Yes — GPT-oss 120B (117B) runs at 9 tok/s on M1 Ultra with 128 GB RAM using Q4_K_M quantization via Ollama. First token latency is 1.0s. OpenAI's 120B open-source model — high quality, needs 128 GB Mac.
Want to run GPT-oss 120B faster — or step up to bigger models? Find your Mac →The LLMCheck index estimates GPT-oss 120B on M1 Ultra using our published methodology: Q4_K_M quantization, memory-bandwidth scaling, and cross-referenced third-party benchmarks where available. Figures are transparent estimates — own this config? Submit a real benchmark →
| Metric | Value |
|---|---|
| Tokens per second | 9 tok/s |
| Time to first token | 1.0s |
| Quantization | Q4_K_M |
| Minimum RAM | 128 GB |
| Recommended engine | Ollama |
| Parameters | 117B |
| Benchmark date | 2026-08 |
Q4_K_M 117B Ollama M1 Ultra
The recommended engine for GPT-oss 120B on M1 Ultra is Ollama. Install Ollama, then pull the model:
Ollama handles quantization automatically — it will download the Q4_K_M variant (~128 GB) and start an interactive chat session.
| Chip | Speed | First Token | Min RAM | Engine |
|---|---|---|---|---|
| M4 Ultra | 10 tok/s | 4.2s | 192 GB | MLX |
| M5 Max | 7 tok/s | 5.5s | 128 GB | Ollama |
To run GPT-oss 120B on M1 Ultra you need:
GPT-oss 120B needs about 128 GB of unified memory. These current Apple Silicon Macs have the headroom to run it comfortably:
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See how GPT-oss 120B stacks up against other models on your specific Mac hardware.
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