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The problem is simple: consumer motherboards don't have that many PCIe slots, and consumer CPUs don't have enough lanes to run 3+ GPUs at full PCIe gen 3 or gen 4 speeds.

My idea was to buy 3-4 computers for cheap, slot a GPU into each of them and use 4 of them in tandem. I imagine this will require some sort of agent running on each node which will be connected through a 10Gbe network. I can get a 10Gbe network running for this project.

Does Ollama or any other local AI project support this? Getting a server motherboard with CPU is going to get expensive very quickly, but this would be a great alternative.

Thanks

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Thank you, but which consumer motherboard + CPU combo is giving me 32 lanes of PCIe Gen 4 neatly divided into 2 x16 slots for me to put 2 GPUs in? I only asked this question because I was going to buy used computers and stuff a GPU in each.

Your point about networking is valid, and I'll be hesitant to invest in 25Gbe right now

[-] CondorWonder@lemmy.ca 4 points 1 year ago* (last edited 1 year ago)

You don’t need cards to have full bandwidth, they only time it will matter is when you’re loading the models on the card. You need a motherboard with x16 slots but even x4 connections would be good enough. Running the model doesn’t need a lot of bandwidth. Remember you only load the model once then reuse it.

An x4 pcie gen 4 slot has ~7.8 GiB/s theoretical transfer rate (after overhead), a x16 has ~31.5GiB/s - so disk I/O is likely your limit even for a x4 slot.

  • overhead was already in calculations

I see. That solves a lot of the headaches I imagined I would have. Thank you so much for clearing that up

this post was submitted on 09 Apr 2025
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