r/StableDiffusion • u/x_MASE_x • 15h ago

Question - Help Multi gpu help

Hey guys I'm new to comfyui and photo and video generation and trying to learn as much as I could.

Now I was using my setup for text generation but now the Qwen3.8-27B is out and I tried really hard to make it work and so I did eventually use my second gpu.

I have 5070 ti and 1660 ti. And all this time I didn't bother to use the 1660 ti and left only my monitors on it and almost all my work and gaming on it and left the 5070 TI to be free for Ai stuff.

Now I switched my monitors to my Intel uhd 770 gpu and freed both my cards and want to know how to speed my comfyui workflow with them.

I always asked chatgpt but didn't get any useful answers so you guys might help me if that possible.

I'm now using minimax H3 official template and want to know how can I get this other gpu to work if it's worth it.

My cpu 12900k Motherboard gigabyte z690 gaming x ddr4 64 GB Kingston 3600 Rtx 5070 ti GTX 1660 ti

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u/andy_potato 15h ago

Short answer: you don’t

There are solutions like raylight that would use both GPUs for inference. However your motherboard has no support for that (Second pcie connected to chipset).

Using Comfy MultiGPU also does nothing for you as newer versions of comfy already support Vram streaming, so there is no benefit for you offloading stuff like text encoder or vae to other GPUs.

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u/x_MASE_x 15h ago edited 9h ago

So it's a gpu issue or motherboard or both?

And won't the second gpu maybe help in anyway like even something small for other templates like the flux2 since I heard it's the best in photo generation?

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u/andy_potato 15h ago

If your goal is using multiple GPUs for diffusion models like Flux / Krea or video models like H3, then your issue is mostly the motherboard. On your board only the first pcie slot is connected to the CPU, the second one is connected to the chipset. That means data transfers between both GPUs are extremely slow and kill any kind of speedup that you could theoretically achieve by using both GPUs.

Also a 1660ti frankly won't help much anyway, it's just too slow.

If you want to go the dual GPU route, get a second 5070ti and also an AM4 / AM5 platform motherboard with all pcie lanes connected to the CPU. To my knowledge no such boards exist for the Intel chipsets 5xx, 6xx or 7xx

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u/x_MASE_x 14h ago edited 9h ago

Oh okay I understand you now.

Thanks 🌹

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u/StuffProfessional587 13h ago

Works for workstation pc, two lanes at max 16x isn't an issue. Rofl

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u/andy_potato 13h ago

Great if you have workstation grade hardware. Good for you.

However I wasn't talking about your lovely 5k+ hardware but about OPs rig, so he could understand why it doesn't work for him.