Z790 Dark Hero - GPU only using 8x PCI lanes

[mrosenbu]

New 14900k build here.  Coming from a 12900k + Maximus VIII mobo + 4 x m.2 drives + 4090.

New build boots fine.  M.2 drives are installed on the mobo in M2_2 through M2_5 slots (leaving M2_1 free for 16x lanes for the 4090).  No other peripherals are installed (though I do have 2 SATA cables plugged in, albeit with no drives plugged in - option value and all).

the 4090 is showing in GPU-z as running at 8x instead of 16x (the old build was indeed running at 16x).

Are any of the other M2 slots using the GPU lanes?  To be clear, M2_1 is free and open (that the slot right above the first GPU PCI-E slot, which is secured via a separate heatsink / cover - I never removed that).

any thoughts would be helpful - thank you.

[achugh]

So I opened the nVidia Control Panel and clicked on System Information link on the bottom left. It shows me that I am running 8 lanes at Gen 4.

In my case, this is correct because RTX 4090 is a GEN 4 card and since I have a drive in M.2_1 slot I am only sending 8 lanes to my PEG slot.

I do not understand why HWiNFO is giving a different information. Maybe someone else here who knows what is going on with HWiNFO can share their knowledge with us.

[mrosenbu]

Right - I think your config is correct, given that you have an NVME drive in m2_1, right?

I don’t have anything in M2_1, so technically I should be at 4.0 x16.

[achugh]

Yes, I do have a drive in M.2_1 so my information is reported correctly.

Have you tried to CLEAR CMOS? If you do, when you go back to the screen where you see PCIEX16(G5)_1 Link Speed, in the GREY TEXT do you still see X8 or does it switch to X16?

[Silent_Scone · Accepted solution]

Hi @mrosenbu 

Seems you're being lead up the garden path here.

1. Update to BIOS 1503

2. Remove all M.2 devices from the system.

3. Inspect PCIE Configuration Page in the UEFI and confirm link speed.

4. If no change, remove any riser cables being used for the GPU and reseat the CPU, inspect the socket for any debris and remount ensuring consistent mounting pressure.

Assuming there aren't any devices occupying the documented slots, there's no configurative reason the GPU would not be detected at 16 lanes

[mrosenbu]

@Silent_Scone and @achugh - I want to let you both know that after a thorough examination of every part in my new build, I unsocketed the CPU and it turns out that I bent a pin on the MoBo socket when installing the CPU.  I got a new board, socketed the CPU (this time without being a clod and bending pins), and voila - x16 PCIE GPU slot.

Sigh - I''m sorry to have wasted your time.  I sincerely appreciate the support and I'll be sure to pay it forward however I can.

[Silent_Scone]

Hi @mrosenbu 

No need to apologise at all, if you hadn't asked you wouldn't have gotten the needed response. These things happen, I'm glad you were able to determine the root cause 👍