Can I Run Mistral Small 3.1 on 128 GB system RAM?

Superseded model. Mistral Small 3.1 has been superseded by Mistral Small 3.2. This page is kept for reference; the newer family is a better starting point. View Mistral Small 3.2 →

作者： Jakub Rusinowski · 最后更新： 2025年3月17日

Yes — comfortably

Yes, comfortably — Mistral Small 3.1 24B at Q3_K_M needs about 12.2 GB of the 102.4 GB usable on 128 GB system RAM, leaving ~90.2 GB spare and running at ~6.2 tok/s (estimated), with room for about 65,536 tokens of context.

Confidence: high · Recommended quantization: Q3_K_M · Estimated speed: ~6.2 tok/s

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128 GB system RAM — what it gives a model

Usable memory for models	102.4 GB
Memory bandwidth	90 GB/s

Mistral Small 3.1 on 128 GB system RAM: memory by quantization

Quant	Memory needed	Fits 102.4 GB?	Max context	Est. speed	Download
F16	49.3 GB	✓ Yes	64K	~1.4 tok/s	47.2 GB
Q8_0	27.2 GB	✓ Yes	64K	~2.6 tok/s	25.1 GB
Q6_K	21.5 GB	✓ Yes	64K	~3.3 tok/s	19.4 GB
Q5_K_M	18.9 GB	✓ Yes	64K	~3.8 tok/s	16.7 GB
Q4_K_M	16.4 GB	✓ Yes	64K	~4.5 tok/s	14.2 GB
Q3_K_M	12.2 GB	✓ Yes	64K	~6.2 tok/s	10.1 GB
Q2_K	9.9 GB	✓ Yes	64K	~7.8 tok/s	7.8 GB

What to watch out for

Q3_K_M is the only quantization that fits, and it is a heavily degraded one — expect noticeably worse output than the same model at Q4_K_M. A smaller model at Q4 is usually the better trade.
These figures assume CPU-only inference. Any discrete GPU, even an 8 GB one, will be several times faster for models that fit in its VRAM.

Recommended setup

llama.cpp (CPU build) or Ollama — both run without a GPU

How these numbers are calculated

Memory need = quantized weights + KV cache at 8,192 tokens (f16) + 0.8 GB runtime overhead.
102.4 GB of the 128 GB is treated as usable for model weights (80% — the rest is the OS and running applications).
DDR5-5600 dual channel at 89.6 GB/s peak. CPU decode is assumed to sustain 35% of that peak, because CPU inference is not purely bandwidth-bound — it also spends real time in compute and thread synchronisation. This figure is an assumption, not a fitted constant: no CPU measurement is in the calibration set.
CPU-only inference: no GPU is assumed. A GPU of any size will beat these figures substantially.
Throughput is a memory-bandwidth roofline estimate, not a measurement. It is labelled "estimated" everywhere it appears.
KV cache is computed from this model's published attention configuration.

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