Why W4A8
int4 weight bandwidth (fast decode) + int8 tensor-core compute (fast prefill) — the best serving quant on the NVIDIA Ampere line (A100 / RTX 3090).
Serving on Ampere (RTX 3090 / A100)
vLLM gates its W4A8 kernels to Hopper. On Ampere the Marlin kernel can run W4A8-int8 but needs a small enablement patch — use vllm-ampere-optimized (prebuilt wheel + Docker image, or the standalone hot-patch). On Hopper it runs out of the box.
Throughput
Same dense Qwen3.6-27B architecture as its base, so the serving profile matches the measured numbers for Avesed/Qwen3.6-27B-W4A8: ~47 tok/s single-user (sub-second TTFT), ~416 tok/s saturated on 2× RTX 3090 (tp2), ~22.8 GiB/card peak.