i imagine you can't use the pcie 1x risers on inference workloads, like you can for crypto mining, as there's no data going between the card and the CPU in crypto and i guess inference is heavily bandwidth restricted. Unfortunate!
The PCI-E slots in something like an 1U R630 or R640 are x8 or x16, the problem is more with the cooling and size/shape of the cards and how they cool themselves. The slots are meant to be used with things like 10 or 100 Gbps network cards or SAS/SATA host adapters which are considerably lower wattage than even a video card that's much weaker than an intel 770.
Commonly you will also find configuration with two or three 'low profile' pci-express slots which have a different card height than the 'standard' height that most GPUs are built at.
that works for crypto because all the CPU sends to the card is the target ledger sha256sum (simplified) and the GPU generates nonces until the `sha256sum(sha256sum(nonce += ledger sum)` has however many zeros in the front. So until a card finds the correct nonce, or the server sends "new work" - a new ledger shasum, there's no traffic, really, between the GPU and the CPU. housekeeping, whatever, but not like 1GB/s!
There are Xeon-based crypto motherboards on AliExpress with ~five x8 slots, I do sometimes wonder if those would work. NVIDIA Tesla K80/P40 24GB are on eBay for minimum $15 apiece. 120GB VRAM under $500 or so. Or maybe you could theoretically do a 96GB per node cluster with one x8 link for bottleneck free interconnect.
But it's likely never going to work, too many driver, compatibility, requisite Kernel development, and power issues, to name a few. Probably cheaper in the end to just go buy 5090 and rant about CUDA.
I had a couple of those boards. The full size slots aren't actually x8, because the CPU those boards support only have 24 PCIe lanes, and over half of them are just running USB, SATA, etc. The full size slots are so you can secure cards to the board, instead of running them zip tied to metal dish racks (like in the video i linked in my reply to your sibling comment: https://www.youtube.com/shorts/rTCInAXSzKA)
