[r/LocalLLaMA] 55 → 282 tok/s: How I got Qwen3.5-397B running at speed on 4x RTX PRO 6000 Blackwell

Summary

A user successfully optimized Qwen3.5-397B, an MoE model, on Blackwell SM120 GPUs (like RTX PRO 6000), increasing inference speed from 55 tok/s to 282 tok/s. This significant performance boost was achieved by developing a custom CUTLASS kernel to resolve issues with MoE GEMM tiles specific to these GPUs. The solution has been submitted as a PR to FlashInfer, and a pre-built Docker image is available for other users.

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