Can Apple M3 Ultra run gpt-oss 20B?

Q: Can Apple M3 Ultra run gpt-oss 20B?

Yes. Measured 115.52 tok/s generation on Apple M3 Ultra, via llama.cpp (Metal, llama-bench), MXFP4. Source: https://github.com/geerlingguy/ai-benchmarks/issues/42

Yes. Measured 115.52 tok/s generation (llama.cpp (Metal, llama-bench), MXFP4; source).

Every measured result for gpt-oss 20B on Apple M3 Ultra

Build	Quant / setup	Engine	tok/s
Mac Studio M3 Ultra 512GB (Geerling test)	MXFP4	llama.cpp (Metal, llama-bench)	115.52	source
Mac Studio M3 Ultra 512GB (Geerling test)		llama.cpp	115.29	source

Memory: Apple M3 Ultra has 512 GB. gpt-oss 20B weights are about 13 GB in its native format (GGUF param count via llamabench.ai (OpenAI model card: 21B total, 3.6B active)). Arithmetic, not a measurement; long contexts need more. Check other quants in the VRAM calculator.

Speeds are decode (generation) tokens/sec as reported by each source; quant, engine and context differ, so small gaps are noise.

All measured speeds for gpt-oss 20B: best home rig for gpt-oss 20B.

gpt-oss 20B on other hardware: Apple M1 Max · Apple M1 Ultra · Apple M2 Ultra · Apple M4 Max · DGX Spark (GB10) · RTX 3060 12GB · RTX 3090 · RTX 4070 Ti · RTX 4090 · RTX 5060 Ti 16GB · RTX 5070 Ti · RTX 5080 · RTX 5090 · RTX A4000 · RTX Pro 6000 (Blackwell, 96 GB) · RTX Spark N1X · Radeon AI Pro R9700

Other models measured on Apple M3 Ultra: DeepSeek R1 671B · DeepSeek V4.1 Flash · MiniMax M3.1 Flash · Mistral Medium 3.5 128B · Muse Spark Open 816B-A42B · Qwen3.8 27B

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