- Aug 31, 2018
It's not a matter of need. I simply have no reason not to use a PCIE 4.0 cable.What do you need a PCIe 4.0 riser for? I asked this same question and quickly realized it was irrelevant. PCIe bandwidth on GPUs is complete overkill at the moment. You don't need even 8 lanes of PCIe gen 3 to run any single GPU at full speed. All PCIe4 is good for at the moment is IO like SSDs that can actually saturate their links, and the only reason this becomes relevant to SSDs is because the M.2 form factor only has enough traces for 4 lanes, so M.2 slots are doubling in speed. If they were PCIe-attached in 8x or 16x slots, the jump to PCIe4 would be irrelevant.
Also, the PCIe Bifurcation case makes all this even more messy. The Bifurcation risers I believe need two cards running at the same PCIe speed to function properly, so I don't think you can even do one 8x slot at PCIe gen4 and one 8x slot at PCIe gen 3, but who knows since the whole "standard" is poorly documented.
So don't get wrapped around the axles on PCIe4 risers. The only place it seems to matter right now are on M.2 SSDs, and generally speaking these don't need risers.