Provenance
- Base model:
Qwen/Qwen3.8-27B
- Source quant:
dbirks/Qwen3.8-27B-W4A16-AutoRound
- Source checkpoint revision:
1f05c441c4e64ae0549de44fa9ea5a6d43610314
- Transformation recipe:
syv-ai/qwen38-27b-rtx3090
- Recipe revision:
e681a8f6b190cca1f86d58b8b333b64d014994d7
- Output format: compressed-tensors
pack-quantized
- Body: symmetric INT4 W4A16, group size 128
- Vocabulary matrices: symmetric INT8, group size 128
The exact transformation scripts and vLLM patch used are included in this
repository.
Important vLLM requirement
The INT8 token embedding table requires a small vLLM patch. Stock vLLM 0.27.1
contains the dequantization kernel but does not pass the quantization config to
Qwen3.5/Qwen3.8's VocabParallelEmbedding constructors.
Apply the included patch to the installed vLLM package:
patch -p1 -d /path/to/site-packages/vllm \
< vllm-qwen3_5-embed-quant.patch
The patch was written and verified against vLLM 0.27.1. Revalidate it after
upgrading vLLM. Without this patch, the checkpoint is not expected to load
correctly.
Text-only serving on a 24 GB GPU
The following profile mirrors the batch-oriented syv-ai recipe:
PYTORCH_CUDA_ALLOC_CONF=expandable_segments:True \
VLLM_USE_FLASHINFER_SAMPLER=0 \
vllm serve XReyRobert/Qwen3.8-27B-W4A16-AutoRound-INT8-Head-Embeddings \
--served-model-name qwen3.8-27b-autoround-int8-head-embeddings \
--language-model-only \
--kv-cache-dtype fp8 \
--max-model-len 150000 \
--max-num-seqs 64 \
--max-num-batched-tokens 2048 \
--gpu-memory-utilization 0.972 \
--async-scheduling \
--compilation-config '{"max_cudagraph_capture_size":64,"custom_ops":["+rms_norm","+silu_and_mul"]}' \
--trust-remote-code
--language-model-only avoids loading the vision tower. The published syv-ai
measurements use an RTX 3090 and describe 150k as the conservative deployment
context; the reported single-request ceiling after requantization is around
195k. Actual capacity depends on the runtime version, CUDA allocator state,
concurrency and prompt shape.
For single-user speculative decoding, use the MTP profile documented in the
source recipe and ensure the second hunk of the included patch is applied.
Sampling
The source model recommends:
- Instruct/non-thinking: temperature
0.7, top-p 0.8
- Thinking: temperature
1.0, top-p 0.95
Reproduction
Starting from the pinned source revision:
python quant_lm_head.py /path/to/checkpoint
python quant_embed.py /path/to/checkpoint
The scripts rewrite the relevant safetensors shards, update
model.safetensors.index.json, and add dedicated compressed-tensors config
groups for lm_head and embed_tokens.
- Safetensors/index consistency: 2,003 indexed tensors, 2,003 present
- Missing indexed tensors: 0
- Extra tensors in indexed shards: 0
lm_head relative round-trip error: 0.0064
embed_tokens relative round-trip error: 0.0056
No accuracy benchmark has been rerun specifically for this published artifact.
Refer to the source AutoRound model card for body-quantization evaluations and
to the syv-ai repository for the INT8 head/embedding serving benchmarks.
Credits
- Qwen team for Qwen3.8-27B
dbirks for the W4A16 AutoRound checkpoint
syv-ai for the INT8 head/embedding transformation and vLLM serving recipe