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Yes. gpt-oss 20B (MoE, MXFP4) fits in fast memory on M3 Max (40c GPU) 64GB at MXFP4 (15.1 GB needed, 48.0 GB usable), about 66 tok/s (estimate).
Hardware: M3 Max (40c GPU) 64GB · Model: gpt-oss 20B (MoE, MXFP4)
M3 Max (40c GPU) 64GB has 64 GB of unified memory and 400 GB/s of memory bandwidth. M1 Max (32c GPU) 64GB and M2 Max (30c GPU) 64GB and M2 Max (38c GPU) 64GB have the same memory and bandwidth, so the fit numbers match; this page is M3 Max (40c GPU) 64GB. The checker leaves macOS a share of unified memory, so Ollama can use 48.0 GB. gpt-oss 20B (MoE, MXFP4) (20.9B, 3.6B active, OpenAI) at MXFP4 is a 14 GB download and needs 15.1 GB with headroom for about 8k tokens.
| Best quant | MXFP4 |
|---|---|
| Download size | 14 GB |
| Memory needed | 15.1 GB |
| Usable fast memory | 48.0 GB |
| Fit | fits in fast memory |
| Estimated speed | ~66 tok/s (estimate) |
| Command | ollama run gpt-oss:20b |
Estimates, not benchmarks. Model sizes are ollama.com download sizes; memory needed adds headroom for ~8k tokens of context; speeds are rough figures from memory bandwidth. Data updated 2026-10-23.
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