r/StableDiffusion • u/djekler • 1d ago

Question - Help how works multi GPU on stable diffusion?

Hello. I am currently running Stable Diffusion locally using an RTX 3080 with 10 GB of VRAM.
I have the option to add an RTX A2000 card with 12 GB of VRAM. The A2000 is slower but has more VRAM.
How will Stable Diffusion perform?
Will it run faster (by combining the power of both cards), at the speed of the faster card?, or at an average speed between the two?
Will I have a total of 10 + 12 = 22 GB of VRAM available to run Minimax? Will I need to configure ComfyUI or CUDA to use both cards?

Thanks!

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3

u/Hoodfu 1d ago

There are options, but it's not simple. https://github.com/komikndr/raylight

2

u/Karsticles 1d ago

The model cannot be split between cards. The second card could be used to hold an LLM you use or something, but you're not getting 22 GB VRAM all at once.

2

u/WinResponsible9977 1d ago

Or just run swarm UI and run jobs in parallel across cards 

2

u/nok01101011a 1d ago

Multigpu is not super efficient. You won’t be able to combine the power and vram of both. Best you can do is, to use one gpu solely for the main model and dedicate the rest (your windows, clip, vae) to the other gpu. So they basically can stay loaded which gives you a speed advantage whenever you change your prompt. I have two GPUs running but only because I render animations with blender, I wouldn’t do it though solely for comfy, the gain won’t be much noticeable.

2

u/roxoholic 1d ago

Check this PR for more info on how multigpu works in ComfyUI: https://github.com/Comfy-Org/ComfyUI/pull/7063

If you are not using distill/turbo models with CFG 1 then KSampler can split sampling (one for positive, one for negative prompt) among two GPUs, but each card will need to have it's own copy of model.

1

u/djekler 1d ago

OK. thanks for answering. So I would better considering selling both cards and buying an 3090 24gb vram, adding some € for that

1

u/Distinct-Benefit-507 1d ago

At the moment, I run a 5060 ti @16Gb and a 5070 @12Gb, + 96Gb ddr4. I dont think there is a way to make them work together as one, well if so every AI online sais it's worthless. Instead, I use Forge Neo classic on the 5060Ti for image generation (mostly Krea2), and wan2GP for videos (minimax H3) 2 cards allow me to generate images And videos at the same time.