Gemma 4 12B on a 16 GB Mac: 11 GB RAM, 2.7 tok/s, and what my benchmark got wrong

Google's Gemma 4 12B uses 11.4 GB of RAM and runs at 2.7 tok/s on an M3 MacBook Air — 2.4× the memory of Llama-3.1-8B at well under half the speed. Its math and factual answers are flawless; its coding can't be cleanly scored. Here's the honest picture, the multimodal tax, and the benchmark bug I found correcting this post.