Can Mac Studio M5 Ultra 128 GB run gpt-oss-120b?
128 GB unified · 1228 GB/s memory bandwidth · gpt-oss-120b has 116.8B parameters (5.1B active per token).
Short answer
Yes, excellent for chat and excellent or better for every workload we test.
Best quantization for chat: MXFP4 (59 GB of weights) on LM Studio. Generation: 120–210 tok/s, leaving about 58 GB free for your other apps.
How it rates for each workload
Same model and machine, different jobs. Agents and long documents send far bigger prompts than chat, so they need much more speed and memory.
| Workload | Verdict | Quant | Generation | First reply | Context | |
|---|---|---|---|---|---|---|
| Chatwith Open WebUI | Excellent | MXFP4 | 120–210 tok/s | under 1 s | 8K | Details |
| Coding questionswith Continue | Excellent | MXFP4 | 120–200 tok/s | under 1 s | 16K | Details |
| Coding in a repositorywith Aider | Excellent | MXFP4 | 110–180 tok/s | ≈2 s | 32K | Details |
| Agentic codingwith OpenCode | Excellent | MXFP4 | 100–170 tok/s | ≈3 s | 32K | Details |
| Long documents (64K)with Open WebUI | Excellent | MXFP4 | 75–130 tok/s | ≈9 s | 64K | Details |
Speeds are bandwidth-based estimates; no direct benchmark exists for this pair. “First reply” is the time to read the workload’s opening prompt. How we calculate
Get it running
Copy-paste commands for the MXFP4 build with a 64K context. Ollama and llama.cpp download the file straight from Hugging Face.
ollama run hf.co/unsloth/gpt-oss-120b-GGUF:F16
Downloads 65.37 GB (F16). Ollama's default context is small: set OLLAMA_CONTEXT_LENGTH=65536 before `ollama serve` for long prompts.
Other models for Mac Studio M5 Ultra 128 GB
The best-rated models for chat on this machine.
- Qwen3.6 35B-A3B140–240 tok/sExcellent
- Qwen3-Next 80B-A3B Instruct140–230 tok/sExcellent
- Gemma 4 26B-A4B110–190 tok/sExcellent
- Qwen3.5 35B-A3B140–240 tok/sExcellent
- LFM2.5 24B-A2B280–460 tok/sExcellent
- Qwen3.5 122B-A10B50–85 tok/sExcellent
Cheapest machines for gpt-oss-120b
Hardware rated comfortable or better for chat, lowest price first.
- Ryzen AI Max+ 395 mini PC / Framework Desktop · 128 GB$2,000 · 50–70 tok/sExcellent
- Mac Studio M2 Max 96 GB$3,799 · 65–85 tok/sExcellent
- MacBook Pro M3 Max 96 GB$3,999 · 50–65 tok/sExcellent
- Mac Studio M4 Max 128 GB$4,099 · 85–110 tok/sExcellent
- Mac Studio M5 Max 128 GB$4,099 · 80–130 tok/sExcellent
- MacBook Pro M2 Max 96 GB$5,099 · 65–85 tok/sExcellent
Different tool, context size or workload?
These pages use typical settings. The full check models your exact setup.