Is using PCIe x16 riser for RTX 3090 for DL training will impact performance ?, and is Lian Li riser good for this ?, I want to use about 60 to 120CM PCIe Riser
I think linus from LTT already made a video about it, albeit from a PCIe Gen3. It could still be true, he started having problems after daisy chaining 6 PCIe risers. So 1 should be fine. IIRC it was an all or nothing failure with cyclic redundancy checks being a thing. No performance loss within margin of error then a hard fault when he gets to 6 risers. Then again this was PCIe gen 3. Newer generations may not be as fault tolerant but 1 riser should still be as good as no riser.
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One Riser is 60cm length, soo… I use only two riser
I build 6x - 8x RTX 3090, with WRX80 platform, It’s very big workstation, I use three 4u rackmount case…
and three 1500w power supply
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PCIe is amazing. It carries digital signals far further than the old bus designs. However each generation doubles the speed and pushes the limits of the design further. If the riser cannot handle PCIe gen3 then it will knock itself down to gen2 or gen1.
You may not notice if it’s gen2 but you will if it’s gen1.
I would say you will be fine but there is potential for it to affect performance.
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WHAT DO YOU MEAN ?, I use PCIE 4.0 Riser, NOT 3.0 or even 2.0, it’s very expensive riser cable, even each 120cm cost half GPU price
You need to check what gen it’s actually running at. Can you lock it to gen 4?
IIRC people had issues with riser cables on PCIe 4.0 when it first came out. The crux of the problem is that PCIe 4.0 is far too sensitive, and sometimes the error rate of the riser is too high. I’m assuming that newer PCIe 4.0 risers work better. The video below shows some tests of various riser cables (though its from two years ago now).
I’d temper your expectations and do some testing of how your workload performs at PCIe 3.0 and PCIe 4.0. You may not have a performance issue at PCIe 3.0 - and that will provide more stability when using riser cables.
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@meowsoft wayland is asking you legit question, no need to get hostile about it. Please keep discussion civil.
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When they first made gen4 they even had trouble getting it to work on the motherboard. It could only reach the first socket reliably. On cheaper motherboards that’s still how it is.
It will probably be fine at gen3. However because computers try their best to work they are usually set to automatically chose the best settings that work. In the case of PCIe it will carry on as if nothing is wrong even if the cables only worked at gen1 x1. You’d obviously spot that immediately because you’d see how slow it was. You would not get an error though. At gen2 x4 you would not know there was a problem until you did benchmarks.
At gen3 x16 even the benchmarks would not show you were not at gen4.
If it was my workstation I’d want to know if my gen4 cards were working at gen4 when there is a risk they may not be. I might even lock them at gen3 just to be safe.
In the bios there is a board explorer, a graphic mimic of the motherboard. Hovering the mouse over the socket tells you what’s plugged in and the rate at which it’s connected, lanes and gen.
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