RTX 4080 + 3090 for ComfyUI: is a Thunderbolt eGPU setup viable?
MrMagic550 · reddit · 2026-10-19
A user with an RTX 4080 picked up an RTX 3090 for ComfyUI but can't fit both cards in their current motherboard and case. The options are a full rebuild (new mobo, case, maybe PSU) or running the 3090 as a Thunderbolt external GPU. They'd accept roughly 70% of a PCIe x8 slot's performance in exchange for a flexible setup, and ask whether that's realistic — a classic multi-GPU trade-off for local AI inference.
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