MSI suprim x 4090 stuck at x8 lanes

lingaraju.g

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I just updated my GPU from 3090 to 4090 suprim x, I am using Asus z790 apex Mobo and seasonic vertex 1200 PSU with dedicated 12vhpwr connector, in bios I set pcie to gen 4 but after reboot it is still stuck at x8 lanes, not sure if this GPU won't run in gen 4 mode even though 4090 has gen 4 host interface, In my bios setup it says if gen5 GPU is installed then it shares lanes with nvme in m.1 and goes to x8 lanes if nvme was gen 5 but my wd sn850 is gen 4 and looks like even though it is set to zen 4 the GPU might be running in gen 5 mode and I don't know how to fix this to get full gen 4 x16 bandwidth, any help appreciated.
 
I'm not familiar with Asus motherboards.....but I'd wager, if it's anything like the MSI boards, if you populate the M.2 slot that has PCIe 5.0 lanes, it will ALWAYS drop the GPU down to x8, doesn't matter if the card installed is PCIe 4.0 or 5.0, it'll always drop because of how those lanes are produced.

Ultimately, move that M.2 to another slot and see if it is x16 then. That's what I'd suggest.
 
I'm not familiar with Asus motherboards.....but I'd wager, if it's anything like the MSI boards, if you populate the M.2 slot that has PCIe 5.0 lanes, it will ALWAYS drop the GPU down to x8, doesn't matter if the card installed is PCIe 4.0 or 5.0, it'll always drop because of how those lanes are produced.

Ultimately, move that M.2 to another slot and see if it is x16 then. That's what I'd suggest.
thank you but i had similar setup before but with 3090, anyways opened and removed the gpu and cleaned pcie slot and found small [iece of tissue paper in there and after reinstall all good and i can see its back to x16 gen 4 with nvme in m.1 also gen4 x4, that piece of tissue was the problem.
 
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