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metadata
base_model:
  - Qwen/Qwen3.8-27B
license: apache-2.0
tags:
  - unsloth
  - imatrix
  - llama.cpp
  - qwen3.8
  - qwen
  - ubergarm
  - 16GB
  - 12GB

Qwen3.8-27B (GGUF target for 16GB VRAM)

  • This repository provides GGUF quantizations for Qwen3.8-27B optimized using ZB-ZipBrain, a custom mixed-precision quantization methodology that optimizes LLM tensor bit allocation using rate-distortion marginal cost combined with importance matrix calibration. It automatically identifies Pareto-optimal BPW "sweet spots" to maximize model quality while fitting precise VRAM and memory footprints.
  • Specifically optimized to fit mainstream GPUs within a 16GB VRAM budget at around 4 BPW, and even 12GB VRAM cards at around 3 BPW.
  • For filenames marked with v5, I combined ZB + Pelicanmaxxing for visual evaluation, iteratively tuning until the output reached the most stable quality before locking it in.

image

Benchmark & Evaluation Results

EvalPlus Benchmark Results

  • HumanEval: 164 tasks
  • MBPP: 378 tasks
  • Scores are pass@1, no-thinking mode , kvcache ctk q4_0, ctv q4_0
  • β€œβ€”β€ indicates data not provided.
Quantization HumanEval HumanEval+ MBPP MBPP+ Note
ZB4.00-MIN-v5.1-IQ4_XS 0.945 0.921 0.897 0.780 πŸ‘‘πŸ’€
Qwen3.8-27B-IQ4_NL 0.951 0.915 0.902 0.778 bartowski
ZB3.88-MIN-v5-IQ3_M_XL 0.945 0.915 0.91 0.775 β€”
ZB4.00-MIN-v5-IQ4_XS 0.927 0.902 β€” β€” oldver
Qwen3.8-27B-Ridge-3.7bpw 0.933 0.896 0.902 0.765 empero-ai
ZB3.73-MIN-v5.1-IQ3_M_L 0.927 0.896 0.881 0.757 β€”
ZB3.70-MIN-v4-IQ3_M_L 0.915 0.896 0.873 0.754 oldver
ZB3.00bpw-IQ3_XXS 0.927 0.884 0.865 0.743 β€”
UD3-IQ4_XS 0.890 0.866 0.897 0.751 unsloth
UD3-Q3_K_XL 0.823 0.805 0.881 0.751 unsloth

Comprehensive Comparison Table

Command llama-perplexity.exe -f /wikitext-2-raw/wiki.test.raw --kl-divergence --kl-divergence-base q38f16baseline.kld -ngl 99 -m model.gguf

All models were evaluated against the BF16 baseline (Mean PPL = 6.950493) using standard Perplexity (PPL) and KL Divergence metrics.

Label Provider Size (GB) Mean KLD Same Top-p (%) Mean PPL
UD-Q8_K_XL unsloth old 29.30 0.000850 98.970% 6.953800
UD-Q6_K_XL unsloth old 24.14 0.001380 98.520% 6.953600
Q6_K unsloth old 21.31 0.002290 97.860% 6.950700
Q5_K_M unsloth old 18.47 0.006220 96.700% 6.974200
UD-Q4_K_XL unsloth old 16.69 0.008606 96.091% 6.979220
ZB4.97-GOD-IQ4_XS ZB-GOD 15.82 0.012249 95.337% 7.004243
UD3-Q4_K_S unsloth UD3 14.30 0.013652 95.149% 6.969514
Autoround-Q4_K_M Autoround 15.66 0.014657 94.859% 6.950294
ZB4.65-PRO-IQ4_XS ZB-PRO 14.81 0.015466 94.766% 7.017278
Q4_K_M unsloth old 15.93 0.015490 94.650% 6.956100
ZB4.60-PRO-IQ4_XS ZB-PRO 14.65 0.016162 94.668% 7.030895
ZB4.55-PRO-IQ4_XS ZB-PRO 14.49 0.016647 94.613% 7.032263
IQ4_NL bartowski 15.20 0.018427 94.230% 7.006472
IQ4_XS unsloth old 14.63 0.018652 94.270% 7.012695
UD3-IQ4_XS unsloth UD3 13.27 0.018772 93.975% 7.004732
ZB4.48-STD-IQ4_XS ZB-STD 14.26 0.018892 94.199% 7.050096
Q4_K_S unsloth old 15.01 0.018921 94.235% 6.966826
IQ4_XS-i1 mradermacher 14.26 0.019271 94.141% 7.012810
Q4_K_S-i1 mradermacher 14.74 0.019805 93.996% 6.989551
ZB4.36-STD-IQ4_XS ZB-STD 13.88 0.020556 93.951% 7.054811
ZB4.36-STD-v4-IQ4_XS ZB-STD 13.88 0.021552 93.886% 6.993211
Q4_0-AutoRound-Code webhie 14.64 0.026586 92.970% 7.067142
ZB4.14-MIN-IQ4_XS ZB-MIN 13.19 0.029334 92.799% 7.045689
⭐ZB4.00-MIN-v5.1-IQ4_XS ZB-MIN 12.74 0.033810 92.309% 7.106519
ZB4.00-MIN-v5-IQ4_XS ZB-MIN 12.79 0.034577 92.277% 7.090583
⭐ZB3.88-MIN-v5-IQ3_M_XL ZB-MIN 12.34 0.042164 91.452% 7.132594
⭐ZB3.73-MIN-v5.1-IQ3_M_L ZB-MIN 11.88 0.048117 90.759% 7.199937
ZB3.70-MIN-v4-IQ3_M_L ZB-MIN 11.82 0.052972 90.363% 7.160063
IQ4_XS-Smaller_3.96 jrell 12.61 0.055499 90.090% 7.252766
Ridge-3.7bpw empero-ai 11.73 0.118430 85.907% 7.547496
⭐ZB3.0BPW-IQ3_XXS ZB-MIN 9.62 0.120503 85.320% 7.474669

Update: Aug 20, 2026

  • The newly released Unsloth Dynamic v3 is truly the best value for performance right now.
  • My ZB is just an experiment, feel free to check it out for fun :)

Update: Aug 22, 2026

  • Quant release ZB-4.00 BPW runs cleanly on 16GB VRAM with MTP support and up to 95K context length.

Update: Aug 24, 2026

  • ZBv3-4.00BPW update maintaining size with KLD and Same top-p performs slightly better. ZBv2-4.00BPW -> ZBv3-4.00BPW: output weights were bumped from Q5_K to Q6_K. Testing shows sharper, more consistent outputs and better one-shot performance. => Go with ZBv3-4.00BPW.
  • ZB3.7-MIN βš”οΈ empero-ai/Qwen3.8-27B-Ridge. 🀣
  • I have just updated empero-ai/Qwen3.8-27B-Ridge. benchmarks; comparing my ZB 3.7bpw metrics, it looks like it easily beats down Qwen3.8-27B-Ridge

Update: Aug 26, 2026

  • ZB3.7-MIN-v4 update PPL slightly better

Update: Aug 28, 2026

  • All use Q6_K for output.weight
  • Please prioritize later development versions, I have removed older ones because I was not satisfied with them.
  • Quant release 4.00bpw & 3.88bpw v5 (v5 = ZB + Pelicanmaxxing and visually check for other aspects of stability. )
  • ZB3.88-MIN-v5-IQ3_M_XL βš”οΈ UD3-Q3_K_XL 😎 If anyone has used this pair, please let me know what you think.
  • 3.0BPW-IQ3_XXS: New release size only 9.62 GB πŸ™€ with metric comparable to Ridgeβ€”3.7 bpw.

Update: Sep 5, 2026

  • ZB4.00-MIN-v5.1-IQ4_XS This version has been updated so that all tensors are β‰₯ IQ3_XXS , previous version contained some IQ2_S tensors. Quality is slightly improved, new file size saves 50MB.

Update: Sep 8, 2026

  • ZB3.73-MIN-v5.1-IQ3_M_L Added new 3.73 bpw. Updated all tensors β‰₯ IQ3_XXS, quality is slightly improved. Change for ZB3.70-MIN-v4-IQ3_M_L.
  • Added HumanEval, MBPP benchmark

Recommended Settings: Set reasoning_effort to medium. At this BPW level, it delivers much more stable outputs and fits well in agentic workflows. You can also use the default settings for higher quality, though it will take longer.

llama-server -m models/qwen38/Qwen3.8-27B-ZB4.00-MIN-IQ4_XS.gguf -mm models/qwen38/Qwen3.8-27B-mmproj-BF16.gguf --host 0.0.0.0 --port 8080 --temp 1 --top-p 0.95 --top-k 20 --min-p 0.00 --reasoning-preserve -ctk q4_0 -ctv q4_0 -fa on --ubatch-size 384 --batch-size 384 --no-mmproj-offload --spec-type draft-mtp,ngram-mod --spec-draft-n-max 2 --spec-ngram-mod-n-match 24 --spec-ngram-mod-n-min 24 --spec-ngram-mod-n-max 32 -ngl 99 -t 7 --ctx-size 95000 -np 1 --load-mode mlock --image-min-tokens 1024 --image-max-tokens 2048 --chat-template-kwargs '{\"reasoning_effort\": \"medium\"}'

ZB Tiers & Recommendations

  • ZB-GOD : God. A singularity appears. Reaches 0.012249 Mean KLD and 95.34% top-probability match.
  • ZB-PRO : Pro. For 16 GB VRAM GPUs with offloading on CPU. Balances quality output with substantial size savings.
  • ZB-STD : Standard. Similar to other standard IQ4_XS models currently available.
  • ZB-MIN : Minimal. Optimal footprint for tight 16 GB memory setups, allowing headroom for longer context windows

Credits & Acknowledgements

  • Base Model: Qwen3.8 27B by Alibaba Cloud / Qwen Team.
  • BF16 Base GGUF: Provided by Unsloth AI.
  • Importance Matrix (imatrix): Generated and curated by ubergarm.
  • Inference & Quantization Framework: llama.cpp by Georgi Gerganov and contributors.