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Pcie slot 1 only 8x?

CoolMan
Level 7
Lo.
I just got an asus rampage v extreme and i'm having issues with the first pcie slot. It will only run at 8x instead of 16x.

I'm running an intel 5960x cpu with 2 780ti's in slot 1 (pcie_x16_1) and slot 4 (pcie_x16/x8_3) as per the manual.
However the bios says the card in slot 1 is detected, but running at 8x native, but the card in slot 4 runs at 16x.
All power including the ez plug are connected.
And if i run uniengine benchmark it says that the card in slot 1 is only at 324Mhz where the card in slot 4 runs at full speed and my scores are way down because of it.

Even using the dip switch to disable all slots except slot 1 and bios still says only 8x even with all sata drives etc disconnected to avoid sharing.
Any idea on what could be wrong?
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11 REPLIES 11

Hopper64
Level 15
Look at page 3-35 in the manual. It's Advanced\System Agent Configuration in the bios. NB PCIe configuration. I think some have had to choose Gen 3, but Auto should work. You might try that.
MZ790AE Bios 1602, GSkill F5-8400J4052G24GX2-TR5S, 14900KS, EKWB D5 TBE 300, Seasonic Prime TX-1600 ATX 3.0, Asus Strix 4090 w/ HK block, Phanteks Enthoo Elite, Asus Claymore 2, Asus Gladius 3, Asus XG349C, Crucial T705, Windows 11 Pro

Chino
Level 15
Try reseating your GPU in the first slot. Meanwhile we're diagnosing the problem, remove your second GPU.

Please list your complete system specifications as well.

CoolMan
Level 7
Lo.
Going to try reseting and reflashing the bios later as i did get a corrupted bios screen when i swapped to EZ mode with f7 during setup.
Gen3 isnt listed in the bios menu, just auto, gen and gen 2, but gen 3 was there earlier, just not now?

I'll probably have to swap the gpu's around to ensure the problem is with slot 1 or the gpu, but water cooling makes it a pain,
not even running with the hard drives or pciessd atm to eliminate shared resources as i dont need to actually boot to windows yet as the bios confirms slot 1 is at 8x.

Specs are:
Intel 5960x, rampage v extreme with bios 1401, 2 way 780ti's, intel 750 pcie ssd, 16 Gigs g.skill ripjaws 4 ram,1500watt psu

CoolMan wrote:
Gen3 isnt listed in the bios menu, just auto, gen and gen 2, but gen 3 was there earlier, just not now?

Hello

Need to be looking ion the correct section of the UEFI. That would be NB PCI-E Configuration not PCH Configuration.

Praz wrote:
Hello

Need to be looking ion the correct section of the UEFI. That would be NB PCI-E Configuration not PCH Configuration.


Found it, i can set it to gen 3 but first slot still at 8x. I'm going to borrow a vid card to test each slot individually.

Chino
Level 15

CoolMan
Level 7
K, checled the cpu and mobo pins, all look perfect, but slot 1 still at 8x.

Any thing else i can try before sending the mobo back?

Chino
Level 15
It's probably a wise decision to borrow a GPU to test your system preferrably one thst isn't watercooled. It would save you from RMAing the wrong component.

CoolMan
Level 7
K, tested with a nvidia 670 and still stuck at 8x so the mobo is going back for a refund and i'll try to find an evga classified instead.