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PCI-E runs at x8 instead of x16

_fess
Level 8
Hello,

I've recently updated BIOS to 0802 and GPU seems to have started running at "native x8 link speed." It used to always run PCI-E 3.0 @ x16, but now BIOS, GPU-Z and CPU-Z all show that it runs PCI-E 3.0 @ x8. Running GPU-Z render test or UNIGINE benchmarks doesn't help. It still shows PCI 3.0 @ x8. Clearing CMOS, reseating vid card didn't help. Running BIOS at optimized defaults didn't help. I'm running out of options here. Do you think I "broke" the mobo or vid card somehow or is it the BIOS issue. I hope it's the latter one. PC is only a month old and I had no issues with it until the recent BIOS update from 0505 to 0802. Here are my specs:

BIOS: 0802
OC'ed? No.
Motherboard: Asus ROG MAXIMUS X HERO (WI-FI AC)
CPU: Intel Core i7-8700K
AIO: Corsair H100i v2
RAM: Corsair Vengeance LPX 32GB (2 x 16GB) DDR4-3200
SSD: Samsung 850 EVO-Series 500GB 2.5"
NVMe (Boot): Samsung 960 PRO 512GB M.2-2280
NVMe (Games): Samsung 960 EVO 1TB M.2-2280
Graphics Card: Asus GeForce GTX 1080 Ti 11GB STRIX GAMING
PSU: EVGA SuperNOVA P2 850W

Thank you for your help!
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52 REPLIES 52

Silent_Scone
Super Moderator
Firstly can you confirm if the GPU is in PCIe x16/x8_1 (the top 16x length slot on the board)?

Is there anything in If PCIe_x8_2? If this slot is occupied, PCIe x16/x8_1will revert to 8x mode.
13900KS / 8000 CAS36 / ROG APEX Z790 / ROG TUF RTX 4090

Are you by chance using a pcie riser cable like the one included with the Thermaltake Core P series cases?

Starscream wrote:
Are you by chance using a pcie riser cable like the one included with the Thermaltake Core P series cases?


No riser cables. The card is plugged straight into top PCI-E x16 slot with 2x8pin cables coming out of it.

When I had this issue on a Maximus IX Hero it was due to a single motherboard pin slightly out of place, moved it back and everything was fine after that. Did you happen to remount your CPU or maybe bumped the case causing an issue with the GPU->PCI-E contact? Check the CPU socket and try reseating the GPU. Also did a screen ever pop up notifying you about a new CPU being installed? If a pin gets bent or something similar causing PCI-E lanes to be halved the Mobo would think a new CPU was installed.

NeoandGeo wrote:
When I had this issue on a Maximus IX Hero it was due to a single motherboard pin slightly out of place, moved it back and everything was fine after that. Did you happen to remount your CPU or maybe bumped the case causing an issue with the GPU->PCI-E contact? Check the CPU socket and try reseating the GPU. Also did a screen ever pop up notifying you about a new CPU being installed? If a pin gets bent or something similar causing PCI-E lanes to be halved the Mobo would think a new CPU was installed.


Nope, never remounted the CPU since it wasn't really giving me any issues. Never had the screen pop up on me unless it was the first POST screen after I had built a PC.

I reseated the GPU and it still shows x8 in BIOS. I switched GPU to a lower PCI-E slot with the same result.

I removed one of the M.2 drives and it still shows x8 in BIOS.

Then I completely removed the video card, pressed the Clear CMOS button, connected DP cable to motherboard DP port, loaded into BIOS, Loaded optimized defaults, reflashed BIOS, and turned PC off. Installed 1080 ti, launched into BIOS and it still showed x8 link speed :((((

I then installed GTX 760 that was laying around and for some reason the speed downgraded to PCI-E x1. WTF!? I removed it, installed on my older Z87K motherboard and it boots no problem with PCI-E 3.0 @ x16 in GPU-Z. I'm trying to think that it's either a BIOS issue or the mobo PCI-E slot failed somehow. I know for sure it was running at x16, but all of a sudden after going from 0505 to 0802 it just defauled to x8. Bizarre. I literally never touched anything inside the PC since I built it and everything was fine until recently.

.fess wrote:
Nope, never remounted the CPU since it wasn't really giving me any issues. Never had the screen pop up on me unless it was the first POST screen after I had built a PC.

I reseated the GPU and it still shows x8 in BIOS. I switched GPU to a lower PCI-E slot with the same result.

I removed one of the M.2 drives and it still shows x8 in BIOS.

Then I completely removed the video card, pressed the Clear CMOS button, connected DP cable to motherboard DP port, loaded into BIOS, Loaded optimized defaults, reflashed BIOS, and turned PC off. Installed 1080 ti, launched into BIOS and it still showed x8 link speed :((((

I then installed GTX 760 that was laying around and for some reason the speed downgraded to PCI-E x1. WTF!? I removed it, installed on my older Z87K motherboard and it boots no problem with PCI-E 3.0 @ x16 in GPU-Z. I'm trying to think that it's either a BIOS issue or the mobo PCI-E slot failed somehow. I know for sure it was running at x16, but all of a sudden after going from 0505 to 0802 it just defauled to x8. Bizarre. I literally never touched anything inside the PC since I built it and everything was fine until recently.



Did you try reflashing in 0505 bios to see if the GPU is running in 16X again ?*

Benson33 wrote:
Did you try reflashing in 0505 bios to see if the GPU is running in 16X again ?*


Yes, I reflashed it to 0505 and it still shows that GPU is running at x8 native. I then removed the 1080 ti card and put it in the Z87K board and now it shows x8 there as well so I think the issue is with the video card and not the motherboard 😞

.fess wrote:
Yes, I reflashed it to 0505 and it still shows that GPU is running at x8 native. I then removed the 1080 ti card and put it in the Z87K board and now it shows x8 there as well so I think the issue is with the video card and not the motherboard 😞


*on the Asus website, to the support of the asus 1080 Ti, you have two different Bios, the original one and another silent mode with the integrated tool to flash the card, try to flash the bios of the graphics card to see if that can correct the problem.

Other thing, *did you make a clear Cmos after reflashing the bios of the motherboard and load seeting default ?

So I returned the video card and got another one and it still shows x8 😞 I have no idea what’s wrong anymore. Am I just unlucky or do all Strix 1080 ti run at x8? Like I said I installed the card into my old z87k computer with latest BIOS and it also showed x8 on that computer as well.*