DeepSeek V4 Quantization: Fixing Conversion Pitfalls and 8x RTX 5090 Benchmarks

gladkos · reddit · 2026-08-12

Developers quantized DeepSeek V4 0731 on 8x RTX 5090s and benchmarked against popular quants. They identified two conversion issues: omitting --no-lazy causes NaN weights, and the default FP8 to Q80 downconversion introduces significant deviation.

By replacing these tensors with BF16, they created a bit-exact baseline. They then built 13 quants using imatrix, noting that cross-comparisons are difficult due to non-standardized naming and GPU-specific fast paths.

Ultimately, they tested 38 files on a single machine. In the 85-135 GB range, their quantization curve shows less drift than community equivalents. For 128 GB hardware, they recommend their 104 GB AD-IQ2M quant.

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