Can I Run Cosmos 3 on RTX 5080 Desktop (16 GB VRAM, 32 GB RAM)?

Written by Jakub Rusinowski · Last updated July 21, 2026

Yes, but it is tight

Yes, but it is tight — Cosmos 3 Nano at Q6_K needs about 15.4 GB of the 16 GB usable on RTX 5080 Desktop (16 GB VRAM, 32 GB RAM), leaving only ~0.6 GB before the runtime starts swapping. Expect ~80.9 tok/s (estimated), with room for about 8,192 tokens of context.

Confidence: low · Recommended quantization: Q6_K · Estimated speed: ~80.9 tok/s

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RTX 5080 Desktop (16 GB VRAM, 32 GB RAM) — what it gives a model

Usable memory for models	16 GB
Memory bandwidth	960 GB/s
Form factor	Desktop
Operating system	Windows or Linux
Memory upgradeable	Yes

Cosmos 3 on RTX 5080 Desktop (16 GB VRAM, 32 GB RAM): memory by quantization

Quant	Memory needed	Fits 16 GB?	Max context	Est. speed	Download
F16	34.2 GB	✗ No	—	—	32 GB
Q8_0	19.2 GB	✗ No	—	—	17 GB
Q6_K	15.4 GB	✓ Yes	8K	~80.9 tok/s	13.1 GB
Q5_K_M	13.6 GB	✓ Yes	16K	~89.9 tok/s	11.3 GB
Q4_K_M	11.9 GB	✓ Yes	16K	~100.4 tok/s	9.7 GB
Q3_K_M	9.1 GB	✓ Yes	16K	~125.2 tok/s	6.8 GB
Q2_K	7.5 GB	✓ Yes	16K	~144.9 tok/s	5.3 GB

Which Cosmos 3 sizes fit

Variant	Needs at Q4_K_M	Fits?	Est. speed
Cosmos 3 Super	41.8 GB	✗ Too large	—
Cosmos 3 Nano	11.9 GB	✓ Fits	~100.4 tok/s
Cosmos 3 Edge	4.1 GB	✓ Fits	~219.7 tok/s

What to watch out for

Only ~0.6 GB of headroom at Q6_K: a longer context or a second application can push this into swapping.
1 larger variant of Cosmos 3 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.

RTX 5080 desktop limitations

16 GB VRAM is the binding constraint, not compute — a slower 24 GB card runs strictly more models.

Recommended setup

Ollama or llama.cpp (CUDA/ROCm) — vLLM if you need concurrent serving

How these numbers are calculated

Memory need = quantized weights + KV cache at 8,192 tokens (f16) + 0.8 GB runtime overhead.
16 GB of VRAM on the NVIDIA GeForce RTX 5080 at 960 GB/s.
32 GB of system RAM available for CPU offload when a model exceeds VRAM.
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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