Riser cable issues?

[Carsomyr]

I've recently ugpraded my mobo to asus maximus hero z890 and core ultra 7 265k cpu
in hwinfo64 I noticed I'm getting PCI/PCIe Bus errors (citing rtx 3080)

So for the sake of testing, when I hook my rtx 3080 (thermaltake core p90 case with pcie 3.0 riser cable) to the pcie 4.0 slot I get the erros in hwinfo64, but the display works fine, I can game and whatnot
Whenever I hook my riser cable to the pcie 5.0 slot on the motherboard, I'm getting artifacts, mouse is slow, the whole system slows down to a crawl. Isn't pcie 5.0 backwards compatible with pcie 3.0?

Am I missing something here. What should I do at this point? Should I worry about the errors I'm seeing in hwinfo64 with my pcie 3.0 riser cable connected to the pcie 4.0 slot?

I'm thinking I could upgrade my riser cable obviously. But I'd like to understand the WHY behind what's been happening.

 

[R-T-B]

The riser cable is a passive part. It's rated for only pcie 3.0 speeds, but has no way to communicate that, so your mobo is likely sending a 4.0 or 5.0 signal over it and its losing packets. The quick fix is to limit the slot to 3.0 speeds in bios, but the better fix is to replace the riser.

 

[lilhasselhoffer]

So...the logical problem solving step is to remove the riser cable, and run the card in the slot.

If you have issues, then the problem is the interface or the card. If the problem suddenly goes away then the issue is the riser.


Barring a driver update (you have a new mobo....so can we assume a clean install or did you migrate?), the other issue is that PCI-e is designed to negotiate. If the card says it can output at full PCI-e 4.0 (what the 3080 is capable of), and you've got a 5.0 slot, but the interference and noise from the riser itself corrupts signal then you're going to have issues. This is generally why people are advised not to install risers and extension cards...unless specifically rated for it. You seem to be using a PCI-e generation 3.0 riser on a system with a 5.0 socket and 4.0 card...there may be noise. That said, checking the card directly installed first is the win here...because buying a new extender or riser isn't exactly a silver bullet solution.

 

[Waldorf]

@Carsomyr
the 3080 only does 4.0, so i would always limit bios to that, even if you have a 5.0 slot/cable.

@lilhasselhoffer
sometimes that's not possible.
had a case where i could only mount the gpu rotated 45*, with no way to use a pcie slot directly, not just because of the wb/loop, but because to "rotate" the (case) cover over the pcie slots
would have required removing the mb/gpu support.

 

[_roman_]

Why #1: waves are reflected wrong on the cable.

 

[lilhasselhoffer]

@Carsomyr
the 3080 only does 4.0, so i would always limit bios to that, even if you have a 5.0 slot/cable.

@lilhasselhoffer
sometimes that's not possible.
had a case where i could only mount the gpu rotated 45*, with no way to use a pcie slot directly, not just because of the wb/loop, but because to "rotate" the (case) cover over the pcie slots
would have required removing the mb/gpu support.

Man, I'd be 100% behind you if the OP didn't include the model of the case they are using. Of note, "thermaltake core p90 case".

Twenty seconds on google images, and I know that you can pop the glass off, and temporarily run the card without the riser. It most definitely isn't the "everyday" solution, but it absolutely is a quick test away from confirming that the issue is or is not their riser card. It's also where you confirm the 3.0 nature of the riser card...so I'd ask that instead of assuming things you read. I know it's easy to project that I did nothing...but assuming that is inaccurate.

 

[Carsomyr]

Thanks guys. I did indeed find the correct setting in the bios. I can tell the motherboard what speed to run the pcie slot I'm using. I set it to pcie 3.0 given that my riser cable isn't 4.0.

I could do the same with the pcie 5.0 slot if I needed. I'll go ahead and upgrade my riser cable to pcie 4.0 and switch the bios setting again accordingly.

Thank you for mentioning the bios setting. That was the solution

 

[Waldorf]

@lilhasselhoffer
nah, didnt mean it as you not trying to help, and example, but now see that wasnt really relevant guess didnt help not being sober and missed to look at the actual case, haha