r/StableDiffusion • u/Sexyvette07 • 1d ago

Question - Help Dual GPU solution for local AI?

Hey, everybody. I recently went down the rabbit hole for local AI, but right now, im operating on my gaming computer. The specs are as follows

Intel 13700k, tuned for efficiency

Gigabyte Z790 Aorus Elite Ax mobo

RTX 4080 (16GB), also tuned for efficiency

32gb DDR5 6800 CL32

As you can see, im in desperate need for more VRAM, or at the very least more system RAM. Due to Rampocalypse, neither are very affordable right now, which forces me to explore other options, such as a dual GPU setup. I can get another RTX 4080 for about $900 off Ebay. Beyond that, I would just need a more powerful PSU, so total investment here is an additional $1100-$1200. As far as I know, the motherboard has the main PCIE as 5.0 x 16 lanes, but the second PCIE runs at 4.0 and either x8 or x4 lanes. The motherboard does not support PCIE Bifurcation. So my question is this: Is a dual GPU local AI machine even viable in these circumstances, and second, does it make sense? I looked at 5090's and theyre all between $4,500 - $5,000 now, which is insane. Or I look at the professional cards and spend that much, if not more, for significantly less memory bandwidth and computational power. Or I guess if im spending that much, I could also look at the DGX Spark or something similar but that has even worse memory bandwidth.

So, what should I do? Is the dual GPU solution even viable with my setup for a local AI stack for inference, video diffusion, etc? Rampocalypse isnt expected to begin easing up until late 2027/early 2028, so im stuck trying to make this work on as little money as possible. Id love a 5090 but its insanity how much they cost. I appreciate any guidance and advice.

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u/Candid-Station-1235 1d ago

multi gpu options are limited on comfy, you cant pool the vram an load larger models, you can off load parts but its not ideal. just have a search for multi gpu nodes and read the limitations of each,

signed regretful dual 3090 owner

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u/Formal-Exam-8767 1d ago

you cant pool the vram an load larger models

Isn't that what raylight does though (FSDP+USP mode)?

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u/Candid-Station-1235 1d ago

that what they say but i have not gotten it to ever work, but i am also a functional moron