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Comment by electronsoup | Hacker News Reader

Which mainboards are cheap and have 4 pcie16x (electrical) slots, that don't need weird risers to fit 4 GPUs

Consumer CPUs don't have enough PCIE lanes to do that. Even if they had physical x16 slots, at most two of them would be x16.

What's cheap to you? You can find Epyc 7002/7003 boards on ebay in the $400 range and those will do it. That's probably the best deal for 4x PCIE 4.0 x16 and DDR4. Probably $500 range with a CPU. That's in the ballpark of a mid to high end consumer setup these days.

That's the path I'm taking. All with all those PCI-e lanes available.

If I had more income, I would also buy 4x 96g Optane drives of p0 swap disks and a few ssd's for p1 swap disks. To evaluate how well you can get a 1T model running in these absurd ram prices.

If your actual gripe is risers, sounds like a "you" problem, not a technical problem.

Even if you're fine with risers, that might not be enough. If the bridge lanes are PCIe Gen 3, as many consumer boards have, your Gen 5 card might not init. I extensively tested several motherboards to try and get my AM5 CPU talking to a triple Radeon AI Pro 9700 XT setup, and they absolutely refuse to come up on PCIe3. I was using dummy EDID plugs for them, so they think they have a display, ruling out that issue.

What I eventually had to do was buy a used Threadripper box to run those cards, because PCIe Gen 4 definitely works.

To be super blunt, this also sounds like a “you” problem.

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