this post was submitted on 09 Apr 2025
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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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[–] [email protected] 9 points 1 week ago* (last edited 1 week ago) (1 children)

Basically no GPU needs a full PCIe x16 slot to run at full speed. There are motherboards out there which will give you 3 or 4 slots of PCIe x8 electrical (x16 physical). I would look into those.

Edit: If you are willing to buy a board that supports AMD Epyc processors, you can get boards with basically as many PCIe slots as you could ever hope for. But that is almost certainly overkill for this task.

[–] [email protected] 2 points 1 week ago (3 children)

Aren't Epyc boards really expensive? I was going to buy 3-4 used computers and stuff a GPU in each.

Are there motherboards on the used market that can run the E5-2600 V4 series CPUs and have multiple PCIe Xi slots? The only ones I found were super expensive/esoteric.

[–] [email protected] 4 points 1 week ago* (last edited 1 week ago) (1 children)

Prior-gen Epyc boards show up on eBay from time to time, often as CPU+mobo bundles from Chinese datacenters that are upgrading to latest gen. These can be had for a deal, if they're still available, and would provide PCIe lanes for days.

[–] [email protected] 3 points 1 week ago* (last edited 1 week ago) (2 children)

Yeah, adding to your post, Threadripper also has lots of PCIe lanes. Here is one that has 4 x16 slots. And, note, I am not endorsing that specific listing. I did very minimal research on that listing, just using it as an example.

Edit: Marauding_gibberish, if you need/want AM5: x670E motherboards have a good number of PCIe lanes and can be bought used now (x870E are newest gen AM5 with lots of lanes as well, but both pale compared to what you can get with Epyc or Threadripper).

[–] [email protected] 2 points 1 week ago

Thanks for the tip on x670, I'll take a look

[–] [email protected] 2 points 1 week ago (1 children)

I see. I must be doing something wrong because the only ones I found were over $1000 on eBay. Do you have any tips/favoured listings?

[–] [email protected] 1 points 1 week ago* (last edited 1 week ago)

All I did for that one was search "Threadripper" and look at the pictures for ones with 4x x16 slots that were not hella expensive. There are technically filters for that, but, I don't trust people to list their things correctly.

For which chipsets, ect to look for, check out this page. If you click on Learn More next to AM5 for example, it tells you how many PCIe lanes are on each chipset type which can give you some initial search criteria to look for. (That is what made me point out x670E as it has the most lanes, but is not newest gen, so you can find used versions.)

[–] [email protected] 3 points 1 week ago* (last edited 1 week ago) (1 children)

Hey I built a micro -atx epyc for work that has tons of pcie slots. Pretty sure it was an ASRock (or ASRack). I can find the details tomorrow if you'd like. Just let me know!

E: well, it looks like I remembered wrong and it was an atx, not micro. I think it is ASRock Rack ROMED8-2T and it has 7 PCIe4.0 x16 (I needed a lot). Unfortunately I don't think it's sold anymore other than really high prices on eBay.

[–] [email protected] 2 points 1 week ago (1 children)

Thank you, and that highlights the problem - I don't see any affordable options (around $200 or so for a motherboard + CPU combo) for a lot of PCIe lanes other than purchasing Frankenstein boards from Aliexpress. Which isn't going to be a thing for much longer with tariffs, so I'm looking elsewhere

[–] [email protected] 4 points 1 week ago

Yes, I inadvertently emphasized your challenge :-/