ComfyUI: Why --cache-classic drastically improves memory management on RTX 5090

EasternAd8821 · reddit · 2026-08-22

User reports severe performance issues with a 60GB BF16 model on an RTX 5090 (32GB VRAM, 128GB RAM) using default dynamic memory settings, causing maxed out VRAM/RAM and SSD swap slowdowns. Switching to the --cache-classic startup flag reduces VRAM usage to 25GB and system RAM to 35GB, restoring acceptable speeds (42s/step). The post questions why the legacy cache mode outperforms modern management on high-end hardware.

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