Can I Run IBM Granite 4.2 on 48 GB system RAM?

Written by Jakub Rusinowski · Last updated September 11, 2026

Yes — comfortably

Yes, comfortably — Granite 4.2 30B at Q2_K needs about 12.4 GB of the 38.4 GB usable on 48 GB system RAM, leaving ~26 GB spare and running at ~6.2 tok/s (estimated), with room for about 65,536 tokens of context.

Confidence: medium · Recommended quantization: Q2_K · Estimated speed: ~6.2 tok/s

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48 GB system RAM — what it gives a model

Usable memory for models	38.4 GB
Memory bandwidth	90 GB/s

IBM Granite 4.2 on 48 GB system RAM: memory by quantization

Quant	Memory needed	Fits 38.4 GB?	Max context	Est. speed	Download
F16	62.6 GB	✗ No	—	—	60 GB
Q8_0	34.5 GB	✓ Yes	16K	~2 tok/s	31.9 GB
Q6_K	27.2 GB	✓ Yes	32K	~2.6 tok/s	24.6 GB
Q5_K_M	23.8 GB	✓ Yes	64K	~3 tok/s	21.3 GB
Q4_K_M	20.7 GB	✓ Yes	64K	~3.5 tok/s	18.1 GB
Q3_K_M	15.4 GB	✓ Yes	64K	~4.9 tok/s	12.8 GB
Q2_K	12.4 GB	✓ Yes	64K	~6.2 tok/s	9.9 GB

Which IBM Granite 4.2 sizes fit

Variant	Needs at Q4_K_M	Fits?	Est. speed
Granite 4.2 30B	20.7 GB	✓ Fits	~3.5 tok/s
Granite 4.2 8B	6.8 GB	✓ Fits	~12.1 tok/s
Granite 4.2 3B	3.5 GB	✓ Fits	~28.2 tok/s

What to watch out for

Q2_K 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.
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.
38.4 GB of the 48 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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