Can Mac Studio M2 Ultra 192GB run gpt-oss-20b?

Apple · 192 GB LPDDR5 · 800 GB/s bandwidth · OpenAI · 21.5B (active 3.6B) · MoE · model ctx up to 128K

Yes — the Mac Studio M2 Ultra 192GB (192 GB LPDDR5) can run gpt-oss-20b. At Q4 with the default 8K context it needs ≈ 13.55 GB VRAM (weights 11.83 GB + KV cache 0.72 GB + 1 GB runtime overhead), which fits within 192 GB. Decode at Q4/8K: ≈ 116.1 tok/s (measured, batch 1). FP16 (≈ 44.72 GB) also fits, at ≈ 38.9 tok/s (estimated). Estimates come from memory-bandwidth math; rows tagged measured override estimates. Relative ranking is more reliable than absolute tok/s. Methodology.

Fit & speed by quant and context

Quant	Context	VRAM needed	Fits?	tok/s (decode)
Q4	4K	13.19 GB	Yes	116.1 measured
Q4	8K default	13.55 GB	Yes	116.1 measured
Q4	32K	15.71 GB	Yes	116.1 measured
FP16	4K	44.36 GB	Yes	38.9 est.
FP16	8K default	44.72 GB	Yes	38.9 est.
FP16	32K	46.88 GB	Yes	38.9 est.

Fits = weights + KV(ctx) + 1 GB overhead ≤ 95% of VRAM. Measured anchors are context-agnostic; the fit verdict is recomputed per context. A missing tok/s means the model is far beyond this card (offload-only territory).

VRAM breakdown at 8K context

Quant	Weights	KV cache	Overhead	Total needed	Mac Studio M2 Ultra 192GB VRAM
Q4	11.83 GB	0.72 GB	1 GB	13.55 GB	192 GB
FP16	43.0 GB	0.72 GB	1 GB	44.72 GB	192 GB

Other GPUs that run gpt-oss-20b

• B200 192GB SXM — ≈1414.1 tok/s Q4 est.
• MI300X 192GB — ≈936.9 tok/s Q4 est.
• H200 141GB SXM5 — ≈848.5 tok/s Q4 est.
• H100 80GB SXM5 — ≈592.2 tok/s Q4 est.
• Gaudi 3 128GB — ≈579.1 tok/s Q4 est.
• A100 80GB SXM4 — ≈360.4 tok/s Q4 est.
• RTX 5090 32GB — ≈282.5 tok/s Q4 measured
• RTX 4090 24GB — ≈225.2 tok/s Q4 measured

All GPUs for gpt-oss-20b →

Other models for the Mac Studio M2 Ultra 192GB

• Qwen3-0.6B — ≈636.4 tok/s Q4 est.
• gemma-3-1b-it — ≈509.1 tok/s Q4 est.
• Llama-3.2-1B-Instruct — ≈424.2 tok/s Q4 est.
• Qwen3-1.7B — ≈254.5 tok/s Q4 est.
• Qwen3-30B-A3B — ≈169.7 tok/s Q4 est.
• Qwen3-Coder-30B-A3B-Instruct — ≈169.7 tok/s Q4 est.
• GLM-4.7-Flash — ≈169.7 tok/s Q4 est.
• Qwen3-30B-A3B-Instruct-2507 — ≈169.7 tok/s Q4 est.

All models on the Mac Studio M2 Ultra 192GB →