Deep|Optics: 6D Torus Points to a 4x Uplift in Optical Content per TPU

Supply-chain rumors suggest Google’s training-oriented TPU 9t might raise the torus dimensionality to 6D while retaining the torus architecture, with deployment targeted for 2027–2028. If realized, wrap-around optical ports per TPU on the scale-up side would rise from 1.5 (3D) to 6, a fourfold increase in OCS ports and optical module content per TPU; combined with the 800G→2.4T Coherent Lite speed and modulation upgrade, the value uplift would exceed 4x. This direction aligns with the two evolution paths we laid out in our earlier report.

Deep|AI Infra 2026: Shifting from "Brain Power" Competition to "Whole-Body" Evolution

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Apr 14

In 2026, the focus of AI development has pivoted from chasing high benchmark scores to pursuing AI Agents capable of multi-step reasoning and autonomous action. This infrastructure arms race is undergoing a transformation akin to biological evolution. If an AI system is viewed as an evolving organism: the GPU/TPU represents the calculating brain; Memory and Storage serve as the memory carriers for experience and context; the CPU acts as the hands coordinating tasks; while Optics and Networking function as the limbs supporting systemic data flow and response sensitivity. Under the framework of the Agent Scaling Law, the core bottleneck is no longer just the FLOPS of a single chip (brain power), but rather the communication efficiency (limbs), the memory wall (memory), and the Total Cost of Ownership (TCO).

In Deep|AI Infra 2026, we argued that, in the agent era, the system bottleneck is shifting from single-chip compute to system-wide communication efficiency. MoE shifts the communication pattern from All-Reduce toward bisection-bandwidth-hungry All-to-All. Per the GShard paper, as experts scale from 128 to 2,048, All-to-All time for MoE dispatch/combine rises from 16% to 36% of MoE + Transformer layer execution time. On that basis, we expected Google to push along two lines:

1. Scale-out expansion: the number of in-rack TH6 switches rises from one to four–six per rack, DCN bandwidth up 4–6x, the scale-out OCS port ratio moves from 0.2:1 to 1:1, and the optical module ratio increases from 1:1–1:2 to 1:3–1:4;

2. Scale-up dimensionality: a 3D torus’s bisection bandwidth grows only as N^(2/3); assuming the torus architecture is retained, adding dimensions is the main practical route to higher bisection bandwidth, with the OCS Port-to-xPU ratio rising from 1.5:1 toward 2:1–10:1.