What level of quantization can preserve accuracy while effectively reducing the model size?

#33
by SeanKd - opened

bit 4? 6? 8? i have 48G ram (mac) and which is the most suitable model for me?

If you have a 48gb mac then use an mxfp8 quant

ExLlamav3 does a great job of retaining accuracy while compressing weights. but beware at lower depths <3.0bpw, you will loose accuracy or all completely. it's a trade-off - you get better compression (compression of KV cache as well) while retaining near-lossless accuracy. It's no longer VRAM bound - you can offload MoE layers onto SYSTEM RAM now and with good performance, add DFLASH/MTP and you have a highly capable 'beast' of a model on 48GB - you lucky local user, you.

i tested Youssofal/Qwen3.8-27B-MTPLX-Optimized-Speed-FP16 by using omlx and the speed is 4.9 tok/s....

Use a 8-bit quant like MXFP8 and compress KV cache to 8-bit for keys and 4-bit for values. Use MTP with up to 3 tokens prediction.

Q8 quant = less quant unpacking, still half the size of FP16 at near zero loss.
Qwen models are quite resilient to KV cache quantization (unlike Gemma 4 for example) but don't overdo it. Long contexts will hurt from too much KV cache quantization. Coding and tool calling are surprisingly intact.

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