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I ran 120B MoE models on my 32GB M1 Max using under 16 GB

mitln.github.io35 points10 comments
Screenshot of I ran 120B MoE models on my 32GB M1 Max using under 16 GB

A prototype inference engine runs GPT-OSS-120B and Qwen3.5-122B-A10B on a 32GB M1 Max while enforcing a 16 GiB process-memory budget. It keeps most mixture-of-experts weights on the SSD and loads what inference needs, aiming not only to fit large models but to keep macOS and other applications responsive. In a controlled comparison using matching GPT-OSS weights, it averaged 7.84 tokens per second versus 5.78 for TUFF, about 36% faster. With another process using 4 GiB of RAM, its speed advantage grew: the prototype slowed about 3%, while TUFF slowed about 23%. The prototype also kept model data out of the macOS file cache and compressed memory near idle levels. A competing process’s 4 GiB page-touch pass took a median 4 ms with the prototype running, compared with 352 ms with TUFF.

The results emerged after correcting misleading benchmarks caused by cached model data and bugs in numerical handling and prefix-cache reuse. In current tests, all nine reference cases for each 120B-class model matched generated token IDs and logit hashes; additional GPT-OSS stress and cancel-and-retry tests also found no corruption. These checks do not establish correctness for every input. The comparison covers one laptop, one request at a time, and mostly decoding; TUFF prefills a long prompt faster in an earlier test. The engine’s code is not yet released, and Qwen’s comparative speed results remain to be redone. The work’s central claim is therefore a promising, carefully measured approach to predictable-memory MoE inference on Apple Silicon - not a general performance ranking or a claim to have invented expert offloading.

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