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Can the Apple M2 Ultra (192GB) run gpt-oss 20B?

Apple M2 Ultra (192GB) × gpt-oss 20B8K context
YesRuns fully on the GPU
Memory at FP1642.8 GB of 144 GB
Weights 41.8 GBKV cache 0.4 GBRuntime 0.6 GB
QuantFP16Full quality
Memory42.8 GBof 144 GB usable
Speed~67tokens per second
  1. FP16
  2. Q8_0
  3. Q6_K
  4. Q5_K_M
  5. Q4_K_M
  6. Q3_K_M
  7. Q2_K

Yes. The Apple M2 Ultra (192GB) can run gpt-oss 20B fully in unified memory at FP16 (full quality), using about 42.8 GB of the 144 GB available, at roughly 67 tokens/second.

Try other context lengths

Run it with Ollama

With Ollama installed, one command downloads and starts gpt-oss 20B:

ollama run gpt-oss:20b

Ollama's default download is Q4_K_M (about 13.7 GB here). You have room for FP16, which is full quality: pick that GGUF in LM Studio or from Hugging Face.

New to this? Step-by-step setup for the Apple M2 Ultra (192GB)

Run it in the cloud

No Apple M2 Ultra (192GB)? Run gpt-oss 20B in the cloud.

Rent a cloud GPU by the hour. No upfront cost, stop any time.

Rent a GPU on RunPodRent a GPU on Vast.ai

Memory needed by quantization

At 8,192 tokens of context. The black line marks the 144 GB the Apple M2 Ultra (192GB) can use. macOS lets the GPU use about 144 GB of the 192 GB unified memory by default.

QuantQualityMemoryFits?Speed
FP16Full quality42.8 GBFits~67 tok/s
Q8_0Near-lossless23.2 GBFits~125 tok/s
Q6_KExcellent18.1 GBFits~163 tok/s
Q5_K_MVery good15.9 GBFits~187 tok/s
Q4_K_MGood, most popular13.7 GBFits~220 tok/s
Q3_K_MNoticeably degraded11.2 GBFits~273 tok/s
Q2_KHeavily degraded8.8 GBFits~356 tok/s

GPUs that run gpt-oss 20B comfortably

Models that run well on the Apple M2 Ultra (192GB)

Frequently asked questions

Can Apple M2 Ultra (192GB) run gpt-oss 20B?

Yes. The Apple M2 Ultra (192GB) can run gpt-oss 20B fully in unified memory at FP16 (full quality), using about 42.8 GB of the 144 GB available, at roughly 67 tokens/second.

How much VRAM does gpt-oss 20B need?

About 13.7 GB at Q4_K_M with 8,192 tokens of context, and about 42.8 GB at full FP16 precision.

How fast is gpt-oss 20B on the Apple M2 Ultra (192GB)?

Roughly 67 tokens per second at FP16, estimated from the Apple M2 Ultra (192GB)'s 800 GB/s memory bandwidth.