I've been experimenting with various language models and image processing tools that really need a lot of VRAM. Currently, I have an RTX 5070 Ti with 16GB for gaming. I also have a couple of older GPUs, an RTX 3070 Ti (8GB) and an RTX 1070 Ti (8GB), just sitting around. I'm curious if I can connect all three GPUs to my MSI Z790 Tomahawk motherboard to tap into a total of 32GB of VRAM.
The board has three PCIe ports: one PCIe 5 x16 is occupied by the 5070 Ti, the PCIe 3 x1 is blocked by it, leaving me with the PCIe 4 x4. My initial plan is to use the PCIe 4 slot to connect both the 3070 Ti and 1070 Ti externally, but I'm not sure if it's possible or if there are better options out there. I'm also open to the idea of setting the two older cards up separately, but I'm unsure how to integrate everything into a single virtual network. Any advice or alternatives would be appreciated! By the way, I've got additional power supplies, but I think my current MSI MEG 1300i should handle everything if needed.
3 Answers
I think your best bet might be to focus on a setup where you can utilize one GPU per task. Instead of trying to combine the older GPUs for your big models, you could run them separately for other workloads or models that can handle smaller VRAM. If you choose to extend a PCIe slot for one of them, make sure the extenders are high-quality to avoid bandwidth issues. Think of using PCIe risers to avoid fitting problems with your case layout.
It sounds like an interesting project! However, you'll likely find that consumer platforms like your MSI board are generally not designed to support more than two GPUs effectively. If you want to run three, you might want to look into workstation setups, like those using Xeon or Threadripper processors. Also, don’t expect to combine the VRAM; each GPU needs access to its VRAM independently for modeling tasks to work efficiently.
Thanks for the insight! I suspected that was the case. I'll have to rethink my setup.
While it's technically possible to get all three GPUs running, you would face significant challenges. For starters, your motherboard doesn’t support bifurcation on the PCIe 4 slot, meaning you can’t run two GPUs on that slot simultaneously. Plus, if you're mixing GPUs with different VRAM amounts, they can slow each other down. It’s generally advisable to use a single high-VRAM GPU for larger models instead of multiple lower-VRAM ones, which won’t work together effectively.
Got it! I had hoped to leverage the different GPUs, but it sounds like that's not a good plan. Thanks for the breakdown!
That makes sense! I’ll definitely look into PCIe risers. Thanks for the practical advice!