Can I Run DeepSeek V4 on 256 GB system RAM?

Autor: Jakub Rusinowski · Ostatnia aktualizacja: 24 kwietnia 2026

Yes, but it is tight

Yes, but it is tight — DeepSeek V4-Flash at Q5_K_M needs about 202.7 GB of the 204.8 GB usable on 256 GB system RAM, leaving only ~2.1 GB before the runtime starts swapping. Expect ~7 tok/s (estimated), with room for about 32,768 tokens of context.

Confidence: low · Recommended quantization: Q5_K_M · Estimated speed: ~7 tok/s

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256 GB system RAM — what it gives a model

Usable memory for models	204.8 GB
Memory bandwidth	90 GB/s

DeepSeek V4 on 256 GB system RAM: memory by quantization

Quant	Memory needed	Fits 204.8 GB?	Max context	Est. speed	Download
F16	569.4 GB	✗ No	—	—	568 GB
Q8_0	303.1 GB	✗ No	—	—	301.8 GB
Q6_K	234.3 GB	✗ No	—	—	232.9 GB
Q5_K_M	202.7 GB	✓ Yes	32K	~7 tok/s	201.3 GB
Q4_K_M	172.8 GB	✓ Yes	256K	~8.1 tok/s	171.5 GB
Q3_K_M	122.4 GB	✓ Yes	256K	~11.2 tok/s	121.1 GB
Q2_K	94.7 GB	✓ Yes	256K	~14.3 tok/s	93.4 GB

Which DeepSeek V4 sizes fit

Variant	Needs at Q4_K_M	Fits?	Est. speed
DeepSeek V4-Pro	967.4 GB	✗ Too large	—
DeepSeek V4-Flash	172.8 GB	✓ Fits	~8.1 tok/s

What to watch out for

1 larger variant of DeepSeek V4 does not fit and would need CPU offload or different hardware.
This model does not publish its full attention configuration, so the KV-cache share of these figures is inferred from its parameter count rather than computed exactly.
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.
204.8 GB of the 256 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 inferred from the parameter count because this model does not publish its full attention configuration.

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