Can Mac Studio M3 Ultra 512 GB run Muse Spark Open 816B-A42B?
512 GB unified · 819 GB/s memory bandwidth · Muse Spark Open 816B-A42B has 816B parameters (42B active per token).
Short answer
Yes, comfortable for chat; borderline for agentic coding.
Best quantization for chat: MXFP4 (408 GB of weights) on LM Studio. Generation: 11–15 tok/s, leaving about 91 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 | Comfortable | MXFP4 | 11–15 tok/s | ≈3 s | 8K | Details |
| Coding questionswith Continue | Acceptable | MXFP4 | 10–14 tok/s | ≈20 s | 16K | Details |
| Coding in a repositorywith Aider | Acceptable | MXFP4 | 9–13 tok/s | ≈75 s | 32K | Details |
| Agentic codingwith OpenCode | Borderline | MXFP4 | 9–12 tok/s | ≈2 min | 32K | Details |
| Long documents (64K)with Open WebUI | Acceptable | MXFP4 | 7–9 tok/s | ≈7 min | 64K | Details |
Speeds are estimates calibrated against measured benchmarks on similar hardware. “First reply” is the time to read the workload’s opening prompt. How we calculate
Other models for Mac Studio M3 Ultra 512 GB
The best-rated models for chat on this machine.
- gpt-oss-120b85–120 tok/sExcellent
- Qwen3.6 35B-A3B100–130 tok/sExcellent
- Qwen3-Next 80B-A3B Instruct100–130 tok/sExcellent
- Gemma 4 26B-A4B80–110 tok/sExcellent
- Qwen3.5 35B-A3B100–130 tok/sExcellent
- LFM2.5 24B-A2B190–260 tok/sExcellent
Cheapest machines for Muse Spark Open 816B-A42B
Hardware rated comfortable or better for chat, lowest price first.
Different tool, context size or workload?
These pages use typical settings. The full check models your exact setup.