the written value is sent to the controller or memory card, and, simultaneously, a byte is received (and stored in RX FIFO if JOY_CTRL.1 or JOY_CTRL.2 is set).
The "TXEN=1" condition is a bit more complex: Writing to SIO_TX_DATA latches the current TXEN value, and the transfer DOES start if the current TXEN value OR the latched TXEN value is set (ie. if TXEN gets cleared after writing to SIO_TX_DATA, then the transfer may STILL start if the old latched TXEN value was set).

1F801040h JOY_RX_DATA (R)
  0-7   Received Data      (1st RX FIFO entry) (oldest entry)
  8-15  Preview            (2nd RX FIFO entry)
  16-23 Preview            (3rd RX FIFO entry)
  24-31 Preview            (4th RX FIFO entry) (5th..8th cannot be previewed)
A data byte can be read when JOY_STAT.1=1. Data should be read only via 8bit memory access (the 16bit/32bit "preview" feature is rather unusable, and usually there shouldn't be more than 1 byte in the FIFO anyways).

1F801044h JOY_STAT (R)
  0     TX Ready Flag 1   (1=Ready/Started)
  1     RX FIFO Not Empty (0=Empty, 1=Not Empty)
  2     TX Ready Flag 2   (1=Ready/Finished)
  3     RX Parity Error   (0=No, 1=Error; Wrong Parity, when enabled)  (sticky)
  4     Unknown (zero)    (unlike SIO, this isn't RX FIFO Overrun flag)
  5     Unknown (zero)    (for SIO this would be RX Bad Stop Bit)
  6     Unknown (zero)    (for SIO this would be RX Input Level AFTER Stop bit)
  7     /ACK Input Level  (0=High, 1=Low)
  8     Unknown (zero)    (for SIO this would be CTS Input Level)
  9     Interrupt Request (0=None, 1=IRQ7) (See JOY_CTRL.Bit4,10-12)   (sticky)
  10    Unknown (always zero)
  11-31 Baudrate Timer    (21bit timer, decrementing at 33MHz)

1F801048h JOY_MODE (R/W) (usually 000Dh, ie. 8bit, no parity, MUL1)
  0-1   Baudrate Reload Factor (1=MUL1, 2=MUL16, 3=MUL64) (or 0=MUL1, too)
  2-3   Character Length       (0=5bits, 1=6bits, 2=7bits, 3=8bits)
  4     Parity Enable          (0=No, 1=Enable)
  5     Parity Type            (0=Even, 1=Odd) (seems to be vice-versa...?)
  6-7   Unknown (always zero)
  8     CLK Output Polarity    (0=Normal:High=Idle, 1=Inverse:Low=Idle)
  9-15  Unknown (always zero)

1F80104Ah JOY_CTRL (R/W) (usually 1003h,3003h,0000h)
  0     TX Enable (TXEN)  (0=Disable, 1=Enable)
  1     /JOYn Output      (0=High, 1=Low/Select) (/JOYn as defined in Bit13)
  2     RX Enable (RXEN)  (0=Normal, when /JOYn=Low, 1=Force Enable Once)
  3     Unknown? (read/write-able) (for SIO, this would be TX Output Level)
  4     Acknowledge       (0=No change, 1=Reset JOY_STAT.Bits 3,9)          (W)
  5     Unknown? (read/write-able) (for SIO, this would be RTS Output Level)
  6     Reset             (0=No change, 1=Reset most JOY_registers to zero) (W)
  7     Not used             (always zero) (unlike SIO, no matter of FACTOR)
  8-9   RX Interrupt Mode    (0..3 = IRQ when RX FIFO contains 1,2,4,8 bytes)
  10    TX Interrupt Enable  (0=Disable, 1=Enable) ;when JOY_STAT.0-or-2 ;Ready
  11    RX Interrupt Enable  (0=Disable, 1=Enable) ;when N bytes in RX FIFO
  12    ACK Interrupt Enable (0=Disable, 1=Enable) ;when JOY_STAT.7  ;/ACK=LOW
  13    Desired Slot Number  (0=/JOY1, 1=/JOY2) (set to LOW when Bit1=1)
  14-15 Not used             (always zero)
Caution: After slot selection (via Bits 1,13), one should issue a delay before sending the first data byte: Digital Joypads may work without delay, Dualshock and Mouse require at least some small delay, and older Analog Joypads require a huge delay (around 500 clock cycles for SCPH-1150), official kernel waits more than 2000 cycles (which is much more than needed).

1F80104Eh JOY_BAUD (R/W) (usually 0088h, ie. circa 250kHz, when Factor=MUL1)
  0-15  Baudrate Reload value for decrementing Baudrate Timer
Timer reload occurs when writing to this register, and, automatically when the Baudrate Timer reaches zero. Upon reload, the 16bit Reload value is multiplied by the Baudrate Factor (see 1F801048h.Bit0-1), divided by 2, and then copied to the 21bit Baudrate Timer (1F801044h.Bit11-31). The 21bit timer decreases at 33MHz, and, it ellapses twice per bit (once for CLK=LOW and once for CLK=HIGH).
  BitsPerSecond = (44100Hz*300h) / MIN(((Reload*Factor) AND NOT 1),1)
The default BAUD value is 0088h (equivalent to 44h cpu cycles), and default factor is MUL1, so CLK pulses are 44h cpu cycles LOW, and 44h cpu cycles HIGH, giving it a transfer rate of circa 250kHz per bit (33MHz divided by 88h cycles).
Note: The Baudrate Timer is always running; even if there's no transfer in progress.

/IRQ7 (/ACK) Controller and Memory Card - Byte Received Interrupt
Gets set after receiving a data byte - that only if an /ACK has been received from the peripheral (ie. there will be no IRQ if the peripheral fails to send an /ACK, or if there's no peripheral connected at all).
  Actually, /IRQ7 means "more-data-request",
  accordingly, it does NOT get triggered after receiving the LAST byte.
I_STAT.7 is edge triggered (that means it can be acknowledge before or after acknowledging JOY_STAT.9). However, JOY_STAT.9 is NOT edge triggered (that means it CANNOT be acknowledged while the external /IRQ input is still low; ie. one must first wait until JOY_STAT.7=0, and then set JOY_CTRL.4=1) (this is apparently a hardware glitch; note: the LOW duration is circa 100 clock cycles).

/IRQ10 (/IRQ) Controller - Lightpen Interrupt
Pin8 on Controller Port. Routed directly to the Interrupt Controller (at 1F80107xh). There are no status/enable bits in the JOY_registers (at 1F80104xh).

RX FIFO / TX FIFO Notes
The JOY registers can hold up to 8 bytes in RX direction, and almost 2 bytes in TX direction (just like the SIO registers, see there for details), however, normally only 1 byte should be in the RX/TX registers (one shouldn't send a 2nd byte until /ACK is sensed, and, since the transfer CLK is dictated by the CPU, the amount of incoming data cannot exceed 1 byte; provided that one reads received response byte after each transfer).
Unlike SIO, the JOY status register doesn't have a RX FIFO Overrun flag.

General Notes
RXEN should be usually zero (the hardware automatically enables receive when /JOYn is low). When RXEN is set, the next transfer causes data to be stored in RX FIFO even when /JOYn is high; the hardware automatically clears RXEN after the transfer.
For existing joypads and memory cards, data should be always transferred as 8bit no parity (although the JOY registers do support parity just like SIO registers).

Plugging and Unplugging Cautions
During plugging and unplugging, the Serial Data line may be dragged LOW for a moment; this may also affect other connected devices because the same Data line is shared for all controllers and memory cards (for example, connecting a joypad in slot 1 may corrupt memory card accesses in slot 2).
Moreover, the Sony Mouse does power-up with /ACK=LOW, and stays stuck in that state until it is accessed at least once (by at least sending one 01h byte to its controller port); this will also affect other devices (as a workaround one should always access BOTH controller ports; even if a game uses only one controller, and, code that waits for /ACK=HIGH should use timeouts).

Emulation Note
After sending a byte, the Kernel waits 100 cycles or so, and does THEN acknowledge any old IRQ7, and does then wait for the new IRQ7. Due to that bizarre coding, emulators can't trigger IRQ7 immediately within 0 cycles after sending the byte.


Controller and Memory Card Misc

BIOS Functions
Controllers can be probably accessed via InitPad and StartPad functions,
BIOS Joypad Functions
Memory cards can be accessed by the filesystem (with device names "bu00:" (slot1) and "bu10:" (slot2) or so). Before using that device names, it seems to be required to call InitCard, StartCard, and _bu_init (?).

Connectors
The PlayStation has four connectors (two controllers, two memory cards),
  Memory Card 1         Memory Card 2
  Controller 1          Controller 2
The controller ports have 9 pins, the memory cards only 8 pins. However, there are only 10 different pins in total.
  JOYDAT,JOYCMD,JOYCLK  Data in/out/clock
  +7.5V,+3.5V,GND       Supply
  /JOY1,/JOY2  Selects controller/memorycard 1, or controller/memorycard 2
  /ACK         Indicates that the device is ready to send more data (IRQ7)
  /IRQ10       Lightgun (controllers only, not memory card) (IRQ10)
Most of these pins are shared for all 4 connectors (eg. a CLK signal meant to be sent to one device will also arrive at the other 3 devices).
The /JOYn signals are selecting BOTH the corresponding controller, and the corresponding memory card (whether it is a controller access or memory card access depends on the first byte transferred via the CMD line; this byte should be:
  01h=Standard Controller         (controller port)
  21h=Special Yaroze Access Card  (memory card slot)
  41h=Special I-Mode Data-cable   (controller port)
  81h=Standard Memory Card        (memory card slot)

Data In/Out
The data is transferred in units of bytes, via separate input and output lines. So, when sending byte, the hardware does simultaneously receive a response byte.
One exception is the first command byte (which selects either the controller, or the memory card) until that byte has been sent, neither the controller nor memory card are selected (and so the first "response" byte should be ignored; probably containing more or less stable high-z levels).
The other exception is, when you have send all command bytes, and still want to receive further data, then you'll need to send dummy command bytes (should be usually 00h) to receive the response bytes.


Controller and Memory Card Signals

Overview
       ____                                                              _____
  /SEL     |____________________________________________________________|
       ______        ____        ____        ____        ____        _________
  CLK        ||||||||    ||||||||    ||||||||    ||||||||    ||||||||
       _______________________________________________________________________
  CMD       X  01h   XXXX  42h   XXXX  00h   XXXX  00h   XXXX  00h   XXXX
            ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
            _____________________________________________________________
  DAT  -----XXXXXXXXXXXXX   ID   XXXX  5Ah   XXXX  key1  XXXX  key2  XXXX-----
            ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  /ACK ---------------|_|---------|_|---------|_|---------|_|-----------------

Top command. First comminucation(device check)
       ____
  /SEL     |__________________________________________________________________
       ______   _   _   _   _   _   _   _   __________________   _   _   _   _
  CLK        |_| |_| |_| |_| |_| |_| |_| |_|                  |_| |_| |_| |_|
       __________                                                  ___
  CMD            |________________________________________________|   |_______
                                                              ____
  DAT  -----XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX    |___________
  /ACK ----------------------------------------------|___|--------------------

X = none, - = Hi-Z

* 0x81 is memory-card, 0x01 is standard-pad at top command.
* serial data transfer is LSB-First format.
* data is down edged output, PSX is read at up edge in shift clock.
* PSX expects No-connection if not returned Acknowledge less than 100 usec.
* clock pulse is 250KHz.
* no need Acknowledge at last data.
* Acknowledge signal width is more than 2 usec.
* time is 16msec between SEL from previous SEL.
* SEL- for memory card in PAD access.


Controller and Memory Card Multitap Adaptor

SCPH-1070 (Multitap)
The Multitap is an external adaptor that allows to connect 4 controllers, and 4 memory cards to one controller port. When using two adaptors (one on each slot), up to 8 controllers and 8 memory cards can be used.

Multitap Controller Access
Normally joypad reading is done by sending this bytes to the pad:
  01 42 00 00 ..   ;normal read
And with the multitap, there are even two different ways how to access extra pads:
  01 42 01 00 ..   ;method 1: receive special ID and data from ALL four pads
  0n 42 00 00 ..   ;method 2: receive data from pad number "n" (1..4)
The first method seems to be the more commonly used one (and its special ID is also good for detecting the multitap); see below for details.
The second method works more like "normal" reads, among other it's allowing to transfer more than 4 halfwords per slot (unknown if any existing games are using that feature).
The IRQ10 signal (for Konami Lightguns) is simply wired to all four slots via small resistors (without special logic for activating/deactivating the IRQ on certain slots).

Multitap Controller Access, Method 1 Details
Below LONG response is activated by sending "01h" as third command byte; observe that sending that byte does NOT affect the current response. Instead, it does request that the NEXT command shall return special data, as so:
  Halfword 0      --> Controller ID for MultiTap (5A80h=Multitap)
  Halfword 1..4   --> Player A (Controller ID, Buttons, Analog Inputs, if any)
  Halfword 5..8   --> Player B (Controller ID, Buttons, Analog Inputs, if any)
  Halfword 9..12  --> Player C (Controller ID, Buttons, Analog Inputs, if any)
  Halfword 13..16 --> Player D (Controller ID, Buttons, Analog Inputs, if any)
With this method, the Multitap is always sending 4 halfwords per slot (padded with FFFFh values for devices like Digital Joypads and Mice; which do use less than 4 halfwords); for empty slots it's padding all 4 halfwords with FFFFh.
Sending the request is possible ONLY if there is a controller in Slot A (if controller Slot A is empty then the Slot A access aborts after the FIRST byte, and it's thus impossible to send the request in the THIRD byte).
Sending the request works on access to Slot A, trying to send another request during the LONG response is glitchy (for whatever strange reason); one must thus REPEATEDLY do TWO accesses: one dummy Slot A access (with the request), followed by the long Slot A+B+C+D access.
  Previous access had REQ=0 and returned Slot A data ---> returns Slot A data
  Previous access had REQ=0 and returned Slot A-D data -> returns Slot A data
  Previous access had REQ=1 and returned Slot A data ---> returns Slot A-D data
  Previous access had REQ=1 and returned Slot A-D data -> returns garbage
  Previous access had REQ=1 and returned garbage -------> returns Slot A-D data
In practice:
Toggling REQ on/off after each command: Returns responses toggling between normal Slot A data and long Slot A+B+C+D data.
Sending REQ=1 in ALL commands: Returns responses toggling between Garbage and long Slot A+B+C+D data.
Both of the above is working (one needs only the Slot A+B+C+D part, and it doesn't matter if the other part is Slot A, or Garbage; as long as the software is able/aware of ignoring the Garbage). Garbage response means that the multitap returns ONLY four bytes, like so: HiZ,80h,5Ah,LSB (ie. the leading HighZ byte, the 5A80h Multitap ID, and the LSB of the Slot A controller ID), and aborts transfer after that four bytes.

Multitap Memory Card Access
Normally memory card access is done by sending this bytes to the card:
  80 xx .. ..      ;normal access
And with the multitap, memory cards can be accessed as so:
  8n xx .. ..      ;access memory card in slot "n" (1..4)
That's the way how its done in Silent Hill. Although for the best of confusion, it doesn't actually work in that game (probably the developer has just linked in the multitap library, without actually supporting the multitap at higher program levels).

Multitap Games
  Bomberman World
  Breakout: Off the Wall Fun
  Circuit Breakers
  Crash Team Racing
  FIFA series soccer games
  Frogger
  Gauntlet: Dark Legacy
  Hot Shots Golf 2 & 3
  NBA Live (any year) (up to 8 players with two multitaps)
  Need For Speed 3
  Need For Speed 5
  Poy Poy (4 players hitting each other with rocks and trees)
  Running Wild

Multitap Versions
                   .------.
   SCPH-1070       |      |        SCPH-111
   (gray case)     |      |        (white case)
   (for PSX)       |    D |        (for PSone)
                   |      |                   .----------------.
        cable      |      |        cable     .'   D        C   '.
            ''--.. |    C |         '''--..__|                  |
                  \|      |                  |                  |
  .----------------'      |                  '.   A        B   .'
  |                       |                   '----------------'
  |                       |
  |    A        B        /
  '---------------------'
The cable connects to one of the PSX controller ports (which also carries the memory card signals). The PSX memory card port is left unused (and is blocked by a small edge on the Multitap's plug).

MultiTap Parsed Controller IDs
Halfword 0 is parsed (by the BIOS) as usually, ie. the LSB is moved to MSB, and LSB is replaced by status byte (so ID 5A80h becomes 8000h=Multitap/okay, or xxFFh=bad). Halfwords 1,5,9,13 are NOT parsed (neither by the BIOS nor by the Multitap hardware), however, some info in the internet is hinting that Sony's libraries might be parsing these IDs too (so for example 5A41h would become 4100h=DigitalPad/okay, or xxFFh=bad).

Power Supply
The Multitap is powered by the +3.5V and +7.7V pins on the PSX controller port. Up to eight controllers and eight cards may scratch some limits (especially when doing things like activating rumble on all joypads). 3.5V Restrictions (digital logic) --> No known restrictions
  7.5V Restrictions (rumble motors) --> See "PadInfoAct" config command
The Multitap hardware itself doesn't do much on supply restrictions (+3.5V is passed through something; maybe some fuse, inductor, or 1 ohm resistor or so) (and +7.5V is passed without any restrictions).

See also
Pinouts - Component List and Chipset Pin-Outs for Multitap, SCPH-1070


Controllers - Communication Sequence

Controller Communication Sequence
  Send Reply Comment
  01h  Hi-Z  Controller Access (unlike 81h=Memory Card access), dummy response
  42h  idlo  Receive ID bit0..7 (variable) and Send Read Command (ASCII "B")
  TAP  idhi  Receive ID bit8..15 (usually/always 5Ah)
  MOT  swlo  Receive Digital Switches bit0..7
  MOT  swhi  Receive Digital Switches bit8..15
  --- transfer stops here for digital pad (or analog pad in digital mode) ---
  00h  adc0  Receive Analog Input 0 (if any) (eg. analog joypad or mouse)
  00h  adc1  Receive Analog Input 1 (if any) (eg. analog joypad or mouse)
  --- transfer stops here for analog mouse ----------------------------------
  00h  adc2  Receive Analog Input 2 (if any) (eg. analog joypad)
  00h  adc3  Receive Analog Input 3 (if any) (eg. analog joypad)
  --- transfer stops here for analog pad (in analog mode) -------------------
  --- transfer stops here for nonstandard devices (steering/twist/paddle) ---
The TAP byte should be usually zero, unless one wants to activate Multitap (multi-player mode), for details, see
Controller and Memory Card Multitap Adaptor
The two MOT bytes are meant to control the rumble motors (for normal non-rumble controllers, that bytes should be 00h), however, the MOT bytes have no effect unless rumble is enabled via config commands, for details, see
Controllers - Configuration Commands
Controllers - Vibration/Rumble Control

Controller ID (Halfword Number 0)
  0-3  Number of following halfwords (01h..0Fh=1..15, or 00h=16 halfwords)
  4-7  Controller Type (or currently selected Controller Mode)
  8-15 Fixed (5Ah)
Known 16bit ID values are:
  xx00h=N/A                 (initial buffer value from InitPad BIOS function)
  5A12h=Mouse               (two button mouse)
  5A23h=NegCon              (steering twist/wheel/paddle)
  5A31h=Konami Lightgun     (IRQ10-type)
  5A41h=Digital Pad         (or analog pad/stick in digital mode; LED=Off)
  5A53h=Analog Stick        (or analog pad in "flight mode"; LED=Green)
  5A63h=Namco Lightgun      (Cinch-type)
  5A73h=Analog Pad          (in normal analog mode; LED=Red)
  5A7xh=Dualshock2          (with variable number of inputs enabled)
  5A79h=Dualshock2          (with all analog/digital inputs enabled)
  5A80h=Multitap            (multiplayer adaptor) (when activated)
  5A96h=Keyboard            (rare lightspan keyboard)
  5AE3h=Jogcon              (steering dial)
  5AE5h=Fishing/Mode1       (fishing controller, ASC-0521TR2 Mode=1)
  5AE8h=Keyboard/Sticks     (rare homebrew keyboard/segasticks adaptor)
  5AF3h=Config Mode         (when in config mode; see rumble command 43h)
  FFFFh=High-Z              (no controller connected, pins floating High-Z)


Controllers - Standard Digital/Analog Controllers 
       ___                      ___           ___                      ___
    __/_L_\__   Analog Pad   __/_R_\__     __/_L_\__  Digital Pad   __/_R_\__
   /    _    \--------------/         \   /    _    \--------------/         \
  |   _| |_   |            |     /\    | |   _| |_   |            |     /\    |
  |  |_ X _|  |SEL      STA|  []    () | |  |_ X _|  |            |  []    () |
  |    |_|  ___   ANALOG   ___   ><    | |    |_|    |  SEL  STA  |     ><    |
  |\______ / L \   LED    / R \ ______/| |\_________/--------------\_________/|
  |       | Joy |--------| Joy |       | |       |                    |       |
  |      / \___/          \___/ \      | |      /                      \      |
   \____/                        \____/   \____/                        \____/

Standard Controllers
  __Halfword 0 (Controller Info)_______________________________________________
  0-15  Controller Info  (5A41h=digital, 5A73h=analog/pad, 5A53h=analog/stick)
  __Halfword 1 (Digital Switches)______________________________________________
  0   Select Button    (0=Pressed, 1=Released)
  1   L3/Joy-button    (0=Pressed, 1=Released/None/Disabled) ;analog mode only
  2   R3/Joy-button    (0=Pressed, 1=Released/None/Disabled) ;analog mode only
  3   Start Button     (0=Pressed, 1=Released)
  4   Joypad Up        (0=Pressed, 1=Released)
  5   Joypad Right     (0=Pressed, 1=Released)
  6   Joypad Down      (0=Pressed, 1=Released)
  7   Joypad Left      (0=Pressed, 1=Released)
  8   L2 Button        (0=Pressed, 1=Released) (Lower-left shoulder)
  9   R2 Button        (0=Pressed, 1=Released) (Lower-right shoulder)
  10  L1 Button        (0=Pressed, 1=Released) (Upper-left shoulder)
  11  R1 Button        (0=Pressed, 1=Released) (Upper-right shoulder)
  12  /\ Button        (0=Pressed, 1=Released) (Triangle, upper button)
  13  () Button        (0=Pressed, 1=Released) (Circle, right button)
  14  >< Button        (0=Pressed, 1=Released) (Cross, lower button)
  15  [] Button        (0=Pressed, 1=Released) (Square, left button)
  __Halfword 2 (Right joystick) (analog pad/stick in analog mode only)_________
  0-7   adc0 RightJoyX (00h=Left, 80h=Center, FFh=Right)
  8-15  adc1 RightJoyY (00h=Up,   80h=Center, FFh=Down)
  __Halfword 3 (Left joystick) (analog pad/stick in analog mode only)__________
  0-7   adc2 LeftJoyX  (00h=Left, 80h=Center, FFh=Right)
  8-15  adc3 LeftJoyY  (00h=Up,   80h=Center, FFh=Down)
  __Further Halfword(s) (Dualshock2 only, and only if enabled)_________________
  0-7   ..   Analog Button (if enabled) (00h=Released, FFh=Max Pressure)
  8-15  ..   Analog Button (if enabled) (00h=Released, FFh=Max Pressure)
  ..    ..   ..

Analog Mode Note
On power-up, the controllers are in digital mode (with analog inputs disabled). Analog mode can be (de-)activated manually by pushing the Analog button. Alternately, analog mode can be (de-)activated by software via rumble configuration commands (though that's supported only on newer pads; those with two rumble motors).
The analog sticks are mechanically restricted to a "circular field of motion" (most joypads can reach "min/max" values only in "straight" horizontal or vertical directions, but not in "diagonal" directions).

Analog Joypad Range
               ...''''''''''...
       ____ .''________________''._____       ___ 00h
      |  .''                      ''.  |
      |.'                            '.|      ___ 10h
      .'                              '.
     :|                                |:
    : |                                | :    ___ 60h
   .' |            .''''''.            | '.
   :  |          .'        '.          |  :
   :  |          :          :          |  :   ___ 80h
   :  |          :          :          |  :
   :  |          '.        .'          |  :
   '. |            '......'            | .'   ___ A0h
    : |                                | :
     :|                                |:
      '.                              .'      ___ F0h
      |'.                            .'|
      |__'..______________________..'__|      ___ FFh
      .     '..                ..'     .
     00h       '''..........'''       FFh


   Big Circle   --> Mechanically possible field of motion
   Square Area  --> Digitally visible 8bit field of motion
   Small Circle --> Resting position when releasing the joystick
Example min/center/max values for three different pads:
  SCPH-1150          Min=(00,00), Mid: (72..90,79..AC), Max=(FF,FF) at 25'C
  SCPH-1200          Min=(0E,0E), Mid: (6C..8A,75..79), Max=(ED,ED) at 16'C
  SCPH-110           Min=(11,11), Mid: (8A..9F,70..96), Max=(FD,FD) at 16'C
Values may vary for other pads and/or different temperatures.

Dual Analog Pad in LED=Green Mode
Basically same as normal analog LED=Red mode, with following differences:
  ID is 5A53h (identifying itself as analog stick) (rather than analog pad)
  Left/right joy-buttons disabled (as for real analog stick, bits are always 1)
  Some buttons are re-arranged: bit9=L1 bit10=[] bit11=/\ bit12=R1 bit15=R2
Concerning the button names, the real analog-stick does NOT have re-arranged buttons (eg. it's L1 button is in bit10), however, concerning the button locations, the analog stick's buttons are arranged completely differently as on analog pads (so it might be rather uncomfortable to play analog stick games on analog pads in LED=Red mode; the LED=Green mode is intended to solve that problem).
Might be useful for a few analog-stick games like MechWarrior 2, Ace Combat 2, Descent Maximum, and Colony Wars. In most other cases the feature is rather confusing (that's probably why the LED=Green mode wasn't implemented on the Dual Shock).

See also
Pinouts - Component List and Chipset Pin-Outs for Digital Joypad, SCPH-1080
Pinouts - Component List and Chipset Pin-Outs for Analog Joypad, SCPH-1150
Pinouts - Component List and Chipset Pin-Outs for Analog Joypad, SCPH-1200
Pinouts - Component List and Chipset Pin-Outs for Analog Joypad, SCPH-110
Pinouts - Component List and Chipset Pin-Outs for Dualshock2, SCPH-10010


Controllers - Mouse

Sony Mouse Controller
  __Halfword 0 (Controller Info)________________
  0-15  Controller Info  (5A12h=Mouse)
  __Halfword 1 (Mouse Buttons)__________________
  0-7   Not used         (All bits always 1)
  8-9   Unknown          (Seems to be always 0) (maybe SNES-style sensitivity?)
  10    Right Button     (0=Pressed, 1=Released)
  11    Left Button      (0=Pressed, 1=Released)
  12-15 Not used         (All bits always 1)
  __Halfword 2 (Mouse Motion Sensors)___________
  0-7   Horizontal Motion (-80h..+7Fh = Left..Right) (00h=No motion)
  8-15  Vertical Motion   (-80h..+7Fh = Up..Down)    (00h=No motion)

Sony Mouse Hardware Bug on Power-On
On Power-on (or when newly connecting it), the Sony mouse does draw /ACK to LOW, and does then hold /ACK stuck in the LOW position.
For reference: Normal controllers and memory cards set /ACK=LOW only for around 100 clk cycles, and only after having received a byte from the console.
The /ACK pin is shared for both controllers and both memory cards, so the stuck /ACK is also "blocking" all other connected controllers/cards. To release the stuck /ACK signal: Send a command (at least one 01h byte) to both controller slots.

Sony Mouse Compatible Games
  3D Lemmings
  Alien Resurrection
  Area 51
  Ark of Time
  Atari Anniversary Edition
  Atlantis: The Lost Tales
  Breakout: Off the Wall Fun
  Broken Sword: The Shadow of the Templars
  Broken Sword II: The Smoking Mirror
  Clock Tower: The First Fear
  Clock Tower II: The Struggle Within
  Command & Conquer: Red Alert
  Command & Conquer: Red Alert - Retaliation
  Constructor (Europe)
  Die Hard Trilogy
  Die Hard Trilogy 2: Viva Las Vegas
  Discworld
  Discworld II: Missing Presumed...!?
  Discworld Noir
  Dune 2000
  Final Doom
  Galaxian 3
  Ghoul Panic
  Klaymen Klaymen: Neverhood no Nazon (Japan)
  Lemmings and Oh No! More Lemmings
  Monopoly
  Music 2000
  Myst
  Neorude (Japan)
  Perfect Assassin
  Policenauts (Japan)
  Puchi Carat
  Quake II
  Railroad Tycoon II
  Rescue Shot
  Risk
  Riven: The Sequel to Myst
  RPG Maker
  Sentinel Returns
  SimCity 2000
  Syndicate Wars
  Tempest 2000 (Tempest X3)
  Theme Aquarium (Japan)
  Transport Tycoon
  Warhammer: Dark Omen
  Warzone 2100
  X-COM: Enemy Unknown
  X-COM: Terror from the Deep
  Z
Note: There are probably many more mouse compatible games.
Plus: Dracula - The Resurrection

Sony Mouse Component List
PCB "TD-T41V/\, MITSUMI"
Component Side:
  1x 3pin   4.00MHz "[M]4000A, 85 2"
  2x 2pin   button (left/right)
  1x 8pin   connector (to cable with shield and 7 wires)
  1x 3pin   "811, T994I"     -----> XXX maybe Mitsumi PST994I System Reset?
  2x 3pin   photo transistor (black)  ;\or so, no idea which one is
  2x 2pin   photo diode (transparent) ;/sender and which is sensor
  1x 2pin   electrolyt capacitor 16V, 10uF
Solder/SMD Side:
  1x 32pin  "(M), SC442116, FB G22K, JSAA815B"
  1x 14pin  "BA10339F, 817 L67" (Quad Comparator)
  2x 3pin   "LC" (amplifier for photo diodes)
  1x 3pin   "24-" (looks like a dual-diode or so)
  plus many SMD resistors/capacitors
Cable:
  PSX.Controller.Pin1 JOYDAT ---- brown  -- Mouse.Pin4
  PSX.Controller.Pin2 JOYCMD ---- red    -- Mouse.Pin3
  PSX.Controller.Pin3 +7.5V  ---- N/A
  PSX.Controller.Pin4 GND    ---- orange -- Mouse.Pin7 GND (G)
  PSX.Controller.Pin5 +3.5V  ---- yellow -- Mouse.Pin1
  PSX.Controller.Pin6 /JOYn  ---- green  -- Mouse.Pin5
  PSX.Controller.Pin7 JOYCLK ---- blue   -- Mouse.Pin2
  PSX.Controller.Pin8 /IRQ10 ---- N/A
  PSX.Controller.Pin9 /ACK   ---- purple -- Mouse.Pin6
  PSX.Controller.Shield --------- shield -- Mouse.Pin8 GND (SHIELD)

PS/2 and USB Mouse Adaptors
Some keyboard adaptors are also including a mouse adpator feature (either by simulating normal Sony Mouse controller data, or via more uncommon ways like using the PSX expansion port).
Controllers - Keyboards

RS232 Mice
Below is some info on RS232 serial mice. That info isn't directly PSX related as the PSX normally doesn't support those mice.
With some efforts, one can upgrade the PSX SIO port to support RS232 voltages, and with such a modded console one could use RS232 mice (in case one wants to do that).
The nocash PSX bios can map a RS232 mouse to a spare controller slot (thereby simulating a Sony mouse), that trick may work with various PSX games.

Standard Serial Mouse
A serial mouse should be read at 1200 bauds, 7 data bits, no parity, 1 stop bit (7N1) with DTR and RTS on. For best compatibility, the mouse should output 2 stop bits (so it could be alternately also read as 7N2 or 8N1). When the mouse gets moved, or when a button gets pressed/released, the mouse sends 3 or 4 characters:
  __First Character____________________
  6    First Character Flag (1)
  5    Left Button  (1=Pressed)
  4    Right Button (1=Pressed)
  2-3  Upper 2bit of Vertical Motion
  0-1  Upper 2bit of Horizontal Motion
  __Second Character___________________
  6    Non-first Character Flag (0)
  5-0  Lower 6bit of Horizontal Motion
  __Third Character____________________
  6    Non-first Character Flag (0)
  5-0  Lower 6bit of Vertical Motion
  __Fourth Character (if any)__________
  6    Non-first Character Flag (0)
  5    Middle Button (1=Pressed)
  4    Unused ???
  3-0  Wheel  ???
Additionally, the mouse outputs a detection character (when switching RTS (or DTR?) off and on:
  "M" = Two-Button Mouse (aka "Microsoft" mouse)
  "3" = Three-Button Mouse (aka "Logitech" mouse)
  "Z" = Mouse-Wheel
Normally, the detection response consist of a single character (usually "M"), though some mice have the "M" followed by 11 additional characters of garbage or version information (these extra characters have bit6=0, so after detection, one should ignore all characters until receiving the first data character with bit6=1).

Mouse Systems Serial Mouse (rarely used)
Accessed at 1200 bauds, just like standard serial mouse, but with 8N1 instead 7N1, and with different data bytes.
  __First Byte_________________________
  7-3  First Byte Code (10000b)
  2    Left? Button   (0=Pressed)
  1    Middle? Button (0=Pressed)
  0    Right? Button  (0=Pressed)
  __Second Byte________________________
  7-0  Horizontal Motion (X1)
  __Third Byte_________________________
  7-0  Vertical Motion   (Y1)
  __Fourth Byte________________________
  7-0  Horizontal Motion (X2)
  __Fifth Byte_________________________
  7-0  Vertical Motion   (Y2)
The strange duplicated 8bit motion values are usually simply added together, ie. X=X1+X2 and Y=Y1+Y2, producing 9bit motion values.

Notes
The Sony Mouse connects directly to the PSX controller port. Alternately serial RS232 mice can be connected to the SIO port (with voltage conversion adaptor) (most or all commercial games don't support SIO mice, nor does the original BIOS do so, however, the nocash BIOS maps SIO mice to unused controller slots, so they can be used even with commercial games; if the game uses BIOS functions to read controller data).
Serial Mice (and maybe also the Sony mouse) do return raw mickeys, so effects like double speed threshold must (should) be implemented by software. Mice are rather rarely used by PSX games. The game "Perfect Assassin" includes ultra-crude mouse support, apparently without threshold, and without properly matching the cursor range to the screen resolution.


Controllers - Racing Controllers

neGcon Racing Controller (Twist) (NPC-101/SLPH-00001/SLEH-0003)
  __Halfword 0 (Controller Info)_______________________________________________
  0-15  Controller Info  (5A23h=neGcon)
  __Halfword 1 (Digital Switches)______________________________________________
  0-2   Not used       (always 1)       (would be Select, L3, R3 on other pads)
  3     Start Button   (0=Pressed, 1=Released)
  4     Joypad Up      (0=Pressed, 1=Released)
  5     Joypad Right   (0=Pressed, 1=Released)
  6     Joypad Down    (0=Pressed, 1=Released)
  7     Joypad Left    (0=Pressed, 1=Released)
  8-10  Not used       (always 1)       (would be L2, R2, L1 on other pads)
  11    R Button       (0=Pressed, 1=Released) (would be R1 on other pads)
  12    B Button       (0=Pressed, 1=Released) (would be /\ on other pads)
  13    A Button       (0=Pressed, 1=Released) (would be () on other pads)
  14-15 Not used       (always 1)              (would be ><, [] on other pads)
  __Halfword 2 (Right joystick) (analog pad/stick in analog mode only)_________
  0-7   Steering Axis    (00h=Left, 80h=Center, FFh=Right) (or vice-versa?)
  8-15  Analog I button  (00h=Out ... FFh=In)  (Out=released, in=pressed?)
  __Halfword 3 (Left joystick) (analog pad/stick in analog mode only)__________
  0-7   Analog II button (00h=Out ... FFh=In)  (Out=released, in=pressed?)
  8-15  Analog L button  (00h=Out ... FFh=In)  (Out=released, in=pressed?)
The Twist controller works like a paddle or steering wheel, but doesn't have a wheel or knob, instead, it can be twisted: To move into one direction (=maybe right?), turn its right end away from you (or its left end towards you). For the opposite direction (=maybe left?), do it vice-versa.
     _____         _  _         _____                              ____
    |__L__\_______/ || \_______/__R__|                            /    \
   /    _   namco   ||   neGcon       \                          /      \
  |   _| |_         ||            B    |                        |       |
  |  |_ X _|    ....||....     II   A  | .... Rotation Axis ... | ...  \|/
  |    |_|          ||            I    |                        |
  |        START    ||                 |                         \
  |       ________  ||  ________       |                          \__\
  |      /        \_||_/        \      |                             /
   \____/                        \____/

Namco Volume Controller (a paddle with two buttons) (SLPH-00015)
This is a cut-down variant of the neGcon, just a featureless small box. It does have the same ID value as neGcon (ID=5A23h), but, it excludes most digital, and all analog buttons.
   _______
  | namco |      Halfword 1 (digital buttons):
  |       |      Bit3  Button A (0=Pressed) (aka neGcon Start button)
  | A   B |      Bit13 Button B (0=Pressed) (aka neGcon A button aka () button)
  |       |      Other bits     (not used, always 1)
  |   _   |      Halfword 2 and 3 (analog inputs):
  |  (_)  |      Steering Axis  (00h..FFh)  (as for neGcon)
  |_______|      Analog I,II,L button values (not used, always 00h)

SANKYO N.ASUKA aka Nasca Pachinco Handle (SLPH-00007)
Another cut-down variant of the neGcon (with ID=5A23h, too). But, this one seems to have only one button. Unlike Namco's volume controller it doesn't look featureless. It looks pretty much as shown in the ascii-arts image below. Seems to be supported by several irem titles. No idea what exactly it is used for, it's probably not a sewing machine controller, nor an electronic amboss.
   ____ ____     Halfword 1 (digital buttons):
  |   /   _ \    Bit12 Button   (0=Pressed) (aka neGcon B button aka /\ button)
  |_ /   (_) )   Other bits     (not used, always 1)
  |_|___    /\   Halfword 2 and 3 (analog inputs):
   ____|   |_    Steering Axis  (00h..FFh)  (as for neGcon)
  |__________|   Analog I,II,L button values (not used, always 00h)

Mad Catz Steering Wheel (SLEH-0006)
A neGcon compatible controller. The Twist-feature has been replaced by a steering wheel (can be turned by 270 degrees), and the analog I and II buttons by foot pedals. The analog L button has been replaced by a digital button (ie. in neGcon mode, the last byte of the controller data can be only either 00h or FFh). When not using the pedals, the I/II buttons on the wheel can be used (like L button, they aren't analog though).
        __________________________
       /   ____________________   \    Stick
      /   /                    \   \    ___        Brakes  Gas
     /   (                      )   \  (   )         II     I
    /  I  \                    /  A  \  \ /          ___   ___
   / /\ II \____________MODE__/  B /\ \  |          |   | |   |
  | |  \ L  _                   R /  | | |          |!!!|_|!!!|___
  | |   ) _| |_   MadCatz        (   | |_|_        /|!!!| |!!!|  /
  | |  | |_ X _|                  |  | | | |      / |___| |___| /
  | |  |   |_|                    |  | |  /      / =========== /
  | |   \         SEL STA        /   | | /      / =========== /
   \ \__/ ______________________ \__/ / /      /_____________/
    \____/                      \____/_/
       |___________________________|

Unlike the neGon, the controller has Select, >< and [] buttons, and a second set of L/R buttons (at the rear-side of the wheel) (no idea if L1/R1 or L2/R2 are at front?). Aside from the neGcon mode, the controller can be also switched to Digital mode (see below for button chart).

MadCatz Dual Force Racing Wheel
Same as above, but with a new Analog mode (additionally to Digital and neGcon modes). The new mode is for racing games that support only Analog Joypads (instead of neGcon). Additionally it supports vibration feedback.

MadCatz MC2 Vibration compatible Racing Wheel and Pedals
Same as above, but with a redesigned wheel with rearranged buttons, the digital pad moved to the center of the wheel, the L/R buttons at the rear-side of the wheel have been replaced by 2-way butterfly buttons ("pull towards user" acts as normal, the new "push away from user" function acts as L3/R3).
            ____________________
           /  ________________  \   ___ Stick      Brakes  Gas
          /  /       MC2      \  \ (   )             ___   ___
         /  /__________________\  \ \ /             |   | |   |
        |    A ()    _|_    I ><   | |              |!!!|_|!!!|___
        |   B /\ _    |    _ II [] | |             /|!!!| |!!!|  /
     ___|  L2   / \  STA  / \ R2   |_|_           / |___| |___| /
    /    \     /   | SEL |   \    /    \         / =========== /
   /  ____\    |___|     |___|   /____  \       / =========== /
  /__/     \____________________/     \__\     /_____________/

MadCatz Button Chart
  Mode     Buttons...................... Gas Brake Stick Wheel
  Digital  >< [] () /\ L1 R1 L2 R2 L1 R1 ><  ()    L1/R1 lt/rt
  Analog   >< [] () /\ L1 R1 L2 R2 L3 R3 UP  DN    L1/R1 LT/RT
  Negcon   I  II A  B  L  R  L  R  L  R  I   II    up/dn Twist
Whereas, lt/rt/up/dn=Digital Pad, UP/DN=Left Analog Pad Up/Down, LT/RT=Right Analog Pad Left/Right. Analog mode is supported only by the Dual Force and MC2 versions, L3/R3 only by the MC2 version.

Namco Jogcon (NPC-105/SLEH-0020/SLPH-00126/SLUH-00059)
  __Halfword 0 (Controller Info)___________________
  0-15  Controller Info  (5AE3h=Jogcon in Jogcon mode) (ie. not Digital mode)
 halfword1: buttons: same as digital pad
 halfword2:
   0    unknown (uh, this isn't LSB of rotation?)
   1-15 dial rotation (signed offset since last read?) (or absolute position?)
 halfword3:
   0    flag: dial was turned left  (0=no, 1=yes)
   1    flag: dial was turned right (0=no, 1=yes)
   2-15 unknown
Rotations of the dial are recognized by an optical sensor (so, unlike potentiometers, the dial can be freely rotated; by more than 360 degrees). The dial is also connected to a small motor, giving it a real force-feedback effect (unlike all other PSX controllers which merely have vibration feedback). Although that's great, the mechanics are reportedly rather cheap and using the controller doesn't feel too comfortable. The Jogcon is used only by Ridge Racer 4 for PS1 (and Ridge Racer 5 for PS2), and Breakout - Off the Wall Fun.
The Mode button probably allows to switch between Jogcon mode and Digital Pad mode (similar to the Analog button on other pads), not sure if the mode can be also changed by software via configuration commands...? Unknown how the motor is controlled; probably somewhat similar to vibration motors, ie. by the M1 and/or M2 bytes, but there must be also a way to select clockwise and anticlockwise direction)...? The controller does reportedly support config command 4Dh (same as analog rumble).
       ___       ________       ___
    __/_L_\__   /        \   __/_R_\__
   /    _    \ / LED MODE \-/         \
  |   _| |_   | SEL    STA |     /\    |
  |  |_ X _|  |  ________  |  []    () |
  |    |_|    | /        \ |     ><    |
  |\_________/\/          \/\__ ______/|
  |       |   |   JOGCON   |   |       |
  |       |   |    DIAL    |   |       |
  |       |    \          /    |       |
  |       |     \________/     |       |
  |       |                    |       |
  |       |                    |       |
   \_____/                      \_____/


Controllers - Lightguns

There are two different types of PSX lightguns (which are incompatible with each other).

Namco Lightgun (GunCon)
Namco's Cinch-based lightguns are extracting Vsync/Hsync timings from the video signal (via a cinch adaptor) (so they are working completely independed of software timings).
Controllers - Lightguns - Namco (GunCon)

Konami Lightgun (IRQ10)
Konami's IRQ10-based lightguns are using the lightgun input on the controller slot (which requires IRQ10/timings being properly handled at software side).
Controllers - Lightguns - Konami Justifier/Hyperblaster (IRQ10)
The IRQ10-method is reportedly less accurate (although that may be just due to bugs at software side).

Third-Party Lightguns
There are also a lot of unlicensed lightguns which are either IRQ10-based, or Cinch-based, or do support both.
For example, the Blaze Scorpion supports both IRQ10 and Cinch, and it does additionally have a rumble/vibration function; though unknown how that rumble feature is accessed, and which games are supporting it).

Lightgun Games
Controllers - Lightguns - PSX Lightgun Games

Compatibilty Notes (IRQ10 vs Cinch, PAL vs NTSC, Calibration)
Some lightguns are reportedly working only with PAL or only with NTSC games (unknown which guns, and unknown what is causing problems; the IRQ10 method should be quite hardware independed, the GunCon variant, too, although theoretically, some GunCon guns might have problems to extract Vsync/Hsync from either PAL or NTSC composite signals).
Lightguns from different manufacturers are reportedly returning slightly different values, so it would be recommended to include a calibration function in the game, using at least one calibration point (that would also resolve different X/Y offsets caused by modifying GP1 display control registers).
Lightguns are needing to sense light from the cathode ray beam; as such they won't work on regions of the screen that contain too dark/black graphics.


Controllers - Lightguns - Namco (GunCon)

GunCon Cinch-based Lightguns (Namco)
  __Halfword 0 (Controller Info)___________________
  0-15  Controller Info  (5A63h=Namco Lightgun; GunCon/Cinch Type)
  __Halfword 1 (Buttons)___________________________
  0-2   Not used              (All bits always 1)
  3     Button A (Left Side)  (0=Pressed, 1=Released) ;aka Joypad Start
  4-12  Not used              (All bits always 1)
  13    Trigger Button        (0=Pressed, 1=Released) ;aka Joypad O-Button
  14    Button B (Right Side) (0=Pressed, 1=Released) ;aka Joypad X-Button
  15    Not used              (All bits always 1)
  __Halfword 2 (X)_________________________________
  0-15  8MHz clks since HSYNC (01h=Error, or 04Dh..1CDh)
  __Halfword 3 (Y)_________________________________
  0-15  Scanlines since VSYNC (05h/0Ah=Error, PAL=20h..127h, NTSC=19h..F8h)
Caution: The gun should be read only shortly after begin of VBLANK.

Error/Busy Codes
Coordinates X=0001h, Y=0005h indicates "unexpected light":
  ERROR: Sensed light during VSYNC (eg. from a Bulb or Sunlight).
Coordinates X=0001h, Y=000Ah indicates "no light", this can mean either:
  ERROR: no light sensed at all (not aimed at screen, or screen too dark).
  BUSY: no light sensed yet (when trying to read gun during rendering).
To avoid the BUSY error, one should read the gun shortly after begin of VBLANK (ie. AFTER rendering, but still BEFORE vsync). Doing that isn't as simple as one might think:
On a NTSC console, time between VBLANK and VSYNC is around 30000 cpu clks, reading the lightgun (or analog joypads) takes around 15000 cpu clks. So, reading two controllers within that timeframe may be problematic (and reading up to eight controllers via multitaps would be absolutely impossible). As a workaround, one may arrange the read-order to read lightguns at VBLANK (and joypads at later time). If more than one lightgun is connected, then one may need to restrict reading to only one (or maybe: max two) guns per frame.

Minimum Brightness
Below are some average minimum brightness values, the gun may be unable to return position data near/below that limits (especially coordinates close to left screen border are most fragile). The exact limits may vary from gun to gun, and will also depend on the TV Set's brightness setting.
  666666h Minimum Gray
  770000h Minimum Blue
  007700h Minimum Green
  000099h Minimum Red
The gun does also work with mixed colors (eg. white bold text on black background works without errors, but the returned coordinates are a bit "jumpy" in that case; returning the position of the closest white pixels).
BUG: On a plain RED screen, aiming at Y>=00F0h, the gun is randomly returning either Y, or Y-80h (that error occurs in about every 2nd frame, ie. at 50% chance). It's strange... no idea what is causing that effect.

Coordinates
The coordinates are updated in all frames (as opposed to some lightguns which do update them only when pulling the trigger).
The absolute min/max coordinates may vary from TV set to TV set (some may show a few more pixels than others). The relation of the gun's Screen Coodinates to VRAM Coordinates does (obviously) depend on where the VRAM is located on the screen; ie. on the game's GP1(06h) and GP1(07h) settings.
Vertical coordinates are counted in scanlines (ie. equal to pixels). Horizontal coordinates are counted in 8MHz units (which would equal a resolution of 385 pixels; which can be, for example, converted to 320 pixel resolution as X=X*320/385).

Misinformation (from bugged homebrew source code)
  __Halfword 2 (X)_________________________________
  0-7   X-Coordinate  (actual: see X-Offset)             ;\with unspecified
  8-15  X-Offset      (00h: X=X-80, Nonzero: X=X-80+220) ;/dotclock?
  __Halfword 3 (Y)_________________________________
  0-7   Y-Coordinate  (actual: Y=Y-25) (but then, max is only 230, not 263 ?)
  8-15  Pad ID        (uh, what id?) (reportedly too dark/bright error flag?)

Namco Lightgun Drawing
           _-_______________________--_
  ----->  |    namco            \\\\   \    Namco G-Con 45 (light gray) (cinch)
  sensor   |............ .. .....\\\\...|_
          |_ :          :..   _____      _\
            |  O        :__../  )))|    (
             \__________/  |_\____/|     \
               :               :   |      |
               :               :   |      |  NPC-103
         A-Button (Left)   Trigger |      |  SLPH-00034/SLEH-0007/SLUH-00035
         B-Button (Right)          |______|

See also
Pinouts - Component List and Chipset Pin-Outs for Namco Lightgun, NPC-103


Controllers - Lightguns - Konami Justifier/Hyperblaster (IRQ10)

Overall IRQ10-Based Lightgun Access
  Send  01h 42h 00h x0h 00h
  Reply HiZ 31h 5Ah buttons
The purpose of the "x0h" byte is probably to enable IRQ10 (00h=off, 10h=on), this would allow to access more than one lightgun (with only one per frame having the IRQ enabled).

Standard IRQ10-based Lightguns (Konami)
The Controller Data simply consists of the ID and buttons states:
  __Halfword 0 (Controller Info)___________________
  0-15  Controller Info  (5A31h=Konami Lightgun; Timer/IRQ10 type)
  __Halfword 1 (Buttons)
  0-2   Not used                 (All bits always 1)
  3     Start Button (Left Side) (0=Pressed, 1=Released)  ;aka Joypad Start
  4-13  Not used                 (All bits always 1)
  14    Back Button  (Rear End)  (0=Pressed, 1=Released)  ;aka Joypad X-Button
  15    Trigger Button           (0=Pressed, 1=Released)  ;aka Joypad []-Button
The coordinates aren't part of the controller data, instead they must be read from Timer 0 and 1 upon receiving IRQ10 (see IRQ10 Notes below).

Konami Lightgun Drawing
     __                 ______ _
   _|__\_______________/  ___ \ \   Konami Justifier/Hyperblaster (light green)
  |   _______________ __ /   \ \ \
  |__|   _ _ _ _     |==|    O| \O\ .... Back Button (Rear End)
     |__:_:_:_:_:__  |___\__ /  ( (
                   |_|  ) \  :   \ \
      Trigger ......  \___/| :...|.|.... Start Button (Left Side)
                           |     | |
                           |     | | SLPH-00013/SLPH-00014/SLEH-0005/SLUH-00017
                          /     _|_|
                          \___--

Konami IRQ10 Notes
The PSX does have a lightgun input (Pin 8 of the controller), but, Sony did apparently "forget" to latch the current cathode ray beam coordinates by hardware when sensing the lightgun signal (quite strange, since that'd be a simple, inexpensive, and very obvious feature for a gaming console).
Instead, the lightgun signal triggers IRQ10, and the interrupt handler is intended to "latch" the coordinates by software (by reading Timer 0 and 1 values, which must configured to be synchronized with the GPU).
That method requires IRQ handling to be properly implemented in software (basically, IRQs should not be disabled for longer periods, and DMA transfers should not block the bus for longer periods). In practice, most programmers probably don't realize how to do that, to the worst, Sony seems to have delivered a slightly bugged library (libgun) to developers.
For details on Timers, see:
Timers
In some consoles, IRQ10 seems to be routed through a Secondary IRQ Controller, see:
EXP2 DTL-H2000 I/O Ports

IRQ10 Priority
For processing IRQ10 as soon as possible, it should be assigned higher priority than all other IRQs (ie. when using the SysEnqIntRP BIOS function, it should be the first/newest element in priority chain 0). The libgun stuff assigns an even higher priority by patching the BIOS exception handler, causing IRQ10 to be processed shortly before processing the priority chains (the resulting IRQ priority isn't actually higher as when using 1st element of chain 0; the main difference is that it skips some time consuming code which pushes registers R4..R30). For details on that patch, see:
BIOS Patches
Even if IRQ10 has highest priority, execution of (older) other IRQs may cause a new IRQ10 to be executed delayed (because IRQs are disabled during IRQ handling), to avoid that problem: Best don't enable any other IRQs except IRQ0 and IRQ10, or, if you need other IRQs, best have them enabled only during Vblank (there are no scanlines drawn during vblank, so IRQ10 should never trigger during that period). DMAs might also slow down IRQ execution, so best use them only during Vblank, too.

IRQ10 Timer Reading
To read the current timer values the IRQ10 handler would be required to be called <immediately> after receiving the IRQ10 signal, which is more or less impossible; if the main program is trying to read a mul/div/gte result while the mul/div/gte operation is still busy may stop the CPU for some dozens of clock cycles, and active DMA transfers or cache hits and misses in the IRQ handler may cause different timings, moreover, timings may become completely different if IRQs are disabled (eg. while another IRQ is processed).
However, IRQ10 does also get triggered in the next some scanlines, so the first IRQ10 is used only as a notification that the CPU should watch out for further IRQ10's. Ie. the IRQ10 handler should disable all DMAs, acknowledge IRQ10, and then enter a waitloop that waits for the IRQ10 bit in I_STAT to become set again (or abort if a timeout occurs) and then read the timers, reportedly like so:
  IF NTSC then X=(Timer0-140)*0.198166, Y=Timer1
  IF PAL  then X=(Timer0-140)*0.196358, Y=Timer1
No idea why PAL/NTSC should use different factors, that factors are looking quite silly/bugged, theoretically, the pixel-to-clock ratio should be the exactly same for PAL and NTSC...?
Mind that reading Timer values in Dotclock/Hblank mode is unstable, for Timer1 this can be fixed by the read-retry method, for Timer0 this could be done too, but one would need to subtract the retry-time to get a correct coordinate; alternately Timer0 can run at system clock (which doesn't require read-retry), but it must be then converted to video clock (mul 11, div 7), and then from video clock to dot clock (eg. div 8 for 320-pixel mode).
Above can be repeated for the next some scanlines (allowing to take the medium values as result, and/or to eliminate faulty values which are much bigger or smaller than the other values). Once when you have collected enough values, disable IRQ10, so it won't trigger on further scanlines within the current frame.

IRQ10 Bugs
BUG: The "libgun" library doesn't acknowledge the old IRQ10 <immediately> before waiting for a new IRQ10, so the timer values after sensing the new IRQ10 are somewhat random (especially for the first processed scanline) (the library allows to read further IRQ10's in further scanlines, which return more stable results).
No idea how many times IRQ10 gets typically repeated? Sporting Clays allocates a buffer for up to 20 scanlines (which would cause pretty much of a slowdown since the CPU is just waiting during that period) (nethertheless, the game uses only the first timer values, ie. the bugged libgun-random values).

Unknown if/how two-player games (with 2 lightguns) are working with the IRQ10 method... if IRQ10 is generated ONLY after pressing the trigger button, then it may work, unless both players have Trigger pressed at the same time... and, maybe one can enable/disable the lightguns by whatever commmand being sent to the controller (presumably that "x0h" byte, see above), so that gun 1 generates IRQ10 only in each second frame, and gun 2 only in each other frame...?

See also
Pinouts - Component List and Chipset Pin-Outs for Konami Lightgun, RU012


Controllers - Lightguns - PSX Lightgun Games

PSX Lightgun Games
Some games are working only with IRQ10 or only with Cinch, some games support both methods:
  Area 51 (Mesa Logic/Midway) (IRQ10)
  Crypt Killer (Konami) (IRQ10)
  Die Hard Trilogy 1: (Probe Entertainment) (IRQ10)
  Die Hard Trilogy 2: Viva Las Vegas (n-Space) (IRQ10/Cinch)
  Elemental Gearbolt (Working Designs) (IRQ10/Cinch)
  Extreme Ghostbusters: Ultimate Invasion (LSP) (Cinch)
  Galaxian 3 (Cinch)
  Ghoul Panic (Namco) (Cinch)
  Gunfighter: The Legend of Jesse James (Rebellion) (Cinch)
  Judge Dredd (Gremlin) (Cinch)
  Lethal Enforcers 1-2 (Konami) (IRQ10)
  Maximum Force (Midway) (IRQ10/Cinch)
  Mighty Hits Special (Altron) (EU/JPN) (Cinch)
  Moorhuhn series (Phenomedia) (Cinch)
  Point Blank 1-3 (Namco) (Cinch)
  Project Horned Owl (Sony) (IRQ10)
  Rescue Shot (Namco) (Cinch)
  Resident Evil: Gun Survivor (Capcom) (JPN/PAL versions) (Cinch)
  Silent Hill (IRQ10) ("used for an easter egg")
  Simple 1500 Series Vol.024 - The Gun Shooting (Cinch)
  Simple 1500 Series Vol.063 - The Gun Shooting 2 (Cinch)
  Snatcher (IRQ10)
  Sporting Clays (Charles Doty) (homebrew with buggy source code) (IRQ10/Cinch)
  Star Wars Rebel Assault II (IRQ10)
  Time Crisis, and Time Crisis 2: Project Titan (Namco) (Cinch)
Note: The RPG game Dragon Quest Monsters does also contain IRQ10 lightgun code (though unknown if/when/where the game does use that code).


Controllers - Configuration Commands

Some controllers can be switched from Normal Mode to Config Mode. The Config Mode was invented for activating the 2nd rumble motor in SCPH-1200 analog joypads. Additionally, the Config commands can switch between analog/digital inputs (without needing to manually press the Analog button), activate more analog inputs (on Dualshock2), and read some type/status bytes.

Normal Mode
  42h "B" Read Buttons (and analog inputs when in analog mode)
  43h "C" Enter/Exit Configuration Mode (stay normal, or enter)
Transfer length in Normal Mode is 5 bytes (Digital mode), or 9 bytes (Analog mode), or up to 21 bytes (Dualshock2).

Configuration Mode
  40h "@" Unused, or Dualshock2: Get/Set ButtonAttr?
  41h "A" Unused, or Dualshock2: Get Reply Capabilities
  42h "B" Read Buttons AND analog inputs (even when in digital mode)
  43h "C" Enter/Exit Configuration Mode (stay config, or exit)
  44h "D" Set LED State (analog mode on/off)
  45h "E" Get LED State (and Type/constants)
  46h "F" Get Variable Response A (depending on incoming bit) ("PadInfoAct")
  47h "G" Get whatever values (response HiZ F3h 5Ah 00h 00h 02h 00h 01h 00h)
  48h "H" Unknown             (response HiZ F3h 5Ah 00h 00h 00h 00h 01h 00h)
  49h "I" Unused
  4Ah "J" Unused
  4Bh "K" Unused (or MORE bytes from "PadInfoComb")
  4Ch "L" Get Variable Response B (depending on incoming bit) (PadInfoMode)
  4Dh "M" Get/Set RumbleProtocol
  4Eh "N" Unused
  4Fh "O" Unused, or Dualshock2: Set ReplyProtocol
Transfer length in Config Mode is always 9 bytes.

 ____________________________ Normal Mode Commands ____________________________

Normal Mode - Command 42h "B" - Read Buttons (and analog inputs when enabled)
  Send  01h 42h 00h xx  yy  (00h 00h 00h 00h) (...)
  Reply HiZ id  5Ah buttons ( analog-inputs ) (dualshock2 buttons...)
The normal read command, see Standard Controller chapter for details on buttons and analog inputs. The xx/yy bytes have effect only if rumble is unlocked; use Command 43h to enter config mode, and Command 4Dh to unlock rumble. Command 4Dh has billions of combinations, among others allowing to unlock only one of the two motors, and to exchange the xx/yy bytes, however, with the default values, xx/yy are assigned like so:
  yy.bit0-7 ---> Left/Large Motor M1 (analog slow/fast) (00h=stop, FFh=fastest)
  xx.bit0   ---> Right/small Motor M2 (digital on/off)  (0=off, 1=on)
The Left/Large motor starts spinning at circa min=50h..60h, and, once when started keeps spinning downto circa min=38h. The exact motor start boundary depends on the current position of the weight (if it's at the "falling" side, then gravity helps starting), and also depends on external movements (eg. it helps if the user or the other rumble motor is shaking the controller), and may also vary from controller to controller, and may also depend on the room temperature, dirty or worn-out mechanics, etc.

Normal Mode - Command 43h "C" - Enter/Exit Configuration Mode
  Send  01h 43h 00h xx  00h (zero padded...)   (...)
  Reply HiZ id  5Ah buttons (analog inputs...) (dualshock2 buttons...)
When issuing command 43h from inside normal mode, the response is same as for command 42h (button data) (and analog inputs when in analog mode) (but without M1 and M2 parameters). While in config mode, the ID bytes are always "F3h 5Ah" (instead of the normal analog/digital ID bytes).
  xx=00h Stay in Normal mode
  xx=01h Enter Configuration mode
Caution: Additionally to activating configuration commands, entering config mode does also activate a Watchdog Timer which does reset the controller if there's been no communication for about 1 second or so. The watchdog timer remains active even when returning to normal mode via Exit Config command. The reset does disable and lock rumble motors, and switches the controller to Digital Mode (with LED=off, and analog inputs disabled). To prevent this, be sure to keep issuing joypad reads even when not needing user input (eg. while loading data from CDROM).
Caution 2: A similar reset occurs when the user pushes the Analog button; this is causing rumble motors to be stopped and locked, and of course, the analog/digital state gets changed.
Caution 3: If config commands were used, and the user does then push the analog button, then the 5Ah-byte gets replaced by 00h (ie. responses change from "HiZ id 5Ah ..." to "HiZ id 00h ...").

 ____________________________ Config Mode Commands ____________________________

Config Mode - Command 42h "B" - Read Buttons AND analog inputs
  Send  01h 42h 00h M2  M1  00h 00h 00h 00h
  Reply HiZ F3h 5Ah buttons  analog-inputs
Same as command 42h in normal mode, but with forced analog response (ie. analog inputs and L3/R3 buttons are returned even in Digital Mode with LED=Off).

Config Mode - Command 43h "C" - Enter/Exit Configuration Mode
  Send  01h 43h 00h xx  00h 00h 00h 00h 00h
  Reply HiZ F3h 5Ah 00h 00h 00h 00h 00h 00h
Equivalent to command 43h in normal mode, but returning 00h bytes rather than button data, can be used to return to normal mode.
  xx=00h Enter Normal mode (Exit Configuration mode)
  xx=01h Stay in Configuration mode
Back in normal mode, the rumble motors (if they were enabled) can be controlled with normal command 42h.

Config Mode - Command 44h "D" - Set LED State (analog mode on/off)
Note: This is called PadSetMainMode in official docs.
  Send  01h 44h 00h Led Key 00h 00h 00h 00h
  Reply HiZ F3h 5Ah 00h 00h Err 00h 00h 00h
The Led byte can be:
  When Led=00h      --> Digital mode, with LED=Off
  When Led=01h      --> Analog mode, with LED=On/red
  When Led=02h..FFh --> Ignored (and, in case of dualshock2: set Err=FFh)
The Key byte can be:
  When Key=00h..02h --> Unlock (allow user to push Analog button)
  When Key=03h      --> Lock (stay in current mode, ignore Analog button)
  When Key=04h..FFh --> Acts same as (Key AND 03h)
The Err byte is usually 00h (except, Dualshock2 sets Err=FFh upon Led=02h..FFh; older PSX/PSone controllers don't do that).

Config Mode - Command 45h "E" - Get LED State (and Type/constants)
  Send  01h 45h 00h 00h 00h 00h 00h 00h 00h
  Reply HiZ F3h 5Ah Typ Num Led Act Com 00h
Returns several interesting bytes:
  Typ: Controller Type (01h=PSX/Analog Pad, 03h=PS2/Dualshock2)
  Num: Number of Modes                  (usually 02h) (for cmd 4Ch)
  Led: Current Mode (usually 00h=Digital/LedOff, 01h=Analog/LedRed)
  Act: Number of Actuators (aka motors) (usually 02h) (for cmd 46h)
  Com: Number of Combiner Lists         (usually 01h) (for cmd 47h)

Config Mode - Command 46h "F" - Get Variable Response A ("PadInfoAct")
  Send  01h 46h 00h ii  00h 00h 00h 00h 00h
  Reply HiZ F3h 5Ah 00h 00h Fnc Sub Siz Pwr
This is called PadInfoAct in official docs, ii is the actuator (aka motor).
The meaning of the return values is:
  Fnc  InfoActFunc  Function type (01h=Continuous-rotation vibration)
  Sub  InfoActSub   Sub-type (rotation-speed when Fnc=01h: 1=Low, 2=High)
  Siz  InfoActSize  Parameter data length
                     (0: 1 bit (ON/OFF only), 1 or greater: number of bytes)
  Pwr  InfoActCurr  Maximum current drain (0Ah=Small, 14h=Big)
Return values are usually:
  When ii=00h   --> returns Fnc,Sub,Siz,Pwr = 01h,02h,00h,0ah  ;small motor
  When ii=01h   --> returns Fnc,Sub,Siz,Pwr = 01h,01h,01h,14h  ;big motor
  When ii=Other --> returns Fnc,Sub,Siz,Pwr = all zeroes
The last response byte contains the 7.5V supply current drain (10 or 20 units). Whereas, Sony insists that controllers should never exceed 60 units (eg. when having more than 2 joypads connected to multitaps).

Config Mode - Command 47h "G" - Get whatever values ("PadInfoComb")
  Send  01h 47h 00h ii  00h 00h 00h 00h 00h
  Reply HiZ F3h 5Ah 00h 00h 02h 00h 01h 00h
When ii=00h --> returns 02h 00h 01h 00h as shown above
   ii  = list number
   02h = num entries in selected list?
   00h,01h = entries in that list? (combining actuator 00h and 01h is allowed)
Otherwise --> returns zeroes

Config Mode - Command 4Ch "L" - Get Variable Response B (PadInfoMode)
Note: This is called PadInfoMode in official docs. (?)
  Send  01h 4Ch 00h ii  00h 00h 00h 00h 00h
  Reply HiZ F3h 5Ah 00h 00h cc  dd  00h 00h
When ii=00h --> returns cc,dd=00h,04h ;ExID=4 ;for 5A41h = Digital Pad mode?
When ii=01h --> returns cc,dd=00h,07h ;ExID=7 ;for 5A73h = Analog Pad mode?
Otherwise --> returns cc,dd=00h,00h.

Config Mode - Command 48h "H" - Unknown
  Send  01h 48h 00h ii  00h 00h 00h 00h 00h
  Reply HiZ F3h 5Ah 00h 00h 00h 00h ee  00h
When ii=00h..01h --> returns ee=01h.
Otherwise --> returns ee=00h.
Purpose unknown. The command does not seem to be used by any games.

Config Mode - Command 4Dh "M" - Get/Set RumbleProtocol
Controllers - Vibration/Rumble Control

Config Mode - Command 40h "@" Dualshock2: Get/Set ButtonAttr?
Config Mode - Command 41h "A" Dualshock2: Get Reply Capabilities
Config Mode - Command 4Fh "O" Dualshock2: Set ReplyProtocol
Controllers - Analog Buttons (Dualshock2)

Config Mode - Command 49h "I" - Unused
Config Mode - Command 4Ah "J" - Unused
Config Mode - Command 4Bh "K" - Unused (or MORE bytes from "PadInfoComb")
Config Mode - Command 4Eh "N" - Unused
Config Mode - Command 40h "@" - Unused (except, used by Dualshock2)
Config Mode - Command 41h "A" - Unused (except, used by Dualshock2)
Config Mode - Command 4Fh "O" - Unused (except, used by Dualshock2)
  Send  01h 4xh 00h 00h 00h 00h 00h 00h 00h
  Reply HiZ F3h 5Ah 00h 00h 00h 00h 00h 00h
These commands do return a bunch of 00h bytes. These commands do not seem to be used by any games (apart from the Dualshock2 commands being used by Dualshock2 games).

Note
Something called "Guitar Hero controller" does reportedly also support Config commands. Unknown if that thing does have the same inputs & rumble motors as normal analog PSX joypads, and if it does return special type values.


Controllers - Vibration/Rumble Control

Rumble (aka "Vibration Function") is basically controlled by two previously unused bytes of the standard controller Read command.
There are two methods to control the rumble motors, the old method is very simple (but supports only one motor), the new method envolves a bunch of new configuration commands (and supports two motors).
  SCPH-1150  DualAnalog Pad with 1 motor                  ;-old rumble method
  SCPH-1200  DualAnalog Pad with 2 motors, PSX-design     ;\new rumble method
  SCPH-110   DualAnalog Pad with 2 motors, PSone-design   ;/
  SCPH-10010 DualAnalog Pad with 2 motors, PS2/Dualshock2 ;-plus analog buttons
  Blaze Scorpion Lightgun with rumble      ;\unknow how to control rumble
  Fishing controllers with rumble          ;/
  SCPH-1180 Analog Pad without rumble      ;\unknow if there're config commands
  SCPH-1110 Analog Stick without rumble    ;/for analog mode (probably not)


 _________________________________ Old Method _________________________________

Old Method, one motor, no config commands (SCPH-1150, SCPH-1200, SCPH-110)
The SCPH-1150 doesn't support any special config commands, instead, rumble is solely done via the normal joypad read command:
  Send  01h 42h 00h xx  yy  (00h 00h 00h 00h)
  Reply HiZ id  5Ah buttons ( analog-inputs )
The rumble motor is simply controlled by three bits in the xx/yy bytes:
  xx --> must be 40h..7Fh            (ie. bit7=0, bit6=1) ;\switches motor on
  yy --> must be 01h,03h,...,FDh,FFh (ie. bit0=1)         ;/
The motor control is digital on/off (no analog slow/fast), recommended values would be yyxx=0140h=on, and yyxx=0000h=off.
LED state is don't care (rumble works with led OFF, RED, and GREEN). In absence of config commands, the LED can be controlled only manually (via Analog button), the current LED state is implied in the controller "id" byte.
For backwards compatibility, the above old method does also work on SCPH-1200 and SCPH-110 (for controlling the right/small motor), alternately those newer pads can use the config commands (for gaining access to both motors).

 _________________________________ New Method _________________________________

New Method, two motors, with config commands (SCPH-1200, SCPH-110)
For using the new rumble method, one must unlock the new rumble mode, for that purpose Sony has invented a "slightly" overcomplicated protocol with not less than 16 new commands (the rumble relevant commands are 43h and 4Dh, also, command 44h may be useful for activating analog inputs by software, and, once when rumble is unlocked, command 42h is used to control the rumble motors; using data from "PadSetAct" function). Anyways, here's the full command set...
Controllers - Configuration Commands
And, the rumble-specific config command is described below...

Config Mode - Command 4Dh "M" - Get/Set RumbleProtocol
This is called "PadSetActAlign" in official docs.
  Send  01h 4Dh 00h aa  bb  cc  dd  ee  ff     ;<-- set NEW aa..ff values
  Reply HiZ F3h 5Ah aa  bb  cc  dd  ee  ff     ;<-- returns OLD aa..ff values
Bytes aa,bb,cc,dd,ee,ff control the meaning of the 4th,5th,6th,7th,8th,9th command byte in the controller read command (Command 42h).
  00h      = Map Right/small Motor (Motor M2) to bit0 of this byte
  01h      = Map Left/Large Motor (Motor M1) to bit0-7 of this byte
  02h..FEh = Unknown (can be mapped, maybe for extra motors/outputs)
  FFh      = Map nothing to this byte
In practice, one would usually send either one of these command/values:
  Send  01h 4Dh 00h 00h 01h FFh FFh FFh FFh    ;enable new method (two motors)
  Send  01h 4Dh 00h FFh FFh FFh FFh FFh FFh    ;disable motor control
Alternately, one could swap the motors by swapping values in aa/bb. Or one could map the motors anywhere to cc/dd/ee/ff (this will increase the command length in digital mode, hence changing digital mode ID from 41h to 42h or 43h). Or, one could map further rumble motors or other outputs to the six bytes (if any such controller would exist).
In the initial state, aa..ff are all FFh, and the controller does then use the old rumble control method (with only one motor). However, that old method gets disabled once when having messed with config commands (unknown if/how one can re-enable the old method by software).

Unknown Dualshock2 Vibration
Dualshock2 does reportedly have "two more levels of vibration", unknown what that means and if it's used by any PSX or PS2 games... it might refer to the small motor which usually has only 2 levels (on/off) and might have 4 levels (fast/med/slow/off) on dualshock2... but, if so, it's unknown how to control/unlock that feature.
Also, the PSone controller (SCPH-110) appear to have been released shortly after Dualshock2, unknown if that means that it might have that feature, too.

Power Consumption
The power consumtion should not exceed "60 units" (when connecting more than 2 joypads via Multitaps, one must take care not to enable too many motors simultaneously).
Config commands can be used to obtain the number of motors (Command 45h), and the power consumption per motor (Command 46h aka PadInfoAct).

Note
Rumble is a potentially annoying feature, so games that do support rumble should also include an option to disable it.


Controllers - Analog Buttons (Dualshock2)

Dualshock2 has three new commands (40h,41h,4Fh) for configuring analog buttons. Additionally, Command 45h does return a different type byte for Dualshock2.
Dualshock2 is a PS2 controller. However, it can be also used with PSX games (either by connecting the controller to a PSX console, or by playing a PSX game on a PS2 console).
The analog button feature is reportedly rarely used by PS2 games (and there aren't any PSX games known to use it).

Config Mode - Command 40h "@" Dualshock2: Get/Set ButtonAttr?
  Send  01h 40h 00h Idx Val 00h 00h 00h 00h  ;<-- Set NEW Val, array[Idx]=Val
  Reply HiZ F3h 5Ah 00h 00h Val 00h 00h 00h  ;<-- Old Val (or FFh when Idx>0Bh)
Allows to change twelve 3bit values (with Idx=00h..0Bh, and Val=00h..03h). Default is Val=02h. Purpose is unknown, the 12 values might be related to the 12 analog buttons, but there is no noticable difference between Val=0,1,2,3. Maybe it does have some subtle effects on things like...
  Digital button sensitivity, or Analog button sensitivity, or
  Analog button bit-depth/conversion speed, or something else?

Config Mode - Command 41h "A" Dualshock2: Get Reply Capabilities
  Send  01h 41h 00h 00h 00h 00h 00h 00h 00h
  Reply HiZ F3h 5Ah FFh FFh 03h 00h 00h 00h
This seems to return a constant bitmask indicating which reply bytes can be enabled/disabled via Command 4Fh (ie. 3FFFFh = 18 bits).

Config Mode - Command 4Fh "O" Dualshock2: Set ReplyProtocol
  Send  01h 41h 00h aa  bb  cc  dd  ee  ff
  Reply HiZ F3h 5Ah 00h 00h 00h 00h 00h 00h
This can output some 48bit value (bit0=aa.bit0, bit47=ff.bit7), used to enable/disable Reply bytes in the controller read command (Command 42h).
  -      HighZ                   (always transferred)      1st byte
  -      ID/Mode/Len             (always transferred)      2nd byte
  -      5Ah                     (always transferred)      3rd byte
  0      LSB of digital buttons  (0=No, 1=Yes)             4th byte
  1      MSB of digital buttons  (0=No, 1=Yes)             5th byte
  2      RightJoyX               (0=No, 1=Yes)             6th byte
  3      RightJoyY               (0=No, 1=Yes)             7th byte
  4      LeftJoyX                (0=No, 1=Yes)             8th byte
  5      LeftJoyY                (0=No, 1=Yes)             9th byte
  6      DPAD Right              (0=No, 1=Yes) button 00h  10th byte
  7      DPAD Left               (0=No, 1=Yes) button 01h  11th byte
  8      DPAD Uup                (0=No, 1=Yes) button 02h  12th byte
  9      DPAD Down               (0=No, 1=Yes) button 03h  13th byte
  10     Button /\               (0=No, 1=Yes) button 04h  14th byte
  11     Button ()               (0=No, 1=Yes) button 05h  15th byte
  12     Button ><               (0=No, 1=Yes) button 06h  16th byte
  13     Button []               (0=No, 1=Yes) button 07h  17th byte
  14     Button L1               (0=No, 1=Yes) button 08h  18th byte
  15     Button R1               (0=No, 1=Yes) button 09h  19th byte
  16     Button L2               (0=No, 1=Yes) button 0Ah  20th byte
  17     Button R2               (0=No, 1=Yes) button 0Bh  21st byte
  18-39  Must be 0 (otherwise command is ignored)
  40-47  Unknown (no effect?)
Usually, one would use one of the following command/values:
  Send  01h 41h 00h 03h 00h 00h 00h 00h 00h  Digital buttons
  Send  01h 41h 00h 3Fh 00h 00h 00h 00h 00h  Digital buttons + analog sticks
  Send  01h 41h 00h FFh FFh 03h 00h 00h 00h  Enable all 18 input bytes
The transfer order is 1st..21st byte as shown above (unless some bits are cleared, eg. if bit0-5=0 and bit6=1 then DPAD Right would appear as 4th byte instead of 10th byte). The command length increases/decreases depending on the number of enabled bits. The transfer length is always 3+N*2 bytes (including a 00h padding byte when the number of enabled bits is odd). The analog mode ID byte changes depending on number of halfwords.
CAUTION: Sending Command 44h does RESET the Command 4Fh setting (either to DigitalMode=000003h or AnalogMode=00003Fh; same happens when toggling mode via Analog button).

Note: Some Dualshock2 Config Mode commands do occassionally send 00h, 5Ah, or FFh as last (9th) reply byte (unknown if that is some error/status thing, or garbage).

Analog Button Sensitivity
The pressure sensors are rather imprecise and results may vary on various factors, including the pressure angle.
  00h       Button released
  01h..2Fh  Normal (soft) pressure
  30h..FEh  Medium pressure
  FFh       Hard pressure
Software can safely distinguish between soft and hard pressure.
Medium pressure is less predictably: The values do not increase linearily, it's difficult to apply a specific amount of medium pressure (such like 80h..9Fh), increasing pressure may sometimes jump from 24h to FFh, completely skipping the medium range.
Relying on the medium range might work for accelleration buttons (where the user could still adjust the pressure when the accelleration is too high or too low); but it would be very bad practice to assign irreversible actions to medium pressure (such like Soft=Load, Medium=Save, Hard=Quit).

Digital Button Sensitivity
Digital inputs are converting the analog inputs as so:
  Analog=00h      --> not pressed
  Analog=01h..FFh --> pressed (no matter if soft, medium, or hard pressure)
Digital inputs are working even when also having analog input enabled for the same button.

See also
  https://gist.github.com/scanlime/5042071 - tech (=mentions unknown details)
  https://store.curiousinventor.com/guides/PS2/ - guide (=omits unknown stuff)


Controllers - Dance Mats

PSX Dance Mats are essentially normal joypads with uncommonly arranged buttons, the huge mats are meant to be put on the floor, so the user could step on them.

Dance Mat vs Joypad Compatibility
There are some differences to normal joypads: First of, the L1/L2/R1/R2 shoulder buttons are missing in most variants. And, the mats are allowing to push Left+Right and Up+Down at once, combinations that aren't mechanically possible on normal joypads (some dancing games do actually require those combinations, whilst some joypad games may get confused on them).

Dance Mat Unknown Things
Unknown if the mat was sold in japan, and if so, with which SLPH/SCPH number.
Unknown if the mat's middle field is also having a button assigned.
Unknown if the mat is having a special controller ID, or if there are other ways to detect mats (the mats are said to be compatible with skateboard games, so the mats are probably identifying themselves as normal digital joypad; assuming that those skateboard games haven't been specifically designed for mats).

Dance Mat Games
  D.D.R. Dance Dance Revolution 2nd Remix
  (and maybe whatever further games)
The mats can be reportedly also used with whatever skateboard games.

Dance Mat Variants
There is the US version (DDR Dance Pad, SLUH-00071), and a slightly different European version (Official Dance Mat, SLEH-00023: shiny latex style with perverted colors, and Start/Select arranged differently). The japanese version (RU017) resembles the US version, but without Triangle/Square symbols drawn in lower left/right edges.
And there is a handheld version (with additional L1/L2/R2/R1 buttons; maybe unlicensed; produced as MINI DDR, and also as Venom Mini Dance Pad).

   US Version (white/black/red/blue)         Handheld Version (blue/gray)
    __________.---------.___________          _____/ MINI  \_____
   |          \         /           |        |      D.D.R.       |
   |  SELECT   '-------'    START   |        |L1 L2 SEL STA R2 R1|
   |------------.------.------------|        | ___    ___    ___ |
   |  .''''.   /        \   .''''.  |        || X |  | ^ |  | O ||
   | |  \/  | |    /\    | | .''. | |        ||___|  |___|  |___||
   | |  /\  | |   /..\   | | '..' | |        | ___   .---.   ___ |
   |  '....'  '.   ||   .'  '....'  |        || < | |Stay | | > ||
   | .-------. .''''''''. .-------. |        ||___| |Cool!| |___||
   |/   /|   .'          '.   |\   \|        | ___   '___'   ___ |
   |   / |-- |            | --| \   |        || []|  | v |  | /\||
   |   \ |-- | Stay Cool! | --| /   |        ||___|  |___|  |___||
   |\   \|   '.          .'   |/   /|        |___________________|
   | '-------' '........' '-------' |
   |  .''''.  .'   ||   '.  .''''.  |        Gothic Dance Mat (black/silver)
   | |  /\  | |   \''/   | | |''| | |         _.----------._
   | | /__\ | |    \/    | | |..| | |        | \ SEL  STA / | This one
   |  '....'   \        /   '....'  |        |  '--------'  | wasn't ever
   '------------'------'------------'        | .----------. | produced,
                                             | |  .''''.  | | as cool as
   European Version (pink/blue/yellow)       | | |  /\  | | | it could have
    __________.---------.___________         | | | /..\ | | | been, the lame
   |          \ SEL STA /           |        | |  '.||.'  | | marketing
   |           '-------'            |        | +----------+ | people didn't
   |----------.----------.----------|        | |  .''''.  | | even think
   |  .''''.  |  .''''.  |  .''''.  |        | | |  /\  | | | about it.
   | |  \/  | | |  /\  | | | .''. | |        | | | /..\ | | |
   | |  /\  | | | /..\ | | | '..' | |        | |  '.||.'  | |
   |  '....'  |  '.||.'  |  '....'  |        | +----------+ |
   |----------+-..    ..-+----------|        | |  .'||'.  | |
   |  .'/|'.  /   ''''   \  .'|\'.  |        | | | \''/ | | |
   | | / |--|/            \|--| \ | |        | | |  \/  | | |
   | | \ |--|\            /|--| / | |        | |  '....'  | |
   |  '.\|.'  \   ....   /  '.|/.'  |        | +----------+ |
   |----------+-''    ''-+----------|        | |  .'||'.  | |
   |  .''''.  |  .'||'.  |  .''''.  |        | | | \''/ | | |
   | |  /\  | | | \''/ | | | |''| | |        | | |  \/  | | |
   | | /__\ | | |  \/  | | | |..| | |        | |  '....'  | |
   |  '....'  |  '....'  |  '....'  |        | '----------' '
   '----------|----------|----------'        '--------------'

Stay Cool?
Despite of the "Stay Cool!" slogan, the mat wasn't very cool - not at all! It offered only two steps back-and-forth, and also allowed to do extremly uncool side-steps. Not to mention that it would melt when dropping a burning cigarette on it. Stay Away!


Controllers - Fishing Controllers

The fishing rods are (next to lightguns) some of the more openly martial playstation controllers - using the credo that "as long as you aren't using dynamite: it's okay to kill them cause they don't have any feelings."

PSX Fishing Controller Games
  Action Bass (Syscom Entertainment) (1999) (SLPH-00100)
  Bass Landing (ASCII/agetec) (1999) (SLPH-00100, SLUH-00063)
  Bass Rise, Fishing Freaks (Bandai) (1999) (BANC-0001)
  Bass Rise Plus, Fishing Freaks (Bandai) (2000) (BANC-0001, SLPH-00100)
  Breath of Fire IV (Capcom) (SLUH-00063)
  Championship Bass (EA Sports) (2000) (SLUH-00063)
  Fish On! Bass (Pony Canyon) (1999) (BANC-0001, SLPH-00100)
  Fisherman's Bait 2/Exiting Bass2 - Big Ol'Bass(Konami)(SLPH-00100,SLUH-00063)
  Fishing Club: (series with 3 titles) (have "headset-logo" on back?)
  Lake Masters II (1999) (Dazz/Nexus) (SLPH-00100)
  Lake Masters Pro (1999) (Dazz/Nexus) (BANC-0001, SLPH-00100)
  Let's Go Bassfishing!: Bass Tsuri ni Ikou! (Banpresto) (1999) (SLPH-00100)
  Matsukata Hiroki no World Fishing (BPS The Choice) (1999) (SLPH-00100)
  Murakoshi Seikai-Bakuchou Nihon Rettou (Victor) (SLPH-00100)
  Murakoshi Masami-Bakuchou Nippon Rettou:TsuriConEdition (1999) (SLPH-00100)
  Pakuchikou Seabass Fishing (JP, 03/25/99) (Victor) (SLPH-00100)
  Perfect Fishing: Bass Fishing (2000) (Seta) (yellow/green logo)
  Perfect Fishing: Rock Fishing (2000) (Seta) (yellow/green logo)
  Oyaji no Jikan: Nechan, Tsuri Iku De! (2000) (Visit) (BANC-0001, SLPH-00100)
  Reel Fishing II / Fish Eyes II (2000)(Natsume/Victor)(SLPH-00100, SLUH-00063)
  Simple 1500 Series Vol. 29: The Tsuri (2000) (yellow/green logo)
  Suizokukan Project: Fish Hunter e no Michi (1999)(Teichiku)(SLPH-00100)
  Super Bass Fishing (1999) (King) (BANC-0001, SLPH-00100, yellow/green logo)
  Super Black Bass X2 (2000) (Starfish) (SLPH-00100)
  Tsuwadou Keiryuu Mizuumihen (Best Edition)(2000) (ASCII PS1+PS2 controllers?)
  Tsuwadou Seabass Fishing (PlayStation the Best) (1999) (Oz Club) (SLPH-00100)
  Uki Uki Tsuri Tengoku Nagami/Uokami Densetsu Oe (2000) (Teichiku)(SLPH-00100)
  Umi no Nushi Tsuri-Takarajima ni Mukatte (1999)(Victor)(BANC-0001,SLPH-00100)
  Winning Lure (Hori) (2000) (for Hori HPS-97 controller)  AKA HPS-98 ?
For more see: http://www.gamefaqs.com/ps/list-109 (sports->nature->fishing)

Logos on CD Covers
US Fishing games should have a "SLUH-00063" logo. European Fishing games don't have any fishing logos; apparently fishing controllers haven't been officially released/supported in Europe.
Japanese Fishing games can have a bunch of logos: Usually BANC-0001 or SLPH-00100 (or both).
Moreover, some japanese games have a yellow/green fishing logo with japanese text (found on Perfect Fishing: Bass Fishing, Perfect Fishing: Rock Fishing, Simple 1500 Series Vol. 29: The Tsuri, Super Bass Fishing) (unknown if that logo refer to other special hardware, or if it means the "normal" BANC-0001 or SLPH-00100 controllers.
And Moreover, some japanese games have some sort of "headset" logos with japanese text, these seem to have same meaning as SLPH-00100; as indicated by photos on CD cover of Tsuwadou Keiryuu Mizuumihen (Best Edition) (2000); that CD cover also has a "headset 2" logo, which seems to mean a newer PS2 variant of the SLPH-00100.

PSX Fishing Controllers
  ASCII ASC-0514TR aka ASCII SLPH-00100 (silver)
  ASCII ASC-0521TR2 (silver) (similar to SLPH-00100, with additional hardware)
  agetec SLUS-00063 (silver) (US version of ASCII's SLPH-00100 controller)
  Bandai BANC-0001 (dark gray/blue) (has less buttons than ASCII/agetec)
  Interact Fission (light gray/blue)(similar to ASCII/agetec, 2 extra buttons?)
  Naki (transparent blue) (looks like a clone of the ASCII/agetec controllers)
  SAMMY SMY-0506FS (looks same as ASC-0521TR2)
  SAMMY SMY-0511FS (shortened joystick, rearranged /\,[],(),>< buttons)
  Hori HPS-97/HPS-98 (black/gray) (a fishing rod attached to a plastic fish)
Of these, the ASCII/agetec controllers seem to be most popular (and most commonly supported). The Bandai contoller is also supported by a couple of games (though the Bandai controller itself seems to be quite rare). The Interact/Naki controllers are probably just clones of the ASCII/agetec ones. The Hori controller is quite rare (and with its string and plastic fish, it's apparently working completely different than the other fishing controllers).

Tech Info (all unknown)
Unknown how to detect fishing controllers.
Unknown how to read buttons, joystick, crank, motion sensors.
Unknown how to control rumble/vibration.
Unknown if/how Bandai differs from ASCII/agetec (aside from less buttons).
Unknown how the Hori thing works.

ASCII ASC-0514TR / ASCII SLPH-00100 / agetec SLUH-00063 (silver)
          ___
       __|___|__
     _|         |_     _   __
    | |         | |   | |=|__| <--- crank handle
    | | SEL STA | |   | |
    | |         | |---|  \                         ASCII SLPH-00100
    |  \       /  |---|  /                         agetec SLUH-00063
   /  L1       R1  \  | |  __
  |  L2  .---.  R2  | |_|=|__|
  |     | joy |     |
  |     |stick|     |  <------- analog thumb controlled joystick
  | /\   '---'   >< |
  |   []       ()   |
   \     ASCII     /
    '.___________.'   \___ 10 buttons (SEL,STA,L1,L2,R1,R2,/\,[],(),><)
       \ _____ /
        |     |           Note: many (not all) agetec controllers
        |     |           have the >< and () buttons exchanged
        |     |
        |     |              Aside from the crank/buttons/joystick,
        |     |              the controller reportedly contains:
        |     |              some sort of motion sensors?
        |     |              some kind of rumble/vibration?
        |     |
        '.___.'
           '--...___ cable

ASCII ASC-0521TR2 / SAMMY SMY-0506FS / SAMMY SMY-0511FS (silver)
Controllers - Fishing Controllers - ASC-0521TR2
Pinouts - Component List and Chipset Pin-Outs for Fishing ASC-0521TR2
          ___
         |   |
       __|___|__       .--------------- star handle
    .''|       |''.    |   _   __
   /   |       |   \   _  | |=|__| <--- crank handle
  |    '       '    | | | | |
  |      1 . 2      |-| |-|  \                         ASCII ASC-0521TR2
  |  L1         R1  |-| |-|  /
  |  L2 SEL STA R2  | |_| | |  __
  |                 |     |_|=|__|
  |  /\  .---.  ><  |
  |     | joy |     |  <------- analog thumb controlled joystick
  |  [] |stick| ()  |           (with L3 button)
   \     '---'     /
    '.___________.'   \___ 10 buttons (SEL,STA,L1,L2,R1,R2,/\,[],(),><)
       \ _____ /           and 3-position switch (with positiona 1 . 2)
        |     |
        |     |            Note: SMY-0511FS has a short joystick stump,
        |     |            and rearranged buttons:
        |     |              /\  left of joystick
        |     |              []  right of joystick
        |     |              ()  below of joystick
        |     |              ><  near index finger (on bottom side of case)
        |ASCII|
        '.___.'
           '--...___ cable

Bandai BANC-0001 (dark gray/blue)
          ___
       __|___|__     .--------------- star handle
     _|         |    |   _   __
    | .---.     |\   _  | |=|__| <--- crank handle
    || joy |    | | | | | |
    ||stick|    | |-| |-|  \
    | '---'     | |-| |-|  /
   / \          |  \|_| | |  __
  |   |   ...   |   |   |_|=|__|
  |   |  :   :  | ()|
  |   |O :___: O|   |   <--- two buttons: () and ><
  |   |- |___| -| ><|        and some slide switch with I and 0 positions?
  |   |         |   |
   \  |  BANDAI |  /      unknown if the joystick is digital or analog
    '._\_______/_.'
       |       |          unknown if there are motion sensors and/or rumble
       '.     .'
        |     |
        |     |
        |     |
        |     |
        |     |
        |     |
        |     |
        '.___.'
           '--...___ cable

Hori HPS-97 / HPS-98 (black/gray)
              ....----------------O
           .''      \              \  HPS-97 (controller bundled with game)
          _:_        \              \ HPS-98 (controller only, for HPS-96 game)
       __|___|__       short         \
     _|         |_     elastic        \
    |             |    pole            \
    |             |                     \    <--- string (from pole to
    |     SW?     |     _   __           \        reel inside of fish)
   /               \   | |=|__|           \
  |      .---.      |  | |                 \
  | ( ) | joy |     |--|  \                 \               ___
  |     |stick|     |--|  /                  \             /   /
  | ( )  '---'      |  | |  __                \     ...---''''''--.  /|
  |                 |  |_|=|__| <--- crank     \   '               '/ |
   \    ( ) ( )    /                 handle     '..|                  |.
    '.___________.'                                |__________________| :
       \       /     \                                plastic fish      :
        |     |       joystick,                  (presumable some heavy :
        |     |       four buttons,              stationary thing that  :
        |     |       and a switch?              rests on floor)        :
        |     |                                  (presumably with       :
        |     |                                  motor-driven reel?)    :
        |     |                                                         :
        |     |     the two cables do probably connect                  :
        |     |     to both of the PSX controller slots                 :
        '.___.'                                            cable 2  ---'
           '--...___ cable 1
The length of the string is unknown. The fish might contain some pull/release mechanics that change the length by some centimeters, rather than meters?


Controllers - Fishing Controllers - ASC-0521TR2

Controller Modes
  Digital Joypad mode (power-up default)
  Mode0 (".")
  Mode1 ("1")
  Mode2 ("2")

Fishing Digital Mode
  __Halfword 0 (Controller Info)_______________________________________________
  0-15  Controller Info  (5A41h=digital)
  __Halfword 1 (Digital Switches)______________________________________________
  0-15  Buttons (with Joystick mapped as DPAD) (and L3 mapped to () button)
Missing: Reel Wheel, Star wheel, 3-axis Piezo sensor, Pendulums
Restrictions: Analog stick and L3 works as DPAD and () button only

Fishing Mode 0
  __Halfword 0 (Controller Info)_______________________________________________
  0-15  Controller Info  (5A73h=analog/pad)
  __Halfword 1 (Digital Switches)______________________________________________
  0-15  Buttons (with Joystick mapped as DPAD) (and L3 mapped to () button)
  __Halfword 2 (Right joystick) (analog pad/stick in analog mode only)_________
  0-7   adc0 Fixed      (always 80h=Center)
  8-15  adc1 Reel Wheel (00h=Backward, 80h=Stopped, FFh=Forward)
  __Halfword 3 (Left joystick) (analog pad/stick in analog mode only)__________
  0-7   adc2 Pendulum X (00h=Left, 80h=Center, FFh=Right)
  8-15  adc3 Pendulum Y (00h=Down, 80h=Center, FFh=Up)
Motor Control bytes:
  Byte00.bit0    Small vibration motor (0=Off, 1=On)
  Byte01.bit7-0  Big vibration motor   (0=Off, FFh=Max)
Missing: Star wheel, 3-axis Piezo sensor, Band brake
Restrictions: Analog stick and L3 works as DPAD and () button only

Fishing Mode 1
  __Halfword 0 (Controller Info)_______________________________________________
  0-15  Controller Info  (5AE5h=custom/fishing)
  __Halfword 1 (Digital Switches)______________________________________________
  0-15  Buttons (with DPAD bits always released) (and L3 mapped as such)
  __Halfword 2 (Right joystick) (analog pad/stick in analog mode only)_________
  0-7   adc0 Fixed      (always 80h=Center)
  8-15  adc1 Fixed      (always 80h=Center)
  __Halfword 3 (Left joystick) (analog pad/stick in analog mode only)__________
  0-7   adc2 Joystick X (00h=Left, 80h=Center, FFh=Right)
  8-15  adc3 Joystick Y (00h=Up,   80h=Center, FFh=Down)
  __Halfword 4
  0-7   adc4 3-Axis sensor (00h, 80h=Center, FFh)
  8-15  adc5 3-Axis sensor (00h, 80h=Center, FFh)
  __Halfword 5
  0-7   adc6 3-Axis sensor (00h, 80h=Center, FFh)
  8-15  adc7 Reel Wheel (00h=Stopped, FFh=Forward)
Motor Control bytes:
  Byte00.bit0    Small vibration motor (0=Off, 1=On)
  Byte01.bit7-0  Big vibration motor   (0=Off, FFh=Max)
Missing: Star wheel, Pendulums, Band brake
Restrictions: Reel Wheel supports forward only (backward is ignored)

Fishing Mode 2
  __Halfword 0 (Controller Info)_______________________________________________
  0-15  Controller Info  (5A73h=analog/pad) (with DPAD LT/RT used as extra ID)
  __Halfword 1 (Digital Switches)______________________________________________
  0-15  Buttons (UP/DN=Star wheel, LT/RT=Stuck, and L3 mapped as such)
  __Halfword 2 (Right joystick) (analog pad/stick in analog mode only)_________
  0-2   adc  Joystick Y (upper 3bit) (00h=Up,   04h=Center, 07h=Down)
  3-7   adc  Joystick X (5bit)       (00h=Left, 10h=Center, 1Fh=Right)
  8     adc  Pendulum Y (upper 1bit) (00h=Down, 10h=Center, 1Fh=Up)
  9-13  adc  Pendulum X (5bit)       (00h=Left, 10h=Center, 1Fh=Right)
  14-15 adc  Joystick Y (lower 2bit) (to be merged with upper 3bit)
  __Halfword 3 (Left joystick) (analog pad/stick in analog mode only)__________
  0-3   adc  3-Axis sensor Y  (4bit) (00h, 08h=Center, 0Fh)
  4-7   adc  Pendulum Y (lower 4bit) (to be merged with upper 1bit)
  8-11  adc  Reel Wheel     (..bit?) (00h=Stopped, 0xh=Forward)
  12-15 adc  3-Axis sensor X  (4bit) (00h, 08h=Center, 0Fh)
Motor Control bytes:
  Byte00.bit0    Small vibration motor (0=Off, 1=On)
  Byte01.bit7-4  Big vibration motor   (0=Off, 0Fh=Max)
  Byte01.bit3-0  Band brake motor      (0=Off, 0Fh=Max)
Missing: 3rd axis of 3-axis Piezo sensor
Restrictions: Reel Wheel supports forward only (backward is ignored)
Accuracy: The inputs/outputs are only 4bit or 5bit wide (instead of 8bit)
Issues: Sometimes returns garbage... Timings problems?

Switch Changes
Changing the switch position appears to be intended to reset the controller into digital mode, however, there are several flaws:
  Mode 0: Works
  Mode 1: Stays in analog mode (if analog mode was enabled)
  Mode 2: Works, but DPAD stays stuck at UP/DN=Released, LT/RT=Pressed)
Alongsides, changing the mode switch changes the 5Ah byte to 00h to indicate mode changes (similar as when pressing Analog button on analog pads).


Controllers - Mahjong and Card Game Controllers

The Mahjong & Card Game controllers contain small LCD displays for showing the player's cards/tiles (without other players seeing them when playing in 2-4 player mode). Obviously, it's a waste of everything, and it would be easier and cheaper to use a real card game.

Hori Wai Wai Jansou Controller (for Mahjong games)
This controller is supported by two games (Wai Wai Jansou, Wai Wai 3-nin Uchi Mahjong). There are at least four contoller versions: The Set includes clear/red & clear/green. Additionally, clear/gray & clear/blue are sold separately. The different colors do apply to the bottom-side of the case, which is barely visible when looking at the transparent top-side.
  HPS-90  Wai Wai Jansou CDROM
  HPS-91  Wai Wai Jansou Set (CDROM with two Jansou controllers)
  HPS-92  Wai Wai Jansou Controller (clear/gray)
  HPS-93  Wai Wai Jansou Controller (clear/blue)
  HPS-94  Wai Wai Jansou Controller (..unknown color..)
  HPS-95  Wai Wai Jansou Controller (..unknown color..)
  HPS-116 Wai Wai 3-nin Uchi Mahjong Set (CDROM with two Jansou Controllers)
   ______________________________________
  |                                      |
  |   .-----------------------------.    |
  |   |   #######################   |    |  LCD display
  |   |__________.---------.________|    |  with DPAD and nine buttons
  |     _                                |
  |   _| |_       SEL START          O   |
  |  |_   _| _                 _   O   O |
  |    |_|  (_)               (_)    O   |
  |__________B_________________A___O_____|
Unknown if somebody can translate the markings on the five yellow buttons
Unknown if the controller supports config commands
Unknown how to detect the controller
Unknown how to read the DPAD and buttons
Unknown how to access the LCD screen
Unknown if the Mahjong symbols are built-in or if one can draw custom bitmaps
Component List and LCD Screen resolution is also unknown.
Some info: http://www.psxdev.net/forum/viewtopic.php?t=3432

Hori Wai Wai Trump Controller (for Card games)
This controller is supported by only one game (Wai Wai Trump Taisen), and there seems to be only one controller version.
  HPS-104 Wai Wai Trump Taisen CDROM
  HPS-105 Wai Wai Trump Taisen Set (CDROM with two Trump Controllers)
  HPS-106 Wai Wai Trump Taisen Controller
   ______________________________________
  |                                      |
  |   .-----------------------------.    |
  |   |   #######################   |    |  LCD display
  |   |__________.---------.________|    |  with six buttons
  |                                      |
  |     _         SEL START         _    |
  |  < (_)   _                 _   (_) A |
  |         (_) >             (_) B      |
  |______________________________________|
Unknown if/how the protocol differs from Wai Wai Jansou
One known difference, in no$psx, with analog pad emulation: The game keeps cycling through Config Cammands, and the controller input is unresponsive (often missing or double-triggering keystrokes) (unknown if this does also happen with analog pads on real hardware).


Controllers - I-Mode Adaptor (Mobile Internet)

The I-Mode Adaptor cable (SCPH-10180) allows to connect an I-mode compatible mobile phone to the playstation's controller port; granting a mobile internet connection to japanese games.

Controllers - I-Mode Adaptor - Controller Port Commands
Controllers - I-Mode Adaptor - Connect Messages
Controllers - I-Mode Adaptor - Transfer Messages
Controllers - I-Mode Adaptor - TLP Transport Layer
Controllers - I-Mode Adaptor - HTTP Requests/Replies
Controllers - I-Mode Adaptor - Software
Controllers - I-Mode Adaptor - Misc
Controllers - I-Mode Adaptor - Libimode Library
Controllers - I-Mode Adaptor - Unknown Features
Controllers - I-Mode Adaptor - References

Pinouts
Pinouts - Component List and Chipset Pin-Outs for I-Mode Cable SCPH-10180


Controllers - I-Mode Adaptor - Controller Port Commands

Controller Port Commands
There are two data streams:
  Small Control Messages     (sent/received via command 14h, 15h, or 18h)
  Large 80h-byte Data Blocks (sent/received via command 14h)
The games are sending data at 500kbit/s (except, the first byte (41h) should be always sent at 250kbit/s, to properly deselect controllers or memory cards). Regardless, the transfer is ways slower: The 88h-byte messages contain only 58h-byte actual data (500*58h/88h = 323kbit/s), and the existing PSX software transfers only one such packet per vblank (58h*8*60 = 42kbit/s), and I-Mode is reportedly supporting only 9.6kbit/s for TLP messages).
BUG: The 1st reply byte is 00h (rather than HighZ), that reply byte will occur even when trying to access other hardware like joypads or memory cards.

Command 11h (len=5) - Unknown (unused in Hamster Club-i)
  Send  41h 11h (0) (0) (0)
  Reply 00h 5Ah 8Eh Stat[2]
Unknown. Hamster Club-i contains some (unused) code for sending this command; without any parameters, and without checking the response (which seems to be always 8Eh, plus Stat[2]).

Command 12h (len=7) - Config ...
  Send  41h 12h NewX NewY (0)  (0) (0)
  Reply 00h 5Ah 6Fh  NewX NewY Stat[2]
Parameters:
  X = usually/always 00h (but can be 00h..04h)               (00h..04h)
  Y = usually 03h=UsedBeforeShutdown, or 06h=UsedAfterWakeup (00h..FFh)
Reply:
  Always 6Fh, followed by echoing the (newly written) parameter values
  (whereas, X=05h..FFh gets forcefully changed to X=00h)
X=00h..04h gets translated to 09h,12h,24h,48h,91h, which is then further multiplied/divided and somehow treated as a "length" value, which seems to affect Command 15h and 18h.

Command 13h (len=5) - Wakeup (sets Stat[2] to 01h,00h)
  Send  41h 13h 0Fh (0) (0)
  Reply 00h 5Ah C0h Stat[2]
Parameters:
  Usually/always 0Fh     ;XXX but in browser: initially 03h, later 0Fh

Command 14h (len=88h) - Dual-Stream Transfer
  Send  41h 14h Data[80h] MsgLen Msg[19h] Chksum (0) (0)
  Reply 00h 5Ah Data[80h] MsgLen Msg[19h] Chksum Stat[2]
Parameters:
  Data[80h] = Data Stream bytes (see below)
  Msglen    = 0..2      ;Hamster Club-i uses only 0..1 for sending though
  Msg[2]    = Message bytes
  Chksum    = Above 83h bytes XORed together
The Data[80h] part can contain one or more data snippets:
  00h 1   1st Snippet Length (1..58h, plus bit7=LastSnippetFlag) ;\
  01h ..  1st Snippet Data                                       ;
  ... 1   2nd Snippet Length (1..58h, plus bit7=LastSnippetFlag) ;
  ... ..  2nd Snippet Data                                       ; if any
  ... 1   3rd Snippet Length (1..58h, plus bit7=LastSnippetFlag) ;
  ... ..  3rd Snippet Data                                       ;
  ... ..  etc.                                                   ;/
  ... 1   End marker (00h) (aka snippet length zero)             ;\end
  ... ..  Unused padding                                         ;/
  7Fh 1   Flags (bit0=PhoneBusy)                                 ;-flags
Packets bigger than 58h bytes can occupy multiple snippets (length bit7=1 indicates the final snippet).
The last 2 data bytes (of the last snippet) contain a CRC16_CCITT_REVERSE in little-endian, with initial value FFFFh, and result XORed by FFFFh.

Command 15h (len=1Fh) - Single-Stream Transfer
  Send  41h 15h MsgLen Msg[19h] Chksum (0) (0)
  Reply 00h 5Ah MsgLen Msg[19h] Chksum Stat[2]
Parameters:
  Msglen   = 0..19h
  Msg[19h] = Message bytes
  Chksum   = Above 1Ah bytes XORed together

Command 16h (len=5) - Config Single/Dual-Stream Mode
  Send  41h 16h MODE (0) (0)
  Reply 00h 5Ah 4Ah  Stat[2]
Parameters:
  MODE = Indicates if Command 14h or 15h will be used (0=Cmd15h, 1=Cmd14h)

Command 17h (len=5) - Config Clear/Reset
  Send  41h 17h FLAG (0) (0)
  Reply 00h 5Ah 56h  Stat[2]
FLAG (03h or 0Ch or 0Fh or 10h):
  bit0  Clear Send queue   ;\clear queue inside of PSX (probably implies
  bit1  Clear Recv queue   ;/request to also clear queue in Fujitsu chip)
  bit2  Ack/swap/apply/discard TX block number?   ;\for 80h-byte data blocks
  bit3  Ack/swap/apply/discard RX block number?   ;/
  bit4  Reset/Shutdown (changes Stat[2] to 00h,00h)

Command 18h (len=6) - Single-Stream Transfer (unused in Hamster Club-i)
  Send  41h 18h MsgLen Msg[1] (0) (0)
  Reply 00h 5Ah MsgLen Msg[1] Stat[2]
Seems to be same as Command 15h, but MsgLen can be only 0..1 bytes, and without checksum.


Controllers - I-Mode Adaptor - Connect Messages

I-Mode Messages
Sending/receiving these messages can be done via command 14h, 15h, and/or 18h.
The messages start with an 8bit value (eg. 85h), followed by several "4bit parameter bytes" (which have the upper 4bits set to zero).

Send:
  85h,01h,01h,02h,plain_random[8],00h,03h,00h,00h,01h    ;-AUTH_START_REQ
  85h,01h,04h,02h,crypted_random[8]                      ;-AUTH_CRYPT_REQ
  85h,01h,05h,02h                                        ;-AUTH_DONE
  85h,01h,06h                                            ;-DEAUTH_REQ
  8Eh     ;<-- is that same 8Eh as in Keitai Eddy?       ;-AUTH_PING_REQ
  F2h,00h,01h,02h,08h,00h,00h,00h,00h                    ;-GW_CONNECT_REQ
  F2h,00h,01h,02h,00h,00h,00h,00h,00h                    ;-GW_DISCONNECT_REQ
  F2h,00h,01h,02h,01h,00h,00h,00h,00h  ;used in browser  ;-GW_PING_REQ
  A8h     ;<-- used in the browser, after entering a 4-digit PIN number

Recv messages (based on code in Hamster Club-i):
  38h,02h                           ;return 06h    ;-Wokeup             ;\
  85h,01h,02h,x,x,H,L,dat(HL)       ;return 02h    ;-AUTH_CRYPT_ACK     ;
  85h,01h,03h,data[3]               ;return 01h    ;-AUTH_error/busy?   ;
  85h,01h,04h,x,dat(8),H,L,dat(HL)  ;return 03h    ;-AUTH_START_ACK     ; STATE
  85h,01h,07h                       ;return 04h    ;-DEAUTH_ACK         ;
  F1h,00h,03h,x,H,L,dat(HL)      ;return 05h,[0Ah] ;state [0Ah]=1=okay? ;
  F2h,00h,02h,x,08h,x,H,L,dat(HL+4) ;return 0Ah    ;-GW_CONNECT_ACK     ;
  F2h,00h,02h,x,00h,x,H,L,dat(HL+4) ;return 0Bh    ;-GW_DISCONNECT_ACK  ;
  F2h,00h,02h,x,01h,x,H,L,dat(1+HL) ;return 0Dh    ;-GW_PING_ACK        ;
  F2h,00h,02h,x,09h,x,H,L,dat(1+HL) ;return 0Dh    ;-GW_PING_ACK, too?  ;
  F2h,00h,03h,..                    ;return 0Ch  ;ready to GW_CONNECT ? ;/
  21h,...     ;used by browser      ;return 14h, modus=0                ;\
  80h         ;not implemented      ;return 1Fh, modus=0                ;
  81h                               ;return 20h, modus=0                ;
  8Ah,..      ;not implemented      ;return 21h, modus=0                ;
  8Bh,..                            ;return 22h, modus=0                ; ?
  A4h,..                            ;return 18h, modus=0                ;
  A5h,..                            ;return 0, modus=40h                ;
  A6h                               ;return 17h, modus=0                ;
  A7h                               ;return 16h, modus=0                ;
  AAh,..      ;\multiple uses       ;return 15h                         ;
  AAh,..      ; depending on        ;return 0, modus=0                  ;
  AAh         ;/state/flags         ;return 23h, modus=0 ;AUTH_PING_ACK ;
  E0h,..      ;\terminated          ;return 0, set modus and 40h or 1   ;
  E6h,..      ;/by AAh ?            ;return 0, set modus and 50h or 2   ;/
  C0h..CFh                          ;ignored                            ;\
  D1h,...                           ;whatever                           ; data?
  00h..0Fh                          ;data bytes?                        ;/

Recv message format (based on message-length tables in Hamster Club-i):
  C0h..CFh
  19h
  missing 21h
  35h,x, ... , endflag(bit0)
  38h,data[1]
  61h,data[10h]
  64h,01h
  64h,02h,data[1]
  64h,03h,data[6]
  64h,04h
  64h,06h
  64h,07h
  64h,0Dh,data[24h]
  64h,0Eh, ... , endflag(bit0)
  6Ch,01h
  6Ch,02h,data[1]
  6Ch,03h
  6Ch,06h,data[7+1],H,L,data[HL*2],data[5],,H,L,data[HL*2],H,L,data[HL*2] ;?
  6Ch,07h
  6Ch,08h
  6Ch,0Ah,data[5+1+3],H,L,data[HL*2],H,L,[HL*2]  ;?
  6Ch,0Ch
  6Ch,0Dh,data[24h]
  6Ch,0Eh, ... , endflag(bit0)
  6Eh,data[1]
  80h
  81h
  85h,x,01h,data[0Eh]
  85h,x,02h,x,x,H,L,data[HL]
  85h,x,03h,data[3]
  85h,x,04h,00h,data[9],H,L,data[HL]
  85h,x,04h,02h,data[8]
  85h,x,05h,data[1]
  85h,x,07h
  86h,data[1]
  87h
  missing 8Ah
  missing 8Bh
  A3h
  missing A4h
  missing A5h
  A6h
  A7h
  missing AAh (but may work as breakout code and ping_ack?)
  missing D1h (but may work as breakout code?)
  missing E0h        ;with end_code=AAh
  E2h,x, ... ,AAh    ;with end_code=AAh
  missing E6h        ;with end_code=AAh
  E7h,data[2]
  E8h,x,x,N,data[N*2]
  F1h,x,03h,x,H,L,data[HL]
  F1h,x,04h,data[2]
  F2h,x,02h,x,00h,x,H,L,data[HL+4]
  F2h,x,02h,x,08h,x,H,L,data[HL+4]
  F2h,x,02h,x,01h,x,H,L,data[HL+1]
  F2h,x,02h,x,09h,x,H,L,data[HL+1]
  F2h,x,03h,x,x,H,L,data[HL]
Whereas,
  x   = don't care for length (but actual code may insist on specific values)
  H,L = high/low nibbles of HL length value
  missing = not handled in length table (but exists in code)
The length table contains many messages that aren't handled in actual code.


Controllers - I-Mode Adaptor - Transfer Messages

I-Mode Messages on 80h-byte stream
Sending/receiving these messages can be done via 58h-byte snippet(s) in the 80h-byte portion of Command 14h.
Commands/Replies are decoded by examining the first 2-3 bytes of the message. The first byte must be 01h or 03h (01 or 11 binary). The second byte consists of several bitfields (with the overall response type in lower 1-2 bits). The TLP messages include a third byte (hardcoded to 01h in the connect code).

I-Mode Send Messages on 80h-byte stream
  01h,BBB*20h+nnn*2,01h,<TLP_MESSAGE>,crc16            req=00xh ;-TLP messages
  01h,BBB*20h+01h,crc16 --> error ?                             ;\
  0xh,BBB*20h+x5h,crc16 --> error ?                    req=020h ;
  01h,BBB*20h+09h,crc16 --> error_wrong_blkno_lsb      req=040h ; handshake
  01h,BBB*20h+11h,crc16 --> error_no_reply                      ; errors
  03h,BBB*20h+01h,crc16 --> transfer_timer             req=010h ;
  03h,BBB*20h+xxh,crc16 --> error ?                             ;/
  0xh,1Fh,crc16         --> unknown                    req=400h ;\
  01h,3Fh,crc16         --> GW_CONNECT_REQ             req=080h ;
  01h,53h,crc16         --> GW_DISCONNECT_REQ          req=100h ; control
  0xh,73h,crc16         --> unknown                    req=200h ;
  03h,87h,0xh,e,a,crc16 --> blkno (expected,actual)    req=800h ;/

I-Mode Reply Messages on 80h-byte stream
Below are the supported replies (in binary):
  x1_bbb0nnn0_00000001    event=0Fh (matching blkno)            ;\
  x1_bbb0xxx0             event=10h (wrong blkno in bit1-3)     ; TLP
  x1_bbb1nnn0_00000001    event=11h (matching blkno)            ; messages
  x1_bbb1xxx0             event=12h (wrong blkno in bit1-3)     ;/
  x1_bbb00001 (aka 01h)   event=14h                             ;\
  x1_bbb00101 (aka 05h)   event=17h                             ;
  x1_bbb01001 (aka 09h)   event=1Ah                             ; handshake
  01_bbb10001 (aka 11h)   event=13h                             ; errors?
  11_bbb10001 (aka 11h)   event=15h                             ;
  01_bbb10101 (aka 15h)   event=16h                             ;
  11_bbb10101 (aka 15h)   event=18h                             ;
  01_bbb11001 (aka 19h)   event=19h (error_wrong_blkno_lsb_ack?);
  11_bbb11001 (aka 19h)   event=1Bh                             ;
  x1_bbb0xx01 (other)     event=27h (invalid)                   ;
  01_bbb1xx01 (other)     event=26h (invalid)                   ;
  11_bbb1xx01 (other)     event=28h (invalid)                   ;/
  01_00001111 (aka_0Fh)   event=23h (force disconnect?)         ;\
  11_00001111 (aka 0Fh)   event=27h (invalid)                   ;
  01_00011111 (aka 1Fh)   event=22h (GW_DISCONNECT_ACK)         ;
  11_00011111 (aka 1Fh)   event=26h (invalid)                   ; control
  x1_00101111 (aka 2Fh)   event=1Eh                             ;
  01_00111111 (aka 3Fh)   event=26h (invalid)                   ;
  11_00111111 (aka 3Fh)   event=1Fh                             ;
  x1_01000011 (aka 43h)   event=20h                             ;
  11_01010011 (aka 53h)   event=21h                             ;
  01_01010011 (aka 53h)   event=26h (invalid)                   ;
  x1_01100011 (aka 63h)   event=1Dh                             ;
  01_01110011 (aka 73h)   event=1Ch (GW_CONNECT_ACK)            ;
  11_01110011 (aka 73h)   event=None/07h/08h (error, ignore/retry/giveup)
  01_10000111 (aka 87h)   event=25h (force disconnect?)         ;
  11_10000111 (aka 87h)   event=27h (invalid)                   ;
  01_10010111 (aka 97h)   event=24h (force disconnect?)         ;
  11_10010111 (aka 97h)   event=26h (invalid)                   ;
  x1_xxx0xx11 (other)     event=27h (invalid)                   ;
  01_xxx1xx11 (other)     event=26h (invalid)                   ;
  11_xxx1xx11 (other)     event=28h (invalid)                   ;/
  xxxxxxxx (other)        ignored (1st byte other than 01h or 03h or 10h+x)
  xxx1xxx0                ignored single-byte reply, do NOT reload timeouts
  xxxxxxxx (other)        ignored single-byte reply, but DO reload timeouts
  xxxxxxxx_xxxxxxxx       reload timeouts (on any reply with 2 or more bytes)
The replies are triggering the events that are shown above, which are then triggering a send_request (numbered 10h, 20h, 40h, 80h, 100h, 200h, 400h, 800h). That send_request does then trigger event 0Ah..0Eh. And those events are then using the send_request or other flags to decide which command message they want to send. Those commands are usually 2 or 5 bytes tall (event 0Ah,0Bh are additionally sending larger commands/packets)


Controllers - I-Mode Adaptor - TLP Transport Layer

I-Mode Packets
TLP packets are send via one of the Command 14h commands:
  000h 3    Send Command (01h,BBB*20h+NNN*2,01h) (imode/cable-specific command)
  003h ..   TLP Packet (contains Checksum, Message Type, ..., Data)
  ...  2    CRC16_CCITT_REVERSE ;little endian, initial=FFFFh, result XOR FFFFh
The second byte consists of:
  bit0    must be 0 (indicates TLP_messages)
  bit1-3  outgoing block number (increased after each message, 0 at gw_connect)
  bit4    unknown (usually 0)
  bit5-7  remote block number (from bit1-3 of remote message) (..plus 0..1 ?)

Logic State
The Logic State byte indicates presence of optional components that will be appended to the message (although most Message Types are using fixed values for the Logic State bits).
  bit4-7 unused (usually zero)
  bit3   allowed in Type=10h
  bit2   unknown, must be set for Type=11h
  bit1   allowed in Type=11h,20h,21h,30h (and implied for Type=31h)
  bit0   allowed in Type=10h,11h,20h,30h
Transmit Segment has flags in upper 2bit, which should be usually both set for the normal communication mode (in other modes the bits seem to be used to indicate first and last segment).

Message Type 10h - TLP_CONNECT_REQ (0Eh+N bytes, Send-only)
This does invoke a HTTP connection, the Transmit Data contains the HTTP request header (eg. GET/POST command, which should hopefully fit into 1400 bytes), plus first some bytes of HTTP request body (if any).
  000h 2    Checksum (sum of following 16bit values plus carry-outs, XOR FFFFh)
  002h 1    Message Type        (10h)
  003h 1    Service Identifier  (0Ah) (whatever, maybe means 0Ah=HTTP)
  004h 1    Logical Number      (01h) (bit0-6=Connection, bit7=Flag?)
  005h 1    Communication Mode  (01h) (bit0-1=Mode, bit2-7=Value?)
  006h 1    Communication Parameters[0] (01h)
  007h 1    Communication Parameters[1] (01h)
  008h 1    Communication Parameters[2] (8Ch) max packet size/10, 8Ch=1400 byte
  009h 1    Communication Parameters[3] (01h)
  00Ah 1    Communication Parameters[4] (FFh) timeout/1000 or so?
  00Bh 1    Communication Parameters[5] (00h)
  00Ch 1    Communication Parameters[6] (0Ah)
  00Dh 1    Logic State (09h) (indicates presence of below optional components)
  ...  2    Operator Specific Information  (4821h)     ;-when bit3=1 ;\
  ...  (1)  Requested Segment Number       (-)         ;-when bit1=1 ;
  ...  1    Transmit Segment Number+Flags  (C0h)       ;\            ; Optional
  ...  2    Transmit Length (1..1400)      (03B7h)     ; when bit0=1 ;
  ...  LEN  Transmit Data ("POST http://ne-net.com/"..);/            ;/
The lower 7bit of the Logical Number contain a Connection ID in range 01h..7Fh (this value is incremented for each new connection; unknown if one could use multiple connections; the PSX games/browser do always DISCONNECT before doing a new CONNECT).

Message Type 11h - TLP_CONNECT_ACK (0Dh+N bytes, Recv-only)
This does acknowledge a HTTP connection, the Transmit Data contains the HTTP response header (usually with HTTP/1.0 200 OK, and Content-Length, and other info), plus first some bytes of HTTP response body (if any).
  000h 2    Checksum
  002h 1    Message Type        (11h)
  003h 1    Logical Number      (01h)
  004h 1    Communication Mode  (01h)     ;\
  005h 1    Communication Parameters[0]   ;
  006h 1    Communication Parameters[1]   ; these can/may/should use same
  007h 1    Communication Parameters[2]   ; values as in message type 10h
  008h 1    Communication Parameters[3]   ;
  009h 1    Communication Parameters[4]   ;
  00Ah 1    Communication Parameters[5]   ;
  00Bh 1    Communication Parameters[6]   ;/
  00Ch 1    Logic State (07h) (indicates presence of below optional components)
  ...  (2)  Operator Specific Information (-)          ;-when bit3=1 ;\
  ...  1    Requested Segment Number (0..3Fh)          ;-when bit1=1 ;
  ...  1    Transmit Segment Number  (0..3Fh+Flags)    ;\            ; Optional
  ...  2    Transmit Length (big-endian)               ; when bit0=1 ;
  ...  ..   Transmit Data ("HTTP/1.0 200 OK"..)        ;/            ;/

Message Type 12h - TLP_CONNECT_REJECT (05h bytes, Recv-only)
This is supposedly used for rejecting connections (possible reasons might be invalid domain name, or perhaps exceeding monthly traffic limit).
  000h 2    Checksum
  002h 1    Message Type        (12h)
  003h 1    Logical Number
  004h 1    Disconnect Reason (00h..08h)

Message Type 20h - TLP_DISCONNECT_REQ (06h+N bytes, Recv/Send)
Message Type 21h - TLP_DISCONNECT_ACK (06h+N bytes, Recv/Send)
Disconnection can be invoked by sender or receiver (or both).
Normally, if one unit does run out of data then it will send DATA_EOF, if the other unit does also run out of data then it will send DISCONNECT_REQ (this behaviour is required for Hamster Club-i).
Additionally, the PSX can examine the Content-Length in HTTP response, and throw DISCONNECT_REQ when reaching that length (this happens in NetFront browser, and it can result in both sides sending DISCONNECT_REQ).
Additionally, the PSX can clip the Content-Length to some maximum value (usually 10240 bytes), and throw DISCONNECT_REQ when reaching that limit.
  000h 2    Checksum
  002h 1    Message Type        (20h/21h)
  003h 1    Logical Number
  004h 1    Disconnect Reason   (00h..08h) (0=Okay/Transfer completed)
  005h 1    Logic State         (usually 00h)
  ...  (2)  Operator Specific Information            ;-when bit3=1 ;\
  ...  1    Requested Segment Number (0..3Fh)        ;-when bit1=1 ; Optional
  ...  1    Transmit Segment Number  (0..3Fh+Flags)  ;\            ; usually
  ...  2    Transmit Length                          ; when bit0=1 ; none such
  ...  ..   Transmit Data                            ;/            ;/
20h/21h have same format... but 21h has extra restrictions on Logic Srate.

Message Type 30h - TLP_DATA (09h+N bytes, Recv/Send)
Used to send/receive additional HTTP data packets (additionally to the first packet in the CONNECT messages), with increasing segment numbers.
  000h 2    Checksum
  002h 1    Message Type        (30h)
  003h 1    Logical Number
  004h 1    Logic State         (usually 03h) (must be xxxx0x11 binary)
  005h 1    Requested Segment Number (0..3Fh)       ;\
  006h 1    Transmit Segment Number  (0..3Fh+Flags) ; always present because
  007h 2    Transmit Length                         ; above bit1,0 are both set
  009h ..   Transmit Data                           ;/

Message Type 31h - TLP_DATA_EOF (05h bytes, Recv/Send)
Indicates that there are no more transmit segments (and requests next segment from opponent).
  000h 2    Checksum
  002h 1    Message Type        (31h)
  003h 1    Logical Number
  004h 1    Requested Segment Number (0..3Fh) (alike as if Logic State bit1=1)

Message Type 40h - TLP_INFO (07h+N bytes, Recv-only)
Contains "info", purpose is unknown (maybe notifications about incoming voice calls, battery state, or such things).
  000h 2    Checksum
  002h 1    Message Type        (40h)
  003h 1    Service Identifier  (must be 09h, unlike as in Message Type 10h)
  004h 1    Communication Mode/Logical Number (bit0-1=Mode, bit2-7=Connection)
  005h 2    Data Length
  007h ..   Data (whatever info)

Message Type 41h - TLP_INFO_ACK (04h bytes, Send-only)
  000h 2    Checksum
  002h 1    Message Type        (41h)
  003h 1    Communication Mode/Logical Number (bit0-1=Mode, bit2-7=Connection)

Message Type 50h - Unknown/Unused (06h+N bytes, Recv/Send)
  000h 2    Checksum
  002h 1    Message Type        (50h)
  003h 1    Logical Number
  004h 1    Transmit Segment Number
  005h 1    Transmit SmallData Length (max 5 bytes or so?)
  006h ..   Transmit SmallData[..]    ;flagbits! (per Communication Mode 6bit)

Message Type 60h - Unknown/Unused (04h bytes, Recv/Send)
  000h 2    Checksum
  002h 1    Message Type        (60h)
  003h 1    Logical Number


Controllers - I-Mode Adaptor - HTTP Requests/Replies

HTTP versions
There are several notable HTTP versions:
  HTTP/1.0 ascii headers                        (1991)
  HTTP/1.1 ascii headers, with Host: domain     (1997)
  HTTP/2   binary headers for faster transfers  (2015)
Although released in 2001, the PSX software does still use the old HTTP/1.0 format (unknown if the I-Mode server would also accept HTTP/1.1 messages).

HTTP domains
HTTP/1.0 didn't use domain names (it did solely rely on the IP address in the TCP/IP packets, which can be a problem when using shared IPs for virtual domains).
HTTP/1.1 did invent a "Host: domain" entry in the HTTP header (this allows to redirect the TCP/IP packets to the desired virtual domain) (although that wasn't originally supported in HTTP/1.0, it's common practice to include that "Host:" entry also in HTTP/1.0 messages).

HTTP custom I-Mode headers
I-Mode is using a simplified TLP protocol (without IP addresses, unlike TCP/IP). This relies on including the domain name in the HTTP header (and the I-Mode server would then care about resolving the IP address). This is using non-standard HTTP requests as so:
  GET http://www.mydomain.net/index.html HTTP/1.0
When communicating with the outside world, the I-Mode server should parse that request to something like this:
  GET /index.html HTTP/1.0
  Host: www.mydomain.net
Alongsides, one may also parse HTTP/1.0 to HTTP/1.1 (in case some servers dislike old HTTP/1.0 packets, or dislike the Host: entry being used as inofficial HTTP/1.0 extension).
And, for old PSX games, most or all old game servers do no longer exist, so one may also need to parse the domain/path to elsewhere.

HTTP requests
The PSX programs are using either GET or POST commands. According to Sony, one could also use HEAD. Theoretically one could also use any other HTTP commands like PUT or DELETE (unless the I-Mode server should somehow refuse to forward them to the actual domain).
  GET   request downloading a HTM file, or GIF file, or anything else
  POST  same as GET, with additional parameters (in request.body)
  HEAD  same as GET, but returns only response.header (without response.body)
An example HTTP request (from Hamster Club-i) looks as so:
  POST http://ne-net.com/hc/i/ps/ArenaParty.cgi HTTP/1.0  ;-request
  User-Agent: DoCoMo/1.0/ex_ps1302
  Content-type: application/x-www-form-urlencoded         ;\for POST body
  Content-Length: 789                                     ;/
                             <blank line>                 ;-end of header
  uid=NULLGWDOCOMO&val=%0A%0A%...%CD%13%03%07             ;-POST body
Unknown if the uid "&val=..." does contain a user ID (that might have been somehow obtained during auth/connect, or stored on the PSX memory card), or maybe the phone or server is supposed to replace the uid "NULLGWDOCOMO" string by the actual phone number or some other kind of docomo user id.

HTTP replies
HTTP replies contain a status code, several optional header fields like Content-Length: and Date: terminated by a blank line, followed by the file body. For example,
  HTTP/1.0 200 OK                                         ;-status code
  Content-Length: 123                                     ;\for body
  Content-Type: text/html                                 ;/
                             <blank line>                 ;-end of header
  <HTML><HEAD><TITLE>Hello</TITLE></HEAD>...</HTML>       ;-file body
Some servers (including problemkaputt.de) will send a HTTP/1.1 reply even when receiving HTTP/1.0 requests (the existing PSX software seems to accept that, without needing to parse the reply to HTTP/1.0).

HTML format
I-Mode phones are using a custom iHTML variant, which is based on cHTML (aka compact html). This is reportedly having restrictions like not supporting things like <TABLE>, and it's generally intended to work on old phones with tiny LCD displays (reportedly 96x95 pixels on DoCoMo P502i) and little RAM.
When using the I-Mode phone as a "modem" for PCs or PSX consoles, browsers could theoretically implement fully-fledged HTML support (although the PSX is having it's own restrictions like 2Mbyte RAM and blurry TV Sets).

HTML browser
The PSX CompactNetFront browser is using 320x224 pixel resolution (actually 296x176, plus gray borders; which should work on blurry and mis-centered TV sets; unknown if the japanese options allow to change the screen resolution for higher resolution displays).
  The PSX browser does support HTM, TXT, GIF
  The PSX browser does support <TABLE>
  The PSX browser does not support JPG (and certainly no STJ or PNG)
  The PSX browser seems to ignore things like <B>, <HR>, <FONT SIZE>
  TXT/HTM/GIF loading aborts after 10K (10240 bytes) in http response.body


Controllers - I-Mode Adaptor - Software

PSX I-Mode Emulation
No$psx v2.3 supports redirecting I-Mode HTTP messages to real internet (that is HTTP only, HTTPS isn't supported, and gets redirected to HTTP where possible). The original game servers and browser start page are no longer working, but they can be redirected to new servers in NO$PSX.INI. For example:
  RedirectURL == http://docomo.ne.jp/mn/ == http://problemkaputt.de/
The TTY debug window displays higher-level I-Mode messages (and enabling JOY logging will also show lower-lever controller messages).

PSX Games/Software for I-Mode Adaptor (Japan only)
  Sxxx-????? Doko Demo Issyo (PlayStation the Best release only) (Sony) 2000
  Sxxx-????? Doko Demo Issyo Deluxe Pack (Bomber eXpress/Sony) 2001
  SLPS-03266 Hamster Club-I (Jorudan) 2002
  SCPS-10141 iMode mo Issyo: Dokodemo Issho Tsuika Disc (Bomber/Sony) 2001
  SLPS-02717 Keitai Eddy (iPC) (phone cable connects to SIO port) 2000
  SLPS-03121 Komocchi (Victor) 2001
  SLPM-87151 Mobile Tomodachi (Hamster) 2002
  SLPS-03321 Motto Trump Shiyouyo! i-Mode de Grand Prix (Pure Sound) 2002
  SLPM-86837 One Piece Mansion (Capcom) (japanese version only) 2001
  PBPX-95013 Keitai Henshuu (CompactNetFront browser) (in SCPH-10180K kit) 2001
The supported games should have the I-Mode adaptor logo on the CD cover (the logo depicts two plugs: a PSone controller plug, and a smaller I-Mode plug).
Within the games, glyphs that look like "iE-t'" appear to refer to I-Mode functions.

Notes
Lightspan Online Connection CD is using a regular dial-up modem for internet (instead of mobile I-mode phones).
"Dragon Quest Monsters 1 & 2" was announced/rumoured to support I-mode (however, its CD cover doesn't show any I-Mode adapter logo; and the game does reportedly require entering passwords for "manual" data transfer between PSX and mobile phones).


Controllers - I-Mode Adaptor - Misc

Hardware Variants
 PSX old Keitai Eddy cable:
  SIO Connector --------- PCB (in middle of cable) --------- I-Mode connector
 PSX new standard cable (SCPH-10180):
  Controller Port (with PCB inside of plug) ---------------- I-Mode connector
 PC Version (Data Link Cable SO003):
  COM port ------ unknown hardware ------------------------- I-Mode connector
 PC Version (USB Data Link Cable F001):
  USB port ------ unknown hardware ------------------------- I-Mode connector
The Keitai Eddy SIO cable was bundled with the Keitei Eddy CDROM. The SIO cable was apparently discontinued and replaced by the SCPH-10180 cable because newer PSone consoles don't have SIO ports.
Unknown if both cables were made by the same manufacturer. The newer SCPH-10180 games are NOT backwards compatible with the old SIO cable.
Keitai Eddy is an untility for editing things like ring tones, the main menu supports dozens or hundreds of phones from different manufacturers - unknown if it does have any "internet support", or if it's merely capable of editing phone settings. Unknown if the Keitai Eddy cable contains a microprocessor, or if it does merely pass-through UART signals with some small voltage protection circuit.

Supported phones (SCPH-10180)
"Compatible only with the iMODE mobile phone that supports "iNavilink" [i-Navi Link]. Currently, the [DoCoMo] P502i, F502it and N502it are the only compatible equipment. The 503 series will be sold after this [which?] winter and all units will be compatible."

ASCII Strings
The games don't contain detailed debug messages. However, some games do contain ASCII strings related to networking:
Hamster Club-I:
 has several ASCII strings:
  800108BC  " HTTP/1.0",0Dh,0Ah,"User-Agent: ",00h
  800108D4  0Dh,0Ah,"Content-type: text/plain",0Dh,0Ah,"Content-Length: ",00h
  80010904  "Content-Length: ",00h
  80013C18  "uid=NULLGWDOCOMO&val=",00h
  80013C30  "http://ne-net.com/hc/i/ps/",00h
  80013C30  "HTTP/1.0",0Dh,0Ah,"User-Agent: ",00h
  80013C64  "DoCoMo/1.0/ex_ps1302",00h
  80013C7C  0Dh,0Ah,"Content-type: application/x-www-form-urlencoded",0Dh,0Ah,
            "Content-Length: ",00h
  80014040  "Ranking.cgi"      ;2580h bytes      +32bit chksum, two such files
  800141DC  "Regist.cgi"       ;10h bytes        +32bit chksum
  800145E0  "HamList.cgi"      ;488h bytes       +32bit chksum
  80014668  "HamSet.cgi"       ;1h byte          +8bit chksum
  800148C0  "ArenaParty.cgi"   ;1h byte          +8bit chksum
  80014948  "ArenaBattle.cgi"  ;394h or 4 bytes  +32bit chksum
  80014958  "ArenaResult.cgi"  ;4h bytes or none +32bit chksum
  80014AEC  "Stroll.cgi"       ;38h bytes        +32bit chksum
  80018B88  "-- autholize pass -2",0Ah,0
  80018DD0  "User-Agent:DoCoMo/1.0/ex_ps",00h
  80018DEC  "User-Agent: DoCoMo/1.0/ex_ps",00h
  80018E0C  "TL_Disconnect Invalid TL handle = %d ",0Ah,00h
  80018E34  "TL_Disconnect TLCF2_ERR_OTHERS",0Ah,00h
  8001910C  "Ayame.log",00h
  80019118  "com1:"
  800D8C60  25h --> "%"
  800E1648  48h,54h,... ---> "HTTP/1.0",0Dh,0Ah,00h
  800E16C8  55h,73h,... ---> "User-Agent: DoCoMo/1.0/",00h
  801018F0  "Access TLm Version 3.0 (Ayame)",00h
  80101910  "Copyright 1997 - 2000 Access Co., Ltd.",00h
  80101938  "Gamma Release 1.3 (Apr. 18, 2000),00h
  801024E8  "GET",00h
  80102500  "POST",00h
  80102728  "POST",00h
 and some known code/data locations:
  800CA80C  code: send joy byte
  800D94BC  code: send imode byte 41h
  800D9F3C  code: send NOT(-42h) aka NOT(FFFFFFBEh) aka 41h
  To get I-Mode transfers: In main menu, select "iE-K" then select "NETWORK
  BATTLE" (or the other option; other than the two RANKING options).
i-mode mo Issho - Doko Demo Issho Tsuika Disc:
 has similar ASCII strings:
  GET http, POST http://dkd.to/p/, User-Agent, com1:, Access TLm, ..
Motto Trump Shiyou yo! i-Mode de Grand Prix:
 has a few ASCII strings:
  8006AB6C-and-up   maybe compare 5Ah for replies?
  80072144 80014548h   "-- autholize pass -2",0Ah,0
  80072CB8 80014790h   "User-Agent:DoCoMo/..."
  80072D34 800147ACh   "User-Agent:DoCoMo/..."
  80073498 800147CCh   "TL_Disconnect Invalid TL handle = %d ",0Ah,0
  8007A9E4 80014ACCh   "Ayame.log"
  8007A9F0 80014AD8h   "com1:"
  800852C0 48h,54h,... "HTTP/1.0",0Dh,0Ah,00h
  80085340 55h,73h,... "User-Agent:"
One Piece Mansion:
 has ASCII strings (only in memory when selecting 3rd main menu option).
Mobile Tomodachi:
 no ASCII strings (and merely accesses phone address book, without internet?).
 requires entering a 4-digit PIN (that part is similar as in Keitai Eddy)


Controllers - I-Mode Adaptor - Libimode Library

I-Mode PSX Library
There is an offical document summarizing the I-Mode features for PSX:
http://lorezan.free.fr/ps1/iMODE.pdf Software Development Seminar: iMode System
It does include some info about a data structure and command/state values for the libimode library:
 sceImode_Param Context Structure
  00h short fCommandType        Command type (00h..07h)
  02h short fPortNo             iMODE cable connection port (0:port1, 1:port2)
  04h short fSlotNo             iMODE cable connection slot (A~D:0~3) (unused)
  06h -     padding             -
  08h char* fSendBuff           Send data buffer address           ;\
  0Ch short fSendBuffSize       Send data buffer size              ; TX
  0Eh short fSendDataSize       Actual size of send data           ;/
  10h char* fRcvBuff            Receive data buffer address        ;\
  14h short fRcvBuffSize        Size of receive data buffer        ; RX
  16h short fRcvDataSize        Size of receive data buffer        ;/
  18h char* fInfoBuff           Info data receive buffer address   ;\
  1Ch short fInfoBuffSize       Info data receive buffer size      ; Info ?
  1Eh short fInfoDataSize       Actual size of info data received  ;/
  20h short fStatus             State variable (00h..10h)
  22h short fLastError          Error class (signed, -63h..+00h)
 Commands:
  0=IMODE_CMD_RCV               Check receive data (default)
  1=IMODE_CMD_SND               Send request
  2=IMODE_CMD_STS               Get state
  3=IMODE_CMD_ABORT             Abort send/receive
  4=IMODE_CMD_AUTH_START        Begin authentication
  5=IMODE_CMD_AUTH_END          End authentication
  6=IMODE_CMD_GW_CONNECT        Connect gateway
  7=IMODE_CMD_GW_DISCONNECT     Disconnect gateway
 States:
  -1 =UNINITIALIZED       Pre-Init / Post-Finalize
  00h=DORMANT             Initial State          ;-
  01h=AUTH_STARTING       Authenticating         ;\CND_AUTH_START
  02h=AUTH_STARTED        Authenticated          ;/
  03h=GW_CONNECTING       Gateway connecting     ;\
  04h=GW_CONNECTED        Gateway connected      ; CMD_GW_CONNECT
  05h=CONNECTING       ?  Connecting             ;/
  06h=CONNECTED        ?  Connected
  07h=SENDING          ?? Sending                ;\IMODE_CMD_SND
  08h=SENDCOMPLETE     ?? Send completed         ;/
  09h=RECEIVING        ?? Receiving              ;\IMODE_CMD_RCV
  0Ah=RECEIVECOMPLETE  ?? Receive completed      ;/
  0Bh=DISCONNECTING    ?  Disconnecting          ;\    CMD_ABORT?
  0Ch=DISCONNECTED     ?  Disconnected           ; CMD_GW_DISCONNECT
  0Dh=GW_DISCONNECTING    Gateway disconnecting  ;
  0Eh=GW_DISCONNECTED     Gateway disconnected   ;/
  0Fh=AUTH_ENDING         Authentication ending  ;\CMD_AUTH_END
  10h=AUTH_ENDED          Authentication ended   ;/

I-Mode Send requests
  req=400h   cmd=0Fh+10h       (1Fh)        ?                     ;\
  req=080h   cmd=2Fh+10h       (3Fh)        gw_connect            ;
  req=100h   cmd=43h+10h       (53h)        gw_disconnect         ; control
  req=200h   cmd=63h+10h       (73h)        ? (event 20h/21h?)    ;
  req=800h   cmd=87h+xx,n,n,n  (87h or 97h) ;5byte ;shutdown?     ;/
  req=010h   cmd=01h+xx        (01h or 11h) misc & transfer_timer ;\handshake
  req=020h   cmd=05h+xx        (05h or 15h) misc                  ; errors?
  req=040h   cmd=09h+xx        (09h or 19h) wrong_blkno_lsb       ;/
  req=00xh   event 0Ah/0Bh --> cmd=00h+xx+ttt+bbb+(Nbyte), or cmd=01h/05h+10h

I-Mode Events
  event=-1  none
  event=00h user_action_05h_11h (connect_stage_1, begin_gw_connect)   ;req=080h
  event=01h unused
  event=02h unused
  event=03h user_action_05h_12h (connect_stage_3, begin_gw_disconnect);req=100h
  event=04h unused
  event=05h trigger ;killer_xfer_req=020h      ;\generated somehow
  event=06h trigger ;killer_xfer_req=010h      ;/(send handshake error?)
  event=07h error_retry  (upon timeout, or incoming_11_01110011 error msg)
  event=08h error_giveup (after four (re-)tries)
  event=09h transfer_timer (triggers req=010h, or req=020h)
  event=0Ah    ;\send 2, 5, or N byte (send data message?) outgoing
  event=0Bh    ;/                                          outgoing
  event=0Ch    ;\                                          outgoing
  event=0Dh    ; send 2, or 5 byte (send control message?) outgoing
  event=0Eh    ;/                                          outgoing
  event=0Fh (matching blkno)     incoming_x1_bbb0nnn0_nnnnnnnn  ;\
  event=10h (wrong blkno bit1-3) incoming_x1_bbb0xxx0           ; TLP
  event=11h (matching blkno)     incoming_x1_bbb1nnn0_nnnnnnnn  ; messages
  event=12h (wrong blkno bit1-3) incoming_x1_bbb1xxx0           ;/
  event=13h   ;\                 incoming_01_bbb10001 (aka 11h) ;\
  event=14h   ;                  incoming_x1_bbb00001 (aka 01h) ;
  event=15h   ;/                 incoming_11_bbb10001 (aka 11h) ; handshake
  event=16h   ;\flags OR 10h     incoming_01_bbb10101 (aka 15h) ; errors?
  event=17h   ; result=20h       incoming_x1_bbb00101 (aka 05h) ;
  event=18h   ;/                 incoming_11_bbb10101 (aka 15h) ;
  event=19h   ;\                 incoming_01_bbb11001 (aka 19h) ;
  event=1Ah   ; flags OR 40h     incoming_x1_bbb01001 (aka 09h) ;
  event=1Bh   ;/                 incoming_11_bbb11001 (aka 19h) ;/
  event=1Ch (GW_CONNECTED)       incoming_01_01110011 (aka 73h) ;\
  event=1Dh    (req_disconnect?) incoming_x1_01100011 (aka 63h) ;
  event=1Eh   ;\                 incoming_x1_00101111 (aka 2Fh) ;
  event=1Fh   ; req=200h, and    incoming_11_00111111 (aka 3Fh) ; control
  event=20h   ; req=400h         incoming_x1_01000011 (aka 43h) ;
  event=21h   ;/                 incoming_11_01010011 (aka 53h) ;
  event=22h (GW_DISCONNECTED)    incoming_01_00011111 (aka 1Fh) ;
  event=23h (force disconnect?)  incoming_01_00001111 (aka_0Fh) ;
  event=24h (force disconnect?)  incoming_01_10010111 (aka 97h) ;
  event=25h (force disconnect?)  incoming_01_10000111 (aka 87h) ;/
  event=26h (invalid)            incoming_01_bbb1nn01 (other)   ;\
  event=27h (invalid)            incoming_x1_bbb0nn01 (other)   ; handshake
  event=28h (invalid)            incoming_11_bbb1nn01 (other)   ;/
  event=26h (invalid)            incoming_01_00111111 (aka 3Fh) ;\
  event=26h (invalid)            incoming_11_00011111 (aka 1Fh) ; control
  event=26h (invalid)            incoming_11_10010111 (aka 97h) ;
  event=26h (invalid)            incoming_01_xxx1xx11 (other)   ;
  event=26h (invalid)            incoming_01_01010011 (aka 53h) ;
  event=27h (invalid)            incoming_11_00001111 (aka 0Fh) ;
  event=27h (invalid)            incoming_11_10000111 (aka 87h) ;
  event=27h (invalid)            incoming_x1_xxx0xx11 (other)   ;
  event=28h (invalid)            incoming_11_xxx1xx11 (other)   ;/


Controllers - I-Mode Adaptor - Unknown Features

I-Mode PSX software is in japanese (unknown if translations would reveal any interesting information).
I-Mode can reportedly also send UDP messages (unknown how and what for).
I-Mode can transfer Info additionally to Data (unknown what that Info stuff is, it seems to be related to TLP Message Type 40h/41h).
I-Mode has some monthly traffic limit (unknown what kind of status/error messages exist).
I-Mode requires nearby radio stations (unknown what kind of status/error messages exist).
I-Mode phones probably requires battery/chargers (unknown what kind of status/error messages exist, unknown if it's possible to connect chargers without removing the I-Mode data cable).
I-Mode phones should have some unique user ID or phone number (unknown what kind of status/error messages exist; unknwn if such IDs are automatically included in HTTP messages).
I-Mode can send emails (in PSX browser, click the option underneath of iMenu) (unknown how the send-protocol works).
I-Mode can probably receive emails (unknown if/how the PSX browser can do such things).
I-Mode cables can access rhe phone's address book (this is used by Keitai Eddy, Mobile Tomodachi, and upper-right PSX browser options) (unknown how that works, it appears to require a PIN number; the PSX seems to await a message from phone instead of sending messages to it)).
I-Mode cables can install custom ringtones (supported by Keitai Eddy, maybe also by PSX browser) (unknown how that works, it appears to require a PIN number).
I-Mode phones do probably include a RTC (unknown if/how the PSX can access that, as by now, the PSX browser's email composer seems to prompt the user to manually enter date/time) (note: paid-for I-Mode services include Time and Weather, but the phone should also have a RTC).
I-Mode can notify of incoming voice calls during internet browsing (unknown if such notifications are also forwarded to PSX).
I-Mode PC-USB-cables support standard modem drivers with Hayes AT commands (alternately to using a dedicated I-Mode driver) (unknown if that Hayes stuff is also accessible on PSX).


Controllers - I-Mode Adaptor - References

Sony's Software Development Seminar: iMode System
http://lorezan.free.fr/ps1/iMODE.pdf contains some basic info about the PSX library and features.

DoCoMo Technical Journal - Special Issue on I-mode Service
The "DoCoMo Technical Journal" includes a "Special Issue on I-mode Service" with four articles:
  Media Concept  ../technology/rd/technical_journal/bn/vol1_1/vol1_1_010en.pdf
  Network System ../technology/rd/technical_journal/bn/vol1_1/vol1_1_014en.pdf
  i-mode Server  ../technology/rd/technical_journal/bn/vol1_1/vol1_1_020en.pdf
  Micro Browser  ../technology/rd/technical_journal/bn/vol1_1/vol1_1_026en.pdf
  (above files can found at www.docomo.ne.jp/english/binary/pdf/corporate/..)
That includes some technical overview about the network layers... instead of "TCP/IP" they are using a custom "TLP" (or short "TL") protocol.

Patents (US6898640 and CA2322290C)
https://patents.google.com/patent/US6898640 contains some basic info about the TL aka TLP protocol (FIG.5 is a TLP packet transfer flowchart, FIG.8,9,10 are TLP packet formats).

HTTP/1.0
http://www.w3.org/Protocols/HTTP/1.0/spec

I-Mode PSX Forum Thread
http://www.psxdev.net/forum/viewtopic.php?f=54&t=408


Controllers - Keyboards

There isn't any official retail keyboard for PSX, however, there is a shitload of obscure ways to connect keyboards...

Sony SCPH-2000 PS/2 Keyboard/Mouse Adaptor (prototype/with cable) (undated)
Sony SCPH-2000 PS/2 Keyboard/Mouse Adaptor (without cable) (undated)
A PS/2 to PSX controller port adaptor. Maybe for educational Lightspan titles?
There are two hardware variants of the adaptor:
  Adaptor with short cable to PSX-controller port (and prototype marking)
  Adaptor without cable, directly plugged into controller port (final version?)
Unknown how to access those adaptors, and unknown if the two versions differ at software side. There seem to be not much more than a handful of people owning that adaptors, and none of them seems to know how to use it, or even how to test if it's working with existing software...
- Keyboard reading might work with the Online Connection CD.
- Mouse reading might work with normal mouse compatible PSX games.

Lightspan Online Connection CD Keyboard (1997)
The Online Connection CD is a web browser from the educational Lightspan series, the CD is extremly rare (there's only one known copy of the disc).
The thing requires a dial-up modem connected to the serial port (maybe simply using the same RS232 adaptor as used by Yaroze). User input can be done via joypad, or optionally, via some external keyboard (or keyboard adaptor) hardware:
  Send  01h 42h 00h 00h 00h 00h 00h 00h 00h 00h 00h 00h 00h 00h 06h
  Reply HiZ 96h 5Ah num dat dat dat dat dat dat dat dat dat dat dat
The num byte indicates number of following scancodes (can be num=FFh, maybe when no keyboard connected?, or num=00h..0Bh for max 11 bytes, unless the last some bytes should have other meaning, like status/mouse data or so).
The keyboard scancodes are in "PS/2 Keyboard Scan Code Set 2" format:
       08 10 18 20   28 30 38 40   48 50 57 5F
  76   05 06 04 0C   03 0B 83 0A   01 09 78 07  pr 7E br
  0E 16 1E 26 25 2E 36 3D 3E 46 45 4E 55 6A 66 '70'6C'7D  77'4A 7C 7B
  0D  15 1D 24 2D 2C 35 3C 43 44 4D 54 5B   5D '71'69'7A  6C 75 7D
  58   1C 1B 23 2B 34 33 3B 42 4B 4C 52 5D  5A            6B 73 74 79
  12 61 1A 22 21 2A 32 31 3A 41 49 4A  51   59    '75     69 72 7A
  14'1F 11            29          '11'27'2F'14 '6B'72'74  70    71'5A
Above values can have prefix bytes:
  xx     -->  Pressed: xx           Released: F0 xx              ;xx=01..83
  'xx    -->  Pressed: E0 xx        Released: E0 F0 xx           ;xx=11..7D
  pr     -->  Pressed: E0 12 E0 7C  Released: E0 F0 7C E0 F0 12
  br     -->  Pressed: E1 14 77     Released: E1 F0 14 F0 77
  And, Logitech keyboards with built-in pointing device use prefix E2.
  Some multimedia keyboards may have '3F=Sleep, '37=Power, '5E=Wake, and/or
  Play/Pause/Volume/Email/whatever buttons (though that may be more common
  on USB keyboards than PS/2 ones).
The binary contains some (unused) code for sending data to the keyboard by changing the 4th-11th byte, and resuming normal operation by setting 4th and 11th byte back to zero:
  Send  ..  ..  ..  01h xxh FFh FFh FFh FFh FFh 00h ..  ..  ..  ..
  Send  ..  ..  ..  00h ..  ..  ..  ..  ..  ..  00h ..  ..  ..  ..
Maybe 4th and 11th byte are number of following bytes, with xxh being some command, and FFh's just being bogus padding; the xxh looks more like an incrementing value though.
Despite of the mouse-based GUI, the browser software doesn't seem to support mouse hardware (neither via PS/2 mice, nor PSX mice). Instead, the mouse arrow can be merely moved via joypad's DPAD, or (in a very clumsy fashion) via keyboard cursor keys.
Note: The browser uses SysEnqIntRP to install some weird IRQ handler that forcefully aborts all controller (or memory card) transfers upon Vblank. Unknown if that's somehow required to bypass bugs in the keyboard hardware. The feature is kinda dangerous for memory card access (especially with fast memcard access in nocash kernel, which allows to transfer more than one sector per frame).

Spectrum Emulator Keyboard Adaptor (v1/serial port) (undated)
Made by Anthony Ball. http://www.sinistersoft.com/psxkeyboard 
  [1F801058h]=00CEh  ;SIO_MODE 8bit, no parity, 2 stop bits (8N2)
  [1F80105Ah]=771Ch  ;SIO_CTRL rx enable (plus whatever nonsense bits)
  [1F80105Eh]=006Ch  ;SIO_BAUD 19200 bps
  RX   Keyboard Scancode (same ASCII-style as in later versions?)
  CTS  Caps-Lock state
  DSR  Num-Lock state

Spectrum Emulator Keyboard & Sega Sticks Adaptor (v2/controller port) (2000)
Made by Anthony Ball. http://www.sinistersoft.com/psxkeyboard
This adaptor can send pad/stick data,
  Send  01h 42h 00h  0h 0h
  Reply HiZ 41h 5Ah  PadA
as well as pad/sticks+keyboard data,
  Send  01h 42h 00h  0h 0h 0h 0h 0h 0h 0h 0h  00h 00h   0h 0h 0h 0h 0h 0h
  Reply HiZ E8h 5Ah  PadA  PadB  PadC  PadD   Ver Lock  Buffer(0..5)
The above mode(s) can be switched via ACPI Power/Sleep/Wake keys (on keyboards that do have such keys).
  Version=1     ; version number
  0  SCROLL          ; scroll lock on
  1  NUM             ; num lock on
  2  CAPS            ; caps lock on
  3  DONETEST        ; keyboard has just done a selftest
  4  EMUA            ; emulation mode a
  5  EMUB            ; emulation mode b
For whatever reason, the PS/2 scancodes are translated to ASCII-style scancode values (with bit7=KeyUp flag):
  01   11 12 13 14  15 16 17 18  19 1A 1B 1C  1D 69 1F
  60 21 22 68 24 25 5E 26 2A 28 29 5F 3D  2D  0B 0E 0F  67 2F 1E 2D
  27  51 57 45 52 54 59 55 49 4F 50 5B 5D 0D  10 61 62  37 38 39
  3B   41 53 44 46 47 48 4A 4B 4C 3A 40 23              34 35 36 2B
  02 5C 5A 58 43 56 42 4E 4D 3C 3E 3F     03     63     31 32 33
  04 05 06           20          07 08 09 0A  65 64 66  30    2E 6A
BUG: The thing conflicts with memory cards: It responds to ANY byte with value 01h (it should do so only if the FIRST byte is 01h).

Homebrew PS/2 Keyboard/Mouse Adaptor (undated/from PSone era)
  Send  01h 42h 00h 00h 00h 00h 00h
  Reply HiZ 12h 5Ah key flg dx  dy
flg:
  bit0-1 = Always 11b       (unlike Sony mouse)
  bit2 = Left Mouse Button  (0=Pressed, 1=Released)  ;\BUG: left/right buttons
  bit3 = Right Mouse Button (0=Pressed, 1=Released)  ;/should be vice-versa
  bit4-5 = Always 11b       (like Sony mouse)
  bit6 = Key Release        (aka F0h prefix) (0=Yes, 1=No)
  bit7 = Key Extended       (aka E0h prefix) (0=Yes, 1=No)
Made by Simon Armstrong. There aren't any known games/demos supporting this adaptor, especially not the keyboard part (the webpage merely recommends to use standard PSX mouse software for testing).
The thing emulates a standard PSX Mouse (and should thus work with most or all mouse compatible games). Additionally, it's sending keyboard flags/scancodes via unused mouse button bits.

Runix hardware add-on USB Keyboard/Mouse Adaptor (2001) (PIO extension port)
Runix is a homebrew linux kernel for PSX, it can be considered to be the holy grail of the open source scene because nobody has successfully compiled it in the past 25 years.
- USB host controller SL811H driver with keyboard and mouse support;
- RTC support.
file: drivers/usb/sl811h.c

TTY Console
The PSX kernel allows to output "printf" debug messages via stdout. In the opposite direction, it's supporting to receive ASCII user input via "std_in_gets" (there isn't any software actually using that feature though, except maybe debug consoles like DTL-H2000).

Key Repeat and LED Control
Unknown if any of the above keyboards/adaptors do support key repeat (and any ways to configure the key repeat rate). However, one can easily implement that feature on PSX side (repeat the most recently pressed key at desired rate, until it gets released).
Also unknown if any of the keyboards/adaptors do support Caps/Num/Scroll LED control (or ways to obtain the current LED states).


Controllers - Additional Inputs

Reset Button
PSX only (not PSone). Reboots the PSX via /RESET signal. Probably including for forcefully getting through the WHOLE BIOS Intro, making it rather useless/annoying? No idea if it clears ALL memory during reboot?

CDROM Shell Open
Status bit of the CDROM controller. Can be used to sense if the shell is opened (and also memorizes if the shell was opened since last check; allowing to sense possible disk changes).

PocketStation
Memory Card with built-in LCD screen and Buttons (which can be used as miniature handheld console). However, when it is connected to the PSX, the buttons are vanishing in the cartridge slot, so the buttons cannot be used as additional inputs for PSX games.

Serial Port PSX only (not PSone)
With an external adaptor (voltage conversion), the serial port can be used (among others) to connect a RS232 Serial Mouse. Although, most or all commercial games with mouse input are probably (?) supporting only Sony's Mouse (on the controller port) (rather than standard RS232 devices on the serial port).

TTY Debug Terminal
If present, the external DUART can be used for external keyboard input, at the BIOS side, this is supported as "std_in".


Controllers - Misc

Standard Controllers
  SCPH-1010  digital joypad (with short cable)
  SCPH-1080  digital joypad (with longer cable)
  SCPH-1030  mouse (with short cable)
  SCPH-1090  mouse (with longer cable)
  SCPH-1092  mouse (european?)
  SCPH-1110  analog joystick
  SCPH-1150  analog joypad (with one vibration motor, with red/green led)
  SCPH-1180  analog joypad (without vibration motors, with red/green led)
  SCPH-1200  analog joypad (with two vibration motors) (dualshock)
  SCPH-110   analog joypad (with two vibration motors) (dualshock for psone)
  SCPH-10010 dualshock2 (analog buttons, except L3/R3/Start/Select) (for ps2)
  SCPH-1070  multitap

Special Controllers
  SCPH-4010 VPick (guitar-pick controller) (for Quest for Fame, Stolen Song)
SLPH-0001 (nejicon)
BANDAI "BANC-0002" - 4 Buttons (Triangle, Circle, Cross, Square) (nothing more)

Joystick
     __________                     __________
    |          |                   |    ^     |     ^
    | L1    R1 |                   | X <+> O  |    <+> = Digital Stick
     \      ___| <--- L2   [] ---> |___ v    /      v
      |    |     <--- R2   /\ --->     |    |
   ___|    |___________________________|    |___   Not sure if all buttons
  |   |    | SEL STA              =?=  |    |   |  are shown at their
  |   |    |                           |    |   |  correct locations?
  |   |    |_         []   /\         _|    |   |    (drawing is based on
  |  _|     /    L1             R1    \     |_  |    below riddle/lyrics)
  |  \_____/          X     O          \_____/  |
  |   /___\      L2             R2      /___\   |
  |                                             |
  |                                             |
   \___________________________________________/


 The thumb buttons on the left act as L1 and R1,
    the trigger is L2, the pinky button is R2
 The thumb buttons on the right act as X and O,
    the trigger is Square and the pinky button is Triangle.
 I find this odd as the triggers should've been L1 and R1,
    the pinkies L2 and R2.
 The buttons are redundantly placed on the base as large buttons like what
    you'd see on a fight/arcade stick. Also with Start and Select.
 There is also a physical analog mode switch,
    not a button like on dual shock.


Memory Card Read/Write Commands

Reading Data from Memory Card
  Send Reply Comment
  81h  N/A   Memory Card Access (unlike 01h=Controller access), dummy response
  52h  FLAG  Send Read Command (ASCII "R"), Receive FLAG Byte
  00h  5Ah   Receive Memory Card ID1
  00h  5Dh   Receive Memory Card ID2
  MSB  (00h) Send Address MSB  ;\sector number (0..3FFh)
  LSB  (pre) Send Address LSB  ;/
  00h  5Ch   Receive Command Acknowledge 1  ;<-- late /ACK after this byte-pair
  00h  5Dh   Receive Command Acknowledge 2
  00h  MSB   Receive Confirmed Address MSB
  00h  LSB   Receive Confirmed Address LSB
  00h  ...   Receive Data Sector (128 bytes)
  00h  CHK   Receive Checksum (MSB xor LSB xor Data bytes)
  00h  47h   Receive Memory End Byte (should be always 47h="G"=Good for Read)
Non-sony cards additionally send eight 5Ch bytes after the end flag.
When sending an invalid sector number, original Sony memory cards respond with FFFFh as Confirmed Address (and do then abort the transfer without sending any data, checksum, or end flag), third-party memory cards typically respond with the sector number ANDed with 3FFh (and transfer the data for that adjusted sector number).

Writing Data to Memory Card
  Send Reply Comment
  81h  N/A   Memory Card Access (unlike 01h=Controller access), dummy response
  57h  FLAG  Send Write Command (ASCII "W"), Receive FLAG Byte
  00h  5Ah   Receive Memory Card ID1
  00h  5Dh   Receive Memory Card ID2
  MSB  (00h) Send Address MSB  ;\sector number (0..3FFh)
  LSB  (pre) Send Address LSB  ;/
  ...  (pre) Send Data Sector (128 bytes)
  CHK  (pre) Send Checksum (MSB xor LSB xor Data bytes)
  00h  5Ch   Receive Command Acknowledge 1
  00h  5Dh   Receive Command Acknowledge 2
  00h  4xh   Receive Memory End Byte (47h=Good, 4Eh=BadChecksum, FFh=BadSector)

Get Memory Card ID Command
  Send Reply Comment
  81h  N/A   Memory Card Access (unlike 01h=Controller access), dummy response
  53h  FLAG  Send Get ID Command (ASCII "S"), Receive FLAG Byte
  00h  5Ah   Receive Memory Card ID1
  00h  5Dh   Receive Memory Card ID2
  00h  5Ch   Receive Command Acknowledge 1
  00h  5Dh   Receive Command Acknowledge 2
  00h  04h   Receive 04h
  00h  00h   Receive 00h
  00h  00h   Receive 00h
  00h  80h   Receive 80h
This command is supported only by original Sony memory cards. Not sure if all sony cards are responding with the same values, and what meaning they have, might be number of sectors (0400h) and sector size (0080h) or whatever.

Invalid Commands
  Send Reply Comment
  81h  N/A   Memory Card Access (unlike 01h=Controller access), dummy response
  xxh  FLAG  Send Invalid Command (anything else than "R", "W", or "S")
Transfer aborts immediately after the faulty command byte, or, occasionally after one more byte (with response FFh to that extra byte).

FLAG Byte
The initial value of the FLAG byte on power-up (and when re-inserting the memory card) is 08h.
Bit3=1 is indicating that the directory wasn't read yet (allowing to sense memory card changes). For some strange reason, bit3 is NOT reset when reading from the card, but rather when writing to it. To reset the flag, games are usually issuing a dummy write to sector number 003Fh, more or less unneccessarily stressing the lifetime of that sector.
Bit2=1 seems to be intended to indicate write errors, however, the write command seems to be always finishing without setting that bit, instead, the error flag may get set on the NEXT command.
Note: Some (not all) non-sony cards also have Bit5 of the FLAG byte set.

Timings
IRQ7 is usually triggered circa 1500 cycles after sending a byte (counted from the begin of the first bit), except, the last byte doesn't trigger IRQ7, and, after the 7th byte of the Read command, an additional delay of circa 31000 cycles occurs before IRQ7 gets triggered (that strange extra delay occurs only on original Sony cards, not on cards from other manufacturers).
There seems to be no extra delays in the Write command, as it seems, the data is written on the fly, and one doesn't need to do any write-busy handling... although, theoretically, the write shouldn't start until verifying the checksum... so it can't be done on the fly at all...?

Notes
Responses in brackets are don't care, (00h) means usually zero, (pre) means usually equal to the previous command byte (eg. the response to LSB is MSB).

Memory cards are reportedly "Flash RAM" which sounds like bullshit, might be battery backed SRAM, or FRAM, or slower EEPROM or FLASH ROM, or vary from card to card...?


Memory Card Data Format

Data Size
  Total Memory 128KB = 131072 bytes = 20000h bytes
  1 Block 8KB = 8192 bytes = 2000h bytes
  1 Frame 128 bytes = 80h bytes
The memory is split into 16 blocks (of 8 Kbytes each), and each block is split into 64 sectors (of 128 bytes each). The first block is used as Directory, the remaining 15 blocks are containing Files, each file can occupy one or more blocks.

Header Frame (Block 0, Frame 0)
  00h-01h Memory Card ID (ASCII "MC")
  02h-7Eh Unused (zero)
  7Fh     Checksum (all above bytes XORed with each other) (usually 0Eh)

Directory Frames (Block 0, Frame 1..15)
  00h-03h Block Allocation State
            00000051h - In use ;first-or-only block of a file
            00000052h - In use ;middle block of a file (if 3 or more blocks)
            00000053h - In use ;last block of a file   (if 2 or more blocks)
            000000A0h - Free   ;freshly formatted
            000000A1h - Free   ;deleted (first-or-only block of file)
            000000A2h - Free   ;deleted (middle block of file)
            000000A3h - Free   ;deleted (last block of file)
  04h-07h Filesize in bytes (2000h..1E000h; in multiples of 8Kbytes)
  08h-09h Pointer to the NEXT block number (minus 1) used by the file
            (ie. 0..14 for Block Number 1..15) (or FFFFh if last-or-only block)
  0Ah-1Eh Filename in ASCII, terminated by 00h (max 20 chars, plus ending 00h)
  1Fh     Zero (unused)
  20h-7Eh Garbage (usually 00h-filled)
  7Fh     Checksum (all above bytes XORed with each other)
Filesize [04h..07h] and Filename [0Ah..1Eh] are stored only in the first directory entry of a file (ie. with State=51h or A1h), other directory entries have that bytes zero-filled.

Filename Notes
The first some letters of the filename should indicate the game to which the file belongs, in case of commercial games this is conventionally done like so: Two character region code:
  "BI"=Japan, "BE"=Europe, "BA"=America
followed by 10 character game code,
  in "AAAA-NNNNN" form     ;for Pocketstation executables replace "-" by "P"
where the "AAAA" part does imply the region too; (SLPS/SCPS=Japan, SLUS/SCUS=America, SLES/SCES=Europe) (SCxS=Made by Sony, SLxS=Licensed by Sony), followed by up to 8 characters,
  "abcdefgh"
(which may identify the file if the game uses multiple files; this part often contains a random string which seems to be allowed to contain any chars in range of 20h..7Fh, of course it shouldn't contain "?" and "*" wildcards).

Broken Sector List (Block 0, Frame 16..35)
  00h-03h Broken Sector Number (Block*64+Frame) (FFFFFFFFh=None)
  04h-7Eh Garbage (usually 00h-filled) (some cards have [08h..09h]=FFFFh)
  7Fh     Checksum (all above bytes XORed with each other)
If Block0/Frame(16+N) indicates that a given sector is broken, then the data for that sector is stored in Block0/Frame(36+N).

Broken Sector Replacement Data (Block 0, Frame 36..55)
  00h-7Fh Data (usually FFh-filled, if there's no broken sector)

Unused Frames (Block 0, Frame 56..62)
  00h-7Fh Unused (usually FFh-filled)

Write Test Frame (Block 0, Frame 63)
Reportedly "write test". Usually same as Block 0 ("MC", 253 zero-bytes, plus checksum 0Eh).

Title Frame (Block 1..15, Frame 0) (in first block of file only)
  00h-01h  ID (ASCII "SC")
  02h      Icon Display Flag
             11h...Icon has 1 frame  (static) (same image shown forever)
             12h...Icon has 2 frames (animated) (changes every 16 PAL frames)
             13h...Icon has 3 frames (animated) (changes every 11 PAL frames)
            Values other than 11h..13h seem to be treated as corrupted file
            (causing the file not to be listed in the bootmenu)
  03h      Block Number (1-15)  "icon block count"  Uh?
                   (usually 01h or 02h... might be block number within
                   files that occupy 2 or more blocks)
                   (actually, that kind of files seem to HAVE title frames
                   in ALL of their blocks; not only in their FIRST block)
                   (at least SOME seem to have such duplicated title frame,
                   but not all?)
  04h-43h  Title in Shift-JIS format (64 bytes = max 32 characters)
  44h-4Fh  Reserved (00h)
  50h-5Fh  Reserved (00h)  ;<-- this region is used for the Pocketstation
  60h-7Fh  Icon 16 Color Palette Data (each entry is 16bit CLUT)
For more info on entries [50h..5Fh], see
Pocketstation File Header/Icons

Icon Frame(s) (Block 1..15, Frame 1..3) (in first block of file only)
  00h-7Fh  Icon Bitmap (16x16 pixels, 4bit color depth)
Note: The icons are shown in the BIOS bootmenu (which appears when starting the PlayStation without a CDROM inserted). The icons are drawn via GP0(2Ch) command, ie. as Textured four-point polygon, opaque, with texture-blending, whereas the 24bit blending color is 808080h (so it's quite the same as raw texture without blending). As semi-transparency is disabled, Palette/CLUT values can be 0000h=FullyTransparent, or 8000h=SolidBlack (the icons are usually shown on a black background, so it doesn't make much of a difference).

Data Frame(s) (Block 1..15, Frame N..63; N=excluding any Title/Icon Frames)
  00h-7Fh  Data
Note: Files that occupy more than one block are having only ONE Title area, and only one Icon area (in the first sector(s) of their first block), the additional blocks are using sectors 0..63 for plain data.

Shift-JIS Character Set (16bit) (used in Title Frames)
Can contain japanese or english text, english characters are encoded like so:
  81h,40h      --> SPC
  81h,43h..97h --> punctuation marks
  82h,4Fh..58h --> "0..9"
  82h,60h..79h --> "A..Z"
  82h,81h..9Ah --> "a..z"
Titles shorter than 32 characters are padded with 00h-bytes.
Note: The titles are <usually> in 16bit format (even if they consist of raw english text), however, the BIOS memory card manager does also accept 8bit characters 20h..7Fh (so, in the 8bit form, the title could be theoretically up to 64 characters long, but, nethertheless, the BIOS displays only max 32 chars).
For displaying Titles, the BIOS includes a complete Shift-JIS character set,
BIOS Character Sets
Shift-JIS is focused on asian languages, and does NOT include european letters (eg. such with accent marks). Although the non-japanese PSX BIOSes DO include a european character set, the BIOS memory card manager DOESN'T seem to translate any title character codes to that character set region.


Memory Card Images

There are a lot of different ways to get a save from a memory card onto your PC's hard disk, and these ways sometimes involve sticking some additional information into a header at the beginning of the file.

Raw Memory Card Images (without header) (ie. usually 128K in size)
  SmartLink .PSM,
  WinPSM .PS,
  DataDeck .DDF,
  FPSX .MCR,
  ePSXe .MCD...
don't stick any header on the data at all, so you can just read it in and treat it like a raw memory card.

All of these (following?) headers contain a signature at the top of the file. The three(?) most common formats and their signatures are:
     Connectix Virtual Game Station format (.MEM): "VgsM", 64 bytes
     PlayStation Magazine format (.PSX): "PSV", 256 bytes

some programs will OMIT any blank or unallocated blocks from the end of the memory card -- if only three save blocks on the card are in use, for example, saving the other twelve is pointless.

Xploder and Action Replay Files (54 byte header)
  00h..14h Filename in ASCII, terminated by 00h (max 20 chars, plus ending 00h)
  15h..35h Title in ASCII, terminated by 00h (max 32 chars, plus ending 00h)
  36h..    File Block(s) (starting with the Title sector)
This format contains only a single file (not a whole memory card). The filename should be the same as used in the Memory Card Directory. The title is more or less don't care; it may be the SHIFT-JIS title from the Title Sector converted to ASCII.

Other
"There exists another single-save format with a 128 byte header containing a raw index frame for the initial block, which must be updated to match the destination card, and the raw save data. I have seen this format once, but I don't remember what it was called or where it came from. You may want to account for this possibility in your format detection logic."

.GME Files (usually 20F40h bytes)
InterAct GME format, produced by the DexDrive.
  000h 12   ASCII String "123-456-STD",00h
  00Ch 4    Usually zerofilled (or meaningless garbage in some files)
  010h 5    Always 00h,00h,01h,00h,01h
  015h 16   Copy of Sector 0..15 byte[00h] ;"M", followed by allocation states
  025h 16   Copy of Sector 0..15 byte[08h] ;00h, followed by next block values
  035h 11   Usually zerofilled (or meaningless garbage in some files)
  040h F00h Fifteen Description Strings (each one 100h bytes, padded with 00h)
  F40h 128K Memory Card Image (128K) (unused sectors 00h or FFh filled)
This is a very strange file format, no idea where it comes from. It contains a F40h bytes header (mainly zerofilled), followed by the whole 128K of FLASH memory (mainly zerofilled, too, since it usually contains only a small single executable file).


Memory Card Notes

Sony PSX Memory Cards
Sony has manufactured only 128KByte memory cards for PSX, no bigger/smaller ones.

Sony PS2 Memory Cards
A special case would be PS2 cards, these are bigger, but PS2 cards won't fit into PSX cards slots (unless when cutting an extra notch in the card edge connector), a PSX game played on a PS2 console could theoretically access PS2 cards (if it supports the different directory structure on that cards).

Third Party Cards with bigger capacity
Some third party cards contain larger memory chips, however, the PSX games/kernel are supporting only regular 128Kbyte cards, so the extra memory can be used only by dividing it into several 128Kbyte memory card images.
Selecting a different memory card image can be done by a switch or button on the card, or via joypad key combinations (joypad/card are sharing the same signals, so the card could watch the traffic on joypad bus, provided that the MIPS CPU is actually reading the joypad).

Third Party Cards with bigger capacity and Data Compression
Some cards are additionally using data compression to increase the card capacity, but that techinque is having rather bad reputation and could result in data loss. For example, if a game has allocated four blocks on the memory card, then it'll expect to be able to overwrite that four blocks at any time (without needing to handle "memory card full" errors), however, if the card is full, and if the newly written data has worse compression ratio, then the card will be unable to store the new game position (and may have already overwritten parts of the old game position). As a workaround, such cards may use a LED to warn users when running low on memory (ideally, there should be always at least 128Kbytes of free memory).

Joytech Smart Card Adaptor
The smart card adaptor plugs into memory card slot, and allows to use special credit card-shaped memory cards. There don't seem to be any special features, ie. the hardware setup does just behave like normal PSX memory cards.

Datel VMEM (virtual memory card storage on expansion port)
The Datel/Interact VMEM exists as standalone VMEM cartridge, and some Datel Cheat Devices do also include the VMEM feature. Either way, the VMEM connects to expansion port, and contain some large FLASH memory, for storing multiple memory cards on it. Unknown, how that memory is accessed (maybe it must be copied to a regular memory card, or maybe they've somehow hooked the Kernel (or even the hardware signals?) so that games could directly access the VMEM?

Passwords (instead of Memory Cards)
Some older games are using passwords instead of memory cards to allow the user to continue at certain game positions. That's nice for people without memory card, but unfortunately many of that games are restricted to it - it'd be more user friendly to support both passwords, and, optionally, memory cards.

Yaroze Access Cards (DTL-H3020)
The Yaroze Access Card connects to memory card slot, the card resembles regular memory cards, but it doesn't contain any storage memory. Instead, it does merely support a very basic Access Card detection command:
  Send Reply Comment
  21h  N/A?  Probably replies HighZ (ie. probably reads FFh)?
  53h  0xh?  Replies unknown 8bit value (upper 4bit are known to be zero)?
Ie. when receiving 21h as first byte, it replies by an ACK, and does then output 0xh as response to the next byte.
Without the Access Card, the Yaroze Bootdisc will refuse to work (the disc contains software for transferring data to/from PC, for developing homebrew games).

Pocketstation (Memory Card with built-in LCD screen and buttons)
Pocketstation


Pocketstation

Pocketstation
Pocketstation Overview
Pocketstation I/O Map
Pocketstation Memory Map
Pocketstation IO Video and Audio
Pocketstation IO Interrupts and Buttons
Pocketstation IO Timers and Real-Time Clock
Pocketstation IO Infrared
Pocketstation IO Memory-Control
Pocketstation IO Communication Ports
Pocketstation IO Power Control
Pocketstation SWI Function Summary
Pocketstation SWI Misc Functions
Pocketstation SWI Communication Functions
Pocketstation SWI Execute Functions
Pocketstation SWI Date/Time/Alarm Functions
Pocketstation SWI Flash Functions
Pocketstation SWI Useless Functions
Pocketstation BU Command Summary
Pocketstation BU Standard Memory Card Commands
Pocketstation BU Basic Pocketstation Commands
Pocketstation BU Custom Pocketstation Commands
Pocketstation File Header/Icons
Pocketstation File Images
Pocketstation XBOO Cable


Pocketstation Overview

Sony's Pocketstation (SCPH-4000) (1998)
The Pocketstation is a memory card with built-in LCD screen and buttons; aside from using it as memory storage device, it can be also used as miniature handheld console.

  CPU        ARM7TDMI (32bit RISC Processor) (variable clock, max 7.995MHz)
  Memory     2Kbytes SRAM (battery backed), 16Kbytes BIOS ROM, 128Kbytes FLASH
  Display    32x32 pixel LCD (black and white) (without any grayscales)
  Sound      Mini Speaker "(12bit PCM) x 1 unit" / "8bit PCM with 12bit range"
  Controls   5 input buttons, plus 1 reset button
  Infrared   Bi-directional (IrDA based)
  Connector  Playstation memory card interface
  RTC        Battery backed Real-Time Clock with time/date function
  Supply     CR2032 Battery (3VDC) (used in handheld mode, and for SRAM/RTC)
    _________
   / _______ \
  | |       | |
  | |  LCD  | |                                __
  | |_______| |                Side Views     | _|
  |\_________/|                               || <-------- Button Cover
  |   O       |          (Closed)      (Open) ||
  | O   O   O |    ____________          _____||  .------- Reset Button
  |   O       |   | LCD  \____ |        | LCD \|__|_
  |___________|   |___________||        |___________| <--- Memory card plug

The RTC Problem
The main problem of the Pocketstation seems to be that it tends to reset the RTC to 1st January 1999 with time 00:00:00 whenever possible.
The BIOS contains so many RTC-reset functions, RTC-reset buttons, RTC-reset flags, RTC-reset communication commands, RTC-reset parameters, RTC-reset exceptions, RTC-reset sounds, and RTC-reset animations that it seems as if Sony actually WANTED the Time/Date to be destroyed as often as possible.
The only possible reason for doing this is that the clock hardware is so inaccurate that Sony must have decided to "solve" the problem at software engineering side, by erasing the RTC values before the user could even notice time inaccuracies.

CPU Specs
For details on the ARM7TDMI CPUs opcodes and exceptions, check GBATEK at,
http://problemkaputt.de/gbatek.htm (or .txt)
The GBA uses an ARM7TDMI CPU, too.

Thanks to Exophase, Orion, Fezzik, Dr.Hell for Pocketstation info.


Pocketstation I/O Map

Memory and Memory-Control Registers
  00000000h RAM        (2KB RAM) (first 512 bytes bytes reserved for kernel)
  02000000h FLASH1     Flash ROM (virtual file-mapped addresses in this region)
  04000000h BIOS_ROM      Kernel and GUI (16KB)
  06000000h F_CTRL        Control of Flash ROM
  06000004h F_STAT        Unknown?
  06000008h F_BANK_FLG    FLASH virtual bank mapping enable flags(16 bits)(R/W)
  0600000Ch F_WAIT1       waitstates...?
  06000010h F_WAIT2       waitstates, and FLASH-Write-Control-and-Status...?
  06000100h F_BANK_VAL    FLASH virtual bank mapping addresses (16 words) (R/W)
  06000300h F_EXTRA       Extra FLASH (256 bytes, including below F_SN, F_CAL)
  06000300h F_SN_LO       Extra FLASH Serial Number LSBs (nocash: 6BE7h)
  06000302h F_SN_HI       Extra FLASH Serial Number MSBs (nocash: 426Ch)
  06000304h F_?           Extra FLASH Unknown ?          (nocash: 05CAh)
  06000306h F_UNUSED1     Extra FLASH Unused halfword    (nocash: FFFFh)
  06000308h F_CAL         Extra FLASH LCD Calibration    (nocash: 001Ah)
  0600030Ah F_UNUSED2     Extra FLASH Unused halfword    (nocash: FFFFh)
  0600030Ch F_?           Extra FLASH Unknown ?          (nocash: 0010h)
  0600030Eh F_UNUSED3     Extra FLASH Unused halfword    (nocash: FFFFh)
  06000310h F_UNUSED4     Extra FLASH Unused (310..3FFh) (nocash: FFFFh-filled)
  08000000h FLASH2        Flash ROM (128KB) (physical addresses in this region)
  08002A54h F_KEY1        Flash Unlock Address 1 (W)
  080055AAh F_KEY2        Flash Unlock Address 2 (W)
Interrupts and Timers
  0A000000h INT_LATCH     Interrupt hold (R)
  0A000004h INT_INPUT     Interrupt Status (R)
  0A000008h INT_MASK_READ Read Interrupt Mask (R)
  0A000008h INT_MASK_SET  Set Interrupt Mask (W)
  0A00000Ch INT_MASK_CLR  Clear Interrupt Mask (W)
  0A000010h INT_ACK       Clear Interrupt hold (W)
  0A800000h T0_RELOAD     Timer 0 Maximum value
  0A800004h T0_COUNT      Timer 0 Current value
  0A800008h T0_MODE       Timer 0 Mode
  0A800010h T1_RELOAD     Timer 1 Maximum value
  0A800014h T1_COUNT      Timer 1 Current value
  0A800018h T1_MODE       Timer 1 Mode
  0A800020h T2_RELOAD     Timer 2 Maximum value
  0A800024h T2_COUNT      Timer 2 Current value
  0A800028h T2_MODE       Timer 2 Mode
  0B000000h CLK_MODE      Clock control (CPU and Timer Speed) (R/W)
  0B000004h CLK_STOP      Clock stop (Sleep Mode)
  0B800000h RTC_MODE      RTC Mode
  0B800004h RTC_ADJUST    RTC Adjust
  0B800008h RTC_TIME      RTC Time (R)
  0B80000Ch RTC_DATE      RTC Date (R)
Communication Ports, Audio/Video
  0C000000h COM_MODE      Com Mode
  0C000004h COM_STAT1     Com Status Register 1 (Bit1=Error)
  0C000008h COM_DATA      Com RX Data (R) and TX Data (W)
  0C000010h COM_CTRL1     Com Control Register 1
  0C000014h COM_STAT2     Com Status Register 2 (Bit0=Ready)
  0C000018h COM_CTRL2     Com Control Register 2
  0C800000h IRDA_MODE     Infrared Control (R/W)
  0C800004h IRDA_DATA     Infrared TX Data
  0C80000Ch IRDA_MISC     Infrared Unknown/Reserved
  0D000000h LCD_MODE      Video Control (R/W)
  0D000004h LCD_CAL       Video Calibration (?)
  0D000100h LCD_VRAM      Video RAM (80h bytes; 32x32bit) (R/W)
  0D800000h IOP_CTRL      IOP control
  0D800004h IOP_STAT      Read Current Start/Stop bits? (R)
  0D800004h IOP_STOP      Stop bits? (W)
  0D800008h IOP_START     Start bits? (W)
  0D80000Ch IOP_DATA      IOP data?   (not used by bios)
  0D800010h DAC_CTRL      DAC Control (R/W)
  0D800014h DAC_DATA      DAC data
  0D800020h BATT_CTRL     Battery Monitor Control
BIOS and FLASH can be read only in 16bit and 32bit units (not 8bit).
Upon reset, BIOS ROM is mirrored to address 00000000h (instead of RAM).
For most I/O ports, it is unknown if they are (R), (W), or (R/W)...?
I/O ports are usually accessed at 32bit width, occassionally some ports are (alternately) accessed at 16bit width. A special case are the F_SN registers which seem to be required to be accessed at 16bit (not 32bit).

Memory Access Time
Memory Access Time for Opcode Fetch:
  WRAM        1 cycle (for ARM and THUMB)
  FLASH       2 cycles (for ARM), or 1 cycle (for THUMB)
  BIOS        ?
Memory Access Time for Data Read/Write:
  WRAM (and some F_xxx ports)                    1 cycle
  VIRT/PHYS/XTRA_FLASH, BIOS, VRAM, I/O          2 cycles
For data access, it doesn't matter if the access is 8bit/16bit/32bit (unlike as for opcode fetch, where 16bit/thumb can be faster than 32bit/arm). There seems to be no timing differences for sequential/non-sequential access.
Additional memory waitstates can be added via F_WAIT2 (and F_WAIT1 maybe).

Invalid/Unused Memory Locations
  00000800h-00FFFFFFh  Mirrors of 00000000h-000007FFh (2K RAM)
  01000000h-01FFFFFFh  Invalid (read causes data abort) (unused 16MB area)
  020xxxxxh-0201FFFFh  Invalid (read causes data abort) (disabled FLASH banks)
  02020000h-02FFFFFFh  Invalid (read causes data abort) (no Virt FLASH mirrors)
  03000000h-03FFFFFFh  Invalid (read causes data abort) (unused 16MB area)
  04004000h-04FFFFFFh  Mirrors of 04000000h-04003FFFh (16K BIOS)
  05000000h-05FFFFFFh  Invalid (read causes data abort)
  06000014h-060000FFh   Zerofilled (or maybe mirror of a ZERO port?) (F_xxx)
  06000140h-060002FFh   Zerofilled (or maybe mirror of a ZERO port?) (F_xxx)
  06000400h-06FFFFFFh   Zerofilled (or maybe mirror of a ZERO port?) (F_xxx)
  07000000h-07FFFFFFh  Invalid (read causes data abort) (unused 16MB area)
  08020000h-08FFFFFFh  Mirrors of 08000000h-0801FFFFh (128K Physical FLASH)
  09000000h-09FFFFFFh  Invalid (read causes data abort) (unused 16MB area)
  0A000014h-0A7FFFFFh  Mirrors of 0A000008h-0A00000Bh (INT_MASK_READ) (I_xxx)
  0A80000Ch            Mirror of 0A800000h-0A800003h (T0_RELOAD) (T0_xxx)
  0A80001Ch            Mirror of 0A800000h-0A800003h (T0_RELOAD) (T1_xxx)
  0A80002Ch            Mirror of 0A800000h-0A800003h (T0_RELOAD) (T2_xxx)
  0A800030h-0AFFFFFFh  Mirrors of 0A800000h-0A800003h (T0_RELOAD) (T_xxx)
  0B000008h-0B7FFFFFh  Mirrors of .... ? (CLK_xxx)
  0B800010h-0BFFFFFFh  Mirrors of 0B800008h-0B80000Bh (RTC_TIME)
  0C00000Ch-0C00000Fh  Zero (COM_xxx)
  0C00001Ch-0C7FFFFFh   Zerofilled (or maybe mirror of a ZERO port?) (COM_xxx)
  0C800008h-0CFFFFFFh   ? (IRDA_xxx)
  0D000008h-0D0000FFh   Zerofilled (or maybe mirror of a ZERO port?) (LCD_xxx)
  0D000180h-0D7FFFFFh   Zerofilled (or maybe mirror of a ZERO port?) (LCD_xxx)
  0D800018h             ? (DAC_xxx)
  0D80001Ch             ? (DAC_xxx)
  0D800024h-0DFFFFFFh   Zerofilled (or maybe mirror of a ZERO port?) (BATT_xxx)
  0E000000h-FFFFFFFFh  Invalid (read causes data abort) (unused 3872MB area)

Unsupported 8bit Reads
  02000000h-0201FFFFh VIRT_FLASH   ;\
  04000000h-04FFFFFFh BIOS_ROM     ; "garbage_byte" (see below)
  06000300h-060003FFh EXTRA_FLASH  ;
  08000000h-08FFFFFFh PHYS_FLASH   ;/
  0A800001h-0AFFFFFFh Timer area, odd addresses (with A0=1) mirror to 0A800001h
  0B800001h-0BFFFFFFh RTC area, odd addresses (with A0=1) mirror to ...?

Unsupported 16bit Reads
  0B800002h-0BFFFFFEh RTC area, odd addresses (with A1=1) mirror to 0B80000Ah

garbage_byte (for unsupported 8bit reads)
The "garbage_byte" depends on the LSBs of the read address, prefetched opcodes, and recent data fetches:
  garbage_word = (prefetch OR (ramdata AND FFFFFFD0h))
  garbage_byte = (garbage_word shr (8*(addr and 3))) AND FFh
For ARM code, the "prefetch" is the 2nd next opcode after the LDRB:
  prefetch.bit0-31  = [curr_arm_opcode_addr+8]    ;-eg. from arm LDRB
For THUMB code, the "prefetch" is the 2nd next opcode after the LDRB (no matter if that opcode is word-aligned or not), combined with the most recent ARM opcode prefetch (eg. from the BX opcode switched from ARM to THUMB mode; that value may get changed on interrupts):
  prefetch.bit0-15  = [recent_arm_opcode_addr+8]  ;-eg. from arm BX to thumb
  prefetch.bit16-31 = [curr_thumb_opcode_addr+4]  ;-eg. from thumb LDRB
The "ramdata" is related to most recent RAM read (eg. from POP or LDR opcodes that have read data from RAM; however, writes to RAM, or literal pool reads from FLASH don't affect it):
  ramdata.bit0-31   = [recent_ram_read_addr]      ;-eg. from LDR/POP from RAM
There might be some more/unknown things that affect the garbage (eg. opcode fetches from RAM instead of FLASH, partial 8bit/16bit data reads from RAM, or reads from I/O areas, current CPU clock speed, or unpredictable things like temperature).
Note: The garbage_byte is "used" by the pocketstation "Rockman" series games.


Pocketstation Memory Map

Overall Memory Map
  00000000h RAM      RAM (2K)   (or mirror of BIOS ROM upon reset)
  02000000h FLASH1   Flash ROM  (virtual file-mapped addresses in this region)
  04000000h BIOS_ROM BIOS (16K) (Kernel and GUI)
  06000300h F_SN...  Seems to contain a bunch of additional FLASH bytes?
  08000000h FLASH2   Flash ROM  (128K) (physical addresses in this region)
  0D000100h LCD_VRAM Video RAM  (128 bytes) (32x32 pixels, 1bit per pixel)

00000000h..000001FFh - Kernel RAM
The first 200h bytes of RAM are reserved for the kernel.
  0000000h 20h  Exception handler opcodes (filled with LDR R15,[$+20h] opcodes)
  0000020h 20h  Exception handler addresses (in ARM state, no THUMB bit here)
  0000040h 80h  Sector buffer (and BU command parameter work space)
  00000C0h 8    ComFlags (see GetPtrToComFlags(), SWI 06h for details)
  00000C8h 2    BU Command FUNC3 Address (see GetPtrToFunc3addr() aka SWI 17h)
  00000CAh 1    Value from BU Command_50h, reset by SWI 05h (sense_auto_com)
  00000CBh 2    Not used
  00000CDh 1    Old Year (BCD, 00h..99h) (for sensing wrapping to new century)
  00000CEh 1    Alternate dir_index (when [0D0h]=0) (see SWI 15h and SWI 16h)
  00000CFh 1    Current Century (BCD, 00h..99h) (see GetBcdDate() aka SWI 0Dh)
  00000D0h 2    Current dir_index (for currently executed file, or 0=GUI)
  00000D2h 2    New dir_index (PrepareExecute(flag,dir_index,param), SWI 08h)
  00000D4h 4    New param     (PrepareExecute(flag,dir_index,param), SWI 08h)
  00000D8h 8    Alarm Setting        (see GetPtrToAlarmSetting() aka SWI 13h)
  00000E0h 4    Pointer to SWI table (see GetPtrToPtrToSwiTable() aka SWI 14h)
  00000E4h 3x4  Memory Card BU Command variables
  00000F0h 1    Memory Card FLAG byte (bit3=new_card, bit2=write_error)
  00000F1h 1    Memory Card Error offhold (0=none, 1=once)
  00000F2h 6    Not used
  00000F8h 4x4  Callback Addresses (set via SetCallbacks(index,proc), SWI 01h)
  0000108h 4    Snapshot ID (0xh,00h,"SE")
  000010Ch 74h  IRQ and SWI stack (stacktop at 180h)
  0000180h 80h  FIQ stack (stacktop at 200h)
Although one can modify that memory, one usually shouldn't do that, or at least one must backup and restore the old values before returning control to the GUI or to other executables. Otherwise, the only way to restore the original values would be to press the Reset button (which would erase the RTC time/date).

00000200h..000007FFh - User RAM and User stack (stacktop at 800h)
This region can be freely used by the game. The memory is zerofilled when the game starts.

02000000h - FLASH1 - Flash ROM (virtual file-mapped addresses in this region)
This region usually contains the currently selected file (including its title and icon sectors), used to execute the file in this region, mapped to continous addresses at 2000000h and up.

08000000h - FLASH2 - Flash ROM (128K) (physical addresses in this region)
This region is used by the BIOS when reading the memory card directory (and when writing data to the FLASH memory). The banking granularity is 2000h bytes (one memory card block), that means that the hardware cannot map Replacement Sectors which may be specified in the for Broken Sector List.

04000000h - BIOS ROM (16K) - Kernel and GUI
  4000000h 1E00h Begin of Kernel (usually 1E00h bytes)
  4000014h 4     BCD Date in YYYYMMDDh format (19981023h for ALL versions)
  4001DFCh 4     Core Kernel Version  (usually "C061" or "C110")
  4001E00h 2200h Begin of GUI (usually 2200h bytes)
  4003FFCh 4     Japanese GUI Version (usually "J061" or "J110")
The "110" version does contain some patches, but does preserve same function addresses as the "061" version, still it'd be no good to expect the BIOS to contain any code/data at fixed locations (except maybe the GUI version string). Kernel functions can be accessed via SWI Opcodes, and, from the PSX-side, via BU Commands.

Bus-Width Restrictions
FLASH and BIOS ROM seem to be allowed to be read only in 16bit and 32bit units, not in 8bit units? Similar restrictions might apply for some I/O ports...? RAM can be freely read/written in 8bit, 16bit, and 32bit units.

Waitstates
Unknown if and how many waitstates are applied to the different memory regions. The F_WAIT1 and F_WAIT2 registers seem to be somehow waitstate related. FLASH memory does probably have a 16bit bus, so 32bit data/opcode fetches might be slower then 16bit reads...? Similar delays might happen for other memory and I/O regions...?


Pocketstation IO Video and Audio

0D000000h - LCD_MODE - LCD control word (R/W)
  0-2  Draw mode; seems to turn off bits of the screen;
         0: All 32 rows on      ;\
         1: First 8 rows on     ;
         2: Second 8 rows on    ;
         3: Third 8 rows on     ; (these are not necessarily all correct?)
         4: Fourth 8 rows on    ;
         5: First 16 rows on    ;
         6: Middle 16 rows on   ;
         7: Bottom 16 rows on   ;/
  3    CPEN      (0=Does some weird fade out of the screen, 1=Normal)
  4-5  Refresh rate
         0: Makes a single blue (yes, blue, yes, on a black/white display)
            line appear at the top or middle of the screen - don't use!
         1: 64Hz? (might be 32Hz too, like 2)
         2: 32Hz
         3: 16Hz (results in less intensity on black pixels)
  6    Display active                (0=Off, 1=On)
  7    Rotate display by 180 degrees (0=For Handheld Mode, 1=For Docked Mode)
  8-31 Unknown (should be zero)
Software should usually set LCD_MODE.7 equal to INT_INPUT.Bit11 (docking flag). In handheld mode, the button-side is facing towards the player, whilst in Docked mode (when the Pocketstation is inserted into the PSX controller port), the button-side is facing towards the PSX, so the screen coordinates become vice-versa, which can be "undone" by the Rotation flag.

0D000004h - LCD_CAL - LCD Calibration (maybe contrast or so?)
Upon the reset, the kernel sets LCD_CAL = F_CAL AND 0000003Fh. Aside from that, it doesn't use LCD_CAL.

0D000100h..D00017Fh - LCD_VRAM - 32x32 pixels, 1bit color depth (R/W)
This region consists of 32 words (32bit values),
  [D000100h]=Top, through [D00017Ch]=Bottom-most scanline
The separate scanlines consist of 32bit each,
  Bit0=Left, through Bit31=Right-most Pixel (0=White, 1=Black)
That [D000100h].Bit0=Upper-left arrangement applies if the Rotate bit in LCD_MODE.7 is set up in the conventional way, if it is set the opposite way, then it becomes [D00017Ch].Bit31=Upper-left.
The LCD_VRAM area is reportedly mirrored to whatever locations?

The LCD consists of a transparent glass plate with black pixels, and a piece of white cardboard with watermarked PS logo underneath of the glass plate.
Depending on light source, the pixels can cast shadows 1-2 pixels apart (for example, black text on white background can appear bolder, and white text on black background may appear invisible if they are obscured by shadows).


0D800010h - DAC_CTRL - Audio Control (R/W)
  0     Audio Enable enable    (0=Off, 1=On)
  1-31  Unknown, usually zero
Note: Aside from the bit in DAC_CTRL, audio must be also enabled/disabled via IOP_STOP/IOP_START bit5. Unknown if/which different purposes that bits have.

0D800014h - DAC_DATA - Audio D/A Converter
Unknown how many bits are passed to the D/A converter, probably bit8-15, ie. 8 bits...?
  0-7   Probably unused, usually zero (or fractional part when lowered volume)
  8-15  Signed Audio Output Level (usually -7Fh..+7Fh)(probably -80h works too)
  16-31 Probably unused, usually sign-expanded from bit15
The Pocketstation doesn't have any square wave or noise generator (nor a sound DMA channel). So the output levels must be written to DAC_DATA by software, this is usually done via Timer1/IRQ-8 (to reduce CPU load caused by high audio frequencies, it may be much more recommended to use Timer2/FIQ-13, because the FIQ handler doesn't need to push r8-r12).
For example, to produce a 1kHz square wave, the register must be toggled high/low at 2kHz rate. If desired, multiple channels can be mixed by software. High frequencies and multiple voices may require high CPU speed settings, and thus increase battery consumption (aside from that, battery consumption is probably increased anyways when the speaker is enabled).


Pocketstation IO Interrupts and Buttons

0A000004h - INT_INPUT - Raw Interrupt Signal Levels (R)
  Bit   Type    Meaning
  0     IRQ     Button Fire     (0=Released, 1=Pressed)
  1     IRQ     Button Right    (0=Released, 1=Pressed)
  2     IRQ     Button Left     (0=Released, 1=Pressed)
  3     IRQ     Button Down     (0=Released, 1=Pressed)
  4     IRQ     Button Up       (0=Released, 1=Pressed)
  5     ?       Unknown?        (?)
  6     FIQ (!) COM              ;for the COM_registers?      (via /SEL Pin?)
  7     IRQ     Timer 0
  8     IRQ     Timer 1
  9     IRQ     RTC (square wave) (usually 1Hz) (when RTC paused: 4096Hz)
  10    IRQ     Battery Low     (0=Normal, 1=Battery Low)
  11    IRQ     Docked ("IOP")  (0=Undocked, 1=Docked to PSX) (via VCC Pin?)
  12    IRQ     Infrared Rx
  13    FIQ (!) Timer 2
  14-15 N/A     Not used
The buttons are usually read directly from this register (rather than being configured to trigger IRQs) (except in Sleep mode, where the Fire Button IRQ is usually used to wakeup). Also, bit9-11 are often read from this register.
The direction keys are separate buttons, ie. unlike as on a joystick or DPAD, Left+Right (or Up+Down) can be simultaneously pressed.

0A000008h - INT_MASK_SET - Set Interrupt Mask (W)
0A00000Ch - INT_MASK_CLR - Clear Interrupt Mask (W)
0A000008h - INT_MASK_READ - Read Interrupt Mask (R)
  INT_MASK_SET  Enable Interrupt Flags         (0=No change, 1=Enable)   (W)
  INT_MASK_CLR  Disable Interrupt Flags        (0=No change, 1=Disable)  (W)
  INT_MASK_READ Current Interrupt Enable Flags (0=Disabled, 1=Enabled)   (R)
The locations of the separate bits are same as in INT_INPUT (see there).

0A000000h - INT_LATCH - Interrupt Request Flags (R)
0A000010h - INT_ACK - Acknowledge Interrupts (W)
  INT_LATCH Latched Interrupt Requests   (0=None, 1=Interrupt Request)   (R)
  INT_ACK   Clear Interrupt Requests     (0=No change, 1=Acknowledge)    (W)
The locations of the separate bits are same as in INT_INPUT (see there).
The interrupts seem to be edge-triggered (?), ie. when the corresponding bits in INT_INPUT change from 0-to-1. Unknown if the request bits get set when the corresponding interrupt is disabled in INT_MASK...?

ATTENTION: The GUI doesn't acknowledge Fire Button interrupts on wakeup... so, it seems as if button interrupts are NOT latched... ie. the button "INT_LATCH" bits seem to be just an unlatched mirror of the "INT_INPUT" bits... that might also apply for some other interrupt...?
However, after wakeup, the gui does DISABLE the Fire Button interrupt, MAYBE that does automatically acknowledge it... in that case it might be latched...?

Reading outside the readable region (that is where exactly?) seems to mirror to 0A000008h. Enabling IRQs for the buttons seems to make it impossible to poll them... is that really true?


Pocketstation IO Timers and Real-Time Clock

Timer and RTC interrupts
  INT_INPUT.7     Timer 0 IRQ    ;used as 30Hz frame rate IRQ by GUI
  INT_INPUT.8     Timer 1 IRQ    ;used as Audio square wave IRQ by GUI
  INT_INPUT.13    Timer 2 FIQ (this one via FIQ vector, not IRQ vector)
  INT_INPUT.9     RTC IRQ (usually 1Hz) (or 4096Hz when RTC paused)

0A800000h - T0_RELOAD - Timer 0 Reload Value
0A800010h - T1_RELOAD - Timer 1 Reload Value
0A800020h - T2_RELOAD - Timer 2 Reload Value
  0-15  Reload Value (when timer becomes less than zero)
Writes to this register are ignored if the timer isn't stopped?

0A800004h - T0_COUNT - Timer 0 Current value
0A800014h - T1_COUNT - Timer 1 Current value
0A800024h - T2_COUNT - Timer 2 Current value
  0-15  Current value (decrementing)
Timer interrupts: The timers will automatically raise interrupts if they're enabled, there's no need to set a bit anywhere for IRQs (but you need to enable the respect interrupts in INT_MASK).

0A800008h - T0_MODE - Timer 0 Control
0A800018h - T1_MODE - Timer 1 Control
0A800028h - T2_MODE - Timer 2 Control
  0-1  Timer Divider (0=Div2, 1=Div32, 2=Div512, 3=Div2 too)
  2    Timer Enable  (0=Stop, 1=Decrement)
  3-15 Unknown (should be zero)
Timers are clocked by the System Clock (usually 4MHz, when CLK_MODE=7), divided by the above divider setting. Note that the System Clock changes when changing the CPU speed via CLK_MODE, so Timer Divider and/or Timer Reload must be adjusted accordingly.

0B800000h - RTC_MODE - RTC control word
  0    Pause RTC (0=Run/1Hz, 1=Pause/4096Hz)
  1-3  Select value to be modified via RTC_ADJUST
  4-31 Not used?
The selection bits can be:
  00h = Second        ;\
  01h = Minute        ;
  02h = Hour          ; used in combination with RTC_ADJUST
  03h = Day of Week   ; while RTC is paused
  04h = Day           ;
  05h = Month         ;
  06h = Year          ;/
  07h = Unknown       ;-usually used when RTC isn't paused
When paused, the RTC IRQ bit in INT_INPUT.9 runs at 4096Hz (instead 1Hz).

0B800004h - RTC_ADJUST - Modify value (write only)
Writing a value here seems to increment the current selected parameter (by the RTC control). What is perhaps (?) clear is that you have to wait for the RTC interrupt signal to go low before writing to this.

0B800008h - RTC_TIME - Real-Time Clock Time (read only) (R)
  0-7   Seconds     (00h..59h, BCD)
  8-15  Minutes     (00h..59h, BCD)
  16-23 Hours       (00h..23h, BCD)
  24-31 Day of week (1=Sunday, ..., 7=Saturday)
Reading RTC_TIME seems to be somewhat unstable: the BIOS uses a read/retry loop, until it has read twice the same value (although it does read the whole 32bit at once by a LDR opcode, the data is maybe passed through a 8bit or 16bit bus; so the LSBs might be a few clock cycles older than the MSBs...?).

0B80000Ch - RTC_DATE - Real-Time Clock Date (read only) (R)
  0-7   Day     (01h..31h, BCD)
  8-11  Month   (01h..12h, BCD)
  16-23 Year    (00h..99h, BCD)
  24-31 Unknown? (this is NOT used as century)
Reading RTC_DATE seems to require the same read/retry method as RTC_TIME (see there). Note: The century is stored in battery-backed RAM (in the reserved kernel RAM region) rather than in the RTC_DATE register. The whole date, including century, can be read via SWI 0Dh, GetBcdDate().


Pocketstation IO Infrared

The BIOS doesn't contain any IR functions (aside from doing some basic initialization and power-down stuff).
IR is used in Final Fantasy 8's Chocobo World (press Left/Right in the Map screen to go to the IR menu), and in Metal Gear Solid Integral (Press Up in the main screen), and in PDA Remote 1 & 2 (one-directional TV remote control).

0C800000h - IRDA_MODE - Controlling the protocol - send/recv, etc. (R/W)
  0    Transfer Direction  (0=Receive, 1=Transmit)
  1    Disable IRDA        (0=Enable, 1=Disable)
  2    Unknown (reportedly IR_SEND_READY, uh?)
  3    Unknown (reportedly IR_RECV_READY, uh?)
  4-31 Unknown (should be zero)

0C800004h - IRDA_DATA - Infrared TX Data
  0    Transmit Data in Send Direction (0=LED Off, 1=LED On)
  1-31 Unknown (should be zero)
Bits are usually encoded as long or short ON pulses, separated by short OFF pulses. Where long is usually twice as long as short.

0C80000Ch - IRDA_MISC
Unknown? Reportedly reserved.

INT_INPUT.12 - IRQ - Infrared RX Interrupt
Seems to get triggered on raising or falling (?) edges of incoming data. The interrupt handler seems to read the current counter value from one of the timers (usually Timer 2, with reload=FFFFh) to determine the length of the incoming IR pulse.

IR Notes
Mind that IR hardware usually adopts itself to the normal light conditions, so if it receives an IR signal for a longer period, then it may treat that as the normal light conditions (ie. as "OFF" state). To avoid that, one would usually send a group of ON-OFF-ON-OFF pulses, instead of sending a single long ON pulse:
   ___------------------___  One HIGH bit send as SINGLE-LONG-ON pulse   (BAD)
   ___-_-_-_-_-_-_-_-_-____  One HIGH bit send as MULTIPLE-ON-OFF pulses (OK)
that might be maybe done automatically by the hardware...?

Reportedly, Bit4 of Port 0D80000Ch (IOP_DATA) is also somewhat IR related...?


Pocketstation IO Memory-Control

06000000h - F_CTRL
  0-31  Unknown
Written values are:
  00000000h  Used when disabling all virtual flash banks
  00000001h  Used before setting new virtual bank values
  00000002h  Used after setting virtual bank enable bits
  03h        Replace ROM at 00000000h by RAM (used after reset)
The GUI does additionally read from this register (and gets itself trapped in a bizarre endless loop if bit0 was zero). Unknown if it's possible to re-enable ROM at location 00000000h by writing any other values to this register?

06000004h F_STAT
  0-31  Unknown
The kernel issues a dummy read from this address (before setting F_CTRL to 00000001h).

06000008h F_BANK_FLG ;FLASH virtual bank mapping enable flags (16 bits)(R/W)
  0-15   Enable physical banks 0..15 in virtual region (0=Disable, 1=Enable)
  16-31  Unknown (should be zero)

06000100h F_BANK_VAL ;FLASH virtual bank mapping addresses (16 words)(R/W)
This region contains 16 words, the first word at 06000100h for physical bank 0, the last word at 0600013Ch for physical bank 15. Each word is:
  0-3    Virtual bank number
  4-31   Should be 0
Unused physical banks are usually mapped to 0Fh (and are additionally disabled in the F_BANK_FLG register).

0600000Ch F_WAIT1 ;waitstates...?
  0..3   Unknown/not tested
  4      hangs hardware? but that bit is used in some cases!
  5..31  Unknown/not tested
Unknown, seems to control some kind of memory waitstates for FLASH (or maybe RAM or BIOS ROM). Normally it is set to the following values:
  F_WAIT1=00000000h when CPU Speed = 00h..07h
  F_WAIT1=00000010h when CPU Speed = 08h..0Fh
Note: The kernels Docking/Undocking IRQ-11 handler does additionally do this: "F_WAIT1=max(08h,(CLK_MODE AND 0Fh))" (that is a bug, what it actually wants to do is to READ the current F_WAIT.Bit4 setting).

06000010h F_WAIT2 ;waitstates, and FLASH-Write-Control-and-Status...?
  0      no effect? but that bit is used in some cases! maybe write-enable?
  1      hangs hardware?
  2      no effect?           READ: indicates 0=write-busy, 1=ready?  (R)
  3      hangs hardware?
  4      makes FLASH slower?
  5      makes WRAM and F_xxx as slow as other memory (0=1 cycle, 1=2 cycles)
  6      hangs hardware? but that bit is used in some cases!
  7      no effect?
  8..31  Unknown/not tested
Unknown, seems to control some kind of memory waitstates, maybe for another memory region than F_WAIT1, or maybe F_WAIT2 is for writing, and F_WAIT1 for reading or so. Normally it is set to the following values:
  F_WAIT2=00000000h when CPU Speed = 00h..07h  ;\same as F_WAIT1
  F_WAIT2=00000010h when CPU Speed = 08h..0Fh  ;/
In SWI 0Fh and SWI 10h it is also set to:
  F_WAIT2=00000021h  ;SWI 10h, FlashWritePhysical(sector,src)
  F_WAIT2=00000041h  ;SWI 0Fh, FlashWriteSerial(serial_number)
Before completion, those SWIs do additionally,
  wait until reading returns F_WAIT2.Bit2 = 1
  and then set F_WAIT2=00000000h

08002A54h - F_KEY1 - Flash Unlock Address 1 (W)
080055AAh - F_KEY2 - Flash Unlock Address 2 (W)
Unlocks FLASH memory for writing. The complete flowchart for writing sector data (or header values) is:
  if write_sector                               ;\
    F_WAIT2=00000021h                           ; write enable or so
  if write_header                               ;
    F_WAIT2=00000041h                           ;/
  [80055AAh]=FFAAh                              ;\
  [8002A54h]=FF55h                              ; unlock flash
  [80055AAh]=FFA0h                              ;/
  if write_sector                               ;\
    for i=0 to 3Fh                              ;
      [8000000h+sector*80h+i*2]=src[i*2]        ; write data
  if write_header                               ;
    [8000000h]=new F_SN_LO value                ;
    [8000002h]=new F_SN_HI value                ;
    [8000008h]=new F_CAL value                  ;/
  first, wait 4000 clock cycles                 ;\wait
  then, wait until F_WAIT2.Bit2=1               ;/
  F_WAIT2=00000000h                             ;-write disable or so
During the write operation one can (probably?) not read data (nor opcodes) from FLASH memory, so the above code must be executed either in RAM, or in BIOS ROM (see SWI 03h, SWI 0Fh, SWI 10h).

06000300h - F_SN_LO - Serial Number LSBs
06000302h - F_SN_HI - Serial Number MSBs
06000308h - F_CAL - Calibration value for LCD
  0-15  Data
This seems to be an additional "header" region of the FLASH memory (additionally to the 128K of data). The F_SN registers contain a serial number or so (purpose unknown, maybe intended as some kind of an "IP" address for more complex infrared network applications), the two LO/HI registers must be read by separate 16bit LDRH opcodes (not by a single 32bit LDR opcode). The F_CAL register contains a 6bit calibration value for LCD_CAL (contrast or so?).
Although only the above 3 halfwords are used by the BIOS, the "header" is unlike to be 6 bytes in size, probably there are whatever number of additional "header" locations at 06000300h and up...?
Note: Metal Gear Solid Integral uses F_SN as some kind of copy protection (the game refuses to run and displays "No copy" if F_SN is different as when the pocketstation file was initially created).

F_BANK_VAL and F_BANK_FLG Notes
Observe that the physical_bank number (p) is used as array index, and that the virtual bank number (v) is stored in that location, ie. table[p]=v, which is unlike as one may have expected it (eg. on a 80386 CPU it'd be vice-versa: table[v]=p).
Due to the table[p]=v assignment, a physical block cannot be mirrored to multiple virtual blocks, instead, multiple physical blocks can be mapped to the same virtual block (unknown what happens in that case, maybe the data becomes ANDed together).


Pocketstation IO Communication Ports

0C000000h - COM_MODE - Com Mode
  0     Data Output Enable  (0=None/HighZ, 1=Output Data Bits)
  1     /ACK Output Level   (0=None/HighZ, 1=Output LOW)
  2     Unknown (should be set when expecting a NEW command...?)
  3-31  Unknown (should be zero)

0C000008h - COM_DATA - Com RX/TX Data
  0-7   Data (Write: to be transmitted to PSX, Read: been received from PSX)
  8-31  Unknown

0C000004h - COM_STAT1 - Com Status Register 1 (Bit1=Error)
  0     Unknown
  1     Error flag or so (0=Okay, 1=Error)
  2-31  Unknown
Seems to indicate whatever error (maybe /SEL disabled during transfer, or timeout, or parity error or something else?) in bit1. Meaning of the other bits is unknown. Aside from checking the error flag, the kernel does issue a dummy read at the end of each transfer, maybe to acknowledge something, maybe the hardware simply resets the error bit after reading (although the kernel doesn't handle the bit like so when receiving the 1st command byte).
Aside from the above error flag, one should check if INT_INPUT.11 becomes zero during transfer (which indicates undocking).

0C000014h - COM_STAT2 - Com Status Register 2 (Bit0=Ready)
  0     Ready flag (0=Busy, 1=Ready) (when 8bits have been transferred)
  1-31  Unknown

0C000010h - COM_CTRL1 - Com Control Register 1
  0     Unknown (should be set AT BEGIN OF A NEW command...?)
  1     Unknown (0=Disable something, 1=Enable something)
  2-31  Unknown (should be zero)
Used values are:
  00000000h = unknown?  disable
  00000002h = unknown?  enable
  00000003h = unknown?  at BEGIN of a new command
When doing the enable thing, Bit1 should be set to 0-then-1...? Bit0 might enable the data shift register... and bit1 might be a master enable and master acknowledge for the COM interrupt... or something else?

0C000018h - COM_CTRL2 - Com Control Register 2
  0     Unknown (should be set, probably starts or acknowledges something)
  1     Unknown (should be set when expecting a NEW command...?)
  2-31  Unknown (should be zero)
Used values are:
  00000001h = unknown?  used before AND after each byte-transfer
  00000003h = unknown?  used after LAST byte of command (and when init/reset)
Maybe that two bits acknowledge the ready/error bits?

INT_INPUT.6 FIQ (!) COM for the COM_registers? (via /SEL Pin?)
  (via FIQ vector, not IRQ vector)

INT_INPUT.11 IRQ Docked ("IOP") (0=Undocked, 1=Docked to PSX)
Probably senses the voltage on the cartridge slots VCC Pin. Becomes zero when Undocked (and probably also when the PSX is switched off).
The Kernel uses IRQ-11 for BOTH sensing docking and undocking, ie. as if the IRQ would be triggered on both 0-to-1 and 1-to-0 transistions... though maybe that feature just relies on switch-bounce. For the same reason (switch bounce), the IRQ-11 handler performs a delay before it checks the new INT_INPUT.11 setting (ie. the delay skips the unstable switch bound period, and allows the signal to stabilize).

IOP_START/IOP_STOP.Bit1
The BIOS adjusts this bit somehow in relation to communication. Unknown when/why/how it must be used. For details on IOP_START/IOP_STOP see Power Control chapter.

Opcode E6000010h (The Undefined Instruction) - Write chr(r0) to TTY
This opcode is used by the SN Systems emulator to write chr(r0) to a TTY style text window. r0 can be ASCII characters 20h and up, or 0Ah for CRLF. Using that opcode is a not too good idea because the default BIOS undef instruction handler simply runs into an endless loop, so games that are using it (eg. Break-Thru by Jason) won't work on real hardware. That, unless the game would change the undef instruction vector at [04h] in Kernel RAM, either replacing it by a MOVS R15,R14 opcode (ignore exception and return to next opcode), or by adding exception handling that outputs the character via IR or via whatever cable connection. Observe that an uninitialized FUNC3 accidently destroys [04h], so first init FUNC3 handler via SWI 17h, before trying to change [04h], moreover, mind that SWI 05h may reset FUNC3, causing the problem to reappear.
Altogether, it'd be MUCH more stable to write TTY characters to an unused I/O port... only problem is that it's still unknown which I/O ports are unused... ie. which do neither trap data aborts, nor do mirror to existing ports...?


Pocketstation IO Power Control

0B000000h - CLK_MODE - Clock control (CPU and Timer Speed) (R/W)
  0-3  Clock Ratio (01h..08h, see below) (usually 7 = 3.99MHz)    (R/W)
  4    Clock Change State (0=Busy, 1=Ready)                       (Read-only)
  5-15 ?
Allows to change the CPU clock (and Timer clock, which is usually one half of the CPU clock, or less, depending on the Timer Divider). Possible values are:
  00h = hangs hardware    ;-don't use
  01h = 0.063488 MHz      ;\
  02h = 0.126976 MHz      ;
  03h = 0.253952 MHz      ; 31*8000h / 1,2,4,8,16
  04h = 0.507904 MHz      ;
  05h = 1.015808 MHz      ;/
  06h = 1.998848 MHz      ;\
  07h = 3.997696 MHz      ; 61*8000h * 1,2,4
  08h = 7.995392 MHz      ;/
  09h..0Fh = same as 08h  ;-aliases
Before changing CLK_MODE, F_WAIT1 and F_WAIT2 should be adjusted accordingly (see there for details). Note that many memory regions have waitstates, the full CPU speed can be reached mainly with code/data in WRAM.

0B000004h - CLK_STOP - Clock stop (Sleep Mode)
Stops the CPU until an interrupt occurs. The pocketstation doesn't have a power-switch nor standby button, the closest thing to switch "power off" is to enter sleep mode. Software should do that when the user hasn't pressed buttons for 1-2 seconds (that, only in handheld mode, not when docked to the PSX; where it's using the PSX power supply instead of the battery).
  0    Stop Clock (1=Stop)
  1-15 ?
Wakeup is usually done by IRQ-0 (Fire Button) and IRQ-11 (Docking). If alarm is enabled, then the GUI also enables IRQ-9 (RTC), and compares RTC_TIME against the alarm setting each time when it wakes up.
Before writing to CLK_STOP, one should do:
  DAC_CTRL=0                         ;\disable sound
  IOP_STOP=20h                       ;/
  LCD_MODE=0                         ;-disable video
  IRDA=whatever                      ;-disable infrared (if it was used)
  BATT_CTRL=BATT_CTRL AND FFFFFFFCh  ;-do whatever
  INT_MASK_SET=801h                  ;-enable Docking/Fire wakeup interrupts
The GUI uses CLK_STOP only for Standby purposes (not for waiting for its 30Hz "frame rate" timer 0 interrupt; maybe that isn't possible, ie. probably CLK_STOP does completely disable the system clock, and thus does stop Timer0-2...?)

0D800000h - IOP_CTRL - Configures whatever...? (R/W)
  0-3  Probably Direction for IOP_DATA bit0..3 (0=Input, 1=Output)
  4-31 Unknown/Unused (seems to be always zero)
Unknown. Set to 0000000Fh by BIOS upon reset. Aside from that, the BIOS does never use that register.

0D800004h - IOP_STAT (R) - Read Current bits? -- No, seems to be always 0
0D800004h - IOP_STOP (W) - Set IOP_DATA Bits
0D800008h - IOP_START (W) - Clear IOP_DATA Bits
These two ports are probably accessing a single register, writing "1" bits to IOP_STOP sets bits in that register, and writing "1" bits to IOP_START clears bits... or vice-versa...? Writing "0" bits to either port seems to leave that bits unchanged. The meaning of most bits is still unknown:
  0    Unknown, STARTED by Kernel upon reset
  1    Red LED, Communication related (START=Whatever, STOP=Whatelse) (?)
  2    Unknown, STARTED by Kernel upon reset
  3    Unknown, STARTED by Kernel upon reset
  4    Never STARTED nor STOPPED by BIOS (maybe an INPUT, read via IOP_DATA)
  5    Sound Enable (START=On, STOP=Off)
  6    Unknown, STOPPED by Kernel upon reset
  7-31 Unknown, never STARTED nor STOPPED by BIOS
Aside from Bit1, it's probably not neccessary to change the unknown bits...?
Sound is usually disabled by setting IOP_STOP=00000020h. IOP_STAT is rarely used. Although, one piece of code in the BIOS disables sound by setting IOP_STOP=IOP_STAT OR 00000020h, that is probably nonsense, probably intended to keep bits stopped if they are already stopped (which would happen anyways), however, the strange code implies that reading from 0D800004h returns the current status of the register, and that the bits in that register seem to be 0=Started, and 1=Stopped...?

0D80000Ch - IOP_DATA (R)
  0    ?
  1    Red LED (0=On, 1=Off)
  2    ?
  3    ?
  4    Seems to be always 1 (maybe Infrared input?)
  5-31 Unknown/Unused (seems to be always zero)
Unknown. Not used by the BIOS. Reportedly this register is 0010h if IR Connection...? This register is read by Rewrite ID, and by Harvest Moon. Maybe bit4 doesn't mean <if> IR connection exist, but rather <contains> the received IR data level...?

0D800020h - BATT_CTRL - Battery Monitor Control?
Unknown. Somehow battery saving related. Upon reset, and upon leaving sleep mode, the BIOS does set BATT_CTRL=00000000h. Before entering sleep mode, it does set BATT_CTRL=BATT_CTRL AND FFFFFFFCh, whereas, assuming that BATT_CTRL was 00000000h, ANDing it with FFFFFFFCh would simply leave it unchanged... unless the hardware (or maybe a game) sets some bits in BATT_CTRL to nonzero values...?

Battery Low Interrupt
  INT_INPUT.10    IRQ     Battery Low     (0=Normal, 1=Battery Low)
Can be used to sense if the battery is low, if so, one may disable sound output and/or reduce the CPU speed to increase the remaining battery lifetime. Unknown how long the battery lasts, and how much the lifetime is affected by audio, video, infrared, cpu speed, and sleep mode...?
The pocketstation can be also powered through the VCC pin (ie. when docked to the PSX, then it's working even if the battery is empty; or even without battery).


Pocketstation SWI Function Summary

SWI Function Summary
BIOS functions can be called via SWI opcodes (from both ARM and THUMB mode) (in ARM mode, the SWI function number is in the lower 8bit of the 24bit field; unlike as for example on the GBA, where it'd be in the upper 8bit). Parameters (if any) are passed in r0,r1,r2. Return value is stored in r0 (all other registers are left unchanged).
  SWI 00h - Reset()   ;don't use            out: everything destroyed
  SWI 01h - SetCallbacks(index,proc)        out: old proc
  SWI 02h - CustomSwi2(r0..r6,r8..r10)      out: r0
  SWI 03h - FlashWriteVirtual(sector,src)   out: 0=okay, 1=failed
  SWI 04h - SetCpuSpeed(speed)              out: old_speed
  SWI 05h - SenseAutoCom()                  out: garbage
  SWI 06h - GetPtrToComFlags()              out: ptr (usually 0C0h)
  SWI 07h - ChangeAutoDocking(flags.16-18)  out: incoming flags AND 70000h
  SWI 08h - PrepareExecute(flag,dir_index,param)  out: dir_index (new or old)
  SWI 09h - DoExecute(snapshot_saving_flag) out: r0=r0 (failed) or r0=param
  SWI 0Ah - FlashReadSerial()               out: F_SN
  SWI 0Bh - ClearComFlagsBit10()            out: new [ComFlags] (with bit10=0)
  SWI 0Ch - SetBcdDateTime(date,time)       out: garbage (RTC_DATE/10000h)
  SWI 0Dh - GetBcdDate()                    out: date (with century in MSBs)
  SWI 0Eh - GetBcdTime()                    out: time and day-of-week
  SWI 0Fh - FlashWriteSerial(serial_number) out: garbage (r0=0) ;old BIOS only!
  SWI 10h - FlashWritePhysical(sector,src)  out: 0=okay, 1=failed
  SWI 11h - SetComOnOff(flag)               out: garbage retadr to swi handler
  SWI 12h - TestSnapshot(dir_index)         out: 0=normal, 1=MCX1 with 1,0,"SE"
  SWI 13h - GetPtrToAlarmSetting()          out: ptr to alarm_setting
  SWI 14h - GetPtrToPtrToSwiTable()         out: ptr-to-ptr to swi_table
  SWI 15h - MakeAlternateDirIndex(flag,dir_index)  out: alt_dir_index (new/old)
  SWI 16h - GetDirIndex()                   out: dir_index (or alternate)
  SWI 17h - GetPtrToFunc3addr()             out: ptr to func3 address
  SWI 18h - FlashReadWhateverByte(sector)   out: [8000000h+sector*80h+7Eh]
  SWI 19h..FFh - garbage
  SWI 100h..FFFFFFh - mirrors of SWI 00h..FFh
The BIOS uses the same memory region for SWI and IRQ stacks, so both may not occur simultaneously, otherwise one stack would be destroyed by the other (normally that is no problem; IRQs are automatically disabled by the CPU during SWI execution, SWIs aren't used from inside of default IRQ handlers, and SWIs shouldn't be used from inside of hooked IRQ handlers).


Pocketstation SWI Misc Functions

SWI 01h - SetCallbacks(index,proc)
  r0=0  Set SWI 02h callback               (r1=proc, or r1=0=reset/default)
  r0=1  Set IRQ callback                   (r1=proc, or r1=0=none/default)
  r0=2  Set FIQ callback                   (r1=proc, or r1=0=none/default)
  r0=3  Set Download Notification callback (r1=proc, or r1=0=bugged/default)
All callbacks are called via BX opcodes (ie. proc.bit0 can be set for THUMB code). SetCallbacks returns the old proc value (usually zero). The callbacks are automatically reset to zero when (re-)starting an executable, or when returning control to the GUI, so there's no need to restore the values by software.

IRQ and FIQ Callbacks
Registers r0,r1,r12 are pushed by the kernels FIQ/IRQ handlers (so the callbacks can use that registers without needing to push them). The FIQ handler can additionally use r8..r11 without pushing them (the CPU uses a separate set of r8..r12 registers in FIQ mode, nethertheless, the kernel DOES push r12 in FIQ mode, without reason). Available stack is 70h bytes for the FIQ callback, and 64h bytes for the IRQ callback.
The callbacks don't receive any incoming parameters, and don't need to respond with a return value. The callback should return to the FIQ/IRQ handler (via normal BX r14) (ie. it should not try to return to User mode).
The kernel IRQ handler does (after the IRQ callback) process IRQ-11 (IOP) (which does mainly handle docking/undocking), and IRQ-9 (RTC) (which increments the century if the year wrapped from 99h to 00h).
And the kernel FIQ handler does (before the FIQ callback) process IRQ-6 (COM) (which does, if ComFlags.Bit9 is set, handle bu_cmd's) (both IRQs and FIQs are disabled, and the main program is stopped until the bu_cmd finishes, or until a joypad command is identified irrelevant, among others that means that sound/timer IRQs aren't processed during that time, so audio output may become distorted when docked).
When docked, the FIQ callback should consist of only a handful of opcodes, eg. it may contain a simple noise, square wave generator, or software based sound "DMA" function, but it should not contain more time-consuming code like sound envelope processing; otherwise IRQ-6 (COM) cannot be executed fast enough to handle incoming commands.

SWI 02h - CustomSwi2(r0..r6,r8..r10) out: r0
Calls the SWI2 callback function (which can be set via SWI 01h). The default callback address is 00000000h (so, by default, it behaves identically as SWI 00h). Any parameters can be passed in r0..r6 and r8..r10 (the other registers aren't passed to the callback function). Return value can be stored in r0 (all other registers are pushed/popped by the swi handler, as usually). Available space on the swi stack is 38h bytes.
SWI2 can be useful to execute code in privileged mode (eg. to initialize FIQ registers r8..r12 for a FIQ based sound engine) (which usually isn't possible because the main program runs in non-privileged user mode).

SWI 04h - SetCpuSpeed(speed) out: old_speed
Changes the CPU speed. The BIOS uses it with values in range 01h..07h. Unknown if value 00h can be also used? The function also handles values bigger than 07h, of which, some pieces of BIOS code look as if 08h would be the maximum value...?
Before setting the new speed, the function sets F_WAIT1 and F_WAIT2 to 00000000h (or to 00000010h if speed.bit3=1). After changing the speed (by writing the parameter to CLK_MODE) it does wait until the new speed is applied (by waiting for CLK_MODE.bit4 to become zero). The function returns the old value of CLK_MODE, anded with 0Fh.


Pocketstation SWI Communication Functions

Communication (aka BU Commands, received from the PSX via the memory card slot) can be handled by the pocketstations kernel even while a game is running. However, communications are initially disabled when starting a game, so the game should enable them via SWI 11h, and/or via calling SWI 05h once per frame.

SWI 11h - SetComOnOff(flag)
Can be used to enable/disable communication. When starting an executable, communication is initially disabled, so it'd be a good idea to enable them (otherwise the PSX cannot communicate with the Pocketstation while the game is running).
When flag=0, disables communication: Intializes the COM_registers, disables IRQ-6 (COM), and clears ComFlags.9. When flag=1, enables communication: Intializes the COM_registers, enables IRQ-6 (COM), sets ComFlags.9 (when docked), or clears Sys.Flags.9 (when undocked), and sets FAST cpu_speed=7 (only when docked). The function returns garbage (r0=retadr to swi_handler).

SWI 06h - GetPtrToComFlags()
Returns a pointer to the ComFlags word in RAM, which contains several communication related flags (which are either modified upon docking/undocking, or upon receiving certain bu_cmd's). The ComFlags word consists of the following bits:
  0-3   Whatever (set/cleared when docked/undocked, and modified by bu_cmd's)
  4-7   Not used (should be zero)
  8     IRQ-11 (IOP) occurred  (set by irq handler, checked/cleared by SWI 05h)
  9     Communication Enabled And Docked (0=No, 1=Yes; prevents DoExecute)
  10    Reject writes to Broken Sector Region (sector 16..55)     (0=No, 1=Yes)
  11    Start file request (set by bu_cmd_59h, processed by GUI, not by Kernel)
  12-15 Not used (should be zero)
  16    Automatically power-down DAC audio on insert/removal      (0=No, 1=Yes)
  17    Automatically power-down IRDA infrared on insert/removal  (0=No, 1=Yes)
  18    Automatically adjust LCD screen rotate on insert/removal  (0=No, 1=Yes)
  19-27 Not used (should be zero)
  28    Indicates if a standard bu_cmd (52h/53h/57h) was received (0=No, 1=Yes)
  29    Set date/time request  (set by bu_cmd FUNC0, processed by BIOS)
  30    Destroy RTC and Start GUI request  (set by bu_cmd_59h, dir_index=FFFEh)
  31    Not used (should be zero)
Bit16-18 can be changed via SWI 07h, ChangeAutoDocking(flags). Bit10 can be cleared by SWI 0Bh, ClearComFlagsBit10().

SWI 07h - ChangeAutoDocking(flags.16-18)
  0-15  Not used (should be zero)
  16    Automatically power-down DAC audio on insert/removal     (0=No, 1=Yes)
  17    Automatically power-down IRDA infrared on insert/removal (0=No, 1=Yes)
  18    Automatically adjust LCD screen rotate on insert/removal (0=No, 1=Yes)
  19-31 Not used (should be zero)
Copies bit16-18 of the incoming parameter to ComFlags.16-18, specifying how the kernel IRQ-11 (IOP) handler shall process docking/undocking from the PSX cartridge slot. The function returns the incoming flags value ANDed with 70000h.

SWI 0Bh - ClearComFlagsBit10()
Resets ComFlags.Bit10, ie. enables bu_cmd_57h (write_sector) to write to the Broken Sector region in FLASH memory (sector 16..55). SWI 0Bh returns the current ComFlags value (the new value, with bit10=0).
Aside from calling SWI 0Bh, ComFlags.10 is also automatically cleared upon IRQ-10 (IOP) (docking/undocking). ComFlags.10 can get set/cleared by the Download Notification callback.

SWI 05h - SenseAutoCom()
Checks if docking/undocking has occurred (by examining ComFlags.8, which gets set by the kernel IRQ-11 (IOP) handler). If that flag was set, then the function does reset it, and does then reset FUNC3=0000h and [0CAh]=00h (both only if docked, not when undocked), and, no matter if docked or undocked, it enables communication; equivalent to SetComOnOff(1); which sets/clears ComFlags.9. The function returns garbage (r0=whatever).
The GUI is calling SWI 05h once per frame. The overall purpose is unknown. It's a good idea to reset FUNC3 and to Enable Communication (although that'd be required only when docked, not when undocked), but SWI 05h is doing that only on (un-)docking transitions (not when it was already docked). In general, it'd make more sense to do proper initializations via SWI 11h and SWI 17h as than trusting SWI 05h to do the job. The only possibly useful effect is that SWI 05h does set/clear ComFlags.9 when docked/undocked.

SWI 17h - GetPtrToFunc3addr()
Returns a pointer to a halfword in RAM which contains the FUNC3 address (for bu_cmd_5bh and bu_cmd_5ch). The address is only 16bit, originated at 02000000h in FLASH (ie. it can be only in the first 64K of the file), bit0 can be set for THUMB code. The default address is zero, which behaves bugged: It accidently sets [00000004h]=00000000h, ie. replaces the Undefined Instruction exception vector by a "andeq r0,r0,r0" opcode, due to that NOP-like opcode, any Undefined Instruction exceptions will run into the SWI vector at [00000008h], and randomly execute an SWI function; with some bad luck that may execute one of the FlashWrite functions and destroy the saved files.
Although setting 0000h acts bugged, one should restore that setting before returning control to GUI or other executables; otherwise the address would still point to the FUNC3 address of the old unloaded executable, which is worse than the bugged effect.
The FUNC3 address is automatically reset to 0000h when (if) SWI 05h (SenseAutoCom) senses new docking.

Download Notification callback
Can be used to mute sound during communication, see SWI 01h, SetCallbacks(index,proc), and BU Command 5Dh for details.


Pocketstation SWI Execute Functions

SWI 08h - PrepareExecute(flag,dir_index,param)
dir_index should be 0=GUI, or 1..15=First block of game. When calling DoExecute, param is passed to the entrypoint of the game or GUI in r0 register (see notes on GUI <param> values belows). For games, param may be interpreted in whatever way.
When flag=0, the function simply returns the old dir_index value. When flag=1, the new dir_index and param values are stored in Kernel RAM (for being used by DoExecute); the values are stored only if dir_index=0 (GUI), or if dir_index belongs to a file with "SC" and "MCX0" or "MCX1" IDs in it's title sector. If dir_index was accepted, then the new dir_index value is returned, otherwise the old dir_index is returned.

GUI <param> values - for PrepareExecute(1,0,param)
PrepareExecute(1,0,param) prepares to execute the GUI (rather than a file). When executing the GUI, <param> consists of the following destructive bits:
  0-7  Command number (see below, MSBs=Primary command, LSBs=another dir_index)
  8    Do not store Alarm setting in Kernel RAM (0=Normal, 1=Don't store)
  9-31 Not used (should be zero)
The command numbers can be:
  Command 0xh --> Erase RTC time/date
  Command 1xh --> Enter GUI Time Screen with speaker symbol
  Command 20h --> Enter GUI Time Screen with alarm symbol
  Command 2xh --> Prompt for new Date/Time, then start dir_index (x)
  Command 3xh --> Enter GUI File Selection Screen, with dir_index (x) selected
  Command xxh --> Erase RTC time/date (same as Command 0xh)
For Command 2xh and 3xh, the lower 4bit of the command (x) must be a valid dir_index of the 1st block of a pocketstation executable, otherwise the BIOS erases the RTC time/date. Bit8 is just a "funny" nag feature, allowing the user to change the alarm setting, but with the changes being ignored (bit8 can be actually useful in BU Command 59h, after FUNC2 was used for changing alarm).

SWI 09h - DoExecute(), or DoExecute(snapshot_saving_flag) for MCX1
Allows to return control to the GUI (when dir_index=0), or to start an executable (when dir_index=1..15). Prior to calling DoExecute, parameters should be set via PrepareExecute(1,dir_index,param), when not doing that, DoExecute would simply restart the current executable (which may be a desired effect in some cases).
The "snapshot_saving_flag" can be ommited for normal (MCX0) files, that parameter is used only for special (MCX1) files (see Snapshot Notes for details).
Caution: DoExecute fails (and returns r0=unchanged) when ComFlags.9=1 (which indicates that communications are enabled, and that the Pocketstation is believed to be docked to the PSX). ComFlags.9 can be forcefully cleared by calling SetComOnOff(0), or it can be updated according to the current docking-state by calling SetComOnOff(1) or SenseAutoCom().

SWI 16h - GetDirIndex()
Returns the dir_index for the currently executed file. If that value is zero, ie. if there is no file executed, ie. if the function is called by the GUI, then it does instead return the "alternate" dir_index (as set via SWI 15h).

SWI 15h - MakeAlternateDirIndex(flag,dir_index) out: alt_dir_index (new/old)
Applies the specified dir_index as "alternate" dir_index (for being retrieved via SWI 16h for whatever purpose). The dir_index is applied only when flag=1, and only if dir_index is 0=none, or if it is equal to the dir_index of the currently executed file (ie. attempts to make other files being the "alternate" one are rejected). If successful, the new dir_index is returned, otherwise the old dir_index is returned (eg. if flag=0, or if the index was rejected).

SWI 12h - TestSnapshot(dir_index)
Tests if the specified file contains a load-able snapshot, ie. if it does have the "SC" and "MCX1" IDs in the title sector, and the 01h,00h,"SE" ID in the snapshot header. If so, it returns r0=1, and otherwise returns r0=0.

Snapshot Notes (MCX1 Files)
Snapshots are somewhat automatically loaded/saved when calling DoExecute:
If the old file (the currently executed file) contains "SC" AND "MCX1" IDs in the title sector, then the User Mode CPU registers and User RAM at 200h..7FFh are automatically saved in the files snapshot region in FLASH memory, with the snapshot_saving_flag being applied as bit0 of the 0xh,00h,"SE" ID of the snapshot header).
If the new file (specified in dir_index) contains load-able snapshot data (ie. if it has "SC" and "MCX1" IDs in title sector, and 01h,00h,"SE" ID in the snapshot region), then the BIOS starts the saved snapshot data (instead of restarting the executable at its entrypoint). Not too sure if that feature is really working... the snapshot loader seems to load User RAM from the wrong sectors... and it seems to jump directly to User Mode return address... without removing registers that are still stored on SWI stack... causing the SWI stack to underflow after loading one or two snapshots...?


Pocketstation SWI Date/Time/Alarm Functions

SWI 0Ch - SetBcdDateTime(date,time)
Sets the time and date, the parameters are having the same format as SWI 0Dh and SWI 0Eh return values (see there). The SWI 0Ch return value contains only garbage (r0=RTC_DATE/10000h).

SWI 0Dh - GetBcdDate()
  0-7   Day     (01h..31h, BCD)
  8-11  Month   (01h..12h, BCD)
  16-31 Year    (0000h..9999h, BCD)
Returns the current date, the lower 24bit are read from RTC_DATE, the century in upper 8bit is read from Kernel RAM.

SWI 0Eh - GetBcdTime()
  0-7   Seconds     (00h..59h, BCD)
  8-15  Minutes     (00h..59h, BCD)
  16-23 Hours       (00h..23h, BCD)
  24-31 Day of week (1=Sunday, ..., 7=Saturday)
Returns the current time and day of week, read from RTC_TIME.

SWI 13h - GetPtrToAlarmSetting()
Returns a pointer to a 64bit value in Kernel RAM, the upper word (Bit32-63) isn't actually used by the BIOS, except that, the bu_cmd FUNC3 does transfer the whole 64bits. The meaning of the separate bits is:
  0-7   Alarm Minute    (00h..59h, BCD)
  8-15  Alarm Hour      (00h..23h, BCD)
  16    Alarm Enable    (0=Off, 1=On)
  17    Button Lock     (0=Normal, 1=Lock) (pressing all 5 buttons in GUI)
  18-19 Volume Shift    (0=Normal/Loud, 1=Medium/Div4, 2=Mute/Off)
  20-22 Not used        (should be zero)
  23    RTC Initialized (0=Not yet, 1=Yes, was initialized from within GUI)
  24-31 Not used        (should be zero)
  32-63 Pointer to 8x8 BIOS Charset (characters "0"..."9" plus strange symbols)
The RTC hardware doesn't have a hardware-based alarm feature, instead, the alarm values must be compared with the current time by software. Alarm is handled only by the GUI portion of the BIOS. The Kernel doesn't do any alarm handling, so alarm won't occur while a game is executed (unless the game contains code that handles alarm).
Games are usually using only the lower 16bit of the charset address, ORed with 04000000h (although the full 32bit is stored in RAM).
  CHR(00h..09h) = Digits "0..9"
  CHR(0Ah) = Space " "
  CHR(0Bh) = Colon ":"
  CHR(0Ch) = Button Lock (used by Final Fantasy 8's Chocobo World)
  CHR(0Dh) = Speaker Medium; or loud if followed by chr(0Eh)
  CHR(0Eh) = Speaker Loud; to be appended to chr(0Dh)
  CHR(0Fh) = Speaker Off
  CHR(10h) = Battery Low (used by PocketMuuMuu's Cars)
  CHR(11h) = Alarm Off
  CHR(12h) = Alarm On
  CHR(13h) = Memory Card symbol


Pocketstation SWI Flash Functions

SWI 10h - FlashWritePhysical(sector,src)
Writes 80h-bytes at src to the physical sector number (0..3FFh, originated at 08000000h), and does then compare the written data with the source data. Returns 0=okay, or 1=failed.

SWI 03h - FlashWriteVirtual(sector,src)
The sector number (0..3FFh) is a virtual sector number (originated at 02000000h), the function uses the F_BANK_VAL settings to translate it to a physical sector number, and does then write the 80h-bytes at src to that location (via the FlashWritePhysical function). Returns 0=okay, or 1=failed (if the write failed, or if the sector number exceeded the filesize aka the virtually mapped memory region).

SWI 0Ah - FlashReadSerial()
Returns the 32bit value from the two 16bit F_SN registers (see F_SN for details).

SWI 0Fh - FlashWriteSerial(serial_number) ;old BIOS only!
Changes the 32bit F_SN value in the "header" region of the FLASH memory. The function also rewrites the F_CAL value (but it simply rewrites the old value, so it's left unchanged). The function isn't used by the BIOS, no idea if it is used by any games. No return value (always returns r0=0).
This function is supported by the old "061" version BIOS only (the function is padded with jump opcodes which hang the CPU in endless loops on newer "110" version).

SWI 18h - FlashReadWhateverByte(sector)
Returns [8000000h+sector*80h+7Eh] AND 00FFh. Purpose is totally unknown... the actual FLASH memory doesn't contain any relevant information at that locations (eg. the in the directory sectors, that byte is unused, usually zero)... and, reading some kind of status or manufacturer information would first require to command the hardware to output that info...?


Pocketstation SWI Useless Functions

SWI 00h - Reset() ;don't use, destroys RTC settings
Reboots the pocketstation, similar as when pressing the Reset button. Don't use! The BIOS bootcode does (without any good reason) reset the RTC registers and alarm/century settings in RAM to Time 00:00:00, Date 01 Jan 1999, and Alarm 00:00 disabled, so, after reset, the user would need to re-enter that values.
Aside from the annoying destroyed RTC settings, the function is rather unstable: it does jump to address 00000000h in RAM, which should usually redirect to 04000000h in ROM, however, most pocketstation games are programmed in C language, where "pointer" is usually pronounced "pointer?" without much understanding of whether/why/how to initialize that "strange things", so there's a good probability that one of the recently executed games has accidently destroyed the reset vector at [00000000h] in battery-backed RAM.

SWI 14h - GetPtrToPtrToSwiTable()
Returns a pointer to a word in RAM, which contains another pointer which usually points to SWI table in ROM. Changing that word could be (not very) useful for setting up a custom SWI table in FLASH or in RAM. When doing that, one must restore the original setting before returning control to the GUI or to another executable (the setting isn't automatically restored).


Pocketstation BU Command Summary

The Pocketstation supports the standard Memory Card commands (Read Sector, Write Sector, Get Info), plus a couple of special commands.

BU Command Summary
  50h  Change a FUNC 03h related value or so
  51h  N/A
  52h  Standard Read Sector command
  53h  Standard Get ID command
  54h  N/A
  55h  N/A
  56h  N/A
  57h  Standard Write Sector command
  58h  Get an ID or Version value or so
  59h  Prepare File Execution with Dir_index, and Parameter
  5Ah  Get Dir_index, ComFlags, F_SN, Date, and Time
  5Bh  Execute Function and transfer data from Pocketstation to PSX
  5Ch  Execute Function and transfer data from PSX to Pocketstation
  5Dh  Execute Custom Download Notification Function   ;via SWI 01h with r0=3
  5Eh  Get-and-Send ComFlags.bit1,3,2
  5Fh  Get-and-Send ComFlags.bit0
Commands 5Bh and 5Ch can use the following functions:
  FUNC 00h - Get or Set Date/Time
  FUNC 01h - Get or Set Memory Block
  FUNC 02h - Get or Set Alarm/Flags
  FUNC 03h - Custom Function 3              ;via SWI 17h, GetPtrToFunc3addr()
  FUNC 80h..FFh - Custom Functions 80h..FFh ;via Function Table in File Header


Pocketstation BU Standard Memory Card Commands

For general info on the three standard memory card commands (52h, 53h, 57h), and for info on the FLAG response value, see:
Memory Card Read/Write Commands

BU Command 52h (Read Sector)
Works much as on normal memory cards, except that, on the Pocketstation, the Read Sector command return 00h as dummy values; instead of the "(pre)" dummies that occur on normal memory cards.
The Read Sector command does reproduce the strange delay (that occurs between 5Ch and 5Dh bytes), similar as on normal original Sony memory cards, maybe original cards did (maybe) actually DO something during that delay period, the pocketstation BIOS simply blows up time in a wait loop (maybe for compatibility with original cards).

BU Command 53h (Get ID)
The Get ID command (53h) returns exactly the same values as normal original Sony memory cards.

BU Command 57h (Write Sector)
The Write Sector command has two new error codes (additonally to the normal 47h="G"=Good, 4Eh="N"=BadChecksum, FFh=BadSector responses). The new error codes are (see below for details):
  FDh Reject write to Directory Entries of currently executed file
  FEh Reject write to write-protected Broken Sector region (sector 16..55)
And, like Read Sector, it returns 00h instead of "(pre)" as dummy values.

Write Error Code FDh (Directory Entries of currently executed file)
The FDh error code is intended to prevent the PSX bootmenu (or other PSX games) to delete the currently executed file (which would crash the pocketstation - once when the deleted region gets overwritten by a new file), because the PSX bootmenu and normal PSX games do not recognize the new FDh error code the pocketstation does additionally set FLAG.3 (new card), which should be understood by all PSX programs.
The FDh error code occurs only on directory sectors of the file (not on its data blocks). However, other PSX games should never modify files that belong to other games (so there should be no compatibility problem with other PSX programs that aren't aware of the file being containing currently executed code).
However, the game that has created the executable pocketstation file must be aware of that situation. If the file is broken into a Pocketstation Executable region and a PSX Gameposition region, then it may modify the Gameposition stuff even while the Executable is running. If the PSX want to overwrite the executable then it must first ensure that it isn't executed (eg. by retrieving the dir_index of the currently executed file via BU Command 5Ah, and comparing it against the first block number in the files FCB at the PSX side; for file handle "fd", the first block is found at "[104h]+fd*2Ch+24h" in PSX memory).

Write Error Code FEh (write-protected Broken Sector region, sector 16..55)
The write-protection is enabled by ComFlags.bit10 (which can be set/cleared via BU Command 5Dh). That bit should be set before writing Pocketstation excecutables (the Virtual Memory banking granularity is 2000h bytes, which allows to map whole blocks only, but cannot map single sectors, which would be required for files with broken sector replacements).
Unlike Error FDh, this error code doesn't set FLAG.3 for notifying normal PSX programs about the error (which is no problem since normally Error FEh should never occur since ComFlags.10 is usually zero). For more info on ComFlags.10, see SWI 0Bh aka ClearComFlagsBit10(), and BU Command 5Dh.


Pocketstation BU Basic Pocketstation Commands

BU Command 50h (Change a FUNC 03h related value or so)
  Send Reply Comment
  81h  N/A   Memory Card Access
  50h  FLAG  Send Command 50h
  VAL  00h   Send new [0CAh], receive length of following data (00h)
Might be somehow related to FUNC 03h...?

BU Command 58h (Get an ID or Version value or so)
  Send Reply Comment
  81h  N/A   Memory Card Access
  58h  FLAG  Send Command 58h
  (0)  02h   Send dummy/zero, receive length of following data (02h)
  (0)  01h   Send dummy/zero, receive whatever value           (01h)
  (0)  01h   Send dummy/zero, receive another value            (01h)

BU Command 59h (Prepare File Execution with Dir_index, and Parameter)
  Send Reply Comment
  81h  N/A   Memory Card Access
  59h  FLAG  Send Command 59h
  (0)  06h   Send dummy/zero, receive length of following data (06h)
  NEW  OLD   Send new dir_index.8-15, receive old dir_index.8-15
  NEW  OLD   Send new dir_index.0-7, receive old dir_index.0-7
  PAR  (0)   Send exec_parameter.0-7, receive dummy/zero
  PAR  (0)   Send exec_parameter.8-15, receive dummy/zero
  PAR  (0)   Send exec_parameter.16-23, receive dummy/zero
  PAR  (0)   Send exec_parameter.24-31, receive dummy/zero
The new dir_index can be the following:
  0000h..000Fh --> Request to Start GUI or File (with above parameter bits)
  0010h..FFFDh --> Not used, acts same as FFFFh (see below)
  FFFEh --> Request to Destroy RTC and Start GUI (with parameter 00000000h)
  FFFFh --> Do nothing (transfer all bytes, but don't store the new values)
Upon dir_index=0000h (Start GUI) or 0001..000Fh (start file), a request flag in ComFlags.11 is set, the GUI does handle that request, but the Kernel doesn't handle it (so it must be handled in the game; ie. check ComFlags.11 in your mainloop, and call DoExecute when that bit is set, there's no need to call PrepareExecute, since that was already done by the BU Command).
Caution: When dir_index=0000h, then <param> should be a value that does NOT erase the RTC time/date (eg. 10h or 20h) (most other values do erase the RTC, see SWI 08h for details).
Upon dir_index=FFFEh, a similar request flag is set in ComFlags.30, and, the Kernel (not the GUI) does handle that request in its FIQ handler (however, the request is: To reset the RTC time/date and to start the GUI with uninitialized irq/svc stack pointers, so this unpleasant and bugged feature shouldn't ever be used). Finally, dir_index=FFFFh allows to read the current dir_index value (which could be also read via BU Command 5Ah).

BU Command 5Ah (Get Dir_index, ComFlags, F_SN, Date, and Time)
  Send Reply Comment
  81h  N/A   Memory Card Access
  5Ah  FLAG  Send Command 5Ah
  (0)  12h   Send dummy/zero, receive length of following data (12h)
  (0)  INDX  Send dummy/zero, receive curr_dir_index.bit8-15   (00h)
  (0)  INDX  Send dummy/zero, receive curr_dir_index.bit0-7    (00h..0Fh)
  (0)  FLG   Send dummy/zero, receive ComFlags.bit0            (00h or 01h)
  (0)  FLG   Send dummy/zero, receive ComFlags.bit1            (00h or 01h)
  (0)  FLG   Send dummy/zero, receive ComFlags.bit3            (00h or 01h)
  (0)  FLG   Send dummy/zero, receive ComFlags.bit2            (00h or 01h)
  (0)  SN    Send dummy/zero, receive F_SN.bit0-7              (whatever)
  (0)  SN    Send dummy/zero, receive F_SN.bit8-15             (whatever)
  (0)  SN    Send dummy/zero, receive F_SN.bit16-23            (whatever)
  (0)  SN    Send dummy/zero, receive F_SN.bit24-31            (whatever)
  (0)  DATE  Send dummy/zero, receive BCD Day                  (01h..31h)
  (0)  DATE  Send dummy/zero, receive BCD Month                (01h..12h)
  (0)  DATE  Send dummy/zero, receive BCD Year                 (00h..99h)
  (0)  DATE  Send dummy/zero, receive BCD Century              (00h..99h)
  (0)  TIME  Send dummy/zero, receive BCD Second               (00h..59h)
  (0)  TIME  Send dummy/zero, receive BCD Minute               (00h..59h)
  (0)  TIME  Send dummy/zero, receive BCD Hour                 (00h..23h)
  (0)  TIME  Send dummy/zero, receive BCD Day of Week          (01h..07h)
At midnight, the function may accidently return the date for the old day, and the time for the new day.

BU Command 5Eh (Get-and-Send ComFlags.bit1,3,2)
  Send Reply Comment
  81h  N/A   Memory Card Access
  5Eh  FLAG  Send Command 5Eh
  (0)  03h   Send dummy/zero, receive length of following data (03h)
  NEW  OLD   Send new ComFlags.bit1, receive old ComFlags.bit1 (00h or 01h)
  NEW  OLD   Send new ComFlags.bit3, receive old ComFlags.bit3 (00h or 01h)
  NEW  OLD   Send new ComFlags.bit2, receive old ComFlags.bit2 (00h or 01h)

BU Command 5Fh (Get-and-Send ComFlags.bit0)
  Send Reply Comment
  81h  N/A   Memory Card Access
  5Fh  FLAG  Send Command 5Fh
  (0)  01h   Send dummy/zero, receive length of following data (01h)
  NEW  OLD   Send new ComFlags.bit0, receive old ComFlags.bit0 (00h or 01h)


Pocketstation BU Custom Pocketstation Commands

BU Command 5Bh (Execute Function and transfer data from Pocketstation to PSX)
  Send Reply Comment
  81h  N/A   Memory Card Access
  5Bh  FLAG  Send Command 5Bh
  FUNC FFh   Send Function Number, receive FFh (indicating variable length)
  (0)  LEN1  Send dummy/zero, receive length of parameters (depending on FUNC)
  ...  (0)   Send parameters (LEN1 bytes), and receive dummy/zero
   <-------- at this point, the function is executed for the first time
  (0)  LEN2  Send dummy/zero, receive length of data (depending on FUNC)
  (0)  ...   Send dummy/zero, receive data (LEN2 bytes) from pocketstation
  (0)  FFh   Send dummy/zero, receive FFh
   <-------- at this point, the function is executed for the second time
See below for more info on the FUNC value and the corresponding functions.

BU Command 5Ch (Execute Function and transfer data from PSX to Pocketstation)
  Send Reply Comment
  81h  N/A   Memory Card Access
  5Ch  FLAG  Send Command 5Ch
  FUNC FFh   Send Function Number, receive FFh (indicating variable length)
  (0)  LEN1  Send dummy/zero, receive length of parameters (depending on FUNC)
  ...  (0)   Send parameters (LEN1 bytes), and receive dummy/zero
   <-------- at this point, the function is executed for the first time
  (0)  LEN2  Send dummy/zero, receive length of data (depending on FUNC)
  ...  (0)   Send data (LEN2 bytes) to pocketstation, receive dummy/zero
  (0)  FFh   Send dummy/zero, receive FFh
   <-------- at this point, the function is executed for the second time
See below for more info on the FUNC value and the corresponding functions.

BU Command 5Dh (Execute Custom Download Notification Function)
Can be used to notify the GUI (or games that do support this function) about following "download" operations (or uploads or other BU commands).
BU commands are handled inside of the kernels FIQ handler, that means both IRQs and FIQs are disabled during a BU command transmission, so any IRQ or FIQ based audio frequency generators will freeze during BU commands. To avoid distorted noise, it's best to disable sound for the duration specified in bit0-7. If the PSX finishes before the originally specified duration has expired, then it can resend this command with bit8=1 to notify the pocketstation that the "download" has completed.
  Send Reply Comment
  81h  N/A   Memory Card Access
  5Dh  FLAG  Send Command 5Dh
  (0)  03h   Send dummy/zero, receive length of following data (03h)
  VAL  (0)   Send receive value.16-23 (whatever), receive dummy/zero
  VAL  (0)   Send receive value.8-15 (download flags), receive dummy/zero
  VAL  (0)   Send receive value.0-7 (download duration), receive dummy/zero
The Download Notification callback address can be set via SWI 01h, SetCallbacks(3,proc), see there for details. At kernel side, the function execution is like so:
  If value.8-15 = 00h, then ComFlags.bit10=1, else ComFlags.bit10=0.
  If download_callback<>0 then call download_callback with r0=value.0-23.
In the GUI, the bu_cmd_5dh_hook/callback handles parameter bits as so (and games should probably handle that bits in the same fashion, too):
  bit0-7  download duration   (in whatever units... 30Hz, RTC, seconds...?)
  bit8    download finished   (0=no, 1=yes, cancel any old/busy duration)
  bit9-23 not used by gui
If PSX games send any of the standard commands (52h,53h,57h) to access the memory card without using command 5Dh, then GUI automatically sets the duration to 01h (and pauses sound only for that short duration).

FUNC 00h - Get or Set Date/Time (FUNC0)
LEN1 is 00h (no parameters), and LEN2 is 08h (eight data bytes):
  DATE  Get or Send BCD Day         (01h..31h)
  DATE  Get or Send BCD Month       (01h..12h)
  DATE  Get or Send BCD Year        (00h..99h)
  DATE  Get or Send BCD Century     (00h..99h)
  TIME  Get or Send BCD Second      (00h..59h)
  TIME  Get or Send BCD Minute      (00h..59h)
  TIME  Get or Send BCD Hour        (00h..23h)
  TIME  Get or Send BCD Day of Week (01h..07h)
At midnight, the function may accidently return the date for the old day, and the time for the new day.

FUNC 01h - Get or Set Memory Block (FUNC1)
LEN1 is 05h (five parameters bytes):
  ADDR  Send Pocketstation Memory Address.bit0-7
  ADDR  Send Pocketstation Memory Address.bit8-15
  ADDR  Send Pocketstation Memory Address.bit16-23
  ADDR  Send Pocketstation Memory Address.bit24-31
  LEN2  Send Desired Data Length (00h..80h, automatically clipped to max=80h)
LEN2 is variable (using the 5th byte of the above parameters):
  ...   Get or Send LEN2 Data byte(s), max 80h bytes
Can be used to write to RAM (and eventually also to I/O ports; when you know what you are doing). In the read direction it can read almost anything: RAM, BIOS ROM, I/O Ports, Physical and Virtual FLASH memory. Of which, trying to read unmapped Virtual FLASH does probably (?) cause a Data Abort exception (and crash the Pocketstation), so that region may be only read if a file is loaded (check that dir_index isn't zero, via BU Command 5Ah, and, take care not to exceed the filesize of that file).
BUG: When sending more than 2 data bytes in the PSX-to-Pocketstation direction, then ADDR must be word-aligned (the BIOS tries to handle odd destination addresses, but when doing that, it messes up the alignment of another internal pointer).

FUNC 02h - Get or Set Alarm/Flags (FUNC2)
LEN1 is 00h (no parameters), and LEN2 is 08h (eight data bytes):
  DATA  Get or Send Alarm.bit0-7,   Alarm Minute    (00h..59h, BCD)
  DATA  Get or Send Alarm.bit8-15,  Alarm Hour      (00h..23h, BCD)
  DATA  Get or Send Alarm.bit16-23, Flags, see SWI 13h, GetPtrToAlarmSetting()
  DATA  Get or Send Alarm.bit24-31, Not used (usually 00h)
  DATA  Get or Send Alarm.bit32-39, BIOS Charset Address.0-7
  DATA  Get or Send Alarm.bit40-47, BIOS Charset Address.8-15
  DATA  Get or Send Alarm.bit48-55, BIOS Charset Address.16-23
  DATA  Get or Send Alarm.bit56-63, BIOS Charset Address.24-31
Changing the alarm value while the GUI is running works only with some trickery: For a sinister reason, the GUI copies the alarm setting to User RAM when it gets started, that copy isn't affected by FUNC2, so the GUI believes that the old alarm setting does still apply (and writes that old values back to Kernel RAM when leaving the GUI). The only workaround is:
Test if the GUI is running, if so, restart it via Command 59h (with dir_index=0, and param=0120h or similar, ie. with param.bit8 set), then execute FUNC2, then restart the GUI again (this time with param.bit8 zero).

FUNC 03h - Custom Function 3 (aka FUNC3)
LEN1 is 04h (fixed) (four parameters bytes):
  VAL   Send Parameter Value.bit0-7
  VAL   Send Parameter Value.bit8-15
  VAL   Send Parameter Value.bit16-23
  VAL   Send Parameter Value.bit24-31
LEN2 is variable (depends on the return value of the 1st function call):
  ...   Get or Send LEN2 Data byte(s)
The function address can be set via SWI 17h, GetPtrToFunc3addr(), see there for details.
Before using FUNC 03h one must somehow ensure that the desired file is loaded (and that it does have initialized the function address via SWI 17h, otherwise the pocketstation would crash).
The FUNC3 address is automatically reset to 0000h when (if) SWI 05h (SenseAutoCom) senses new docking.
Note: The POC-XBOO circuit uses FUNC3 to transfer TTY debug messages.

FUNC 80h..FFh - Custom Function 80h..FFh
LEN1 is variable (depends on the LEN1 value in Function Table in File Header):
  ...   Send LEN1 Parameter Value(s), max 80h bytes (destroys Kernel when >80h)
LEN2 is variable (depends on the return value of the 1st function call):
  ...   Get or Send LEN2 Data byte(s), max 80h bytes (clipped to max=80h)
The function addresses (and LEN1 values) are stored in the Function Table FLASH memory (see Pocketstation File Header for details).
      ;above LEN1 should be 00h..80h (the parameters are stored
      ;in a 80h-byte buffer in kernel RAM, so len LEN1=81h..FFh would
      ;destroy the kernel RAM that is located after that buffer)
Before using FUNC 80h..FFh one must somehow ensure that the desired file is loaded (ie. that the function table with the desired functions is mapped to flash memory; otherwise the pocketstation would crash).

First Function Call (Pre-Data)
Incoming parameters on 1st Function Call:
  r0=flags (09h=Pre-Data to PSX, or 0Ah=Pre-Data from PSX)
  r1=pointer to parameter buffer (which contains LEN1 bytes) (in Kernel RAM)
Return Value on 1st Function Call:
  r0 = Pointer to 64bit memory location (or r0=00000000h=Failed)
That 64bits are:
  0-31    BUF2 address of data buffer (src/dst)
  32-63   LEN2 (00000000h..00000080h) (clipped to max 00000080h if bigger)
dst is written in 8bit units
src is read in 16bit units (and then split to 8bit units)

Second Function Call (Post-Data)
Incoming parameters on 2nd Function Call:
  r0=flags (11h=Post-Data to PSX, 12h=Post-Data from PSX; plus 04h if Bad-Data)
  r1=pointer to data buffer (which contains LEN2 bytes) (BUF2 address)
Return Value on 2nd Function Call:
  There's no return value required on 2nd call (although the kernel
  functions seem to return the same stuff as on 1st call).

Function flags (r0)
For each function, there is only one single function vector which is called for both To- and From-PSX, and both Pre- and Post-Data, and also on errors. The function must decipher the flags in r0 to figure out which of that operations it should handle:
  0    To-PSX   (when used by Command 5Bh)
  1    From-PSX (when used by Command 5Ch)
  2    Error occurred during Data transfer
  3    Pre-Data
  4    Post-Data
  5-31 Not used (zero)
There are only six possible flags combinations:
  09h Pre-Data to PSX
  0Ah Pre-Data from PSX
  11h Post-Data to PSX
  12h Post-Data from PSX
  15h Post-Bad-Data to PSX
  16h Post-Bad-Data from PSX
The kernel doesn't call FUNC 03h if the Error bit is set (ie. Post-Bad-Data needs to be handled only by FUNC 80h..FFh, not by FUNC 03h.)


Pocketstation File Header/Icons

Pocketstation File Content
Pocketstation files consists of the following elements (in that order):
  PSX Title Sector              ;80h bytes
  PSX Colored Icon(s)           ;(hdr[02h] AND 0Fh)*80h bytes
  Pocketstation Saved Snapshot  ;800h bytes if hdr[52h]="MCX1", else 0 bytes
  Pocketstation Function Table  ;(hdr[57h]*8+7Fh) AND NOT 7Fh bytes
  Pocketstation File Viewer Mono Icon     ;hdr[50h]*80h bytes
  Pocketstation Executable Mono Icon List ;hdr[56h]*8 bytes
  Body (Pocketstation Executable Code/Data, PSX Game Position, Exec-Icons)
The Title sector contains some information about the size of the above regions, but not about their addresses (ie. to find a given region, one must compute the size of the preceeding regions).

Special "P" Filename in Directory Sector
For pocketstation executables, the 7th byte of the filename must be a "P" (for other files that location does usually contain a "-", assuming the file uses a standard filename, eg. "BESLES-12345abcdefgh" for a Sony licensed european title).

Special Pocketstation Entries in the Title Sector at [50h..5Fh]
  50h 2  Number of File Viewer Mono Icon Frames (or 0000h=Use Exec-Icons)
  52h 4  Pocketstation Identifier ("MCX0"=Normal, "MCX1"=With Snapshot)
  56h 1  Number of entries in Executable Mono Icon List (01h..FFh)
  57h 1  Number of BU Command 5Bh/5Ch Get/Set Functions (00h..7Fh, usually 00h)
  58h 4  Reserved (zero)
  5Ch 4  Entrypoint in FLASH1 (ie. Fileoffset plus 02000000h) (bit0=THUMB)
In normal PSX files, the region at 50h..5Fh is usually zerofilled. For more info on the standard entries in the Title Sector (and for info on Directory Entries), see:
Memory Card Data Format

Snapshot Region (in "MCX1" Files only)
For a load-able snapshot the Snapshot ID must be 01h,00h,"SE", the Kernel uses snapshots only once (after loading a snapshot, it forcefully changes the ID to 00h,00h,"SE" in FLASH memory).
  000h  r1..r12 (ie. without r0)
  030h  r13_usr (sp_usr)
  034h  r14_usr (lr_usr)
  038h  r15     (pc)
  03Ch  psr_fc
  040h  Snapshot ID (0xh,00h,"SE")
  044h  unused (3Ch bytes)
  200h  Copy of user RAM at 200h..7FFh
For MCX1 files, snapshots can be automatically loaded and saved via the SWI 09h, DoExecute function (the snapshot handling seems to be bugged though; see SWI 09h for details).

Function Table (FUNC 80h..FFh)
The table can contain 00h..7Fh entries, for FUNC 80h..FFh. Each entry occupies 8 bytes:
  00h 4   LEN1 (00000000h..00000080h) (destroys Kernel RAM if bigger)
  04h 4   Function Address (bit0 can be set for THUMB code)
If the number of table entries isn't a multiple of 10h, then the table should be zero-padded to a multiple of 80h bytes (the following File Viewer Mono Icon data is located on the next higher 80h-byte boundary after the Function Table).
For details see BU Commands 5Bh and 5Ch.

File Viewer Mono Icon
Animation Length (0001h..any number) (icon frames) is stored in hdr[50h], for the File Viewer Icon, the Animation Delay is fixed (six 30Hz units per frame).
The File Viewer Icon is shown in the Directory Viewer (which is activated when holding the Down-button pressed for some seconds in the GUI screen with the speaker and memory card symbols, and which shows icons for all files, including regular PSX game positions, whose colored icons are converted without any contrast optimizations to unidentify-able dithered monochrome icons). If the animation length of the File Viewer Icon is 0000h, then the Directory Viewer does instead display the first Executable Mono Icon.
Each icon frame is 32x32 pixels with 1bit color depth (32 words, =128 bytes),
  1st word = top-most scanline, 31st word = bottom-most scanline
  bit0 = left-most pixel, bit31 = right-most pixel (0=white, 1=black)
A normal icon occupies 80h bytes, animated icons have more than one frame and do occupy N*80h bytes.

Executable Mono Icon List
The number of entries in the Executable Mono Icon List is specified in hdr[56h] (usually 01h). Each entry in the Icon List occupies 8 bytes:
  00h 2  Animation Length (0001h..any number) (icon frames)
  02h 2  Animation Delay (N 30Hz units per icon frame)
  04h 4  Address of icon frame(s) in Virtual FLASH (at 02000000h and up)
The icon frame(s) can be anywhere on a word-aligned location in the file Body (as specified in the above Address entry), the format of the frame(s) is the same as for File Viewer Mono Icons (see there).
The Executable Icons are shown in the Executable File Selection Menu (which occurs when pressing Left/Right buttons in the GUI). Pressing Fire button in that menu starts the selected executable. If the Icon List has more than 1 entry, then pressing Up/Down buttons moves to the previous/next entry (this just allows to view the corresponding icons, but doesn't have any other purpose, namely, the current list index is NOT passed to the game when starting it).
The Executable Mono Icon List is usually zero-padded to 80h-bytes size (although that isn't actually required, the following file Body could start at any location).

Entrypoint
The whole file (including the header and icons) gets mapped to 02000000h and up. The entrypoint can be anywhere in the file Body, and it gets called with a parameter value in r0 (when started by the GUI, that parameter is always zero, but it may be nonzero when the executable was started by a game, ie. the <param> from SWI 08h, PrepareExecute, or the <param> from BU Command 59h).
Caution: Games (and GUI) are started with the ARM CPU running in Non-privileged User Mode (however, there are several ways to hook IRQ/FIQ handlers, and from there one can switch to Privileged System Mode).

Returning to the GUI
Games should always include a way to return to the GUI (eg. an option in the game over screen, a key combination, a watchdog timer, and/or the docking signal) (conventionally, games should prompt Exit/Continue when holding Fire pressed for 5 seconds), otherwise it wouldn't be possible to start other games - except by pushing the Reset button (which is no good idea since the bizarre BIOS reset handler does reset the RTC time for whatever reason).
The kernel doesn't pass any return address to the entrypoint (neither in R14, nor on stack). To return control to the GUI, use SWI functions PrepareExecute(1,0,GetDirIndex()+30h), and then DoExecute(0).


Pocketstation File Images

Pocketstation files are normally stored in standard Memory Card images,
Memory Card Images

Pocketstation specific files
Aside from that standard formats, there are two Pocketstation specific formats, the "SC" and "SN" variants. Both contain only the raw file, without any Directory sectors, and thus not including a "BESLESP12345"-style filename string. The absence of the filename means that a PSX game couldn't (re-)open these files via filenames, so they are suitable only for "standalone" pocketstation games.

Pocketstation .BIN Files ("SC" variant)
Contains the raw Pocketstation Executable (ie. starting with the "SC" bytes in the title sector, followed by icons, etc.), the filesize should be padded to a 2000h-byte block boundary.

Pocketstation .BIN Files ("SN" variant)
This is a strange incomplete .BIN file variant which starts with a 4-byte ID ("SN",00h,00h), which is directly followed by executable code, without any title sector, and without any icons.
  It seems as if the file (including the 4-byte ID) is intended to be
  mapped to address 02000000h, and that the entrypoint is fixed at
  02000004h (in ARM state).
  Since the File doesn't have a valid file header with "SC" and "MCXn" IDs,
  it won't be recognized by real hardware, the PSX BIOS would treat it as
  a corrupted/deleted file, the Pocketstation BIOS would treat it as a
  non-executable file.
  So, that fileformat is apparently working only on whatever emulators,
  apparently on the one developed by SN Systems.
  If one should want to use that files on real hardware, one could add
  a 2000h byte stub at the begin of the file; with valid headers, and
  with a small executable that remaps the "SN" stuff to 02000000h via
  the F_BANK_VAL registers.
  Ah, and the "SN" files seem to access RAM at 01000000h and up, unknown
  if RAM is mirrored to that location on real hardware, reportedly that
  region is unused... and doesn't contain RAM...?
    Some games use The Undefined Instruction for TTY Output.
    Most games do strange 8bit writes to LCD_MODE+0 and LCD_MODE+1
    The games usually don't allow to return to the GUI (except by Reset).
The filesize is don't care (no padding to block, sector, word, or halfword boundaries required).


Pocketstation XBOO Cable

This circuit allows to connect a pocketstation to PC parallel port, allowing to upload executables to real hardware, and also allowing to download TTY debug messages (particulary useful as the 32x32 pixel LCD screen is ways too small to display any detailed status info).

POC-XBOO Circuit
Use a standard parallel port cable (with 36pin centronics connector or 25pin DB connector) and then build a small adaptor like this:
  Pin CNTR  DB25          Pocketstation          _______________________
  ACK 10    10  --------- 1 JOYDTA              |       |       |       |
  D0  2     2   --------- 2 JOYCMD              | 9 7 6 | 5 4 3 |  2 1  | CARD
  GND 19-30 18-25 ------- 4 GND                 |_______|_______|_______|
  D1  3     3   --------- 6 /JOYSEL              _______________________
  D2  4     4   --------- 7 JOYCLK              |       |       |       |
  PE  12    12  --------- 9 /JOYACK (/IRQ7)     | 9 8 7 | 6 5 4 | 3 2 1 | PAD
  NC -------------------- 8 /JOYGUN (/IRQ10)     \______|_______|______/
  NC -------------------- 3 7.5V (rumble.supply)
  SUPPLY.5V --|>|---|>|-- 5 3.5V (VCC) (eg. PC's +5V via two 1N4001 diodes)
  SUPPLY.0V ------------- 4 GND (not needed when same as GND on CNTR/DB25)
The circuit is same as for "Direct Pad Pro" (but using a memory card connector instead of joypad connector, and needing +5V from PC power supply instead of using parallel port D3..D7 as supply). Note: IRQ7 is optional (for faster/early timeout).

POC-XBOO Upload
The upload function is found in no$gba "Utility" menu. It does upload the executable and autostart it via standard memory card/pocketstation commands (ie. it doesn't require any special transmission software installed on the pocketstation side).
Notes: Upload is overwriting ALL files on the memory card, and does then autostart the first file. Upload is done as "read and write only if different", this provides faster transfers and higher lifetime.

POC-XBOO TTY Debug Messages
TTY output is conventionally done by executing the ARM CPU's Undefined Opcode with an ASCII character in R0 register (for that purpose, the undef opcode handler should simply point to a MOVS PC,LR opcode).
That kind of TTY output works in no$gba's pocketstation emulation. It can be also used via no$gba's POC-XBOO cable, but requires some small customization in the executable:
First of, the executable needs "TTY+" ID in some reserved bytes of the title sector (telling the xboo uploader to stay in transmission mode and to keep checking for TTY messages after the actual upload):
  TitleSector[58h] = "TTY+"
With that ID, and with the XBOO-hardware being used, the game will be started with "TTY+" in R0 (notifying it that the XBOO hardware is present, and that it needs to install special transmission handlers):
 ;------------------
 .data?
 org  200h
 ...
 tty_bufsiz equ 128  ;max=128=fastest (can be smaller if you are short of RAM)
 func3_info:                                       ;\ ;\
  func3_buf_base     dd 0   ;fixed="func3_buf"     ;  ;  func3_info+00h
  func3_buf_len      dd 0   ;range=0..128          ;/ ;  func3_info+04h
  func3_stack        dd 0                             ;  func3_info+08h
  func3_buffer:      defs tty_bufsiz                  ;/ func3_info+0Ch
 ptr_to_comflags     dd 0
 ...
 .code
 ...
 ;------------------
 tty_wrchr:   ;in: r0=char
  dd      0e6000010h ;=undef opcode            ;-Write chr(r0) to TTY
  bx      lr
 ;------------------
 init_tty:  ;in: r0=param (from entrypoint)
  ldr     r1,=2B595454h ;"TTY+"                ;\check if xboo-cable present
  cmp     r1,r0                                ; (r0=incoming param from
  beq     @@tty_by_xboo_cable                  ;/executable's entrypoint)
 ;- - -
  mov     r1,0                                 ;\dummy und_handler
  ldr     r2,=0e1b0f00eh  ;=movs r15,r14       ; (just return from exception,
  str     r2,[r1,04h]  ;und_handler            ;/for normal cable-less mode)
  b       @@finish
 ;---
 @@tty_by_xboo_cable:
  swi     17h  ;GetPtrToFunc3addr()            ;\
  ldr     r1,=(tty_func3_handler AND 0ffffh)   ; init FUNC3 aka TTY handler
  strh    r1,[r0]                              ;/
  ldr     r1,=func3_info                       ;\
  mov     r0,0                             ;\  ; mark TTY as len=empty
  str     r0,[r1,4]        ;func3_buf_len  ;/  ; and
  add     r0,r1,0ch ;=func3_buffer         ;\  ; init func3 base
  str     r0,[r1,0]        ;func3_buf_base ;/  ;/
  mov     r1,0                                 ;\
  ldr     r2,=0e59ff018h  ;=ldr r15,[pc,NN]    ;
  str     r2,[r1,04h]  ;und_handler            ; special xboo und_handler
  add     r2,=tty_xboo_und_handler             ;
  str     r2,[r1,24h]  ;und_vector             ;/
 @@finish:
  swi     06h ;GetPtrToComFlags()              ;\
  ldr     r1,=ptr_to_comflags                  ; get ptr to ComFlags
  str     r0,[r1]                              ;/
  bx      lr
 ;------------------
 tty_xboo_und_handler:   ;in: r0=char
  ldr     r13,=func3_info ;aka sp_und          ;-base address (in sp_und)
  str     r12,[r13,8] ;func3_stack             ;-push r12
 @@wait_if_buffer_full:                        ;\
  ldr     r12,=ptr_to_comflags                 ; ;\exit if execute file request
  ldr     r12,[r12]  ;ptr to ComFlags          ; ; ComFlg.Bit11 ("bu_cmd_59h"),
  ldr     r12,[r12]  ;read ComFlags            ; ; ie. allow that flag to be
  tst     r12,1 shl 11  ;test bit11            ; ; processed by main program,
  bne     @@exit                               ; ;/without hanging here
  ldrb    r12,[r13,4] ;func3_buf_len           ; wait if buffer full
  cmp     r12,tty_bufsiz                       ; (until drained by FIQ)
  beq     @@wait_if_buffer_full                ;/
  mov     r12,1bh+0c0h  ;mode=und, FIQ/IRQ=off ;\disable FIQ (no COMMUNICATION
  mov     cpsr_ctl,r12                         ;/interrupt during buffer write)
  ldrb    r12,[r13,4]  ;func3_buf_len          ;\
  add     r12,1        ;raise len              ; write char to buffer
  strb    r12,[r13,4]  ;func3_buf_len          ; and raise buffer length
  add     r12,0ch-1    ;=func3_buffer+INDEX    ;
  strb    r0,[r13,r12] ;append char to buf     ;/
 @@exit:
  ldr     r12,[r13,8]  ;func3_stack            ;-pop r12
  movs    r15,r14        ;return from exception (and restore old IRQ/FIQ state)
 ;------------------
 tty_func3_handler:   ;in: r0=flags, r1=ptr
  tst     r0,10h  ;test if PRE/POST data (pre: Z, post: NZ)
 ;ldreq   r1,[r1]   ;read 32bit param (aka the four LEN1 bytes of FUNC3)
  ldr     r0,=func3_info   ;ptr to two 32bit values (FUNC3 return value)
  movne   r1,0                           ;\for POST data: mark buffer empty
  strne   r1,[r0,4] ;func3_buf_len=0     ;/
  bx      lr                             ;-for PRE data: return r0=func3_info
Usage: Call "init_tty" at the executable's entrypoint (with incoming R0 passed on). Call "tty_wrchr" to output ASCII characters.
Note: The TTY messages are supported only in no$gba debug version (not no$gba gaming version).


Serial Port (SIO)

1F801050h SIO_TX_DATA (W)
  0-7   Data to be sent
  8-31  Not used
Writing to this register starts transmit (if, or as soon as, TXEN=1 and CTS=on and SIO_STAT.2=Ready). Writing to this register while SIO_STAT.0=Busy causes the old value to be overwritten.
The "TXEN=1" condition is a bit more complex: Writing to SIO_TX_DATA latches the current TXEN value, and the transfer DOES start if the current TXEN value OR the latched TXEN value is set (ie. if TXEN gets cleared after writing to SIO_TX_DATA, then the transfer may STILL start if the old latched TXEN value was set; this appears for SIO transfers in Wipeout 2097).

1F801050h SIO_RX_DATA (R)
  0-7   Received Data      (1st RX FIFO entry) (oldest entry)
  8-15  Preview            (2nd RX FIFO entry)
  16-23 Preview            (3rd RX FIFO entry)
  24-31 Preview            (4th RX FIFO entry) (5th..8th cannot be previewed)
A data byte can be read when SIO_STAT.1=1. Data should be read only via 8bit memory access (the 16bit/32bit "preview" feature is rather unusable).

1F801054h SIO_STAT (R)
  0     TX Ready Flag 1   (1=Ready/Started)  (depends on CTS) (TX requires CTS)
  1     RX FIFO Not Empty (0=Empty, 1=Not Empty)
  2     TX Ready Flag 2   (1=Ready/Finished) (depends on TXEN and on CTS)
  3     RX Parity Error   (0=No, 1=Error; Wrong Parity, when enabled) (sticky)
  4     RX FIFO Overrun   (0=No, 1=Error; Received more than 8 bytes) (sticky)
  5     RX Bad Stop Bit   (0=No, 1=Error; Bad Stop Bit) (when RXEN)   (sticky)
  6     RX Input Level    (0=Normal, 1=Inverted) ;only AFTER receiving Stop Bit
  7     DSR Input Level   (0=Off, 1=On) (remote DTR) ;DSR not required to be on
  8     CTS Input Level   (0=Off, 1=On) (remote RTS) ;CTS required for TX
  9     Interrupt Request (0=None, 1=IRQ)                             (sticky)
  10    Unknown           (always zero)
  11-25 Baudrate Timer    (15bit timer, decrementing at 33MHz)
  26-31 Unknown (usually zero, sometimes all bits set)
Note: Bit0 gets cleared after sending the Startbit, Bit2 gets cleared after sending all bits up to including the Stopbit.

1F801058h SIO_MODE (R/W) (eg. 004Eh --> 8N1 with Factor=MUL16)
  0-1   Baudrate Reload Factor (1=MUL1, 2=MUL16, 3=MUL64) (or 0=STOP)
  2-3   Character Length       (0=5bits, 1=6bits, 2=7bits, 3=8bits)
  4     Parity Enable          (0=No, 1=Enable)
  5     Parity Type            (0=Even, 1=Odd) (seems to be vice-versa...?)
  6-7   Stop bit length        (0=Reserved/1bit, 1=1bit, 2=1.5bits, 3=2bits)
  8-15  Not used (always zero)

1F80105Ah SIO_CTRL (R/W)
  0     TX Enable (TXEN)  (0=Disable, 1=Enable, when CTS=On)
  1     DTR Output Level  (0=Off, 1=On)
  2     RX Enable (RXEN)  (0=Disable, 1=Enable)  ;Disable also clears RXFIFO
  3     TX Output Level   (0=Normal, 1=Inverted, during Inactivity & Stop bits)
  4     Acknowledge       (0=No change, 1=Reset SIO_STAT.Bits 3,4,5,9)      (W)
  5     RTS Output Level  (0=Off, 1=On)
  6     Reset             (0=No change, 1=Reset most SIO_registers to zero) (W)
  7     Unknown? (read/write-able when FACTOR non-zero) (otherwise always zero)
  8-9   RX Interrupt Mode    (0..3 = IRQ when RX FIFO contains 1,2,4,8 bytes)
  10    TX Interrupt Enable  (0=Disable, 1=Enable) ;when SIO_STAT.0-or-2 ;Ready
  11    RX Interrupt Enable  (0=Disable, 1=Enable) ;when N bytes in RX FIFO
  12    DSR Interrupt Enable (0=Disable, 1=Enable) ;when SIO_STAT.7  ;DSR=On
  13-15 Not used (always zero)

1F80105Ch SIO_MISC (R/W)
This is an internal register, which usually shouldn't be accessed by software. Messing with it has rather strange effects: After writing a value "X" to this register, reading returns "X ROR 8" eventually "ANDed with 1F1Fh and ORed with C0C0h or 8080h" (depending on the character length in SIO_MODE).

1F80105Eh SIO_BAUD (R/W) (eg. 00DCh --> 9600 bauds; when Factor=MUL16)
  0-15  Baudrate Reload value for decrementing Baudrate Timer
The Baudrate is calculated (based on SIO_BAUD, and on Factor in SIO_MODE):
  BitsPerSecond = (44100Hz*300h) / MIN(((Reload*Factor) AND NOT 1),Factor)

SIO_TX_DATA Notes
The hardware can hold (almost) 2 bytes in the TX direction (one being currently transferred, and, once when the start bit was sent, another byte can be stored in SIO_TX_DATA). When writing to SIO_TX_DATA, both SIO_STAT.0 and SIO_STAT.2 become zero. As soon as the transfer starts, SIO_STAT.0 becomes set (indicating that one can write a new byte to SIO_TX_DATA; although the transmission is still busy). As soon as the transfer of the most recently written byte ends, SIO_STAT.2 becomes set.

SIO_RX_DATA Notes
The hardware can hold 8 bytes in the RX direction (when receiving further byte(s) while the RX FIFO is full, then the last FIFO entry will by overwritten by the new byte, and SIO_STAT.4 gets set; the hardware does NOT automatically disable RTS when the FIFO becomes full).
Data can be read from SIO_RX_DATA when SIO_STAT.1 is set, that flag gets automatically cleared after reading from SIO_RX_DATA (unless there are still further bytes in the RX FIFO). Note: The hardware does always store incoming data in RX FIFO (even when Parity or Stop bits are invalid).
Note: A 16bit read allows to read two FIFO entries at once; nethertheless, it removes only ONE entry from the FIFO. On the contrary, a 32bit read DOES remove FOUR entries (although, there's nothing that'd indicate if the FIFO did actually contain four entries).
Reading from Empty RX FIFO returns either the most recently received byte or zero (the hardware stores incoming data in ALL unused FIFO entries; eg. if five entries are used, then the data gets stored thrice, after reading 6 bytes, the FIFO empty flag gets set, but nethertheless, the last byte can be read two more times, but doing further reads returns 00h).

Interrupt Acknowledge Notes
First reset I_STAT.8, then set SIO.CTRL.4 (when doing it vice-versa, the hardware may miss a new IRQ which may occur immediately after setting SIO.CTRL.4) (and I_STAT.8 is edge triggered, so that bit can be reset even while SIO_STAT.9 is still set).
When acknowledging via SIO_CTRL.4 with the enabled condition(s) in SIO_CTRL.10-12 still being true (eg. the RX FIFO is still not empty): the IRQ does trigger again (almost) immediately (it goes off only for a very short moment; barely enough to allow I_STAT.8 to sense a edge).

SIO_BAUD Notes
Timer reload occurs when writing to SIO_BAUD, and, automatically when the Baudrate Timer reaches zero. There should be two 16bit SIO timers (for TX and RX), the upper 15bit of one of that timers can be read from SIO_STAT (not sure which one, and no idea if there's a way to read the other timer, too).
Or... maybe there is only ONE timer, and RX/TX are separated only by separate "timer ellapsed" counters, in that case the MUL1 factor won't work properly, but, with the MUL16 or MUL64 factors, RX could start anytime (eg. when TX has already ellapsed a bunch of times)...?
The maximum baud rate may vary depending on the length and quality of the cable, whether and how many inverters and anti-inverters are used (on the mainboard and in external adaptor, and on whether signals are externally converted to +/-12V levels)... anyways, rates up to 9600 baud should be working in all cases.
However, running in no$psx, Wipeout 2097 seems to use about 2 million bauds... although, in older no$psx versions, I believe I did see it using some kind of baudrate detection, where it did try different rates in steps of 200 bauds or so...?

SIO Ports vs JOY Ports
SIO uses I/O Addresses 1F801050h..1F80105Fh, which seem to be organized similar to the Controller/Memory Card registers at 1F801040h..1F80104Fh, though not identical, and with an additional register at 1F80105Ch, which has no corresponding port at 1F80104Ch.
SIO_BAUD is <effectively> same as for JOY_BAUD, but, <internally> they are a bit different:
  JOY_BAUD is multiplied by Factor, and does then ellapse "2" times per bit.
  SIO_BAUD is NOT multiplied, and, instead, ellapses "2*Factor" times per bit.
Unlike for the Controller/Memory Card ports, the data is transferred without CLK signal, instead, it's using RS232 format, ie. the transfer starts with a start bit, and is then transferred at a specific baudrate (which must be configured identically at the receiver side). For RS232, data is usually 8bit, and may optionally end with a parity bit, and one or two stop bits.

Note
For SIO Pinouts, PSone SIO upgrading, and for building RS232 adaptors, see:
Pinouts - SIO Pinouts
Aside from the internal SIO port, the PSX BIOS supports two additional external serial ports, connected to the expansion port,
EXP2 Dual Serial Port (for TTY Debug Terminal)

SIO Games
The serial port is used (for 2-player link) by Wipeout 2097 (that game accidently assumes BAUDs based on 64*1024*1025 Hz rather than on 600h*44100 Hz).
Ridge Racer Revolution is also said to support 2P link.
Keitai Eddy seems to allow to connect a mobile phone to the SIO port (the games CD cover suggests so; this seems to be something different than the "normal" I-Mode adaptor, which would connect to controller port, not to SIO port).

8251A Note
The Playstation Serial Port is apparently based/inspired on the Intel 8251A USART chip; which has very similar 8bit Mode/Command/Status registers.


Expansion Port (PIO)

Expansion Port can contain ROM, RAM, I/O Ports, etc. For ROM, the first 256 bytes would contain the expansion ROM header.

For region 1, the CPU outputs a chip select signal (CPU Pin 98, /EXP).
For region 2, the CPU doesn't produce a chip select signal (the region is intended to contain multiple I/O ports, which do require an address decoder anyways, that address decoder could treat any /RD or /WR with A13=Hi and A23=Hi and A22=Lo as access to expansion region 2 (for /WR, A22 may be ignored; assuming that the BIOS is read-only).

Size/Bus-Width
The BIOS initalizes Expansion Region 1 to 512Kbyte with 8bit bus, and Region 2 to 128 bytes with 8bit bus. However, the size and data bus-width of these regions can be changed, see:
Memory Control
For Region 1, 32bit reads are supported even in 8bit mode (eg. 32bit opcode fetches are automatically processed as four 8bit reads).
For Region 2, only 8bit access seems to be supported (except that probably 16bit mode allows 16bit access), anyways, larger accesses seem to cause exceptions... not sure if that can be disabled...?

Expansion 1 - EXP1 - Intended to contain ROM
EXP1 Expansion ROM Header

Expansion 2 - EXP2 - Intended to contain I/O Ports
EXP2 Dual Serial Port (for TTY Debug Terminal)
EXP2 DTL-H2000 I/O Ports
EXP2 Post Registers
EXP2 Nocash Emulation Expansion

Expansion 3 - EXP3 - Intended to contain RAM
Not used by BIOS nor by any games. Seems to contain 1Mbyte RAM with 16bit databus (ie. 512Kx16) in DTL-H2000.

Other Expansions
Aside from the above, the Expansion regions can be used for whatever purpose, however, mind that the BIOS is reading from the ROM header region, and is writing to the POST register (so 1F000000h-1F0000FFh and 1F802041h should be used only if the hardware isn't disturbed by those accesses).

Missing Expansion Port
The expansion port is installed only on older PSX boards, newer PSX boards and all PSone boards don't have that port. However, the CPU should still output all expansion signals, and there should be big soldering points on the board, so it'd be easy to upgrade the console.

Latched Address Bus
Note that A0..A23 are latched outputs, so they can be used as general purpuse 24bit outputs, provided that the system bus isn't used for other purposes (such like /BIOS, /SPU, /CD accesses) (A0..A23 are not affected by Main RAM and GPU addressing, nor by internal I/O ports like Timer and IRQ registers).


EXP1 Expansion ROM Header

Expansion 1 - ROM Header (accessed with 8bit databus setting)
  Address  Size Content
  1F000000h 4   Post-Boot Entrypoint (eg. 1F000100h and up)
  1F000004h 2Ch Post-Boot ID ("Licensed by Sony Computer Entertainment Inc.")
  1F000030h 50h Post-Boot TTY Message (must contain at least one 00h byte)
  1F000080h 4   Pre-Boot Entrypoint  (eg. 1F000100h and up)
  1F000084h 2Ch Pre-Boot ID  ("Licensed by Sony Computer Entertainment Inc.")
  1F0000B0h 50h Not used     (should be zero, but may contain code/data/io)
  1F000100h ..  Code, Data, I/O Ports, etc.
The entrypoints are called if their corresonding ID strings are present, return address to BIOS is passed in R31, so the expansion ROM may return control to BIOS, if that should be desired.
Aside from verifying the IDs, the BIOS will also display the Post-Boot ID string (and the following message string) via TTY (done right before calling the Post-Boot Entrypoint).

Pre-Boot Function
The Pre-Boot function is called almost immediately after Reset, with only some Memory Control registers initialized, the BIOS function vectors at A0h, B0h, and C0h are NOT yet initialized, so the Pre-Boot function can't use them.

Post-Boot Function
The Post-Boot function gets called while showing the "PS" logo, but before loading the .EXE file. The BIOS function vectors at A0h, B0h, and C0h are already installed and can be used by the Post-Boot Function.
Note that the Post-Boot Function is called ONLY when the "PS" logo is shown (ie. not if the CDROM drive is empty, or if it contains an Audio CD).

Mid-Boot Hook
One common trick to hook the Kernel after BIOS initialization, but before CDROM loading is to use the Pre-Boot handler to set a COP0 opcode fetch hardware breakpoint at 80030000h (after returning from the Pre-Boot handler, the Kernel will initialize important things like A0h/B0h/C0h tables, and will then break again when starting the GUI code at 80030000h) (this trick is used by Action Replay v2.0 and up).

Note
Expansion ROMs are most commonly used in cheat devices,
Cheat Devices


EXP2 Dual Serial Port (for TTY Debug Terminal)

SCN2681 Dual Asynchronous Receiver/Transmitter (DUART)
The PSX/PSone retail BIOS contains some TTY Debug Terminal code; using an external SCN2681 chip which can be connected to the expansion port.
Whilst supported by all PSX/PSone retail BIOSes on software side, there aren't any known PSX consoles/devboards/expansions actually containing DUARTs on hardware side.

1F802023h/Read - RHRA - DUART Rx Holding Register A (FIFO) (R)
1F80202Bh/Read - RHRB - DUART Rx Holding Register B (FIFO) (R)
1F802023h/Write - THRA - DUART Tx Holding Register A (W)
1F80202Bh/Write - THRB - DUART Tx Holding Register B (W)
  7-0  Data (aka Character)
The hardware can hold max 2 Tx characters per channel (1 in the THR register, and one currently processed in the Tx Shift Register), and max 4 Rx characters (3 in the RHR FIFO, plus one in the Rx Shift Register) (when receiving a 5th character, the "old newest" value in the Rx Shift Register is lost, and the overrun flag is set).

1F802020h/FirstAccess - MR1A - DUART Mode Register 1.A (R/W)
1F802028h/FirstAccess - MR1B - DUART Mode Register 1.B (R/W)
  7    RxRTS Control       (0=No, 1=Yes)
  6    RxINT Select        (0=RxRDY, 1=FFULL)
  5    Error Mode          (0=Char, 1=Block)
  4-3  Parity Mode   (0=With Parity, 1=Force Parity, 2=No Parity, 3=Multidrop)
  2    Parity Type         (0=Even, 1=Odd)
  1-0  Bits per Character  (0=5bit, 1=6bit, 2=7bit, 3=8bit)
Note: In block error mode, block error conditions must be cleared by using the error reset command (command 4) or a receiver reset (command 2).

1F802020h/SecondAccess - MR2A - DUART Mode Register 2.A (R/W)
1F802028h/SecondAccess - MR2B - DUART Mode Register 2.B (R/W)
  7-6  Channel Mode       (0=Normal, 1=Auto-Echo, 2=Local loop, 3=Remote loop)
  5    TxRTS Control      (0=No, 1=Yes) (when 1 --> OP0=RTSA / OP1=RTSB)
  4    CTS Enable         (0=No, 1=Yes) (when 1 --> IP0=CTSA / IP1=CTSB)
  3-0  Tx Stop Bit Length (00h..0Fh = see below)
Stop Bit Lengths:
  0=0.563  1=0.625  2=0.688  3=0.750  4=0.813  5=0.875  6=0.938  7=1.000
  8=1.563  9=1.625  A=1.688  B=1.750  C=1.813  D=1.875  E=1.938  F=2.000
Add 0.5 to values shown for 0..7 if channel is programmed for 5 bits/char.

1F802021h/Write - CSRA - DUART Clock Select Register A (W)
1F802029h/Write - CSRB - DUART Clock Select Register B (W)
  7-4  Rx Clock Select  (0..0Ch=See Table, 0Dh=Timer, 0Eh=16xIP, 0Fh=1xIP)
  3-0  Tx Clock Select  (0..0Ch=See Table, 0Dh=Timer, 0Eh=16xIP, 0Fh=1xIP)
The 2681 has some sets of predefined baud rates (set1/set2 selected via ACR.7), additionally, in BRG Test Mode, set3/set4 are used instead of set1/set2), the baud rates for selections 00h..0Dh are:
  Rate 00h  01h 02h   03h   04h   05h   06h    07h  08h   09h  0Ah   0Bh  0Ch
  Set1 50   110 134.5 200   300   600   1200   1050 2400  4800 7200  9600 38400
  Set2 75   110 134.5 150   300   600   1200   2000 2400  4800 1800  9600 19200
  Set3 4800 880 1076  19200 28800 57600 115200 1050 57600 4800 57600 9600 38400
  Set4 7200 880 1076  14400 28800 57600 115200 2000 57600 4800 14400 9600 19200
Selection 0Eh/0Fh are using an external clock source (derived from IP3,IP4,IP5,IP6 pins; for TxA,RxA,TxB,RxB respectively).

1F802022h/Write - CRA - DUART Command Register A (W)
1F80202Ah/Write - CRB - DUART Command Register B (W)
  7    Not used    (should be 0)
  6-4  Miscellaneous Commands (0..7 = see below)
  3    Disable Tx  (0=No change, 1=Disable)
  2    Enable Tx   (0=No change, 1=Enable) ;Don't use with Command 3 (Reset Rx)
  1    Disable Rx  (0=No change, 1=Disable)
  0    Enable Rx   (0=No change, 1=Enable) ;Don't use with Command 2 (Reset Tx)
The command values for CRA (or CRB) are:
  0 No command          ;no effect
  1 Reset MR pointer    ;force "FirstAccess" state for MR1A (or MR1B) access
  2 Reset receiver      ;reset RxA (or RxB) registers, disable Rx, flush Fifo
  3 Reset transmitter   ;reset TxA (or TxB) registers
  4 Reset Error Flags           ;reset SRA.7-4 (or SRB.7-4) to zero
  5 Reset Break-Change IRQ Flag ;reset ISR.2 (or ISR.6) to zero
  6 Start break  ;after current char, pause Tx with TxDA=Low (or TxDB=Low)
  7 Stop break   ;output one High bit, then continue Tx (ie. undo pause)
Access to the upper four bits of the command register should be separated by 3 edges of the X1 clock. A disabled transmitter cannot be loaded.

1F802025h/Read - ISR - DUART Interrupt Status Register (R)
1F802025h/Write - IMR - DUART Interrupt Mask Register (W)
  7    Input Port Change   (0=No, 1=Yes) (Ack via reading IPCR) ;see ACR.3-0
  6    Break Change B      (0=No, 1=Yes) (Ack via CRB/Command5)
  5    RxRDYB/FFULLB       (0=No, 1=Yes) (Ack via reading data) ;see MR1B.6
  4    THRB Empty (TxRDYB) (0=No, 1=Yes) (Ack via writing data) ;same as SRB.2
  3    Counter Ready       (0=No, 1=Yes) (Ack via CT_STOP)
  2    Break Change A      (0=No, 1=Yes) (Ack via CRA/Command5)
  1    RxRDYA/FFULLA       (0=No, 1=Yes) (Ack via reading data) ;see MR1A.6
  0    THRA Empty (TxRDYA) (0=No, 1=Yes) (Ack via writing data) ;same as SRA.2

1F802021h/Read - SRA - DUART Status Register A (R)
1F802029h/Read - SRB - DUART Status Register B (R)
  7    Rx Received Break*        (0=No, 1=Yes) ;received 00h without stop bit
  6    Rx Framing Error*         (0=No, 1=Yes) ;received data without stop bit
  5    Rx Parity Error*          (0=No, 1=Yes) ;received data with bad parity
  4    Rx Overrun Error          (0=No, 1=Yes) ;Rx FIFO full + RxShiftReg full
  3    Tx Underrun  (TxEMT)      (0=No, 1=Yes) ;both TxShiftReg and THR empty
  2    Tx THR Empty (TxRDY)      (0=No, 1=Yes) ;same as ISR.0 / ISR.4
  1    Rx FIFO Full (FFULL)      (0=No, 1=Yes) ;set upon 3 or more characters
  0    Rx FIFO Not Empty (RxRDY) (0=No, 1=Yes) ;set upon 1 or more characters
Bit7-5 are appended to the corresponding data character in the receive FIFO. A read of the status provides these bits (7:5) from the top of the FIFO together with bits (4:0). These bits are cleared by a "reset error status" command. In character mode they are discarded when the corresponding data character is read from the FIFO. In block error mode, block error conditions must be cleared by using the error reset command (command 4x) or a receiver reset.

1F802024h/Write - ACR - DUART Aux. Control Register (W)
  7    Select Baud Rate Generator (BRG) Set   (0=Set1/Set3, 1=Set2/Set4)
  6-4  Counter/Timer Mode and Source          (see below)
  3-0  IP3..IP0 Change Interrupt Enable Flags (0=Off, 1=On)
Counter/Timer Mode and Clock Source Settings:
  Num  Mode      Clock Source
  0h   Counter   External (IP2)
  1h   Counter   TxCA - 1x clock of Channel A transmitter
  2h   Counter   TxCB - 1x clock of Channel B transmitter
  3h   Counter   Crystal or external clock (x1/CLK) divided by 16
  4h   Timer     External (IP2)
  5h   Timer     External (IP2) divided by 16
  6h   Timer     Crystal or external clock (x1/CLK)
  7h   Timer     Crystal or external clock (x1/CLK) divided by 16
In Counter Mode, the Counter Ready flag is set on any underflow, and the counter wraps to FFFFh and keeps running (but may get stopped by software).
In Timer Mode, automatic reload occurs on any underflow, the counter flag (which can be output to OP3) is toggled on any underflow, but the Counter Ready flag is set only on each 2nd underflow (unlike as in Counter mode).

1F802024h/Read - IPCR - DUART Input Port Change Register (R)
  7-4  IP3..IP0 Change Occured Flags (0=No, 1=Yes)    ;auto reset after read
  3-0  Current IP3-IP0 Input states  (0=Low, 1=High)  ;Same as IP.3-0
Reading from this register automatically resets IPCR.7-4 and ISR.7.

1F80202Dh/Read - IP - DUART Input Port (R)
  7    Not used (always 1)
  6-0  Current IP6-IP0 Input states (0=Low, 1=High)  ;LSBs = Same as IPCR.3-0
IP0-6 can be used as general purpose inputs, or for following special purposes:
  IP6 External RxB Clock     ;see CSRB.7-4
  IP5 External TxB Clock     ;see CSRB.3-0
  IP4 External RxA Clock     ;see CSRA.7-4
  IP3 External TxA Clock     ;see CSRA.3-0
  IP2 External Timer Input   ;see AUX.6-4
  IP1 Clear to Send B (CTSB) ;see MR2B.5
  IP0 Clear to Send A (CTSA) ;see MR2A.5
Note: The 24pin chip doesn't have any inputs, the 28pin chip has only one input (IP2), the 40pin/44pin chips have seven inputs (IP0-IP6).

1F80202Eh/Write - DUART Set Output Port Bits Command (Set means Out=LOW)
1F80202Fh/Write - DUART Reset Output Port Bits Command (Reset means Out=HIGH)
  7-0  Change "OPR" OP7-OP0 Output states (0=No change, 1=Set/Reset)
Note: The 24pin chip doesn't have any outputs, the 28pin chip has only two outputs (OP0,OP1), the 40pin/44pin chips have eight outputs (OP0-OP7).

1F80202Dh/Write - OPCR - DUART Output Port Configuration Register (W)
  7    OP7      (0=OPR.7, 1=TxRDYB)
  6    OP6      (0=OPR.6, 1=TxRDYA)
  5    OP5      (0=OPR.5, 1=RxRDY/FFULLB)
  4    OP4      (0=OPR.4, 1=RxRDY/FFULLA)
  3-2  OP3      (0=OPR.3, 1=Clock/Timer Output, 2=TxCB(1x), 3=RxCB(1x))
  1-0  OP2      (0=OPR.2, 1=TxCA(16x), 2=TxCA(1x), 3=RxCA(1x))
Additionally, the OP0 and OP1 outputs are controlled via MR2A.5 and MR2B.5.

1F802022h/Read - - DUART Toggle Baud Rate Generator Test Mode (Read=Strobe)
1F80202Ah/Read - - DUART Toggle 1X/16X Test Mode (Read=Strobe)
  7-0  Not used (just issue a dummy-read to toggle the test mode on/off)
BGR Test switches between Baud Rate Set1/Set2 and Set3/Set4.
1X/16X Test switches between whatever...?

1F80202Eh/Read - CT_START - DUART Start Counter Command (Read=Strobe)
1F80202Fh/Read - CT_STOP - DUART Stop Counter Command (Read=Strobe)
  7-0  Not used (just issue a dummy-read to strobe start/stop command)
Start: Forces reload (copies CTLR/CTUR to CTL/CTU), and starts the timer.
Stop-in-Counter-Mode: Resets ISR.3, and stops the timer.
Stop-in-Timer-Mode: Resets ISR.3, but doesn't stop the timer.

1F802026h/Read - CTU - DUART Counter/Timer Current Value, Upper/Bit15-8 (R)
1F802027h/Read - CTL - DUART Counter/Timer Current Value, Lower/Bit7-0 (R)
1F802026h/Write - CTUR - DUART Counter/Timer Reload Value, Upper/Bit15-8 (W)
1F802027h/Write - CTLR - DUART Counter/Timer Reload Value, Lower/Bit7-0 (W)
The CTLR/CTUR reload value is copied to CTL/CTU upon Start Counter Command. In Timer mode (not in Counter mode), it is additionally copied automatically when the timer undeflows.

1F80202Ch - N/A - DUART Reserved Register (neither R nor W)
Reserved.

Chip versions
The SCN2681 is manufactured with 24..44 pins, the differences are:
  24pin basic cut-down version          ;without IP0-1/OP0-1 = without CTS/RTS
  28pin additional IP2,OP0,OP1,X2       ;without IP0-1 = without CTS
  40pin additional IP0-IP6,OP0-OP7,X2   ;full version
  44pin same as 40pin with four NC pins ;full version (SMD)
Unknown which of them is supposed to be used with the PSX?
Note: The Motorola 68681 should be the same as the Philips/Signetics 2681.

Notes
Unknown if the Interrupt signal is connected to the PSX... there seems to be no spare IRQ for it, though it <might> share an IRQ with whatever other hardware...?
The BIOS seems to use only one of the two channels; for the std_io functions:
BIOS TTY Console (std_io)
Aside from the external DUART, the PSX additionally contains an internal UART,
Serial Port (SIO)
The DTL-H2000 devboard uses a non-serial "ATCONS" channel for TTY stuff,
EXP2 DTL-H2000 I/O Ports


EXP2 DTL-H2000 I/O Ports

The DTL-H2000 contains extended 8Mbyte Main RAM (instead of normal 2Mbyte), plus additional 1MByte RAM in Expansion Area at 1FA00000h, plus some I/O ports at 1F8020xxh:

1F802000h - DTL-H2000: EXP2: - ATCONS STAT (R)
  0    Unknown, used for something
  1    Unknown/unused
  2    Unknown, used for something
  3    TTY/Atcons TX Ready     (0=Busy, 1=Ready)
  4    TTY/Atcons RX Available (0=None, 1=Yes)
  5-7  Unknown/unused

1F802002h - DTL-H2000: EXP2: - ATCONS DATA (R and W)
  0-7  TTY/Atcons RX/TX Data
TTY channel for message output (TX) and debug console keyboard input (RX). The DTL-H2000 is using this "ATCONS" stuff instead of the DUART stuff used in retail console BIOSes ("CONS" seems to refer to "Console", and "AT" might refer to PC/AT or whatever).

1F802004h - DTL-H2000: EXP2: - 16bit - ?
  0-15 Data...?

1F802030h - DTL-H2000: Secondary IRQ10 Controller (IRQ Flags)
This register does expand IRQ10 (Lightgun) to more than one IRQ source. The register contains only Secondary IRQ Flags (there seem to be no Secondary IRQ Enable bits; at least not for Lightguns).
  0     ... used for something
  1    Lightgun IRQ (write: 0=No change, 1=Acknowledge) (read: 0=None, 1=IRQ)
  2-3  Unknown/unused (write: 0=Normal)
  4     ... acknowledged at 1FA00B04h, otherwise unused
  5     ... TTY RX ?
  6-7  Unknown/unused (write: 0=Normal)
  8-31 Not used by DTL-H2000 BIOS (but Lightgun games write 0 to these bits)
Retail games that support IRQ10-based "Konami" Lightguns are containing code for detecting and accessing port 1F802030h. The detection works by examining a value in the BIOS ROM like so:
  IF [BFC00104h]=00002000h then Port 1F802030h does exist     (DTL-H2000)
  IF [BFC00104h]=00002500h then Port 1F802030h does NOT exist
  IF [BFC00104h]=00000003h then Port 1F802030h does NOT exist (default)
  IF [BFC00104h]= <other>  then Port 1F802030h does NOT exist
Normal consoles don't include Port 1F802030h, and IRQ10 is wired directly to the controller port, and the value at [BFC00104h] is always 00000003h. Accordingly, one cannot upgrade the console just by plugging a Secondary IRQ10 controller to the expansion port (instead, one would need to insert the controller between the CPU and controller plug, and to install a BIOS with [BFC00104h]=00002000h).
The DTL-H2000 BIOS accesses 1F802030h with 8bit load/store opcodes, however, the Lightgun games use 32bit load/store - which is theoretically overlapping port 1F802032h, though maybe the memory system does ignore the upper bits.

1F802032h - DTL-H2000: EXP2: - maybe IRQ enable?
  0    Used for something (CLEARED on some occassions)
  1-3  Unknown/unused
  4    Used for something (SET on some occassions)
  5-7  Unknown/unused

1F802040h - DTL-H2000: EXP2: 1-byte - DIP Switch?
  0-7  DIP Value (00h..FFh, but should be usually 00h..02h)
This register selects the DTL-H2000 boot mode, for whatever reason it's called "DIP Switch" register, although the DTL-H2000 boards don't seem to contain any such DIP Switches (instead, it's probably configured via some I/O ports on PC side). Possible values are:
  DIP=0 --> .. long delay before TTY?   with "PSX>" prompt, throws CDROM cmds
  DIP=1 --> .. long delay before TTY?   no "PSX>" prompt           PSY-Q?
  DIP=2 --> .. instant TTY?             with "PSX>" prompt
  DIP=3 --> Lockup
  DIP=04h..FFh --> Lockup with POST=04h..FFh

1F802042h - DTL-H2000: EXP2: POST/LED (R/W)
EXP2 Post Registers


EXP2 Post Registers

1F802041h - POST - External 7-segment Display (W)
  0-3  Current Boot Status (00h..0Fh)
  4-7  Not used by BIOS    (always set to 0)
During boot, the BIOS writes incrementing values to this register, allowing to display the current boot status on an external 7 segment display (much the same as Port 80h used in PC BIOSes).

1F802042h - DTL-H2000: EXP2: POST/LED (R/W)
  0-7 Post/LED value
8bit wide, otherwise same as POST 1F802041h on retail consoles.

1F802070h - POST2 - Unknown? (W) - PS2
Might be a configuration port, or it's another POST register (which is used prior to writing the normal POST bytes to 1FA00000h).
The first write to 1F802070h is 32bit, all further writes seem to be 8bit.

1FA00000h - POST3 - External 7-segment Display (W) - PS2
Similar to POST, but PS2 BIOS uses this address.


EXP2 Nocash Emulation Expansion

1F802060h Emu-Expansion ID1 "E" (R)
1F802061h Emu-Expansion ID2 "X" (R)
1F802062h Emu-Expansion ID3 "P" (R)
1F802063h Emu-Expansion Version (01h) (R)
Contains ID and Version.

1F802064h Emu-Expansion Enable1 "O" (R/W)
1F802065h Emu-Expansion Enable2 "N" (R/W)
Activates the Halt and Turbo Registers (when set to "ON").

1F802066h Emu-Expansion Halt (R)
When enabled (see above), doing an 8bit read from this address stops the CPU emulation unless/until an Interrupt occurs (when "CAUSE AND SR AND FF00h" becomes nonzero). Can be used to reduce power consumption, and to make the emulation faster.

1F802067h Emu-Expansion Turbo Mode Flags (R/W)
When enabled (see above), writing to this register activates/deactivates "turbo" mode, which is causing new data to arrive immediately after acknowledging the previous interrupt.
  0   CDROM Turbo       (0=Normal, 1=Turbo)
  1   Memory Card Turbo (0=Normal, 1=Turbo)
  2   Controller Turbo  (0=Normal, 1=Turbo)
  3-6 Reserved (must be zero)
  7   VRAM Viewer       (0=Normal, 1=Disable Swap Buffers; for testing)


Memory Control

The Memory Control registers are initialized by the BIOS, and, normally software doesn't need to change that settings. Some registers are useful for expansion hardware (allowing to increase the memory size and bus width).

1F801000h - Expansion 1 Base Address (usually 1F000000h)
1F801004h - Expansion 2 Base Address (usually 1F802000h)
  0-23   Base Address   (Read/Write)
  24-31  Fixed          (Read only, always 1Fh)
For Exansion 1, the address is forcefully aligned to the selected expansion size (see below), ie. if the size is bigger than 1 byte, then the lower bit(s) of the base address are ignored.
For Expansion 2, trying to use ANY other value than 1F802000h seems to disable the Expansion 2 region, rather than mapping it to the specified address (ie. Port 1F801004h doesn't seem to work).
For Expansion 3, the address seems to be fixed (1FA00000h).

1F801008h - Expansion 1 Delay/Size (usually 0013243Fh) (512Kbytes, 8bit bus)
1F80100Ch - Expansion 3 Delay/Size (usually 00003022h) (1 byte)
1F801010h - BIOS ROM Delay/Size (usually 0013243Fh) (512Kbytes, 8bit bus)
1F801014h - SPU Delay/Size (200931E1h) (use 220931E1h for SPU-RAM reads)
1F801018h - CDROM Delay/Size (00020843h or 00020943h)
1F80101Ch - Expansion 2 Delay/Size (usually 00070777h) (128 bytes, 8bit bus)
  0-3   Unknown (R/W)
  4-7   Access Time        (00h..0Fh=00h..0Fh Cycles)
  8     Use COM0 Time      (0=No, 1=Yes, add to Access Time)
  9     Use COM1 Time      (0=No, 1=Probably Yes, but has no effect?)
  10    Use COM2 Time      (0=No, 1=Yes, add to Access Time)
  11    Use COM3 Time      (0=No, 1=Yes, clip to MIN=(COM3+6) or so?)
  12    Data Bus-width     (0=8bit, 1=16bit)
  13-15 Unknown (R/W)
  16-20 Memory Window Size (1 SHL N bytes) (0..1Fh = 1 byte ... 2 gigabytes)
  21-23 Unknown (always zero)
  24-27 Unknown (R/W) ;must be non-zero for SPU-RAM reads
  28    Unknown (always zero)
  29    Unknown (R/W)
  30    Unknown (always zero)
  31    Unknown (R/W) (Port 1F801008h only; always zero for other ports)
Trying to access addresses that exceed the selected size causes an exception. Maximum size would be Expansion 1 = 17h (8MB), BIOS = 16h (4MB), Expansion 2 = 0Dh (8KB), Expansion 3 = 15h (2MB). Trying to select larger sizes would overlap the internal I/O ports, and crash the PSX. The Size bits seem to be ignored for SPU/CDROM. The SPU timings seem to be applied for both the 200h-byte SPU region at 1F801C00h and for the 200h-byte unknown region at 1F801E00h.

1F801020h - COM_DELAY / COMMON_DELAY (00031125h or 0000132Ch or 00001325h)
  0-3   COM0 - Offset A   ;used for SPU/EXP2 (and for adjusted CDROM timings)
  4-7   COM1 - No effect? ;used for EXP2
  8-11  COM2 - Offset B   ;used for BIOS/EXP1/EXP2
  12-15 COM3 - Min Value  ;used for CDROM
  16-17 COM? - Unknown    ;used for whatever
  18-31 Unknown/unused (read: always 0000h)
This register contains clock cycle offsets that can be added to the Access Time values in Port 1F801008h..1Ch. Works (somehow) like so:
  1ST=0, SEQ=0, MIN=0
  IF Use_COM0 THEN 1ST=1ST+COM0-1, SEQ=SEQ+COM0-1
  IF Use_COM2 THEN 1ST=1ST+COM2,   SEQ=SEQ+COM2
  IF Use_COM3 THEN MIN=COM3
  IF 1ST<6 THEN 1ST=1ST+1   ;(somewhat like so)
  1ST=1ST+AccessTime+2, SEQ=SEQ+AccessTime+2
  IF 1ST<(MIN+6) THEN 1ST=(MIN+6)
  IF SEQ<(MIN+2) THEN SEQ=(MIN+2)
The total access time is the sum of First Access, plus any Sequential Access(es), eg. for a 32bit access with 8bit bus: Total=1ST+SEQ+SEQ+SEQ.
If the access is done from code in (uncached) RAM, then 0..4 cycles are added to the Total value (the exact number seems to vary depending on the used COMx values or so).
And the purpose... probably allows to define the length of the chipselect signals, and of gaps between that signals...?

1F801060h - RAM_SIZE (R/W) (usually 00000B88h) (or 00000888h)
  0-2   Unknown (no effect)
  3     Crashes when zero (except PU-7 and EARLY-PU-8, which <do> use bit3=0)
  4-6   Unknown (no effect)
  7     Delay on simultaneous CODE+DATA fetch from RAM (0=None, 1=One Cycle)
  8     Unknown (no effect) (should be set for 8MB, cleared for 2MB)
  9-11  Define 8MB Memory Window (first 8MB of KUSEG,KSEG0,KSEG1)
  12-15 Unknown (no effect)
  16-31 Unknown (Garbage)
Possible values for Bit9-11 are:
  0 = 1MB Memory + 7MB Locked
  1 = 4MB Memory + 4MB Locked
  2 = 1MB Memory + 1MB HighZ + 6MB Locked
  3 = 4MB Memory + 4MB HighZ
  4 = 2MB Memory + 6MB Locked              ;<--- would be correct for PSX
  5 = 8MB Memory                           ;<--- default by BIOS init
  6 = 2MB Memory + 2MB HighZ + 4MB Locked     ;<-- HighZ = Second /RAS
  7 = 8MB Memory
The BIOS initializes this to setting 5 (8MB) (ie. the 2MB RAM repated 4 times), although the "correct" would be setting 4 (2MB, plus other 6MB Locked). The remaining memory, after the first 8MB, and up to the Expansion/IO/BIOS region seems to be always Locked.
The HighZ regions are FFh-filled, that even when grounding data lines on the system bus (ie. it is NOT a mirror of the PIO expansion region).
Locked means that the CPU generates an exception when accessing that area.
Note: Wipeout uses a BIOS function that changes RAM_SIZE to 00000888h (ie. with corrected size of 2MB, and with the unknown Bit8 cleared). Gundam Battle Assault 2 does actually use the "8MB" space (with stacktop in mirrored RAM at 807FFFxxh).
Clearing bit7 causes many games to hang during CDROM loading on both EARLY-PU-8 and LATE-PU-8 (but works on PU-18 through PM-41).

FFFE0130h Cache Control (R/W)
  0-2   Unknown (Read/Write)                                            (R/W)
  3     Scratchpad Enable 1 (0=Disable, 1=Enable when Bit7 is set, too) (R/W)
  4-5   Unknown (Read/Write)                                            (R/W)
  6     Unknown (read=always zero)                  (R) or (W) or unused..?
  7     Scratchpad Enable 2 (0=Disable, 1=Enable when Bit3 is set, too) (R/W)
  8     Unknown                                                         (R/W)
  9     Crash (0=Normal, 1=Crash if code-cache enabled)                 (R/W)
  10    Unknown (read=always zero)                  (R) or (W) or unused..?
  11    Code-Cache Enable (0=Disable, 1=Enable)                         (R/W)
  12-31 Unknown                                                         (R/W)
Used by BIOS to initialize cache (in combination with COP0), like so:
 Init Cache Step 1:
  [FFFE0130h]=00000804h, then set cop0_sr=00010000h, then
  zerofill each FOURTH word at [0000..0FFFh], then set cop0_sr=zero.
 Init Cache Step 2:
  [FFFE0130h]=00000800h, then set cop0_sr=00010000h, then
  zerofill ALL words at [0000h..0FFFh], then set cop0_sr=zero.
 Finish Initialization:
  read 8 times 32bit from [A0000000h], then set [FFFE0130h]=0001E988h
Note: FFFE0130h is described in LSI's "L64360" datasheet, chapter 14 (and probably also in their LR33300/LR33310 datasheet, if it were available in internet).
  0     LOCK   Lock Mode
  1     INV    Invalidate Mode
  2     TAG    Tag Test Mode
  3     RAM    Scratchpad RAM
  4-5   DBLKSZ D-Cache Refill Size
  6     0      Zero
  7     DS     D-Cache Enable
  8-9   IBLKSZ I-Cache Refill Size (IS USED, crashes when bit9=1)
  10    IS0    I-Cache Set 0 (unused? should be 0)
  11    IS1    I-Cache Set 1 IRAM Enable (aka code cache)
  12    INTP   Interrupt Polarity (unused? should be 0)
  13    RDPRI  Read Priority
  14    NOPAD  No Waitstate
  15    BGNT   Bus Grant (unused? should be 0)
  16    LDSCH  Load Scheduling (1=Enable)
  17    NOSTR  No Streaming (unused? should be 0)
  18-31 R      Reserved (should be 0)


Unpredictable Things

Normally, I/O ports should be accessed only at their corresponding size (ie. 16bit read/write for 16bit ports), and of course, only existing memory and I/O addresses should be used. When not recursing that rules, some more or less (un-)predictable things may happen...

I/O Write Datasize
  Address               Content         W.8bit  W.16bit W.32bit
  00000000h-00xFFFFFh   Main RAM        OK      OK      OK
  1F800000h-1F8003FFh   Scratchpad      OK      OK      OK
  1F801000h-1F801023h   MEMCTRL         (w32)   (w32)   OK
  1F80104xh             JOY_xxx         (w16)   OK      CROP
  1F80105xh             SIO_xxx         (w16)   OK      CROP
  1F801060h-1F801063h   RAM_SIZE        (w32)   (w32)   OK        (with crash)
  1F801070h-1F801077h   IRQCTRL         (w32)   (w32)   OK
  1F8010x0h-1F8010x3h   DMAx.ADDR       (w32)   (w32)   OK
  1F8010x4h-1F8010x7h   DMAx.LEN        OK      OK      OK
  1F8010x8h-1F8010xFh   DMAx.CTRL/MIRR  (w32)   (w32)   OK
  1F8010F0h-1F8010F7h   DMA.DPCR/DICR   (w32)   (w32)   OK
  1F8010F8h-1F8010FFh   DMA.unknown     IGNORE  IGNORE  IGNORE
  1F801100h-1F80110Bh   Timer 0         (w32)   (w32)   OK
  1F801110h-1F80111Bh   Timer 1         (w32)   (w32)   OK
  1F801120h-1F80112Bh   Timer 2         (w32)   (w32)   OK
  1F801800h-1F801803h   CDROM           OK      ?       ?
  1F801810h-1F801813h   GPU.GP0         ?       ?       OK
  1F801814h-1F801817h   GPU.GP1         ?       ?       OK
  1F801820h-1F801823h   MDEC.CMD/DTA    ?       ?       OK
  1F801824h-1F801827h   MDEC.CTRL       ?       ?       OK
  1F801C00h-1F801E7Fh   SPU             (i16)   OK      LOSSY
  1F801E80h-1F801FFFh   SPU.UNUSED      IGNORE  IGNORE  IGNORE
  1F802020h-1F80202Fh   DUART           OK      ?       ?
  1F802041h             POST            OK      ?       ?
  FFFE0130h-FFFE0133h   CACHE.CTRL      (i32)   (i32)   OK
Whereas,
  OK    works
  LOSSY works often, but may leave lower 16bit unchanged at 1:8 chance
  (w32) write full 32bits (left-shifted if address isn't word-aligned)
  (w16) write full 16bits (left-shifted if address isn't halfword-aligned)
  (i32) write full 32bits (ignored if address isn't word-aligned)
  (i16) write full 16bits (ignored if address isn't halfword-aligned)
  CROP  write only lower 16bit (and leave upper 16bit unchanged)
It's somewhat "legit" to use 16bit writes on 16bit registers like RAM_SIZE, I_STAT, I_MASK, and Timer 0-2.
Non-4-byte aligned 8bit/16bit writes to RAM_SIZE do crash (probably because the "(w32)" effect is left-shifting the value, so lower 8bit become zero).
Results on unaligned I/O port writes (via SWL/SWR opcodes) are unknown.

I/O Read Datasize
In most cases, I/O ports can be read in 8bit, 16bit, or 32bit units, regardless of their size, among others allowing to read two 16bit ports at once with a single 32bit read. If there's only one 16bit port within a 32bit region, then 32bit reads often return garbage in the unused 16bits. Also, 8bit or 16bit VRAM data reads via GPUREAD probably won't work? Expansion 2 Region can be accessed only via 8bit reads, and 16bit/32bit reads seem to cause exceptions (or rather: no such exception!) (except, probably 16bit reads are allowed when the region is configured to 16bit databus width).
There are at least some special cases:
  FFFE0130h-FFFE0133h  8bit (+16bit?) read works ONLY from word-aligned address

Cache Problems
The functionality of the Cache is still widely unknown. Not sure if DMA transfers are updating or invalidating cache. Cached Data within KSEG0 should be automatically also cached at the corresponding mirrored address in KUSEG and vice versa. Mirrors within KSEG1 (or within KUSEG) may be a different thing, eg. when using addresses spead across the first 8MB region to access the 2MB RAM. Same problems may occor for Expansion and BIOS mirrors, although, not sure if that regions are cached.

Writebuffer Problems
The writebuffer seems to be disabled for the normal I/O area at 1F801000h, however, it appears to be enabled for the Expansion I/O region at 1F802000h (after writing to 1F802041h, the BIOS issues 4 dummy writes to RAM, apparently (?) in order to flush the writebuffer). The same might apply for Expansion Memory region at 1F000000h, although usually that region would contain ROM, so it'd be don't care whether it is write-buffered or not.

CPU Load/Store Problems
XXcpuREG ---> applies ONLY to LOAD (not to store)
Memory read/write opcodes take a 1-cycle delay until the data arrives at the destination, ie. the next opcode should not use the destination register (or more unlikely, the destination memory location) as source operand. Usually, when trying to do so, the second opcode would receive the OLD value - however, if an exception occurs between the two opcodes, then the read/write operation may finish, and the second opcode would probably receive the NEW value.

CPU Register Problems - R1 (AT), R26 (K0), R29 (SP)
Exception handlers cannot preserve all registers, before returning, they must load the return address into a general purpose register (conventionally R26 aka K0), so be careful not to use that register, unless you are 100% sure that no interrupts and no other exceptions can occur. Some exception handlers might also destroy R27 aka K1 (though execption handler in the PSX Kernel leaves that register unchanged).
Some assemblers (not a22i in nocash syntax mode) are internally using R1 aka AT as scratch register for some pseudo opcodes, including for a "sw rx,imm32" pseudo opcode (which is nearly impossible to separate from the normal "sw rx,imm16" opcode), be careful not to use R1, unless you can trust your assembler not to destroy that register behind your back.
The PSX Kernel uses "Full-Decrementing-Wasted-Stack", where "Wasted" means that when calling a sub-function with N parameters, then the caller must pre-allocate N works on stack, and the sub-function may freely use and destroy these words; at [SP+0..N*4-1].

Locked Locations in Memory and I/O Area
  00800000h           ;-when Main RAM configured to end at 7FFFFFh
  1F080000h 780000h   ;-when Expansion 1 configured to end at 7FFFFh
  1F800400h C00h      ;-region after Scratchpad
  1F801024h 1Ch       ;\
  1F801064h 0Ch       ;
  1F801078h 08h       ;
  1F801140h 6C0h      ; gaps in I/O region
  1F801804h 0Ch       ;
  1F801818h 08h       ;
  1F801828h 3D8h      ;/
  1F802080h 3FDF80h   ;-when Expansion 2 configured to end at 7Fh
  1FC80000h 60380000h ;-when BIOS ROM configured to end at 7FFFFh
  C0000000h 1FFE0000h ;\
  FFFE0020h E0h       ; gaps in KSEG2 (cache control region)
  FFFE0140h 1FEC0h    ;/
Trying to access these locations generates an exception. For KSEG0 and KSEG1, locked regions are same as for first 512MB of KUSEG.
BUG: The PSX hardware doesn't immediately trigger those memory exceptions, the CPU seems to keep executing the next 1-3 opcodes before triggering the exception (that is, EPC won't point to the opcode that has caused the memory error). This effect depends on whether CODE cache is enabled, and if it's enabled it does also depend on the opcode location (within 10h-byte aligned windows), and it does (?) also seem to depend on whether the next opcodes use the result from faulty memory load opcodes.

Mirrors in I/O Area
  1F80108Ch+N*10h - D#_CHCR Mirrors - (N=0..6, for DMA channel 0..6)
Read/writeable mirrors of DMA Control registers at 1F801088h+N*10h.

Garbage Locations in I/O Area
  1F801062h (2 bytes)  ;\
  1F801072h (2 bytes)  ; unused addresses in Memory and Interrupt Control area
  1F801076h (2 bytes)  ;/
  1F801102h (2 bytes)  ;\
  1F801106h (2 bytes)  ; unused addresses in Timer 0 area
  1F80110Ah (6 bytes)  ;/
  1F801112h (2 bytes)  ;\
  1F801116h (2 bytes)  ; unused addresses in Timer 1 area
  1F80111Ah (6 bytes)  ;/
  1F801122h (2 bytes)  ;\
  1F801126h (2 bytes)  ; unused addresses in Timer 2 area and next some bytes
  1F80112Ah (6 bytes)  ;
  1F801130h (16 bytes) ;/
  1F801820h (4 bytes)  ;-read MDEC Data-Out port (if there is no data)
  FFFE0000h (32 bytes) ;\
  FFFE0100h (48 bytes) ; unused addresses in Cache control area
  FFFE0132h (2 bytes)  ; (including write-only upper 16bit of Port FFFE0130h)
  FFFE0134h (12 bytes) ;/
Unlike all other unused I/O addresses, these addresses are unlocked (ie. they do not trigger exceptions on access), however they do not seem to contain anything useful. The BIOS never seems to use them. Writing any values to them seems to have no effect. And reading acts somewhat unstable:
Usually returns zeros in most cases. Except that, the first byte on a 10h-byte boundary often returns the lower 8bit of the memory address (eg. [FFFE0010h]=10h). And, if Code-Cache is disabled via [FFFE0130h].Bit11=0, then reading from these registers does return the 32bit opcode that is to be executed next (or at some locations, the opcode thereafter).
Note: Gran Turismo 2 (MagDemo27: GT2\*) reads 16bit from 1F801130h for generating a random seed (the game seems to think that there are four (not three) hardware timers at 1F8011x0h).

PSX as Abbreviation for Playstation 1
In gaming and programming scene, "PSX" is most commonly used as abbreviation for the original Playstation series (occasionally including PSone). Sony has never officially used that abbreviation, however, the Playstation BIOS contains the ASCII strings "PSX" and "PS-X" here and there. The letters "PS" are widely believed to stand for PlayStation, and the meaning of the "X" is totally unknown (although, actually it may stand for POSIX.1, see below).

PSX as Abbreviation for POSIX.1
According to JMI Software Systems, "PSX" is a trademark of themselves, and stands for "single-user, single-group, subset of POSIX.1" (POSIX stands for something commonly used by HLL programmers under UNIX or so). That "PSX" kernel from JMI is available for various processors, including MIPS processors, and like the playstation, it does include functions like "atoi", and does support TTY access via Signetics 2681 DUART chips. The DTL-H2000 does also have POSIX-style "PSX>" prompt. So, altogether, it's quite possible that Sony has licensed the kernel from JMI.

PSX as Abbreviation for an Extended Playstation 2
As everybody agrees, PSX should be used only as abbreviation for Playstation 1, and nobody should never ever use it for the Playstation 2. Well, nobody, except Sony... despite of the common use as abbreviation for Playstation 1 (and despite of the JMI trademark)... in 2003, Sony has have released a "Playstation 2 with built-in HDD/DVD Videorecorder" and called that thing "PSX" for the best of confusion.


CPU Specifications

CPU
CPU Registers
CPU Opcode Encoding
CPU Load/Store Opcodes
CPU ALU Opcodes
CPU Jump Opcodes
CPU Coprocessor Opcodes
CPU Pseudo Opcodes

System Control Coprocessor (COP0)
COP0 - Register Summary
COP0 - Exception Handling
COP0 - Misc
COP0 - Debug Registers


CPU Registers

All registers are 32bit wide.
  Name       Alias    Common Usage
  (R0)       zero     Constant (always 0) (this one isn't a real register)
  R1         at       Assembler temporary (destroyed by some pseudo opcodes!)
  R2-R3      v0-v1    Subroutine return values, may be changed by subroutines
  R4-R7      a0-a3    Subroutine arguments, may be changed by subroutines
  R8-R15     t0-t7    Temporaries, may be changed by subroutines
  R16-R23    s0-s7    Static variables, must be saved by subs
  R24-R25    t8-t9    Temporaries, may be changed by subroutines
  R26-R27    k0-k1    Reserved for kernel (destroyed by some IRQ handlers!)
  R28        gp       Global pointer (rarely used)
  R29        sp       Stack pointer
  R30        fp(s8)   Frame Pointer, or 9th Static variable, must be saved
  R31        ra       Return address (used so by JAL,BLTZAL,BGEZAL opcodes)
  -          pc       Program counter
  -          hi,lo    Multiply/divide results, may be changed by subroutines
R0 is always zero.
R31 can be used as general purpose register, however, some opcodes are using it to store the return address: JAL, BLTZAL, BGEZAL. (Note: JALR can optionally store the return address in R31, or in R1..R30. Exceptions store the return address in cop0r14 - EPC).

R29 (SP) - Full Decrementing Wasted Stack Pointer
The CPU doesn't explicitly have stack-related registers or opcodes, however, conventionally, R29 is used as stack pointer (SP). The stack can be accessed with normal load/store opcodes, which do not automatically increase/decrease SP, so the SP register must be manually modified to (de-)allocate data.
The PSX BIOS is using "Full Decrementing Wasted Stack".
Decrementing means that SP gets decremented when allocating data (that's common for most CPUs) - Full means that SP points to the first ALLOCATED word on the stack, so the allocated memory is at SP+0 and above, free memory at SP-1 and below, Wasted means that when calling a sub-function with N parameters, then the caller must pre-allocate N works on stack, and the sub-function may freely use and destroy these words; at [SP+0..N*4-1].

For example, "push ra,r16,r17" would be implemented as:
  sub  sp,20h
  mov  [sp+14h],ra
  mov  [sp+18h],r16
  mov  [sp+1Ch],r17
where the allocated 20h bytes have the following purpose:
  [sp+00h..0Fh]  wasted stack (may, or may not, be used by sub-functions)
  [sp+10h..13h]  8-byte alignment padding (not used)
  [sp+14h..1Fh]  pushed registers



CPU Opcode Encoding

Primary opcode field (Bit 26..31)
  00h=SPECIAL 08h=ADDI  10h=COP0 18h=N/A   20h=LB   28h=SB   30h=LWC0 38h=SWC0
  01h=BcondZ  09h=ADDIU 11h=COP1 19h=N/A   21h=LH   29h=SH   31h=LWC1 39h=SWC1
  02h=J       0Ah=SLTI  12h=COP2 1Ah=N/A   22h=LWL  2Ah=SWL  32h=LWC2 3Ah=SWC2
  03h=JAL     0Bh=SLTIU 13h=COP3 1Bh=N/A   23h=LW   2Bh=SW   33h=LWC3 3Bh=SWC3
  04h=BEQ     0Ch=ANDI  14h=N/A  1Ch=N/A   24h=LBU  2Ch=N/A  34h=N/A  3Ch=N/A
  05h=BNE     0Dh=ORI   15h=N/A  1Dh=N/A   25h=LHU  2Dh=N/A  35h=N/A  3Dh=N/A
  06h=BLEZ    0Eh=XORI  16h=N/A  1Eh=N/A   26h=LWR  2Eh=SWR  36h=N/A  3Eh=N/A
  07h=BGTZ    0Fh=LUI   17h=N/A  1Fh=N/A   27h=N/A  2Fh=N/A  37h=N/A  3Fh=N/A

Secondary opcode field (Bit 0..5) (when Primary opcode = 00h)
  00h=SLL   08h=JR      10h=MFHI 18h=MULT  20h=ADD  28h=N/A  30h=N/A  38h=N/A
  01h=N/A   09h=JALR    11h=MTHI 19h=MULTU 21h=ADDU 29h=N/A  31h=N/A  39h=N/A
  02h=SRL   0Ah=N/A     12h=MFLO 1Ah=DIV   22h=SUB  2Ah=SLT  32h=N/A  3Ah=N/A
  03h=SRA   0Bh=N/A     13h=MTLO 1Bh=DIVU  23h=SUBU 2Bh=SLTU 33h=N/A  3Bh=N/A
  04h=SLLV  0Ch=SYSCALL 14h=N/A  1Ch=N/A   24h=AND  2Ch=N/A  34h=N/A  3Ch=N/A
  05h=N/A   0Dh=BREAK   15h=N/A  1Dh=N/A   25h=OR   2Dh=N/A  35h=N/A  3Dh=N/A
  06h=SRLV  0Eh=N/A     16h=N/A  1Eh=N/A   26h=XOR  2Eh=N/A  36h=N/A  3Eh=N/A
  07h=SRAV  0Fh=N/A     17h=N/A  1Fh=N/A   27h=NOR  2Fh=N/A  37h=N/A  3Fh=N/A

Opcode/Parameter Encoding
  31..26 |25..21|20..16|15..11|10..6 |  5..0  |
   6bit  | 5bit | 5bit | 5bit | 5bit |  6bit  |
  -------+------+------+------+------+--------+------------
  000000 | N/A  | rt   | rd   | imm5 | 0000xx | shift-imm
  000000 | rs   | rt   | rd   | N/A  | 0001xx | shift-reg
  000000 | rs   | N/A  | N/A  | N/A  | 001000 | jr
  000000 | rs   | N/A  | rd   | N/A  | 001001 | jalr
  000000 | <-----comment20bit------> | 00110x | sys/brk
  000000 | N/A  | N/A  | rd   | N/A  | 0100x0 | mfhi/mflo
  000000 | rs   | N/A  | N/A  | N/A  | 0100x1 | mthi/mtlo
  000000 | rs   | rt   | N/A  | N/A  | 0110xx | mul/div
  000000 | rs   | rt   | rd   | N/A  | 10xxxx | alu-reg
  000001 | rs   | 00000| <--immediate16bit--> | bltz
  000001 | rs   | 00001| <--immediate16bit--> | bgez
  000001 | rs   | 10000| <--immediate16bit--> | bltzal
  000001 | rs   | 10001| <--immediate16bit--> | bgezal
  000001 | rs   | xxxx0| <--immediate16bit--> | bltz  ;\undocumented dupes
  000001 | rs   | xxxx1| <--immediate16bit--> | bgez  ;/(when bit17-19=nonzero)
  00001x | <---------immediate26bit---------> | j/jal
  00010x | rs   | rt   | <--immediate16bit--> | beq/bne
  00011x | rs   | N/A  | <--immediate16bit--> | blez/bgtz
  001xxx | rs   | rt   | <--immediate16bit--> | alu-imm
  001111 | N/A  | rt   | <--immediate16bit--> | lui-imm
  100xxx | rs   | rt   | <--immediate16bit--> | load rt,[rs+imm]
  101xxx | rs   | rt   | <--immediate16bit--> | store rt,[rs+imm]
  x1xxxx | <------coprocessor specific------> | coprocessor (see below)

Coprocessor Opcode/Parameter Encoding
  31..26 |25..21|20..16|15..11|10..6 |  5..0  |
   6bit  | 5bit | 5bit | 5bit | 5bit |  6bit  |
  -------+------+------+------+------+--------+------------
  0100nn |0|0000| rt   | rd   | N/A  | 000000 | MFCn rt,rd_dat  ;rt = dat
  0100nn |0|0010| rt   | rd   | N/A  | 000000 | CFCn rt,rd_cnt  ;rt = cnt
  0100nn |0|0100| rt   | rd   | N/A  | 000000 | MTCn rt,rd_dat  ;dat = rt
  0100nn |0|0110| rt   | rd   | N/A  | 000000 | CTCn rt,rd_cnt  ;cnt = rt
  0100nn |0|1000|00000 | <--immediate16bit--> | BCnF target ;jump if false
  0100nn |0|1000|00001 | <--immediate16bit--> | BCnT target ;jump if true
  0100nn |1| <--------immediate25bit--------> | COPn imm25
  010000 |1|0000| N/A  | N/A  | N/A  | 000001 | COP0 01h  ;=TLBR   ;\if any
  010000 |1|0000| N/A  | N/A  | N/A  | 000010 | COP0 02h  ;=TLBWI  ; (not on
  010000 |1|0000| N/A  | N/A  | N/A  | 000110 | COP0 06h  ;=TLBWR  ; psx)
  010000 |1|0000| N/A  | N/A  | N/A  | 001000 | COP0 08h  ;=TLBP   ;/
  010000 |1|0000| N/A  | N/A  | N/A  | 010000 | COP0 10h  ;=RFE
  1100nn | rs   | rt   | <--immediate16bit--> | LWCn rt_dat,[rs+imm]
  1110nn | rs   | rt   | <--immediate16bit--> | SWCn rt_dat,[rs+imm]

Illegal Opcodes
All opcodes that are marked as "N/A" in the Primary and Secondary opcode tables are causing a Reserved Instruction Exception (excode=0Ah).
The unused operand bits (eg. Bit21-25 for LUI opcode) should be usually zero, but do not necessarily trigger exceptions if set to nonzero values.


CPU Load/Store Opcodes

Load instructions
  movbs rt,[imm+rs]  lb  rt,imm(rs)    rt=[imm+rs]  ;byte sign-extended
  movb  rt,[imm+rs]  lbu rt,imm(rs)    rt=[imm+rs]  ;byte zero-extended
  movhs rt,[imm+rs]  lh  rt,imm(rs)    rt=[imm+rs]  ;halfword sign-extended
  movh  rt,[imm+rs]  lhu rt,imm(rs)    rt=[imm+rs]  ;halfword zero-extended
  mov   rt,[imm+rs]  lw  rt,imm(rs)    rt=[imm+rs]  ;word
Load instructions can read from the data cache (if the data is not in the cache, or if the memory region is uncached, then the CPU gets halted until it has read the data) (however, the PSX doesn't have a data cache).

Caution - Load Delay
The loaded data is NOT available to the next opcode, ie. the target register isn't updated until the next opcode has completed. So, if the next opcode tries to read from the load destination register, then it would (usually) receive the OLD value of that register (unless an IRQ occurs between the load and next opcode, in that case the load would complete during IRQ handling, and so, the next opcode would receive the NEW value).

Store instructions
  movb  [imm+rs],rt  sb  rt,imm(rs)    [imm+rs]=(rt AND FFh)   ;store 8bit
  movh  [imm+rs],rt  sh  rt,imm(rs)    [imm+rs]=(rt AND FFFFh) ;store 16bit
  mov   [imm+rs],rt  sw  rt,imm(rs)    [imm+rs]=rt             ;store 32bit
Store operations are passed to the write-buffer, so they can execute within a single clock cycle (unless the write-buffer was full, in that case the CPU gets halted until there's room in the buffer). But, the PSX doesn't have a writebuffer...?

Load/Store Alignment
Halfword addresses must be aligned by 2, word addresses must be aligned by 4, trying to access mis-aligned addresses will cause an exception. There's no alignment restriction for bytes.

Unaligned Load/Store (Right=LSBs, Left=MSBs)
  movr  rt,[imm+rs]  lwr   rt,imm(rs)  load rt.LSBs from memory (usually imm+0)
  movl  rt,[imm+rs]  lwl   rt,imm(rs)  load rt.MSBs from memory (usually imm+3)
  movr  [imm+rs],rt  swr   rt,imm(rs)  store rt.LSBs to memory  (usually imm+0)
  movl  [imm+rs],rt  swl   rt,imm(rs)  store rt.MSBs to memory  (usually imm+3)
There's no delay required between lwl and lwr, so you can use them directly following eachother, eg. to load a word anywhere in memory without regard to alignment:
  lwl   r2,$0003(t0)   ;\no delay required between these
  lwr   r2,$0000(t0)   ;/(although both access r2)
  nop                  ;-requires load delay HERE (before reading from r2)
  and   r2,r2,0ffffh   ;-access r2 (eg. reducing it to unaligned 16bit data)

Unaligned Load/Store (Details)
LWR/SWR transfers the right (=lower) bits of Rt, up-to 32bit memory boundary:
  lwr/swr [N*4+0]     transfer whole 32bit of Rt to/from [N*4+0..3]
  lwr/swr [N*4+1]     transfer lower 24bit of Rt to/from [N*4+1..3]
  lwr/swr [N*4+2]     transfer lower 16bit of Rt to/from [N*4+2..3]
  lwr/swr [N*4+3]     transfer lower  8bit of Rt to/from [N*4+3]
LWL/SWL transfers the left (=upper) bits of Rt, down-to 32bit memory boundary:
  lwl/swl [N*4+0]     transfer upper  8bit of Rt to/from [N*4+0]
  lwl/swl [N*4+1]     transfer upper 16bit of Rt to/from [N*4+0..1]
  lwl/swl [N*4+2]     transfer upper 24bit of Rt to/from [N*4+0..2]
  lwl/swl [N*4+3]     transfer whole 32bit of Rt to/from [N*4+0..3]
The CPU has four separate byte-access signals, so, within a 32bit location, it can transfer all fragments of Rt at once (including for odd 24bit amounts). The transferred data is not zero- or sign-expanded, eg. when transferring 8bit data, the other 24bit of Rt and [mem] will remain intact.

Note: The aligned variant can also misused for blocking memory access on aligned addresses (in that case, if the address is known to be aligned, only one of the opcodes are needed, either LWL or LWR).... Uhhhhhhhm, OR is that NOT allowed... more PROBABLY that doesn't work?


CPU ALU Opcodes

arithmetic instructions
  addt rd,rs,rt    add   rd,rs,rt         rd=rs+rt (with overflow trap)
  add  rd,rs,rt    addu  rd,rs,rt         rd=rs+rt
  subt rd,rs,rt    sub   rd,rs,rt         rd=rs-rt (with overflow trap)
  sub  rd,rs,rt    subu  rd,rs,rt         rd=rs-rt
  addt rt,rs,imm   addi  rt,rs,imm        rt=rs+(-8000h..+7FFFh) (with ov.trap)
  add  rt,rs,imm   addiu rt,rs,imm        rt=rs+(-8000h..+7FFFh)
The opcodes "with overflow trap" do trigger an exception (and leave rd unchanged) in case of overflows.

comparison instructions
  setlt slt   rd,rs,rt  if rs<rt then rd=1 else rd=0 (signed)
  setb  sltu  rd,rs,rt  if rs<rt then rd=1 else rd=0 (unsigned)
  setlt slti  rt,rs,imm if rs<(-8000h..+7FFFh)  then rt=1 else rt=0 (signed)
  setb  sltiu rt,rs,imm if rs<(FFFF8000h..7FFFh) then rt=1 else rt=0(unsigned)

logical instructions
  and  rd,rs,rt    and  rd,rs,rt         rd = rs AND rt
  or   rd,rs,rt    or   rd,rs,rt         rd = rs OR  rt
  xor  rd,rs,rt    xor  rd,rs,rt         rd = rs XOR rt
  nor  rd,rs,rt    nor  rd,rs,rt         rd = FFFFFFFFh XOR (rs OR rt)
  and  rt,rs,imm   andi rt,rs,imm        rt = rs AND (0000h..FFFFh)
  or   rt,rs,imm   ori  rt,rs,imm        rt = rs OR  (0000h..FFFFh)
  xor  rt,rs,imm   xori rt,rs,imm        rt = rs XOR (0000h..FFFFh)

shifting instructions
  shl  rd,rt,rs    sllv rd,rt,rs          rd = rt SHL (rs AND 1Fh)
  shr  rd,rt,rs    srlv rd,rt,rs          rd = rt SHR (rs AND 1Fh)
  sar  rd,rt,rs    srav rd,rt,rs          rd = rt SAR (rs AND 1Fh)
  shl  rd,rt,imm   sll  rd,rt,imm         rd = rt SHL (00h..1Fh)
  shr  rd,rt,imm   srl  rd,rt,imm         rd = rt SHR (00h..1Fh)
  sar  rd,rt,imm   sra  rd,rt,imm         rd = rt SAR (00h..1Fh)
  mov  rt,i*10000h lui  rt,imm            rt = (0000h..FFFFh) SHL 16
Unlike many other opcodes, shifts use 'rt' as second (not third) operand.
The hardware does NOT generate exceptions on SHL overflows.

Multiply/divide
  smul rs,rt       mult   rs,rt           hi:lo = rs*rt (signed)
  umul rs,rt       multu  rs,rt           hi:lo = rs*rt (unsigned)
  sdiv rs,rt       div    rs,rt           lo = rs/rt, hi=rs mod rt (signed)
  udiv rs,rt       divu   rs,rt           lo = rs/rt, hi=rs mod rt (unsigned)
  mov  rd,hi       mfhi   rd              rd=hi  ;move from hi
  mov  rd,lo       mflo   rd              rd=lo  ;move from lo
  mov  hi,rs       mthi   rs              hi=rs  ;move to hi
  mov  lo,rs       mtlo   rs              lo=rs  ;move to lo
The mul/div opcodes are starting the multiply/divide operation, starting takes only a single clock cycle, however, trying to read the result from the hi/lo registers while the mul/div operation is busy will halt the CPU until the mul/div has completed. For multiply, the execution time depends on rs (ie. "small*large" can be much faster than "large*small").
  __umul_execution_time_____________________________________________________
  Fast  (6 cycles)   rs = 00000000h..000007FFh
  Med   (9 cycles)   rs = 00000800h..000FFFFFh
  Slow  (13 cycles)  rs = 00100000h..FFFFFFFFh
  __smul_execution_time_____________________________________________________
  Fast  (6 cycles)   rs = 00000000h..000007FFh, or rs = FFFFF800h..FFFFFFFFh
  Med   (9 cycles)   rs = 00000800h..000FFFFFh, or rs = FFF00000h..FFFFF801h
  Slow  (13 cycles)  rs = 00100000h..7FFFFFFFh, or rs = 80000000h..FFF00001h
  __udiv/sdiv_execution_time________________________________________________
  Fixed (36 cycles)  no matter of rs and rt values
For example, when executing "umul 123h,12345678h" and "mov r1,lo", one can insert up to six (cached) ALU opcodes, or read one value from PSX Main RAM (which has 6 cycle access time) between the "umul" and "mov" opcodes without additional slowdown.
The hardware does NOT generate exceptions on divide overflows, instead, divide errors are returning the following values:
  Opcode  Rs              Rd       Hi/Remainder  Lo/Result
  udiv    0..FFFFFFFFh    0   -->  Rs            FFFFFFFFh
  sdiv    0..+7FFFFFFFh   0   -->  Rs            -1
  sdiv    -80000000h..-1  0   -->  Rs            +1
  sdiv    -80000000h      -1  -->  0             -80000000h
For udiv, the result is more or less correct (as close to infinite as possible). For sdiv, the results are total garbage (about farthest away from the desired result as possible).
Note: After accessing the lo/hi registers, there seems to be a strange rule that one should not touch the lo/hi registers in the next 2 cycles or so... not yet understood if/when/how that rule applies...?


CPU Jump Opcodes

jumps and branches
Note that the instruction following the branch will always be executed.
  jmp  dest        j      dest        pc=(pc and F0000000h)+(imm26bit*4)
  call dest        jal    dest        pc=(pc and F0000000h)+(imm26bit*4),ra=$+8
  jmp  rs          jr     rs          pc=rs
  call rs,ret=rd   jalr (rd,)rs(,rd)  pc=rs, rd=$+8 ;see caution
  je   rs,rt,dest  beq    rs,rt,dest  if rs=rt  then pc=$+4+(-8000h..+7FFFh)*4
  jne  rs,rt,dest  bne    rs,rt,dest  if rs<>rt then pc=$+4+(-8000h..+7FFFh)*4
  js   rs,dest     bltz   rs,dest     if rs<0   then pc=$+4+(-8000h..+7FFFh)*4
  jns  rs,dest     bgez   rs,dest     if rs>=0  then pc=$+4+(-8000h..+7FFFh)*4
  jgtz rs,dest     bgtz   rs,dest     if rs>0   then pc=$+4+(-8000h..+7FFFh)*4
  jlez rs,dest     blez   rs,dest     if rs<=0  then pc=$+4+(-8000h..+7FFFh)*4
  calls  rs,dest   bltzal rs,dest     ra=$+8, if rs<0  then pc=$+4+(..)*4
  callns rs,dest   bgezal rs,dest     ra=$+8, if rs>=0 then pc=$+4+(..)*4
Note: The two conditional call opcodes do ALWAYS set ra=$+8 (even when condition=false).

JALR cautions
Caution: The JALR source code syntax varies (IDT79R3041 specs say "jalr rs,rd", but MIPS32 specs say "jalr rd,rs"). Moreover, JALR may not use the same register for both operands (eg. "jalr r31,r31") (doing so would destroy the target address; which is normally no problem, but it can be a problem if an IRQ occurs between the JALR opcode and the following branch delay opcode; in that case BD gets set, and EPC points "back" to the JALR opcode, so JALR is executed twice, with destroyed target address in second execution).

exception opcodes
Unlike for jump/branch opcodes, exception opcodes are immediately executed (ie. without executing the following opcode).
  syscall  imm20        generates a system call exception
  break    imm20        generates a breakpoint exception
The 20bit immediate doesn't affect the CPU (however, the exception handler may interprete it by software; by examing the opcode bits at [epc-4]).


CPU Coprocessor Opcodes

Coprocessor Instructions (COP0..COP3)
  mov  rt,cop#Rd(0-31)       mfc# rt,rd       ;rt = cop#datRd ;data regs
  mov  rt,cop#Rd(32-63)      cfc# rt,rd       ;rt = cop#cntRd ;control regs
  mov  cop#Rd(0-31),rt       mtc# rt,rd       ;cop#datRd = rt ;data regs
  mov  cop#Rd(32-63),rt      ctc# rt,rd       ;cop#cntRd = rt ;control regs
  mov  cop#cmd,imm25         cop# imm25       ;exec cop# command 0..1FFFFFFh
  mov  cop#Rt(0-31),[rs+imm] lwc# rt,imm(rs)  ;cop#dat_rt = [rs+imm]  ;word
  mov  [rs+imm],cop#Rt(0-31) swc# rt,imm(rs)  ;[rs+imm] = cop#dat_rt  ;word
  jf   cop#flg,dest          bc#f dest        ;if cop#flg=false then pc=$+disp
  jt   cop#flg,dest          bc#t dest        ;if cop#flg=true  then pc=$+disp
  rfe                        rfe              ;return from exception (COP0)
  tlb<xx>                    tlb<xx>          ;virtual memory related (COP0)

Caution - Load Delay
When reading from a coprocessor register, the next opcode cannot use the destination register as operand (much the same as the Load Delays that occur when reading from memory; see there for details).
Reportedly, the Load Delay applies for the next TWO opcodes after coprocessor reads, but, that seems to be nonsense (the PSX does finish both COP0 and COP2 reads after ONE opcode).

Caution - Store Delay
In some cases, a similar delay occurs when writing to a coprocessor register. COP0 is more or less free of store delays (eg. one can read from a cop0 register immediately after writing to it), the only known exception is the cop2 enable bit in cop0r12.bit30 (setting that cop0 bit acts delayed, and cop2 isn't actually enabled until after 2 clock cycles or so).
Writing to cop2 registers has a delay of 2..3 clock cycles. In most cases, that is probably (?) only 2 cycles, but special cases like writing to IRGB (which does additionally affect IR1,IR2,IR3) take 3 cycles until the result arrives in all registers).
Note that Store Delays are counted in numbers of clock cycles (not in numbers of opcodes). For 3 cycle delay, one must usually insert 3 cached opcodes (or one uncached opcode).


CPU Pseudo Opcodes

Pseudo instructions (native/spasm)
  nop                  ;alias for sll r0,r0,0
  move rd,rs           ;alias for addu rd,rs,r0
  la   rx,imm32        ;load address   (alias for lui rx / addiu rx)
  li   rx,imm32        ;load immediate (alias for lui rx / ori   rx)
  li   rx,imm16        ;load immediate (alias for ori, range 0..FFFFh)
  li   rx,-imm15       ;load immediate (alias for addiu, range -1..-8000h)
  li   rx,imm16*10000h ;load immediate (alias for lui)
  lw   rx,imm32        ;load from address (lui rx / lw rx,rx)
  sw   rx,imm32        ;store to address  (lui r1 / sw rx,r1) (destroys r1!)
  lb,lh,lwl,lwr,lbu,lhu;as above pseudo lw
  sb,sh,swl,swr        ;as above pseudo sw (ie. also destroys r1!)
  alu  rx,op           ;alias for alu  rx,rx,op
  alu(u) rx,rx,imm     ;alias for alui(u) rx,rx,imm
  jalr  rx             ;alias for jalr (RA,)rx(,RA)
  subi(u) rt,rs,imm    ;alias for addi(u) rt,rs,-imm
  beqz rx,dest         ;alias for beq rx,r0,dest
  bnez rx,dest         ;alias for bne rx,r0,dest
  b   dest             ;alias for beq r0,r0,dest (jump relative/spasm)
  bra dest             ;alias for ...? (jump relative/gnu)
  bal dest             ;alias for ...? (call relative/spasm)

Pseudo instructions (nocash/a22i)
  mov  rx,NNNN0000h    ;alias for lui  rx,NNNNh
  mov  rx,0000NNNNh    ;alias for or   rx,r0,NNNNh  ;max +FFFFh
  mov  rx,-imm15       ;alias for add  rx,r0,-NNNNh ;min -8000h
  mov  rx,ry           ;alias for or   rx,ry,0  (or "addiu")
  nop                  ;alias for shl  r0,r0,0
  jrel dest            ;alias for blez R0,dest   ;relative jump
  crel dest            ;alias for callns R0,dest ;relative call
  jz   rx,dest         ;alias for je   rx,R0,dest
  jnz  rx,dest         ;alias for jne  rx,R0,dest
  call rx              ;alias for call rx,ret=RA
  ret                  ;alias for jmp  ra
  subt rt,rs,imm       ;alias for addt rt,rs,-imm
  sub  rt,rs,imm       ;alias for add  rt,rs,-imm
  alu  rx,op           ;alias for alu  rx,rx,op
  neg(t) rx,ry         ;alias for sub(t) rx,R0,ry
  not    rx,ry         ;alias for nor    rx,R0,ry
  neg(t)/not rx        ;alias for neg(t)/not rx,rx
  setz rx,ry           ;alias for setb rx,ry,1   (set if zero)
  setnz rx,ry          ;alias for setb rx,R0,ry  (set if nonzero)
  syscall/break        ;alias for syscall/break 000000h
Below are pseudo instructions combined of two 32bit opcodes...
  movp rx,imm32        ;alias for lui  rx,imm16 -plus- ori rx,rx,imm16)
  movpa rx,imm32       ;alias for lui  rx,imm16 -plus- addiu rx,rx,imm16)
  mov(bhs)p rx,[imm32] ;load from address (lui rx,imm16 / mov rx,[rx+imm16])
  movu [rs+imm]        ;alias for lwr/swr [rs+imm] plus lwl/swl [rs+imm+3]
  reti                 ;alias for jmp k0 plus rfe
Below are pseudo instructions combined of two or more 32bit opcodes...
  push rlist           ;alias for sub sp,n*4 -- mov [sp+(1..n)*4],r1..rn
  pop  rlist           ;alias for mov r1..rn,[sp+(1..n)*4] -- add sp,n*4
  pop  pc,rlist        ;alias for pop ra,rlist -- jmp ra

Possible more Pseudos...
  call x0000000h ;call y0000000h (could be half-working for mem mirrors?)
  setae,setge    ;--> setb,setlt with swapped operands

Directives (nocash)
  .mips          ;select MIPS instruction set (alternately .hc05 for MC68HC05)
  .bios          ;create a .ROM file (instead of .EXE)
  .auto_nop      ;append NOPs to jumps ;unless next opcode starts with a +
  .auto_nop_off  ;don't append NOPs to jumps
  org imm        ;assume following code to be originated at address "imm"
  db n(,n(..)))  ;define 8bit data values(s) or quoted ASCII strings
  dw n(,n(..)))  ;define 16bit data values(s) (not 32bit data!)
  dd n(,n(..)))  ;define 32bit data values(s)
  .align imm
  0              ;alias for immediate 0 and register R0 (whichever fits)

Directives (native)
  org imm        ;self-explaining (but, default=$80010000 for spasm!)
  align imm      ;self-explaining (probably zeropadded?)
  db n(,n(..)))  ;define 8bit data values(s) or quoted ASCII strings
  dh n(,n(..)))  ;define 16bit data values(s)
  dw n(,n(..)))  ;define 32bit data values(s) (not 16bit data!)
  dcb len,value  ;fill <len> bytes by <value> (different as DCB on ARM CPUs)
  xyz            ;define label "xyz" at current address (without colon)
  xyz equ n      ;assign value n to xyz
  xyz = n        ;probably same/sililar as "equ"
  ;xyz           ;comments invoked with semicolon (spasm)
  incbin file.bin       ;import binary file
  include file.asm      ;import asm file
  zero           ;alias for r0
  >imm32         ;alias for (i-(i AND 8000h))/10000h,  and/or i/10000h ?
  <imm32         ;alias for (i AND 0FFFFh), used for SW(+/-) and ORI(+)?
  end       ;N/A ;no "end" or ".end" directive needed/used by spasm
  r1 aka at ;N/A ;some assemblers may (optionally) reject to use r1/at

Syntax for unknown assembler (for pad.s)
It uses "0x" for HEX values (but doesn't use "$" for registers).
It uses "#" instead of ";" for comments.
It uses ":" for labels (fortunately).
The assembler has at least one directive: ".byte" (equivalent to "db" on other assemblers).
I've no clue which assembler is used for that syntax... could that be the Psy-Q assembler?


COP0 - Register Summary

COP0 Register Summary
  cop0r0-r2   - N/A
  cop0r3      - BPC - Breakpoint on execute (R/W)
  cop0r4      - N/A
  cop0r5      - BDA - Breakpoint on data access (R/W)
  cop0r6      - JUMPDEST - Randomly memorized jump address (R)
  cop0r7      - DCIC - Breakpoint control (R/W)
  cop0r8      - BadVaddr - Bad Virtual Address (R)
  cop0r9      - BDAM - Data Access breakpoint mask (R/W)
  cop0r10     - N/A
  cop0r11     - BPCM - Execute breakpoint mask (R/W)
  cop0r12     - SR - System status register (R/W)
  cop0r13     - CAUSE - (R)  Describes the most recently recognised exception
  cop0r14     - EPC - Return Address from Trap (R)
  cop0r15     - PRID - Processor ID (R)
  cop0r16-r31 - Garbage
  cop0r32-r63 - N/A - None such (Control regs)


COP0 - Exception Handling

cop0r13 - CAUSE - (Read-only, except, Bit8-9 are R/W)
Describes the most recently recognised exception
  0-1   -      Not used (zero)
  2-6   Excode Describes what kind of exception occured:
                 00h INT     Interrupt
                 01h MOD     Tlb modification (none such in PSX)
                 02h TLBL    Tlb load         (none such in PSX)
                 03h TLBS    Tlb store        (none such in PSX)
                 04h AdEL    Address error, Data load or Instruction fetch
                 05h AdES    Address error, Data store
                             The address errors occur when attempting to read
                             outside of KUseg in user mode and when the address
                             is misaligned. (See also: BadVaddr register)
                 06h IBE     Bus error on Instruction fetch
                 07h DBE     Bus error on Data load/store
                 08h Syscall Generated unconditionally by syscall instruction
                 09h BP      Breakpoint - break instruction
                 0Ah RI      Reserved instruction
                 0Bh CpU     Coprocessor unusable
                 0Ch Ov      Arithmetic overflow
                 0Dh-1Fh     Not used
  7     -      Not used (zero)
  8-15  Ip     Interrupt pending field. Bit 8 and 9 are R/W, and
               contain the last value written to them. As long
               as any of the bits are set they will cause an
               interrupt if the corresponding bit is set in IM.
  16-27 -      Not used (zero)
  28-29 CE     Opcode Bit26-27 (aka coprocessor number in case of COP opcodes)
  30    -      Not used (zero) / Undoc: When BD=1, Branch condition (0=False)
  31    BD     Branch Delay (set when last exception points to the branch
               instruction instead of the instruction in the branch delay
               slot, where the exception occurred)

cop0r12 - SR - System status register (R/W)
  0     IEc Current Interrupt Enable  (0=Disable, 1=Enable) ;rfe pops IUp here
  1     KUc Current Kernal/User Mode  (0=Kernel, 1=User)    ;rfe pops KUp here
  2     IEp Previous Interrupt Disable                      ;rfe pops IUo here
  3     KUp Previous Kernal/User Mode                       ;rfe pops KUo here
  4     IEo Old Interrupt Disable                       ;left unchanged by rfe
  5     KUo Old Kernal/User Mode                        ;left unchanged by rfe
  6-7   -   Not used (zero)
  8-15  Im  8 bit interrupt mask fields. When set the corresponding
            interrupts are allowed to cause an exception.
  16    Isc Isolate Cache (0=No, 1=Isolate)
              When isolated, all load and store operations are targetted
              to the Data cache, and never the main memory.
              (Used by PSX Kernel, in combination with Port FFFE0130h)
  17    Swc Swapped cache mode (0=Normal, 1=Swapped)
              Instruction cache will act as Data cache and vice versa.
              Use only with Isc to access & invalidate Instr. cache entries.
              (Not used by PSX Kernel)
  18    PZ  When set cache parity bits are written as 0.
  19    CM  Shows the result of the last load operation with the D-cache
            isolated. It gets set if the cache really contained data
            for the addressed memory location.
  20    PE  Cache parity error (Does not cause exception)
  21    TS  TLB shutdown. Gets set if a programm address simultaneously
            matches 2 TLB entries.
            (initial value on reset allows to detect extended CPU version?)
  22    BEV Boot exception vectors in RAM/ROM (0=RAM/KSEG0, 1=ROM/KSEG1)
  23-24 -   Not used (zero)
  25    RE  Reverse endianness   (0=Normal endianness, 1=Reverse endianness)
              Reverses the byte order in which data is stored in
              memory. (lo-hi -> hi-lo)
              (Has affect only to User mode, not to Kernal mode) (?)
              (The bit doesn't exist in PSX ?)
  26-27 -   Not used (zero)
  28    CU0 COP0 Enable (0=Enable only in Kernal Mode, 1=Kernal and User Mode)
  29    CU1 COP1 Enable (0=Disable, 1=Enable) (none such in PSX)
  30    CU2 COP2 Enable (0=Disable, 1=Enable) (GTE in PSX)
  31    CU3 COP3 Enable (0=Disable, 1=Enable) (none such in PSX)
When writing to SR: Changing SR.bit0 from 0-to-1 won't trigger any IRQ until after executing the next opcode. On the other hand, changing SR.bit8-15 from 0-to-1 can immediately trigger IRQs (if SR.bit0 was already set). Another special case is the RFE opcode, which will also immediately trigger IRQs when changing SR.bit0 from 0-to-1.

cop0r14 - EPC - Return Address from Trap (R)
  0-31  Return Address from Exception
This address is the instruction at which the exception took place, unless BD is set in CAUSE, then the instruction was at EPC+4.
Interrupts should always return to EPC+0, no matter of the BD flag. That way, if BD=1, the branch gets executed again, that's required because EPC stores only the current program counter, but not additionally the branch destination address.
Other exceptions may require to handle BD. In simple cases, when BD=0, the exception handler may return to EPC+0 (retry execution of the opcode), or to EPC+4 (skip the opcode that caused the exception). Note that jumps to faulty memory locations are executed without exception, but will trigger address errors and bus errors at the target location, ie. EPC (and BadVAddr, in case of address errors) point to the faulty address, not to the opcode that has jumped to that address).

Interrupts vs GTE Commands
If an interrupt occurs "on" a GTE command (cop2cmd), then the GTE command is executed, but nethertheless, the return address in EPC points to the GTE command. So, if the exception handler would return to EPC as usually, then the GTE command would be executed twice. In best case, this would be a waste of clock cycles, in worst case it may lead to faulty result (if the results from the 1st execution are re-used as incoming parameters in the 2nd execution). To fix the problem, the exception handler must do:
  if (cause AND 7Ch)=00h                ;if excode=interrupt
   if ([epc] AND FE000000h)=4A000000h   ;and opcode=cop2cmd
    epc=epc+4                           ;then skip that opcode
Note: The above exception handling is working only in newer PSX BIOSes, but in very old PSX BIOSes, it is only incompletely implemented (see "BIOS Patches" chapter for common workarounds; or write your own exception handler without using the BIOS).
Of course, the above exeption handling won't work in branch delays (where BD gets set to indicate that EPC was modified) (best workaround is not to use GTE commands in branch delays).

cop0cmd=10h - RFE opcode - Prepare Return from Exception
The RFE opcode moves some bits in cop0r12 (SR): bit2-3 are copied to bit0-1, and bit4-5 are copied to bit2-3, all other bits (including bit4-5) are left unchanged.
The RFE opcode does NOT automatically jump to EPC. Instead, the exception handler must copy EPC into a register (usually R26 aka K0), and then jump to that address. Because of branch delays, that would look like so:
  mov  k0,epc  ;get return address
  push k0      ;save epc in memory (if you expect nested exceptions)
  ...          ;whatever (ie. process CAUSE)
  pop  k0      ;restore from memory (if you expect nested exceptions)
  jmp  k0      ;jump to K0 (after executing the next opcode)
  +rfe         ;move SR bit4/5 --> bit2/3 --> bit0/1
If you expect exceptions to be nested deeply, also push/pop SR. Note that there's no way to leave all registers intact (ie. above code destroys K0).

cop0r8 - BadVaddr - Bad Virtual Address (R)
Contains the address whose reference caused an exception. Set on any MMU type of exceptions, on references outside of kuseg (in User mode) and on any misaligned reference. BadVaddr is updated ONLY by Address errors (Excode 04h and 05h), all other exceptions (including bus errors) leave BadVaddr unchanged.

Exception Vectors (depending on BEV bit in SR register)
  Exception     BEV=0         BEV=1
  Reset         BFC00000h     BFC00000h   (Reset)
  UTLB Miss     80000000h     BFC00100h   (Virtual memory, none such in PSX)
  COP0 Break    80000040h     BFC00140h   (Debug Break)
  General       80000080h     BFC00180h   (General Interrupts & Exceptions)
Note: Changing vectors at 800000xxh (kseg0) seems to be automatically reflected to the instruction cache without needing to flush cache (at least it worked SOMETIMES in my test proggy... but NOT always? ...anyways, it'd be highly recommended to flush cache when changing any opcodes), whilst changing mirrors at 000000xxh (kuseg) seems to require to flush cache.
The PSX uses only the BEV=0 vectors (aside from the reset vector, the PSX BIOS ROM doesn't contain any of the BEV=1 vectors).

Exception Priority
  Reset At any time (highest)            ;-reset
  AdEL Memory (Load instruction)         ;\
  AdES Memory (Store instruction)        ; memory (data load/store)
  DBE  Memory (Load or store)            ;/
  MOD  ALU (Data TLB)                    ;\
  TLBL ALU (DTLB Miss)                   ; none such
  TLBS ALU (DTLB Miss)                   ;/
  Ovf  ALU                               ;-overflow
  Int  ALU                               ;-interrupt
  Sys  RD (Instruction Decode)           ;\
  Bp   RD (Instruction Decode)           ;
  RI   RD (Instruction Decode)           ;
  CpU  RD (Instruction Decode)           ;/
  TLBL I-Fetch (ITLB Miss)               ;-none such
  AdEL IVA (Instruction Virtual Address) ;\memory (opcode fetch)
  IBE  RD (end of I-Fetch, lowest)       ;/


COP0 - Misc

cop0r15 - PRID - Processor ID (R)
  0-7   Revision
  8-15  Implementation
  16-31 Not used
PRID=00000001h on Playstation with CPU CXD8530BQ/CXD8530CQ
PRID=00000002h on Playstation with CPU CXD8606CQ

cop0r6 - JUMPDEST - Randomly memorized jump address (R)
The is a rather strange totally useless register. After certain exceptions, the CPU does memorize a jump destination address in the register. Once when it has memorized an address, the register becomes locked, and the memorized value won't change until it becomes unlocked by a new exception. Exceptions that do unlock the register are Reset and Interrupts (cause.bit10). Exceptions that do NOT unlock the register are syscall/break opcodes, and software generated interrupts (eg. cause.bit8).
In the unlocked state, the CPU does more or less randomly memorize one of the next some jump destinations - eg. the destination from the second jump after reset, or from a jump that occured immediately before executing the IRQ handler, or from a jump inside of the IRQ handler, or even from a later jump that occurs shortly after returning from the IRQ handler.
The register seems to be read-only (although the Kernel initialization code writes 0 to it for whatever reason).

cop0r0..r2, cop0r4, cop0r10, cop0r32..r63 - N/A
Registers 0,1,2,4,10 control virtual memory on some MIPS processors (but there's none such in the PSX), and Registers 32..63 (aka "control registers") aren't used in any MIPS processors. Trying to read any of these registers causes a Reserved Instruction Exception (excode=0Ah).

cop0cmd=10h - RFE
Return from exception.

cop0cmd=01h,02h,06h,08h - TLBR,TLBWI,TLBWR,TLBP
The PSX supports only one cop0cmd (cop0cmd=10h aka RFE). Trying to execute the TLBxx opcodes causes a Reserved Instruction Exception (excode=0Ah).

cop0cmd=00h,03h..05h,07h,09h..0Fh,11h..1Fh - Unused
These are unused commands (unknown if they have any function). They can be executed without triggering exceptions (unlike RFE, that works even in User Mode with COP0 disabled).

cop0cmd=20h..1FFFFFFh - mirrors of cop0cmd=00h..1Fh
Mirrors, the upper 16bit of the 25bit command number are ignored.

jf/jt cop0flg,dest - conditional cop0 jumps
mov [mem],cop0reg / mov cop0reg,[mem] - coprocessor cop0 load/store
These opcodes are not implemented on PSX. However, there are some glitches when trying to execute them:
When SR.bit28=1, doesn't trigger any exception, but doesn't do anything useful:
  jump condition seems to be always false (jf jumps always, jt jumps never)
  mov [mem],cop0reg - stores garbage (next opcode) in memory
  mov cop0reg,[mem] - does dummy memory read without changing cop0reg?
When SR.bit28=0, triggers Coprocessor Unusable Exception (excode=0Bh), this does happen even in Kernal Mode (unlike other COP0 opcodes which do ignore SR.bit28=0 in Kernal Mode).

cop0r16-r31 - Garbage
Trying to read these registers returns garbage (but doesn't trigger any exception). When reading one of the garbage registers shortly after reading a valid cop0 register, the garbage value is usually the same as that of the valid register. When doing the read later on, the return value is usually 00000020h, or when reading much later it returns 00000040h, or even 00000100h. No idea what is causing that effect...?
Note: The garbage registers can be accessed (without causing an exception) even in "User mode with cop0 disabled" (SR.Bit1=1 and SR.Bit28=0); accessing any other existing cop0 registers (or executing the rfe opcode) in that state is causing Coprocessor Unusable Exceptions (excode=0Bh).


COP0 - Debug Registers

The COP0 debug registers seem to be PSX specific, normal R30xx CPUs like IDT's R3041 and R3051 don't have anything similar.

cop0r7 - DCIC - Breakpoint control (R/W)
  0      Automatically set by hardware upon Any break            (R/W)
  1      Automatically set by hardware upon BPC Code break       (R/W)
  2      Automatically set by hardware upon BDA Data break       (R/W)
  3      Automatically set by hardware upon BDA Data-Read break  (R/W)
  4      Automatically set by hardware upon BDA Data-Write break (R/W)
  5      Automatically set by hardware upon any-jump break       (R/W)
  6-11   Not used (always zero)
  12-13  Jump Redirection (0=Disable, 1..3=Enable) (see note)    (R/W)
  14-15  Unknown? (R/W)
  16-22  Not used (always zero)
  23     Super-Master Enable 1 for bit24-29
  24     Execution breakpoint     (0=Disabled, 1=Enabled) (see BPC, BPCM)
  25     Data access breakpoint   (0=Disabled, 1=Enabled) (see BDA, BDAM)
  26     Break on Data-Read       (0=No, 1=Break/when Bit25=1)
  27     Break on Data-Write      (0=No, 1=Break/when Bit25=1)
  28     Break on any-jump        (0=No, 1=Break on branch/jump/call/etc.)
  29     Master Enable for bit28 (..and/or exec-break at address>=80000000h?)
  30     Master Enable for bit24-27
  31     Super-Master Enable 2 for bit24-29
When a breakpoint address match occurs the PSX jumps to 80000040h (ie. unlike normal exceptions, not to 80000080h). The Excode value in the CAUSE register is set to 09h (same as BREAK opcode), and EPC contains the return address, as usually. One of the first things to be done in the exception handler is to disable breakpoints (eg. if the any-jump break is enabled, then it must be disabled BEFORE jumping from 80000040h to the actual exception handler).

cop0r7.bit12-13 - Jump Redirection Note
If one or both of these bits are nonzero, then the PSX seems to check for the following opcode sequence,
  mov rx,[mem]   ;load rx from memory
  ...            ;one or more opcodes that do not change rx
  jmp/call rx    ;jump or call to rx
if it does sense that sequence, then it sets PC=[00000000h], but does not store any useful information in any cop0 registers, namely it does not store the return address in EPC, so it's impossible to determine which opcode has caused the exception. For the jump target address, there are 31 registers, so one could only guess which of them contains the target value; for "POP PC" code it'd be usually R31, but for "JMP [vector]" code it may be any register. So far the feature seems to be more or less unusable...?

cop0r5 - BDA - Breakpoint on Data Access Address (R/W)
cop0r9 - BDAM - Breakpoint on Data Access Mask (R/W)
Break condition is "((addr XOR BDA) AND BDAM)=0".

cop0r3 - BPC - Breakpoint on Execute Address (R/W)
cop0r11 - BPCM - Breakpoint on Execute Mask (R/W)
Break condition is "((PC XOR BPC) AND BPCM)=0".

Note (BREAK Opcode)
Additionally, the BREAK opcode can be used to create further breakpoints by patching the executable code. The BREAK opcode uses the same Excode value (09h) in CAUSE register. However, the BREAK opcode jumps to the normal exception handler at 80000080h (not 80000040h).

Note (LibCrypt)
The debug registers are mis-used by "Legacy of Kain: Soul Reaver" (and maybe also other games) for storing libcrypt copy-protection related values (ie. just as a "hidden" location for storing data, not for actual debugging purposes).
CDROM Protection - LibCrypt

Note (Cheat Devices/Expansion ROMs)
The Expansion ROM header supports only Pre-Boot and Post-Boot vectors, but no Mid-Boot vector. Cheat Devices are often using COP0 breaks for Mid-Boot Hooks, either with BPC=BFC06xxxh (break address in ROM, used in older cheat firmwares), or with BPC=80030000h (break address in RAM aka relocated GUI entrypoint, used in later cheat firmwares). Moreover, aside from the Mid-Boot Hook, the Xplorer cheat device is also supporting a special cheat code that uses the COP0 break feature.

Note (Datasheet)
Note: COP0 debug registers are described in LSI's "L64360" datasheet, chapter 14. And in their LR33300/LR33310 datasheet, chapter 4.


Kernel (BIOS)

BIOS Overview
BIOS Memory Map
BIOS Function Summary
BIOS File Functions
BIOS File Execute and Flush Cache
BIOS CDROM Functions
BIOS Memory Card Functions
BIOS Interrupt/Exception Handling
BIOS Event Functions
BIOS Event Summary
BIOS Thread Functions
BIOS Timer Functions
BIOS Joypad Functions
BIOS GPU Functions
BIOS Memory Allocation
BIOS Memory Fill/Copy/Compare (SLOW)
BIOS String Functions
BIOS Number/String/Character Conversion
BIOS Misc Functions
BIOS Internal Boot Functions
BIOS More Internal Functions
BIOS PC File Server
BIOS TTY Console (std_io)
BIOS Character Sets
BIOS Control Blocks
BIOS Boot State
BIOS Versions
BIOS Patches


BIOS Overview

BIOS CDROM Boot
The main purpose of the BIOS is to boot games from CDROM, unfortunately, before doing that, it displays the Sony intro. It's also doing some copy protection and region checks, and refuses to boot unlicensed games, or illegal copies, or games for other regions.

BIOS Bootmenu
The bootmenu shows up when starting the Playstation without CDROM inserted. The menu allows to play Audio CDs, and to erase or copy game positions on Memory Cards.

BIOS Functions
The BIOS contains a number of more or less useful, and probably more or less inefficient functions that can be used by software.
No idea if it's easy to take full control of the CPU, ie. to do all hardware access and interrupt handling by software, without using the BIOS at all?
Eventually the BIOS functions for accessing the CDROM drive are important, not sure how complicated/compatible it'd be to access the CDROM drive directly via I/O ports... among others, there might be different drives used in different versions of the Playstation, which aren't fully compatible with each other?

BIOS Memory
The BIOS occupies 512Kbyte ROM with 8bit address bus (so the BIOS ROM is rather slow, for faster execution, portions of it are relocated to the first 64K of RAM). For some very strange reason, the original PSX BIOS executes all ROM functions in uncached ROM, which is incredible slow (nocash BIOS uses cached ROM, which does work without problems).
The first 64Kbyte of the 2Mbyte Main RAM are reserved for the BIOS (containing exception handlers, jump tables, other data, and relocated code). That reserved region does unfortunately include the "valuable" first 32Kbytes (valuable because that memory could be accessed directly via [R0+immediate], without needing to use R1..R31 as base register).


BIOS Memory Map

BIOS ROM Map (512Kbytes)
  BFC00000h Kernel Part 1  (code/data executed in uncached ROM)
  BFC10000h Kernel Part 2  (code/data relocated to cached RAM)
  BFC18000h Intro/Bootmenu (code/data decompressed and relocated to RAM)
  BFC64000h Character Sets

BIOS ROM Header/Footer
  BFC00100h Kernel BCD date  (YYYYMMDDh)
  BFC00104h Console Type     (see Port 1F802030h, Secondary IRQ10 Controller)
  BFC00108h Kernel Maker/Version Strings (separated by one or more 00h bytes)
  BFC7FF32h GUI Version/Copyright Strings (if any) (separated by one 00h byte)

BIOS RAM Map (1st 64Kbytes of RAM) (fixed addresses mainly in 1st 500h bytes)
  00000000h 10h    Garbage Area (see notes below)
  00000010h 30h    Unused/reserved
  00000040h 20h    COP0 debug-break vector (not used by Kernel) (in KSEG0)
  00000060h 4      RAM Size (in megabytes) (2 or 8)
  00000064h 4      Unknown (set to 00000000h)
  00000068h 4      Unknown (set to 000000FFh)
  0000006Ch 14h    Unused/reserved
  00000080h 10h    Exception vector (actually in KSEG0, ie. at 80000080h)
  00000090h 10h    Unused/reserved
  000000A0h 10h    A(nnh) Function Vector
  000000B0h 10h    B(nnh) Function Vector
  000000C0h 10h    C(nnh) Function Vector
  000000D0h 30h    Unused/reserved
  00000100h 58h    Table of Tables (BIOS Control Blocks) (see below)
  00000158h 28h    Unused/reserved
  00000180h 80h    Command line argument from SYSTEM.CNF; BOOT = fname argument
  00000200h 300h   A(nnh) Jump Table
  00000500h ...    Kernel Code/Data (relocated from ROM)
  0000Cxxxh ...    Unused/reserved (C160h and up; depends on kernel versions)
  0000DF80h 80h    Used for BIOS Patches (ie. used by games, not used by BIOS)
  0000DFFCh 4      Response value from Intro/Bootmenu
  0000E000h 2000h  Kernel Memory; ExCBs, EvCBs, and TCBs allocated via B(00h)

User Memory (not used by Kernel)
  00010000h ...    Begin of User RAM (Exefile, Data, Heap, Stack, etc.)
  001FFF00h ...    Default Stacktop (usually in KSEG0)
  1F800000h 400h   Scratchpad (Data-Cache mis-used as Fast RAM)

Table of Tables (see BIOS Control Blocks for details)
Each table entry consists of two 32bit values; containing the base address, and total size (in bytes) of the corresponding control blocks.
  00000100h  ExCB Exception Chain Entrypoints (addr=var, size=4*08h)
  00000108h  PCB  Process Control Block       (addr=var, size=1*04h)
  00000110h  TCB  Thread Control Blocks       (addr=var, size=N*C0h)
  00000118h  -    Unused/reserved
  00000120h  EvCB Event Control Blocks        (addr=var, size=N*1Ch)
  00000128h  -    Unused/reserved
  00000130h  -    Unused/reserved
  00000138h  -    Unused/reserved
  00000140h  FCB  File Control Blocks         (addr=fixed, size=10h*2Ch)
  00000148h  -    Unused/reserved
  00000150h  DCB  Device Control Blocks       (addr=fixed, size=0Ah*50h)
File handles (fd=00h..0Fh) can be simply converted as fcb=[140h]+fd*2Ch.
Event handles (event=F10000xxh) as evcb=[120h]+(event AND FFFFh)*1Ch.

Garbage Area at Address 00000000h
The first some bytes of memory address 00000000h aren't actually used by the Kernel, except for storing some garbage at that locations. However, this garbage is actually important for bugged games like R-Types and Fade to Black (ie. games that do read from address 00000000h due to using uninitialized pointers).
Initially, the garbage area is containing a copy of the 16-byte exception handler at address 80h, but the first 4-bytes are typically smashed (set to 00000003h from some useless dummy writes in some useless CDROM delays). Ie. the 16-bytes should have these values:
  [00000000h]=3C1A0000h  ;<-- but overwritten by 00000003h after soon
  [00000004h]=275A0C80h  ;<-- or 275A0C50h (in older BIOS)
  [00000008h]=03400008h
  [0000000Ch]=00000000h
For R-Types, the halfword at [0] must non-zero (else the game will do a DMA to address 0, and thereby destroy kernel memory). Fade to Black does several garbage reads from [0..9], a wrong byte value at [5] can cause the game to crash with an invalid memory access exception upon memory card access.


BIOS Function Summary

Parameters, Registers, Stack
Argument(s) are passed in R4,R5,R6,R7,[SP+10h],[SP+14h],etc.
Caution: When calling a sub-function with N parameters, the caller MUST always allocate N words on the stack, and, although the first four parameters are passed in registers rather than on stack, the sub-function is allowed to use/destroy these words at [SP+0..N*4-1].
BIOS Functions (and custom callback functions) are allowed to destroy registers R1-R15, R24-R25, R31 (RA), and HI/LO. Registers R16-R23, R29 (SP), and R30 (FP) must be left unchanged (if the function uses that registers, then it must push/pop them). R26 (K0) is reserved for exception handler and should be usually not used by other functions. R27 (K1) and R28 (GP) are left more or less unused by the BIOS, so one can more or less freely use them for whatever purpose.
The return value (if any) is stored in R2 register.

A-Functions (Call 00A0h with function number in R9 Register)
  A(00h) or B(32h) FileOpen(filename,accessmode)
  A(01h) or B(33h) FileSeek(fd,offset,seektype)
  A(02h) or B(34h) FileRead(fd,dst,length)
  A(03h) or B(35h) FileWrite(fd,src,length)
  A(04h) or B(36h) FileClose(fd)
  A(05h) or B(37h) FileIoctl(fd,cmd,arg)
  A(06h) or B(38h) exit(exitcode)
  A(07h) or B(39h) FileGetDeviceFlag(fd)
  A(08h) or B(3Ah) FileGetc(fd)
  A(09h) or B(3Bh) FilePutc(char,fd)
  A(0Ah) todigit(char)
  A(0Bh) atof(src)     ;Does NOT work - uses (ABSENT) cop1 !!!
  A(0Ch) strtoul(src,src_end,base)
  A(0Dh) strtol(src,src_end,base)
  A(0Eh) abs(val)
  A(0Fh) labs(val)
  A(10h) atoi(src)
  A(11h) atol(src)
  A(12h) atob(src,num_dst)
  A(13h) SaveState(buf)
  A(14h) RestoreState(buf,param)
  A(15h) strcat(dst,src)
  A(16h) strncat(dst,src,maxlen)
  A(17h) strcmp(str1,str2)
  A(18h) strncmp(str1,str2,maxlen)
  A(19h) strcpy(dst,src)
  A(1Ah) strncpy(dst,src,maxlen)
  A(1Bh) strlen(src)
  A(1Ch) index(src,char)
  A(1Dh) rindex(src,char)
  A(1Eh) strchr(src,char)  ;exactly the same as "index"
  A(1Fh) strrchr(src,char) ;exactly the same as "rindex"
  A(20h) strpbrk(src,list)
  A(21h) strspn(src,list)
  A(22h) strcspn(src,list)
  A(23h) strtok(src,list)  ;use strtok(0,list) in further calls
  A(24h) strstr(str,substr) - buggy
  A(25h) toupper(char)
  A(26h) tolower(char)
  A(27h) bcopy(src,dst,len)
  A(28h) bzero(dst,len)
  A(29h) bcmp(ptr1,ptr2,len)      ;Bugged
  A(2Ah) memcpy(dst,src,len)
  A(2Bh) memset(dst,fillbyte,len)
  A(2Ch) memmove(dst,src,len)     ;Bugged
  A(2Dh) memcmp(src1,src2,len)    ;Bugged
  A(2Eh) memchr(src,scanbyte,len)
  A(2Fh) rand()
  A(30h) srand(seed)
  A(31h) qsort(base,nel,width,callback)
  A(32h) strtod(src,src_end) ;Does NOT work - uses (ABSENT) cop1 !!!
  A(33h) malloc(size)
  A(34h) free(buf)
  A(35h) lsearch(key,base,nel,width,callback)
  A(36h) bsearch(key,base,nel,width,callback)
  A(37h) calloc(sizx,sizy)            ;SLOW!
  A(38h) realloc(old_buf,new_siz)     ;SLOW!
  A(39h) InitHeap(addr,size)
  A(3Ah) SystemErrorExit(exitcode)
  A(3Bh) or B(3Ch) std_in_getchar()
  A(3Ch) or B(3Dh) std_out_putchar(char)
  A(3Dh) or B(3Eh) std_in_gets(dst)
  A(3Eh) or B(3Fh) std_out_puts(src)
  A(3Fh) printf(txt,param1,param2,etc.)
  A(40h) SystemErrorUnresolvedException()
  A(41h) LoadExeHeader(filename,headerbuf)
  A(42h) LoadExeFile(filename,headerbuf)
  A(43h) DoExecute(headerbuf,param1,param2)
  A(44h) FlushCache()
  A(45h) init_a0_b0_c0_vectors
  A(46h) GPU_dw(Xdst,Ydst,Xsiz,Ysiz,src)
  A(47h) gpu_send_dma(Xdst,Ydst,Xsiz,Ysiz,src)
  A(48h) SendGP1Command(gp1cmd)
  A(49h) GPU_cw(gp0cmd)   ;send GP0 command word
  A(4Ah) GPU_cwp(src,num) ;send GP0 command word and parameter words
  A(4Bh) send_gpu_linked_list(src)
  A(4Ch) gpu_abort_dma()
  A(4Dh) GetGPUStatus()
  A(4Eh) gpu_sync()
  A(4Fh) SystemError
  A(50h) SystemError
  A(51h) LoadAndExecute(filename,stackbase,stackoffset)
  A(52h) SystemError ----OR---- "GetSysSp()" ?
  A(53h) SystemError            ;PS2: set_ioabort_handler(src)
  A(54h) or A(71h) CdInit()
  A(55h) or A(70h) _bu_init()   ;DTL-H2000: SystemError
  A(56h) or A(72h) CdRemove()
  A(57h) return 0
  A(58h) return 0
  A(59h) return 0
  A(5Ah) return 0
  A(5Bh) dev_tty_init()                                      ;PS2: SystemError
  A(5Ch) dev_tty_open(fcb,and unused:"path\name",accessmode) ;PS2: SystemError
  A(5Dh) dev_tty_in_out(fcb,cmd)                             ;PS2: SystemError
  A(5Eh) dev_tty_ioctl(fcb,cmd,arg)                          ;PS2: SystemError
  A(5Fh) dev_cd_open(fcb,"path\name",accessmode)
  A(60h) dev_cd_read(fcb,dst,len)
  A(61h) dev_cd_close(fcb)
  A(62h) dev_cd_firstfile(fcb,"path\name",direntry)
  A(63h) dev_cd_nextfile(fcb,direntry)
  A(64h) dev_cd_chdir(fcb,"path")
  A(65h) dev_card_open(fcb,"path\name",accessmode)                ;\
  A(66h) dev_card_read(fcb,dst,len)                               ;
  A(67h) dev_card_write(fcb,src,len)                              ; SystemError
  A(68h) dev_card_close(fcb)                                      ; on
  A(69h) dev_card_firstfile(fcb,"path\name",direntry)             ; DTL-H2000
  A(6Ah) dev_card_nextfile(fcb,direntry)                          ;
  A(6Bh) dev_card_erase(fcb,"path\name")                          ;
  A(6Ch) dev_card_undelete(fcb,"path\name")                       ;
  A(6Dh) dev_card_format(fcb)                                     ;
  A(6Eh) dev_card_rename(fcb1,"path\name1",fcb2,"path\name2")     ;
  A(6Fh) dev_card_clear_error_or_so(fcb)   ;[r4+18h]=00000000h    ;
  A(70h) or A(55h) _bu_init()                                     ;/
  A(71h) or A(54h) CdInit()
  A(72h) or A(56h) CdRemove()
  A(73h) return 0
  A(74h) return 0
  A(75h) return 0
  A(76h) return 0
  A(77h) return 0
  A(78h) CdAsyncSeekL(src)
  A(79h) return 0              ;DTL-H2000: CdAsyncSeekP(src)
  A(7Ah) return 0              ;DTL-H2000: CdAsyncGetlocL(dst?)
  A(7Bh) return 0              ;DTL-H2000: CdAsyncGetlocP(dst?)
  A(7Ch) CdAsyncGetStatus(dst)
  A(7Dh) return 0              ;DTL-H2000: CdAsyncGetParam(dst?)
  A(7Eh) CdAsyncReadSector(count,dst,mode)
  A(7Fh) return 0              ;DTL-H2000: CdAsyncReadWithNewMode(mode)
  A(80h) return 0              ;DTL-H2000: CdAsyncReadFinalCount1(r4)
  A(81h) CdAsyncSetMode(mode)
  A(82h) return 0              ;DTL-H2000: CdAsyncMotorOn()
  A(83h) return 0              ;DTL-H2000: CdAsyncPause()
  A(84h) return 0              ;DTL-H2000: CdAsyncPlayOrReadS()
  A(85h) return 0              ;DTL-H2000: CdAsyncStop()
  A(86h) return 0              ;DTL-H2000: CdAsyncMute()
  A(87h) return 0              ;DTL-H2000: CdAsyncDemute()
  A(88h) return 0              ;DTL-H2000: CdSetAudioVolume(src)  ;4-byte src
  A(89h) return 0              ;DTL-H2000: CdAsyncSetSession1(dst)
  A(8Ah) return 0              ;DTL-H2000: CdAsyncSetSession(session,dst)
  A(8Bh) return 0              ;DTL-H2000: CdAsyncForward()
  A(8Ch) return 0              ;DTL-H2000: CdAsyncBackward()
  A(8Dh) return 0              ;DTL-H2000: CdAsyncPlay()
  A(8Eh) return 0              ;DTL-H2000: CdAsyncGetStatSpecial(r4,r5)
  A(8Fh) return 0              ;DTL-H2000: CdAsyncGetID(r4,r5)
  A(90h) CdromIoIrqFunc1()
  A(91h) CdromDmaIrqFunc1()
  A(92h) CdromIoIrqFunc2()
  A(93h) CdromDmaIrqFunc2()
  A(94h) CdromGetInt5errCode(dst1,dst2)
  A(95h) CdInitSubFunc()
  A(96h) AddCDROMDevice()
  A(97h) AddMemCardDevice()    ;DTL-H2000: SystemError
  A(98h) AddDuartTtyDevice()   ;DTL-H2000: AddAdconsTtyDevice ;PS2: SystemError
  A(99h) AddDummyTtyDevice()
  A(9Ah) SystemError           ;DTL-H: AddMessageWindowDevice
  A(9Bh) SystemError           ;DTL-H: AddCdromSimDevice
  A(9Ch) SetConf(num_EvCB,num_TCB,stacktop)
  A(9Dh) GetConf(num_EvCB_dst,num_TCB_dst,stacktop_dst)
  A(9Eh) SetCdromIrqAutoAbort(type,flag)
  A(9Fh) SetMemSize(megabytes)
Below functions A(A0h..B4h) not supported on pre-retail DTL-H2000 devboard:
  A(A0h) WarmBoot()
  A(A1h) SystemErrorBootOrDiskFailure(type,errorcode)
  A(A2h) EnqueueCdIntr()  ;with prio=0 (fixed)
  A(A3h) DequeueCdIntr()
  A(A4h) CdGetLbn(filename) ;get 1st sector number (or garbage when not found)
  A(A5h) CdReadSector(count,sector,buffer)
  A(A6h) CdGetStatus()
  A(A7h) bu_callback_okay()
  A(A8h) bu_callback_err_write()
  A(A9h) bu_callback_err_busy()
  A(AAh) bu_callback_err_eject()
  A(ABh) _card_info(port)
  A(ACh) _card_async_load_directory(port)
  A(ADh) set_card_auto_format(flag)
  A(AEh) bu_callback_err_prev_write()
  A(AFh) card_write_test(port)  ;CEX-1000: jump_to_00000000h
  A(B0h) return 0               ;CEX-1000: jump_to_00000000h
  A(B1h) return 0               ;CEX-1000: jump_to_00000000h
  A(B2h) ioabort_raw(param)     ;CEX-1000: jump_to_00000000h
  A(B3h) return 0               ;CEX-1000: jump_to_00000000h
  A(B4h) GetSystemInfo(index)   ;CEX-1000: jump_to_00000000h
  A(B5h..BFh) N/A ;jump_to_00000000h

B-Functions (Call 00B0h with function number in R9 Register)
  B(00h) alloc_kernel_memory(size)
  B(01h) free_kernel_memory(buf)
  B(02h) init_timer(t,reload,flags)
  B(03h) get_timer(t)
  B(04h) enable_timer_irq(t)
  B(05h) disable_timer_irq(t)
  B(06h) restart_timer(t)
  B(07h) DeliverEvent(class, spec)
  B(08h) OpenEvent(class,spec,mode,func)
  B(09h) CloseEvent(event)
  B(0Ah) WaitEvent(event)
  B(0Bh) TestEvent(event)
  B(0Ch) EnableEvent(event)
  B(0Dh) DisableEvent(event)
  B(0Eh) OpenThread(reg_PC,reg_SP_FP,reg_GP)
  B(0Fh) CloseThread(handle)
  B(10h) ChangeThread(handle)
  B(11h) jump_to_00000000h
  B(12h) InitPad(buf1,siz1,buf2,siz2)
  B(13h) StartPad()
  B(14h) StopPad()
  B(15h) OutdatedPadInitAndStart(type,button_dest,unused,unused)
  B(16h) OutdatedPadGetButtons()
  B(17h) ReturnFromException()
  B(18h) SetDefaultExitFromException()
  B(19h) SetCustomExitFromException(addr)
  B(1Ah) SystemError  ;PS2: return 0
  B(1Bh) SystemError  ;PS2: return 0
  B(1Ch) SystemError  ;PS2: return 0
  B(1Dh) SystemError  ;PS2: return 0
  B(1Eh) SystemError  ;PS2: return 0
  B(1Fh) SystemError  ;PS2: return 0
  B(20h) UnDeliverEvent(class,spec)
  B(21h) SystemError  ;PS2: return 0
  B(22h) SystemError  ;PS2: return 0
  B(23h) SystemError  ;PS2: return 0
  B(24h) jump_to_00000000h
  B(25h) jump_to_00000000h
  B(26h) jump_to_00000000h
  B(27h) jump_to_00000000h
  B(28h) jump_to_00000000h
  B(29h) jump_to_00000000h
  B(2Ah) SystemError  ;PS2: return 0
  B(2Bh) SystemError  ;PS2: return 0
  B(2Ch) jump_to_00000000h
  B(2Dh) jump_to_00000000h
  B(2Eh) jump_to_00000000h
  B(2Fh) jump_to_00000000h
  B(30h) jump_to_00000000h
  B(31h) jump_to_00000000h
  B(32h) or A(00h) FileOpen(filename,accessmode)
  B(33h) or A(01h) FileSeek(fd,offset,seektype)
  B(34h) or A(02h) FileRead(fd,dst,length)
  B(35h) or A(03h) FileWrite(fd,src,length)
  B(36h) or A(04h) FileClose(fd)
  B(37h) or A(05h) FileIoctl(fd,cmd,arg)
  B(38h) or A(06h) exit(exitcode)
  B(39h) or A(07h) FileGetDeviceFlag(fd)
  B(3Ah) or A(08h) FileGetc(fd)
  B(3Bh) or A(09h) FilePutc(char,fd)
  B(3Ch) or A(3Bh) std_in_getchar()
  B(3Dh) or A(3Ch) std_out_putchar(char)
  B(3Eh) or A(3Dh) std_in_gets(dst)
  B(3Fh) or A(3Eh) std_out_puts(src)
  B(40h) chdir(name)
  B(41h) FormatDevice(devicename)
  B(42h) firstfile(filename,direntry)
  B(43h) nextfile(direntry)
  B(44h) FileRename(old_filename,new_filename)
  B(45h) FileDelete(filename)
  B(46h) FileUndelete(filename)
  B(47h) AddDevice(device_info)  ;subfunction for AddXxxDevice functions
  B(48h) RemoveDevice(device_name_lowercase)
  B(49h) PrintInstalledDevices()
Below functions B(4Ah..5Dh) not supported on pre-retail DTL-H2000 devboard:
  B(4Ah) InitCard(pad_enable)  ;uses/destroys k0/k1 !!!
  B(4Bh) StartCard()
  B(4Ch) StopCard()
  B(4Dh) _card_info_subfunc(port)  ;subfunction for "_card_info"
  B(4Eh) write_card_sector(port,sector,src)
  B(4Fh) read_card_sector(port,sector,dst)
  B(50h) allow_new_card()
  B(51h) Krom2RawAdd(shiftjis_code)
  B(52h) SystemError  ;PS2: return 0
  B(53h) Krom2Offset(shiftjis_code)
  B(54h) GetLastError()
  B(55h) GetLastFileError(fd)
  B(56h) GetC0Table
  B(57h) GetB0Table
  B(58h) get_bu_callback_port()
  B(59h) testdevice(devicename)
  B(5Ah) SystemError  ;PS2: return 0
  B(5Bh) ChangeClearPad(int)
  B(5Ch) get_card_status(slot)
  B(5Dh) wait_card_status(slot)
  B(5Eh..FFh) N/A ;jump_to_00000000h    ;CEX-1000: B(5Eh..F6h) only
  B(100h....) N/A ;garbage              ;CEX-1000: B(F7h.....) and up

C-Functions (Call 00C0h with function number in R9 Register)
  C(00h) EnqueueTimerAndVblankIrqs(priority) ;used with prio=1
  C(01h) EnqueueSyscallHandler(priority)     ;used with prio=0
  C(02h) SysEnqIntRP(priority,struc)
  C(03h) SysDeqIntRP(priority,struc)
  C(04h) get_free_EvCB_slot()
  C(05h) get_free_TCB_slot()
  C(06h) ExceptionHandler()
  C(07h) InstallExceptionHandlers()  ;destroys/uses k0/k1
  C(08h) SysInitMemory(addr,size)
  C(09h) SysInitKernelVariables()
  C(0Ah) ChangeClearRCnt(t,flag)
  C(0Bh) SystemError  ;PS2: return 0
  C(0Ch) InitDefInt(priority) ;used with prio=3
  C(0Dh) SetIrqAutoAck(irq,flag)
  C(0Eh) return 0               ;DTL-H2000: dev_sio_init
  C(0Fh) return 0               ;DTL-H2000: dev_sio_open
  C(10h) return 0               ;DTL-H2000: dev_sio_in_out
  C(11h) return 0               ;DTL-H2000: dev_sio_ioctl
  C(12h) InstallDevices(ttyflag)
  C(13h) FlushStdInOutPut()
  C(14h) return 0               ;DTL-H2000: SystemError
  C(15h) tty_cdevinput(circ,char)
  C(16h) tty_cdevscan()
  C(17h) tty_circgetc(circ)    ;uses r5 as garbage txt for ioabort
  C(18h) tty_circputc(char,circ)
  C(19h) ioabort(txt1,txt2)
  C(1Ah) set_card_find_mode(mode)  ;0=normal, 1=find deleted files
  C(1Bh) KernelRedirect(ttyflag)   ;PS2: ttyflag=1 causes SystemError
  C(1Ch) AdjustA0Table()
  C(1Dh) get_card_find_mode()
  C(1Eh..7Fh) N/A ;jump_to_00000000h
  C(80h.....) N/A ;mirrors to B(00h.....)

SYS-Functions (Syscall opcode with function number in R4 aka A0 Register)
  SYS(00h) NoFunction()
  SYS(01h) EnterCriticalSection()
  SYS(02h) ExitCriticalSection()
  SYS(03h) ChangeThreadSubFunction(addr) ;syscall with r4=03h, r5=addr
  SYS(04h..FFFFFFFFh) calls DeliverEvent(F0000010h,4000h)
The 20bit immediate in the "syscall imm" opcode is unused (should be zero).

BREAK-Functions (Break opcode with function number in opcode's immediate)
BRK opcodes may be used within devkits, however, the standard BIOS simply calls DeliverEvent(F0000010h,1000h) and A(40h) SystemErrorUnresolvedException upon any BRK opcodes (as well as on any other unresolved exceptions).
  BRK(1C00h) Division by zero (commonly checked/invoked by software)
  BRK(1800h) Division overflow (-80000000h/-1, sometimes checked by software)
Below breaks are used in DTL-H2000 BIOS:
  BRK(1h) Whatever lockup or so?
  BRK(101h) PCInit()   Inits the fileserver
  BRK(102h) PCCreat(filename, fileattributes)
  BRK(103h) PCOpen(filename, accessmode)
  BRK(104h) PCClose(filehandle)
  BRK(105h) PCRead(filehandle, length, memory_destination_address)
  BRK(106h) PCWrite(filehandle, length, memory_source_address)
  BRK(107h) PClSeek(filehandle, file_offset, seekmode)
  BRK(3C400h) User has typed "break" command in debug console
The break functions have argument(s) in A1,A2,A3 (ie. unlike normal BIOS functions not in A0,A1,A2), and TWO return values (in R2, and R3). These functions require a commercial/homebrew devkit... consisting of a Data Cable (for accessing the PC's harddisk)... and an Expansion ROM (for handling the BREAK opcodes)... or so?


BIOS File Functions

A(00h) or B(32h) - FileOpen(filename, accessmode) - Opens a file for IO
  out: V0  File handle (00h..0Fh), or -1 if error.
Opens a file on the target device for io. Accessmode is set like this:
  bit0     1=Read  ;\These bits aren't actually used by the BIOS, however, at
  bit1     1=Write ;/least 1 should be set; won't work when all 32bits are zero
  bit2     1=Exit without waiting for incoming data (when TTY buffer empty)
  bit9     0=Open Existing File, 1=Create New file (memory card only)
  bit15    1=Asynchronous mode (memory card only; don't wait for completion)
  bit16-31 Number of memory card blocks for a new file on the memory card
The PSX can have a maximum of 16 files open at any time, of which, 2 handles are always reserved for std_io, so only 14 handles are available for actual files. Some functions (chdir, testdevice, FileDelete, FileUndelete, FormatDevice, firstfile, FileRename) are temporarily allocating 1 filehandle (FileRename tries to use 2 filehandles, but, it does accidently use only 1 handle, too). So, for example, FileDelete would fail if more than 13 file handles are opened by the game.

A(01h) or B(33h) - FileSeek(fd, offset, seektype) - Move the file pointer
   seektype 0 = from start of file        (with positive offset)
            1 = from current file pointer (with positive/negative offset)
            2 = Bugs. Should be from end of file.
Moves the file pointer the number of bytes in A1, relative to the location specified by A2. Movement from the eof is incorrect. Also, movement beyond the end of the file is not checked.

A(02h) or B(34h) - FileRead(fd, dst, length) - Read data from an open file
  out: V0  Number of bytes actually read, -1 if failed.
Reads the number of bytes from the specified open file. If length is not specified an error is returned. Read per $0080 bytes from memory card (bu:) and per $0800 from cdrom (cdrom:).

A(03h) or B(35h) - FileWrite(fd, src, length) - Write data to an open file
  out: V0  Number of bytes written.
Writes the number of bytes to the specified open file. Write to the memory card per $0080 bytes. Writing to the cdrom returns 0.

A(04h) or B(36h) - FileClose(fd) - Close an open file
Returns r2=fd (or r2=-1 if failed).

A(08h) or B(3Ah) - FileGetc(fd) - read one byte from file
  out: R2=character (sign-expanded) or FFFFFFFFh=error
Internally redirects to "FileRead(fd,tempbuf,1)". For some strange reason, the returned character is sign-expanded; so, a return value of FFFFFFFFh could mean either character FFh, or error.

A(09h) or B(3Bh) - FilePutc(char,fd) - write one byte to file
Observe that "fd" is the 2nd parameter (not the 1st parameter as usually).
  out:  R2=Number of bytes actually written, -1 if failed
Internally redirects to "FileWrite(fd,tempbuf,1)".

B(40h) - chdir(name) - Change the current directory on target device
Changes the current directory on the specified device, which should be "cdrom:" (memory cards don't support directories). The PSX supports only a current directory, but NOT a current device (ie. after chdir, the directory name may be ommited from filenames, but the device name must be still included in all filenames).
  in:  A0  Pointer to new directory path (eg. "cdrom:\path")
Returns 1=okay, or 0=failed.
The function doesn't verify if the directory exists. Caution: For cdrom, the function does always load the path table from the disk (even if it was already stored in RAM, so chdir is causing useless SLOW read/seek delays).

B(42h) - firstfile(filename,direntry) - Find first file to match the name
Returns r2=direntry (or r2=0 if no matching files).
Searches for the first file to match the specified filename; the filename may contain "?" and "*" wildcards. "*" means to ignore ALL following characters; accordingly one cannot specify any further characters after the "*" (eg. "DATA*" would work, but "*.DAT" won't work). "?" is meant to ignore a single character cell. Note: The "?" wildcards (but not "*") can be used also in all other file functions; causing the function to use the first matching name (eg. FileDelete "????" would erase the first matching file, not all matching files).
Start the name with the device you want to address. (ie. pcdrv:) Different drives can be accessed as normally by their drive names (a:, c:, huh?) if path is omitted after the device, the current directory will be used.
A direntry structure looks like this:
  00h 14h Filename, terminated with 00h
  14h 4   File attribute (always 0 for cdrom) (50h=norm or A0h=del for card)
  18h 4   File size
  1Ch 4   Pointer to next direntry? (not used?)
  20h 4   First Sector Number
  24h 4   Reserved (not used)
BUG: If "?" matches the ending 00h byte of a name, then any further characters in the search expression are ignored (eg. "FILE?.DAT" would match to "FILE2.DAT", but accidently also to "FILE").
BUG: For CDROM, the BIOS includes some code that is intended to realize disk changes during firstfile/nextfile operations, however, that code is so bugged that it does rather ensure that the BIOS does NOT realize new disks being inserted during firstfile/nextfile.
BUG: firstfile/nextfile is internally using a FCB. On the first call to firstfile, the BIOS is searching a free FCB, and does apply that as "search fcb", but it doesn't mark that FCB as allocated, so other file functions may accidently use the same FCB. Moreover, the BIOS does memorize that "search fcb", and, even when starting a new search via another call to firstfile, it keeps using that FCB for search (without checking if the FCB is still free). A possible workaround is not to have any files opened during firstfile/nextfile operations.

B(43h) - nextfile(direntry) - Searches for the next file to match the name
Returns r2=direntry (or r2=0 if no more matching files).
Uses the settings of a previous firstfile/nextfile command.

B(44h) - FileRename(old_filename, new_filename)
Returns 1=okay, or 0=failed.

B(45h) - FileDelete(filename) - Delete a file on target device
Returns 1=okay, or 0=failed.

B(46h) - FileUndelete(filename)
Returns 1=okay, or 0=failed.

B(41h) - FormatDevice(devicename)
Erases all files on the device (ie. for formatting memory cards).
Returns 1=okay, or 0=failed.

B(54h) - GetLastError()
Indicates the reason of the most recent file function error (FileOpen, FileSeek, FileRead, FileWrite, FileClose, GetLastFileError, FileIoctl, chdir, testdevice, FileDelete, FileUndelete, FormatDevice, FileRename). Use GetLastError() ONLY if an error has occured (the error code isn't reset to zero by functions that are passing okay). firstfile/nextfile do NOT affect GetLastError(). See below list of File Error Numbers for more info.

B(55h) - GetLastFileError(fd)
Basically same as B(54h), but allowing to specify a file handle for which error information is to be received; accordingly it doesn't work for functions that do use 'hidden' internal file handles (eg. FileDelete, or unsuccessful FileOpen). Returns FCB[18h], or FFFFFFFFh if the handle is invalid/unused.

A(05h) or B(37h) FileIoctl(fd,cmd,arg)
Used only for TTY.

A(07h) or B(39h) FileGetDeviceFlag(fd)
Returns bit1 of the file's DCB flags. That bit is set only for Duart/TTY, and is cleared for Dummy/TTY, Memory Card, and CDROM.

B(59h) - testdevice(devicename)
Whatever. Checks the devicename, and if it's accepted, calls a device specific function. For the existing devices (cdrom,bu,tty) that specific function simply returns without doing anything. Maybe other devices (like printers or modems) would do something more interesting.

File Error Numbers for B(54h) and B(55h)
  00h okay (though many successful functions leave old error code unchanged)
  02h file not found
  06h bad device port number (tty2 and up)
  09h invalid or unused file handle
  10h general error (physical I/O error, unformatted, disk changed for old fcb)
  11h file already exists error (create/undelete/rename)
  12h tried to rename a file from one device to another device
  13h unknown device name
  16h sector alignment error, or fpos>=filesize, unknown seektype or ioctl cmd
  18h not enough free file handles
  1Ch not enough free memory card blocks
  FFFFFFFFh invalid or unused file handle passed to B(55h) function


BIOS File Execute and Flush Cache

A(41h) - LoadExeHeader(filename, headerbuf)
Loads the 800h-byte exe file header to an internal sector buffer, and does then copy bytes [10h..4Bh] of that header to headerbuf[00h..3Bh].

A(42h) - LoadExeFile(filename, headerbuf)
Same as LoadExeHeader (see there for details), but additionally loads the body of the executable (using the size and destination address in the file header), and does call FlushCache. The exe can be then started via DoExecute (this isn't done automatically by LoadExeFile). Unlike "LoadAndExecute", the "LoadExeFile/DoExecute" combination allows to return the new exe file to return to the old exe file (instead of restarting the boot executable).
BUG: Uses the unstable FlushCache function (see there for details).

A(43h) - DoExecute(headerbuf, param1, param2)
Can be used to start a previously loaded executable. The function saves R16,R28,R30,SP,RA in the reserved region of headerbuf (rather than on stack), more or less slowly zerofills the memfill region specified in headerbuf, reads the stack base and offset values and sets SP and FP to base+offset (or leaves them unchanged if base=0), reads the GP value from headerbuf and sets GP to that value. Then calls the excecutables entrypoint, with param1 and param2 passed in r4,r5.
If the executable (should) return, then R16,R28,R30,SP,RA are restored from headerbuf, and the function returns with r2=1.

A(51h) - LoadAndExecute(filename, stackbase, stackoffset)
This is a rather bizarre function. In short, it does load and execute the specified file, and thereafter, it (tries to) reload and restart to boot executable.
Part1: Takes a copy of the filename, with some adjustments: Everything up to the first ":" or 00h byte is copied as is (ie. the device name, if it does exist, or otherwise the whole path\filename.ext;ver), the remaining characters are copied and converted to uppercase (ie. the path\filename.ext;ver part, or none if the device name didn't exist), finally, checks if a ";" exists (ie. the version suffix), if there's none, then it appends ";1" as default version. CAUTION: The BIOS allocates ONLY 28 bytes on stack for the copy of the filename, that region is followed by 4 unused bytes, so the maximum length would be 32 bytes (31 characters plus EOL) (eg. "device:\pathname\filename.ext;1",00h).
Part2: Enables IRQs via ExitCriticalSection, memorizes the stack base/offset values from the previously loaded executable (which should have been the boot executable, unless LoadAndExecute should have been used in nested fashion), does then use LoadExeFile to load the desired file, replaces the stack base/offset values in its headerbuf by the LoadAndExecute parameter values, and does then execute it via DoExecute(headerbuf,1,0).
Part3: If the exefile returns, or if it couldn't be loaded, then the boot file is (unsuccessfully) attempted to be reloaded: Enables IRQs via ExitCriticalSection, loads the boot file via LoadExeFile, replaces the stack base/offset values in its headerbuf by the values memorized in Part2 (which <should> be the boot executable's values from SYSTEM.CNF, unless the nesting stuff occurred), and does then execute the boot file via DoExecute(headerbuf,1,0).
Part4: If the boot file returns, or if it couldn't be loaded, then the function looks up in a "JMP $" endless loop (normally, returning from the boot exe causes SystemErrorBootOrDiskFailure("B",38Ch), however, after using LoadAndExecute, this functionality is replaced by the "JMP $" lockup.
BUG: Uses the unstable FlushCache function (see there for details).
BUG: Part3 accidently treats the first 4 characters of the exename as memory address (causing an invalid memory address exception on address 6F726463h, for "cdrom:filename.exe").

A(9Ch) - SetConf(num_EvCB, num_TCB, stacktop)
Changes the number of EvCBs and TCBs, and the stacktop. That values are usually initialized from the settings in the SYSTEM.CNF file, so using this function usually shouldn't ever be required.
The function deallocates all old ExCBs, EvCBs, TCBs (so all Exception handlers, Events, and Threads (except the current one) are lost, and all other memory that may have been allocated via alloc_kernel_memory(size) is deallocated, too. It does then allocate the new control blocks, and enqueue the default handlers. Despite of the changed stacktop, the current stack pointer is kept intact, and the function returns to the caller.

A(9Dh) - GetConf(num_EvCB_dst, num_TCB_dst, stacktop_dst)
Returns the number of EvCBs, TCBs, and the initial stacktop. There's no return value in the R2 register, instead, the three 32bit return values are stored at the specified "dst" addresses.

A(44h) - FlushCache()
Flushes the Code Cache, so opcodes are ensured to be loaded from RAM. This is required when loading program code via DMA (ie. from CDROM) (the cache controller apparently doesn't realize changes to RAM that are caused by DMA). The LoadExeFile and LoadAndExecute functions are automatically calling FlushCache (so FlushCache is required only when loading program code via "FileRead" or via "CdReadSector").
FlushCache may be also required when relocating or modifying program code by software (the cache controller doesn't seem to realize modifications to memory mirrors, eg. patching the exception handler at 80000080h seems to be work without FlushCache, but patching the same bytes at 00000080h doesn't).
Note: The PSX doesn't have a Data Cache (or actually, it has, but it's misused as Fast RAM, mapped to a fixed memory region, and which isn't accessable by DMA), so FlushCache isn't required for regions that contain data.
BUG: The FlushCache function contains a handful of opcodes that do use the k0 register without having IRQs disabled at that time, if an IRQ occurs during those opcodes, then the k0 value gets destroyed by the exception handler, causing FlushCache to get trapped in an endless loop.
One workaround would be to disable all IRQs before calling FlushCache, however, the BIOS does internally call the function without IRQs disabled, that applies to:
  load_file  A(42h)
  load_exec  A(51h)
  add_device B(47h) (and all "add_xxx_device" functions)
  init_card  B(4Ah)
  and by intro/boot code
for load_file/load_exec, IRQ2 (cdrom) and IRQ3 (dma) need to be enabled, so the "disable all IRQs" workaround cannot be used for that functions, however, one can/should disable as many IRQs as possible, ie. everything except IRQ2/IRQ3, and all DMA interrupts except DMA3 (cdrom).

Executable Memory Allocation
LoadExeFile and LoadAndExecute are simply loading the file to the address specified in the exe file header. There's absolutely no verification whether that memory is (or isn't) allocated via malloc, or if it is used by the boot executable, or by the kernel, or if it does contain RAM at all.
When using the "malloc" function combined with loading exe files, it may be recommended not to pass all memory to InitHeap (ie. to keep a memory region being reserved for loading executables).

Note
For more info about EXE files and their headers, see
CDROM File Formats


BIOS CDROM Functions

General File Functions
CDROMs are basically accessed via normal file functions, with device name "cdrom:" (which is an abbreviation for "cdrom0:", anyways, the port number is ignored).
BIOS File Functions
BIOS File Execute and Flush Cache
Before starting the boot executable, the BIOS automatically calls CdInit(), so the game doesn't need to do any initializations before using CDROM file functions.

Absent CD-Audio Support
The Kernel doesn't include any functions for playing Audio tracks. Also, there's no BIOS function for setting the XA-ADPCM file/channel filter values. So CD Audio can be used only by directly programming the CDROM I/O ports.

Asynchronous CDROM Access
The normal File functions are always using synchroneous access for CDROM (ie. the functions do wait until all data is transferred) (unlike as for memory cards, accessmode.bit15 cannot be used to activate asynchronous cdrom access).
However, one can read files in asynchrouneous fashion via CdGetLbn, CdAsyncSeekL, and CdAsyncReadSector. CDROM files are non-fragmented, so they can be read simply from incrementing sector numbers.

A(A4h) - CdGetLbn(filename)
Returns the first sector number used by the file, or -1 in case of error.
BUG: The function accidently returns -1 for the first file in the directory (the first file should be a dummy entry for the current or parent directory or so, so that bug isn't much of a problem), if the file is not found, then the function accidently returns garbage (rather than -1).

A(A5h) - CdReadSector(count,sector,buffer)
Reads <count> sectors, starting at <sector>, and writes data to <buffer>. The read is done in mode=80h (double speed, 800h-bytes per sector). The function waits until all sectors are transferred, and does then return the number of sectors (ie. count), or -1 in case of error.

A(A6h) - CdGetStatus()
Retrieves the cdrom status via CdAsyncGetStatus(dst) (see there for details; especially for cautions on door-open flag). The function waits until the event indicates completion, and does then return the status byte (or -1 in case of error).

A(78h) - CdAsyncSeekL(src)
Issues Setloc and SeekL commands. The parameter (src) is a pointer to a 3-byte sector number (MM,SS,FF) (in BCD format).
The function returns 0=failed, or 1=okay. Completion is indicated by events (class=F0000003h, and spec=20h, or 8000h).

A(7Ch) - CdAsyncGetStatus(dst)
Issues a GetStat command. The parameter (dst) is a pointer to a 1-byte location that receives the status response byte.
The function returns 0=failed, or 1=okay. Completion is indicated by events (class=F0000003h, and spec=20h, or 8000h).
Caution: The command acknowledges the door-open flag, but doesn't automatically reload the path table (which is required if a new disk is inserted); if the door-open flag was set, one should call a function that does forcefully load the path table (like chdir).

A(7Eh) - CdAsyncReadSector(count,dst,mode)
Issues SetMode and ReadN (when mode.bit8=0), or ReadS (when mode.bit8=1) commands. count is the number of sectors to be read, dst is the destination address in RAM, mode.bit0-7 are passed as parameter to the SetMode command, mode.bit8 is the ReadN/ReadS flag (as described above). The sector size (for DMA) depends on the mode value: 918h-bytes (bit4=1, bit5=X), 924h-bytes (bit4=0, bit5=1), or 800h-bytes (bit4,5=0).
Before CdAsyncReadSector, the sector number should be set via CdAsyncSeekL(src).
The function returns 0=failed, or 1=okay. Completion is indicated by events (class=F0000003h, and spec=20h, 80h, or 8000h).

A(81h) - CdAsyncSetMode(mode)
Similar to CdAsyncReadSector (see there for details), but issues only the SetMode command, without any following ReadN/ReadS command.

A(94h) - CdromGetInt5errCode(dst1,dst2)
Returns the first two response bytes from the most recent INT5 error: [dst1]=status, [dst2]=errorcode. The BIOS doesn't reset these values in case of successful completion, so the values are quite useless.

A(54h) or A(71h) - CdInit()
A(56h) or A(72h) - CdRemove()
A(90h) - CdromIoIrqFunc1()
A(91h) - CdromDmaIrqFunc1()
A(92h) - CdromIoIrqFunc2()
A(93h) - CdromDmaIrqFunc2()
A(95h) - CdInitSubFunc() ;subfunction for CdInit()
A(9Eh) - SetCdromIrqAutoAbort(type,flag)
A(A2h) - EnqueueCdIntr() ;with prio=0 (fixed)
A(A3h) - DequeueCdIntr()
Internally used CDROM functions for initialization and IRQ handling.


BIOS Memory Card Functions

General File Functions
Memory Cards aka Backup Units (bu) are basically accessed via normal file functions, with device names "bu00:" (Slot 1) and "bu10:" (Slot 2),
BIOS File Functions
Before using the file functions for memory cards, first call InitCard(pad_enable), then StartCard(), and then _bu_init().

File Header, Filesize, and Sector Alignment
The first 100h..200h bytes (2..4 sectors) of the file must contain the title and icon bitmap(s). For details, see:
Memory Card Data Format
The filesize must be a multiple of 2000h bytes (one block), the maximum size would be 1E000h bytes (when using all 15 blocks on the memory card). The filesize must be specified when creating the file (ie. accessmode bit9=1, and bit16-31=number of blocks). Once when the file is created, the BIOS does NOT allow to change the filesize (unless by deleting and re-creating the file).
When reading/writing files, the amount of data must be a multiple of 80h bytes (one sector), and the file position must be aligned to a 80h-byte boundary, too. There's no restriction on fragmented files (ie. one may cross 2000h-byte block boundaries within the file).

Poor Memcard Performance
PSX memory card accesses are typically super-slow. That, not so much because the hardware would be slow, but rather because of improper inefficent code at the BIOS side. The original BIOS tries to synchronize memory card accesses with joypad accesses simply by accessing only one sector per frame (although it could access circa two sectors). To the worst, the BIOS accesses Slot 1 only on each second frame, and Slot 2 only each other frame (although in 99% of all cases only one slot is accessed at once, so the access time drops to 0.5 sectors per frame).
Moreover, the memory card id, directory, and broken sector list do occupy 26 sectors (although the whole information would fit into 4 or 5 sectors) (a workaround would be to read only the first some bytes, and to skip the additional unused bytes - though that'd also mean to skip the checksums which are unfortunately stored at the end of the sector).
And, anytime when opening a file (in synchronous mode), the BIOS does additionally read sector 0 (which is totally useless, and gets especially slow when opening a bunch of files; eg. when extracting the title/icon from all available files on the card).

Asynchronous Access
The BIOS supports synchronous and asynchronous memory card access. Synchronous means that the BIOS function doesn't return until the access has completed (which means, due to the poor performance, that the function spends about 75% of the time on inactivity) (except in nocash PSX bios, which has better performance), whilst asynchronous access means that the BIOS function returns immediately after invoking the access (which does then continue on interrupt level, and does return an event when finished).
The file "FileRead" and "FileWrite" functions act asynchronous when accessmode bit15 is set when opening the file. Additionally, the A(ACh) _card_async_load_directory(port) function can be used to tell the BIOS to load the directory entries and broken sector list to its internal RAM buffers (eg. during the games title screen, so the BIOS doesn't need to load that data once when the game enters its memory card menu). All other functions like FileDelete or FormatDevice always act synchronous. The FileOpen/findfirst/findnext functions do normally complete immediately without accessing the card at all (unless the directory wasn't yet read; in that case the directory is loading in synchronous fashion).
Unfortunately, the asynchronous response doesn't rely on a single callback event, but rather on a bunch of different events which must be all allocated and tested by the game (and of which, one event is delivered on completion) (which one depends on whether function completed okay, or if an error occurred).

Multitap Support (and Multitap Problems)
The BIOS does have some partial support for accessing more than two memory cards (via Multitap adaptors). Device/port names "bu01:", "bu02:", "bu03:" allow to access extra memory carts in slot1 (and "bu11:", "bu12:", "bu13:" in slot2). Namely, those names will send values 82h, 83h, 84h to the memory card