Info [PSA] Your Riser Might be the Cause of Weird Behaviors of SSDs or Graphics Cards on PCIE 4.0 slots


Feb 5, 2016
TL;DR: Force you PCIE version to gen3 or gen2 on the device connected to riser if you are running Ryzen 3rd gen or later on a motherboard 5th series or later.

I scratched my head for MONTHS on the problems I experienced in my rig so you don't have to!

I built a mini-ITX PC in Phanteks Evolv Shift at the beginning of this year and it just cannot stop having problems. At first it was that the SSDs will randomly malfunction during gaming sessions, and exclusively to the drive that the games run on. The games also freeze whenever I switch to another window then switch back, and I won't be able to play a video on the second screen while I play games on another because one of them will freeze. Then the graphics card start crashing constantly, forcing me to lower their clock rate to stabilize them. After a while even at the lowest clockrate I can get, my 1080 ti still kept crashing even when I try to open a browser tab when running Furmark. I tried everything: updating UEFI BIOS, moving the game between drives, even swapping the graphics cards, the issue seems to come back eventually. I even feared that I have tightened the waterblock too hard and killed my GPU.

And finally, one day the machine just quit booting altogether. I was just about to disassemble my rig and send the motherboard to RMA (since it clearly looks like a PCIE issue), a gleam of possibility crossed my mind, and a brief search brought me to this post: View:

So basically, due to the higher bandwidth of PCIE gen4, the range before the electric signal could reach the device before decaying is far shorter than that of gen3. Therefore, when the motherboard is forcing gen4 on my 1080 ti through the riser, it is causing all sorts of weird behaviors. I suspect it is either losing a lot of data and has to limit its bandwidth or the error-correcting simply throttled the performance of the entire system. If you have more insight into this please let me know.

Unlike the post suggested, I simply stepped down my PCIE_x16 to gen3, and left the two M.2 slots at gen4, et voila, all my weird problems are gone, and I am actually getting more frames in games!

So, if you are also experiencing weird problems with PCIE devices, I hope this post would help you to get one step closer to resolution.