Looking for some help to diagnose why GPU is only running x8

[5950xSlowNvme]

Hi all,

I need some help to understand why my GPU appears to only be running x8 when installed to x16 slot. Confirmed via testing on GPU-Z.

1. MSI MEG Godlike x570
   1. PCIE-1 - GPU (3090)
   2. PCIE-2 - EMPTY
   3. PCIE-3 - Expander-Z card @ 4x4
   4. PCIE-4 - Soundcard
   5. M2_1 (PCH) - SN850
   6. M2_2 (PCH) - Samsung Pro
   7. M2_3 (CPU) - SN850
   8. SATA Slots - Not occupied
2. All onboard devices that are not used are disabled via BIOS, so audio and such.
3. All devices that may continue to interfere, like Bluetooth and unused LAN ports and such, disabled via Device Manager

Any ideas? From what I've researched, the above setup should not theoretically have any impact on the PCIE lanes for the GPU but I'm loathe to start taking hardware out and testing, just because of the size of the GPU and the install locations of the M2 drives.

 

[TheoneandonlyMrK]

As a guy running three nvme and a GPU on AMD I am very sorry to have to tell you someone has misinformed you if you believe your pc should be able to run all that and a GPU at x16., It's that simple, the lanes are shared such that it cannot be done.

 

[5950xSlowNvme]

As a guy running three nvme and a GPU on AMD I am very sorry to have to tell you someone has misinformed you if you believe your pc should be able to run all that and a GPU at x16., It's that simple, the lanes are shared such that it cannot be done.

Thanks, can you elaborate a bit on what specific conflicts and reasons are causing that? I wasn't under the impression that M2 slot NVMEs would conflict, so are we talking the Expander-Z and Soundcard?

 

[newtekie1]

As a guy running three nvme and a GPU on AMD I am very sorry to have to tell you someone has misinformed you if you believe your pc should be able to run all that and a GPU at x16., It's that simple, the lanes are shared such that it cannot be done.

The 3 M.2 slots on the motherboard can all be used with the graphics card still running at x16.

The issue is the Expander-Z card installed in the PCIE-3 slot. PCIE-1, PCIE-2, and PCIE-3 all share the x16 link. So if one slot is in use it runs as x16/x0/x0, if two cards are inserted it runs at x8/x0/x8(This is the OP's situation), if 3 cards are inserted it runs at x8/x4/x4.

If you aren't using it, take out the Expander-Z, or take out the sound card and move the Expander-Z to PCIE-4.

 

[5950xSlowNvme]

The 3 M.2 slots on the motherboard can all be used with the graphics card still running at x16.

The issue is the Expander-Z card installed in the PCIE-3 slot. PCIE-1, PCIE-2, and PCIE-3 all share the x16 link. So if one slot is in use it runs as x16/x0/x0, if two cards are inserted it runs at x8/x0/x8(This is the OP's situation), if 3 cards are inserted it runs at x8/x4/x4.

If you aren't using it, take out the Expander-Z, or take out the sound card and move the Expander-Z to PCIE-4.

Thanks a ton for that breakdown, thoroughly appreciated. I'm actively using the Expander card for two more NVME storage, so happy to take the tiny hit to GPU performance by dropping to 8x. I just really wanted to be sure on why it was happening.

Thanks again for taking the time.

 

[TheoneandonlyMrK]

Thanks a ton for that breakdown, thoroughly appreciated. I'm actively using the Expander card for two more NVME storage, so happy to take the tiny hit to GPU performance by dropping to 8x. I just really wanted to be sure on why it was happening.

Thanks again for taking the time.

I take the same hit to have two pciex nvme in the pciex Slot. One other nvme direct to CPU pciex Slot and SATA turned off, given the drive's and lanes available it's the best way.

 

[SuperTweaker]

TheoneandonlyMrK​

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