logoalt Hacker News

RandyOriontoday at 5:41 AM1 replyview on HN

From the perspective of a local llm user, I think the qat doesn't solve the major problem of the gemma models.

Gemma family (gen 1 to gen 4) is consistent with extreme range of activations, i.e., 600000, essentially forcing people to use bf16 kv cache and accept a short context window, e.g., 31b, iq4_xs quantization, 100k context window on 32gb memory. Or, people use q8 kv cache, 200k context window, and accept a large performance penalty.

In contrast, for qwen 3.5 family, the largest activation is below 2000, making q8 or even lower-precision kv cache essentially free estates. Together with linear attention, which doesn't require kv cache, full 262k context window can be easily reached.

Qat training with w4a16 target, while improving performance on inference with low-precision weighs, doesn't solve kv cache problem at all.

In the end, a qat is a qat, and there are unseen efforts behind qat checkpoints. Thank you gemma team for releasing qat checkpoints.


Replies

RandyOriontoday at 5:42 AM

More rants about local inference, consider yourself warned.

Together with bf16 related deliberate hardward degrades on consumer-level nvidia gpus, i.e., gtx 10, rtx 20, 30, 40, 50 series, things gets sour really quickly.