Overview
Qwen3.8-27B-GPTQ-Pro-4bit-g64-calib128 is a GPTQ-quantized checkpoint intended for efficient GPU inference, published by groxaxo.
It is intended for open-source evaluation, reproducible experimentation, and compatible local or
hosted inference workflows. The wording below is deliberately limited to what can be verified
from this repository's metadata and artifacts.
At a glance
Table with columns: Field, Details| Field | Details |
|---|
| Format | GPTQ |
| Source / base | Qwen/Qwen3.8-27B |
| Intended task | image-text-to-text |
| License | apache-2.0 |
What is included
*.safetensors (5 files)
config.json
generation_config.json
tokenizer.json
tokenizer_config.json
processor_config.json
chat_template.jinja
quantize_config.json
- Additional configuration, tokenizer, processor, or shard files (15 visible artifacts total)
Quick start
vLLM (documented configuration)
vllm serve groxaxo/Qwen3.8-27B-GPTQ-Pro-4bit-g64-calib128 \
--tensor-parallel-size 2 \
--disable-custom-all-reduce \
--dtype bfloat16 --language-model-only \
--max-model-len 260000 --gpu-memory-utilization 0.92 --max-num-seqs 2 \
--speculative-config '{"method":"mtp","num_speculative_tokens":3}'
This command is taken from the repository documentation. Adjust tensor parallelism, context
length, and cache settings to match your hardware and vLLM version.
Compatibility and responsible use
- Use a runtime that explicitly supports this format, architecture, and modality.
- Keep configuration, tokenizer, processor, projection, and weight files from the same revision together.
- Review the source model card and license before redistribution or deployment.
- Hardware needs depend on parameter count, context length, cache precision, quantization, and concurrency.
- Report reproducible issues with the runtime version, hardware, launch command, and a minimal example.
Quantization or conversion changes numerical behavior, memory use, and throughput relative to the source checkpoint; validate quality on your own workload.
Generated outputs may be inaccurate or unsuitable for a given use case. Users are responsible for
testing behavior, applying appropriate safeguards, and complying with applicable licenses and laws.
INT4 GPTQ-Pro quantization of the official Qwen/Qwen3.8-27B, with the MTP (multi-token prediction) draft head preserved and verified working in vLLM speculative decoding.
Sister build (abliterated source): groxaxo/Huihui-Qwen3.8-27B-abliterated-GPTQ-Pro-4bit-g64-calib128 — same recipe, same loss profile.
Quantization details
Table with columns: Parameter, Value| Parameter | Value |
|---|
| Tool | GPTQModel 6.1.0-dev (GPTQ-Pro) |
| Bits / symmetry | 4-bit, symmetric |
| Group size | 64 (desc_act=False) |
| Calibration | text mode, 128 samples |
| Preset | quality (true-sequential, activation-weighted MSE, group-aware) |
| Coverage | 400/400 linear modules across all 64 layers (48 linear-attention GDN + 16 full-attention) |
| MTP head | preserved unquantized ( tensors kept; ) |
MTP verification + a critical serving flag
vLLM 0.24.0, TP=2: Qwen3_5MTP drafter resolves and loads; drafts accepted (25/26 on smoke test); coherent generations. Single RTX 3090 cannot fit INT4 27B + MTP drafter — use TP≥2.
⚠ If you serve this on multi-GPU RTX 3090 (PCIe, no NVLink) and get garbage output (e.g. !!!!...), pass --disable-custom-all-reduce. vLLM's custom allreduce kernel silently corrupts tensor-parallel output on this hardware class. Verified empirically: identical checkpoint, identical prompts — broken without the flag, byte-identical correct output with it. This affects any TP-served model on such boxes, not just this quant.
Speed reference from the sister Huihui build (identical recipe/arch, 2× RTX 3090 TP=2, temp 0.7, 256 tok): 78–87 tok/s single-stream with MTP draft-3 vs ~71 no-MTP; draft acceptance ~59–77% depending on temperature.
Usage
vllm serve groxaxo/Qwen3.8-27B-GPTQ-Pro-4bit-g64-calib128 \
--tensor-parallel-size 2 \
--disable-custom-all-reduce \
--dtype bfloat16 --language-model-only \
--max-model-len 260000 --gpu-memory-utilization 0.92 --max-num-seqs 2 \
--speculative-config '{"method":"mtp","num_speculative_tokens":3}'
min_p and logit_bias do not work with speculative decoding (vLLM limitation).
Acknowledgements