Qwen3.8-27B-GPTQ-Int4-V100

GPTQ Int4 quantization of Qwen/Qwen3.8-27B, prepared and tested for inference on an NVIDIA Tesla V100-SXM2-32GB (compute capability 7.0 / sm_70).

The main goal of this build is to provide a practical 4-bit variant that can run on Volta GPUs, where some newer AWQ / compressed-tensors kernels require a newer compute capability.

Model

• Base model: Qwen/Qwen3.8-27B
• Quantization: GPTQ
• Weight bits: 4
• Group size: 128
• desc_act: false
• sym: true
• Intended use: text generation
• Tested GPU: NVIDIA Tesla V100-SXM2-32GB
• Compute capability: 7.0 (sm_70)

Quantization configuration

The model was quantized with:

from gptqmodel import QuantizeConfig

quant_config = QuantizeConfig(
    bits=4,
    group_size=128,
    desc_act=False,
    sym=True,
)

Quantization was performed from the original Qwen/Qwen3.8-27B weights using GPTQModel.

Tested environment

The following environment was used successfully:

GPU: NVIDIA Tesla V100-SXM2-32GB
Compute capability: 7.0 / sm_70
CUDA toolkit: 12.8
PyTorch: 2.10.0+cu128
vLLM: source build based on 0.18.x
GDN prefill backend: Triton

The vLLM build was compiled from source with support for sm_70.

Example build environment:

export CUDA_HOME=/usr/local/cuda-12.8
export TORCH_CUDA_ARCH_LIST="7.0"

vLLM compatibility note

This model was tested with a patched source build of vLLM.

Stock vLLM compatibility depends on the version. In the tested source checkout, several compatibility fixes were required for the Qwen3.8 text-only path and for CUDA Graph / hybrid KV-cache initialization.

In particular:

• Qwen3.8 uses Qwen3.5-family model classes internally.
• The text-only Qwen3_5ForCausalLM architecture required explicit routing in the tested vLLM source.
• Multimodal initialization had to be disabled for this text-only use case.
• CUDA Graph profiling hit an ambiguous hybrid KV-cache layout when the profiling cache shape was [2, 2, ...].
• Removing the ambiguity check for that profiling case allowed CUDA Graph mode to initialize correctly.

Because of this, do not assume every stock vLLM release will run this model unchanged.

Recommended vLLM launch command

The tested launch configuration was:

vllm serve /path/to/Qwen3.8-27B-GPTQ-Int4 \
  --host 0.0.0.0 \
  --port 8002 \
  --served-model-name qwen38 \
  --gpu-memory-utilization 0.90 \
  --max-model-len 4096 \
  --max-num-seqs 1 \
  --gdn-prefill-backend triton

For the tested V100 setup, do not use --enforce-eager unless you need it for debugging or compatibility. CUDA Graph / compiled execution was much faster after warmup.

Performance

Measured on one NVIDIA Tesla V100-SXM2-32GB:

Test	Result
100 generated tokens, first warmed request	~15 s
100 generated tokens, subsequent request	~2.7 s
500 generated tokens	~12.5 s
Steady-state generation	~37–40 tokens/s

These measurements were taken with:

max_model_len = 4096
max_num_seqs = 1
GPTQ Int4
Triton GDN backend
compiled / CUDA Graph execution

The first request after startup can be significantly slower because Triton kernels and execution graphs need to warm up.

Example OpenAI-compatible request

curl http://127.0.0.1:8002/v1/completions \
  -H "Content-Type: application/json" \
  -d '{
    "model": "qwen38",
    "prompt": "Кратко объясни, что такое квантование нейросетей.",
    "max_tokens": 100,
    "temperature": 0.2
  }'

Reasoning output

Depending on the tokenizer / chat template and API endpoint, the model may emit reasoning blocks such as:

<think>
...
</think>

If you use the model in an application, you may want to configure the chat template or post-processing so reasoning is handled separately from the visible assistant answer.

Longer context

The model was initially validated with:

--max-model-len 4096

Longer context sizes such as 8192, 16384, or 32768 should be tested incrementally because available KV-cache memory depends on:

• GPU memory utilization
• vLLM version
• CUDA Graph memory usage
• number of concurrent sequences
• hybrid attention / recurrent-state cache layout

Why this quantization exists

Some pre-quantized AWQ / compressed-tensors builds use kernels that require a GPU compute capability newer than Volta.

On a Tesla V100 (sm_70), those builds can fail with messages indicating a minimum compute capability such as 7.5.

This GPTQ Int4 build was created specifically to provide a working alternative for V100-class hardware.

Known limitations

• Tested primarily for text generation.
• Vision / multimodal functionality is not claimed or validated for this quantized build.
• The tested vLLM environment required source-level compatibility patches.
• First inference after startup can be much slower than subsequent requests.
• FlashAttention 2 is not available on V100; the tested setup uses Triton-based kernels.
• Performance may vary significantly between vLLM, PyTorch, CUDA and Triton versions.

Suggested repository naming

A descriptive Hugging Face repository name would be:

Qwen3.8-27B-GPTQ-Int4-V100

or:

Qwen3.8-27B-GPTQ-Int4-sm70

Base model

Original model:

Qwen/Qwen3.8-27B

Please review and comply with the original model's license and usage terms when using or redistributing this quantized derivative.

Credits

• Qwen team for the original Qwen3.8 model.
• GPTQModel contributors for GPTQ quantization tooling.
• vLLM contributors for the inference engine.