RTX 5090 MiniMax H3 performance degrades 8.7× at 2MP resolution

Suspicious-Walk-815 · reddit · 2026-08-30

A user running MiniMax H3 (ref2va, 20GB int8) via ComfyUI on an RTX 5090 (32GB) reports severe super-linear performance degradation. At 1MP resolution, per-step time is 30s (vs 21s reference), but at 2MP it spikes to 590s (vs 68s reference), an 8.7× slowdown. This suggests VRAM thrashing where the working set (model + activations) exceeds 32GB, causing CPU offloading every step. The setup includes PyTorch 2.12, CUDA 13.0, sageattention, and specific ComfyUI launch arguments. Adjustments like --reserve-vram 1 did not resolve the issue, and the process stalled at 1.5MP. The user seeks help diagnosing the configuration and valid workflows for RTX 5090.

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