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Flash-MoE: Running a 397B Parameter Model on a Laptop

GitHub - danveloper/flash-moe: Running a big model on a small laptop

github.com

March 22, 2026

6 min read

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65/100

Summary

Flash-Moe is a pure C/Metal inference engine that runs the Qwen3.5-397B-A17B model, a 397 billion parameter Mixture-of-Experts model, on a MacBook Pro with 48GB RAM at over 4.4 tokens per second. The 209GB model streams from SSD using a custom Metal compute pipeline without relying on Python or other frameworks.

Key Takeaways

A 397 billion parameter Mixture-of-Experts model, Qwen3.5-397B-A17B, runs on a MacBook Pro with 48GB RAM at over 4.4 tokens per second using a custom C/Metal inference engine.
The model utilizes a 209GB data size, streamed from SSD with no reliance on Python or frameworks, employing only C, Objective-C, and hand-tuned Metal shaders.
The architecture includes 60 transformer layers with 512 experts per layer, activating K=4 experts per token for processing.
The system achieves a 71% hit rate for expert data caching using the OS page cache, outperforming custom caching approaches.

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Analysis ready

Community Sentiment

Mixed

Positives

Running the 397B parameter Qwen 3.5 model on consumer devices is now feasible, showcasing advancements in model quantization and accessibility.
Achieving an 87.86% score on the MMLU benchmark indicates that the model performs well even on limited hardware, which is promising for broader AI applications.
The success of running the model on an M1 Ultra with substantial context length highlights the potential for high-performance AI on consumer-grade devices.

Concerns

Reducing the number of experts per token to fit the model on consumer hardware may significantly degrade performance, raising concerns about the trade-offs in quality.
The reliance on 2-bit quantization for running large models could lead to inadequate performance for real-world applications, limiting its practical usability.