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Qwen3.5-0.8B, 1-bit Q1_0 (QAT, round 3)

This is Qwen/Qwen3.5-0.8B (revision 2fc06364) with all 150 text-decoder weight matrices (497,025,024 weights) in llama.cpp Q1_0 format: one sign bit per weight plus an fp16 mean|w| scale per 128 inputs. It was trained by quantization-aware distillation from the bf16 original.

It is a research artifact for the Overlay project, which is replicating Lamb Labs' 1-bit "Larry" and compiling models into silicon tiles.

Files

File What
model-0000*.safetensors + index Standard HF weights. The 1-bit matrices are stored as their dequantized values (sign × scale) in bf16. Loads with Qwen3_5ForConditionalGeneration.from_pretrained.
q1_0.safetensors (67 MB) The packed 1-bit content. For each quantized matrix: <name>.signs uint8 [out, in/8] (little-endian bits, 1 = positive) and <name>.scales fp16 [out, in/128].
export.json Export manifest with SHA-256 of each file

Not quantized (bf16, as in the original):

  • the tied embedding / LM head (254M parameters);
  • the vision tower and the MTP head;
  • all norms, conv1d, A_log, dt_bias, in_proj_a, in_proj_b.

Training

Three rounds, 290M tokens of forward-KL distillation over the full vocabulary from the frozen bf16 teacher.

  • Round 1: 150M tokens, 50% FineWeb-Edu and 50% chat (UltraChat-200k plus Tülu-3 persona instruction-following).
  • Rounds 2 and 3: 40M and 100M tokens. 15% of the data is on-policy: the student's own answers, scored by the teacher.
  • Optimizer: straight-through estimator onto fp32 latent weights, AdamW, peak LR 5e-5 then 2.5e-5.
  • Hardware: 1× A100 / H100.

Results (vs. the bf16 teacher)

This model Teacher
Top-1 next-token agreement, wikitext-2 / chat 67.1% / 74.2% 100%
Perplexity, wikitext-2 / chat 29.4 / 10.85 18.6 / 8.8
IFEval prompt-strict, greedy (541 prompts, thinking off) 29.4% 54.3%
IFEval prompt-strict, repetition penalty 1.1 31.1% 50.8%
IFEval instruction-strict, repetition penalty 1.1 42.3% 62.1%

Rounding the same model to 1 bit without training gives 0.4% top-1 agreement.

Usage notes

  • Use a repetition penalty of about 1.1. Under greedy decoding the model falls into repetition loops on about half of IFEval's prompts; the penalty cuts that to 17%.
  • Chat template with thinking off: enable_thinking=False.
  • Expect large quality loss. It keeps only about 57% of the original's instruction-following. Small models lose much more at 1 bit than large ones, so this is not a drop-in replacement for the original.

Verification

  • The export reproduces the training-time forward exactly: max difference 0.0 on all 150 matrices.
  • q1_0.safetensors unpacks to exactly the HF weights (150/150 matrices).
  • Local CPU greedy output matches the GPU evaluation output.

License: Apache-2.0, inherited from Qwen3.5-0.8B.

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