Qwen3.8-27B-W4A16-AutoRound

Qwen3.8-27B · 4-bit (INT4)

A 4-bit quant of Qwen/Qwen3.8-27B.
Weights are INT4. Activations stay BF16. 19.5 GB on disk (BF16 is ~54 GB).

This is AutoRound, not AWQ, not GGUF, not NVFP4. Packed as compressed-tensors for vLLM Marlin. Runs on Ampere and newer (3090, 4090, A6000, A100). You do not need a 5090.

Use this on 3090 / 4090 / A100 class cards.
Use cyankiwi's AWQ-INT4 if you want their AWQ.
Use an NVFP4 build only on Blackwell (50-series / B200).

Serve (vLLM)

The model can take 262,144 tokens of context. --max-model-len is how much of that you reserve in GPU memory. Set it to 262144 if you have the VRAM (we do, on two 3090s). Set it lower if you run out of memory, or if you want more than one request in flight — leftover VRAM goes to the KV cache.

pip install "transformers>=5.15"

vllm serve MIRALABS/Qwen3.8-27B-W4A16-AutoRound \
  --tensor-parallel-size 2 \
  --max-model-len 262144 \
  --kv-cache-dtype fp8 \
  --enable-prefix-caching \
  --enable-chunked-prefill \
  --reasoning-parser qwen3 \
  --enable-auto-tool-choice \
  --tool-call-parser qwen3_coder \
  --trust-remote-code

Need transformers>=5.15 for Qwen3_5Config. vLLM 0.19 still asks for <5; install 5.15 anyway.

One 3090

The weights fit in 24 GB. Context does not — not at 262k. Start around 8k and raise --max-model-len until it OOMs.

vllm serve MIRALABS/Qwen3.8-27B-W4A16-AutoRound \
  --tensor-parallel-size 1 \
  --max-model-len 8192 \
  --gpu-memory-utilization 0.95 \
  --kv-cache-dtype fp8 \
  --reasoning-parser qwen3 \
  --enable-auto-tool-choice \
  --tool-call-parser qwen3_coder \
  --trust-remote-code

For long context on a single 3090, use a GGUF in llama.cpp and offload what does not fit.

1M context (YaRN)

VLLM_ALLOW_LONG_MAX_MODEL_LEN=1 vllm serve MIRALABS/Qwen3.8-27B-W4A16-AutoRound \
  --max-model-len 1000000 \
  --hf-overrides '{"text_config":{"rope_parameters":{"mrope_interleaved":true,"mrope_section":[11,11,10],"rope_type":"yarn","rope_theta":10000000,"partial_rotary_factor":0.25,"factor":4.0,"original_max_position_embeddings":262144}}}' \
  --trust-remote-code

Thinking

Thinking is on by default (reasoning_effort=xhigh). The model writes inside <think>…</think>, then the answer. --reasoning-parser qwen3 puts the think in reasoning and the answer in content.

Give it room. A tiny max_tokens cuts it off mid-thought and you get an empty answer.

• xhigh — default
• medium / low — shorter think
• enable_thinking=false — skip thinking

Qwen's sampling: thinking temperature=1.0, top_p=0.95, top_k=20. No-think: temperature=0.7, top_p=0.8, presence_penalty=1.5.

Recipe

FAQ

Is this 4-bit?
Yes. INT4 weights. W4A16 means 4-bit weights, 16-bit activations.

Is this AWQ?
No. AutoRound. AWQ is a different 4-bit method — see cyankiwi.

3090 or 5090?
3090 / 4090 / A100 → this. Blackwell → NVFP4 will be faster on those tensor cores.

License

Apache 2.0, same as the base.