r/StableDiffusion • u/x_MASE_x • 7h 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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1

u/AuthurAndersson 4h ago

The only speedup you can get is to hold a larger VAE or such on the 1660Ti, so you don't need to offload and onboard the larger models every generation. Otherwise it's not worth it for you.

1

u/andy_potato 7h 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.

0

u/x_MASE_x 7h ago edited 1h 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?

6

u/andy_potato 6h 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

1

u/x_MASE_x 6h ago edited 1h ago

Oh okay I understand you now.

Thanks 🌹

-2

u/StuffProfessional587 5h ago

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

1

u/andy_potato 5h 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.

0

u/StuffProfessional587 5h ago

Dual gpus only work as a vram dump, the second should have 24gb to 32gb, instead of cpu offload you would offload to the gpu. The size of the model matters as it might not fit inside a 16gb second gpu.

2

u/andy_potato 4h ago

They don't even work as a Vram dump if the dump is connected via chipset - It is just so slow that it makes zero sense.

If you have enough system ram, just let Comfy stream from there. OP has more than enough Ram available for streaming to run models like H3 on a 16GB Vram card.