[r/LocalLLaMA] I spent 8+ hours benchmarking every MoE backend for Qwen3.5-397B NVFP4 on 4x RTX PRO 6000 (SM120). Here's what I found.

Summary

A user benchmarked MoE backends for Qwen3.5-397B NVFP4 on 4x RTX PRO 6000 GPUs, achieving a sustained decode rate of 50.5 tok/s. This performance is significantly lower than claims of 130+ tok/s, with the discrepancy attributed to broken NVIDIA CUTLASS kernels on their own workstation Blackwell GPUs (SM120). The finding exposes a critical software-hardware compatibility issue impacting real-world performance for users of this specific setup.

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