PCIe 3.0 x16 slot works only at x8

[1noon1]

I use ROG CROSSHAIR VI HERO with AMD Ryzen 7 1800X and sata disk. In the first PCIe 3.0 x16 slot - GeForce GTX 680. Other slots are free. The video card works in x8 mode always. This is displayed in the BIOS and various programs in Windows. I tried to clean contacts, but it did not help.
In my case, it's difficult for me to get a replacement motherboard from warranty service. Also I can not test it with another processor. I found some similar stories, but it's not always clear how they ended. In most cases, after replacing the motherboard, this problem was solved. I would like to hear from those who had the same problem as they solved it. What replacement solved the problem? Motherboard or CPU?

[jpmboy]

the 680 is not going to saturate x8/3.0 or x8/2.0 for that matter. Before looking ot RMA the board, I'd try a new(er) video card in that C6H.

[1noon1]

jpmboy wrote:
the 680 is not going to saturate x8/3.0 or x8/2.0 for that matter. Before looking ot RMA the board, I'd try a new(er) video card in that C6H.

I do not have such an opportunity. I wrote this above. This video card worked in my old system with Core i7-2600k. And there it was always in x16 mode. I moved it to the new system in August.

[Korth]

You've tried cleaning the electrical contacts on the PCIe card. Also the electrical contacts in the PCIe card slot?

You've tried re-seating the PCIe card, making sure it's firmly secured, wiggling it, etc? Does your motherboard have some sort of latch or locking mechanism you've overlooked?

If one card works at x16 but another only works at x8 then inspect the pins and traces on the x8 card for damage.

Is the second card getting sufficient PCIE_12V power from the PSU? It might have a faulty or damaged 12V input pins.

You can backprobe with a DMM to confirm electrical power is being delivered to all necessary PCIe pins and PSU pins, although this can be time-consuming.

If it's not a hardware fault then it has to be a firmware/software misconfiguration.

[1noon1]

Korth wrote:
You've tried cleaning the electrical contacts on the PCIe card. Also the electrical contacts in the PCIe card slot?

You've tried re-seating the PCIe card, making sure it's firmly secured, wiggling it, etc? Does your motherboard have some sort of latch or locking mechanism you've overlooked?

If one card works at x16 but another only works at x8 then inspect the pins and traces on the x8 card for damage.

Is the second card getting sufficient PCIE_12V power from the PSU? It might have a faulty or damaged 12V input pins.

You can backprobe with a DMM to confirm electrical power is being delivered to all necessary PCIe pins and PSU pins, although this can be time-consuming.

If it's not a hardware fault then it has to be a firmware/software misconfiguration.

I have only one card installed. This video card worked in 16x mode in another system. I'm not new. But I checked all the connections several times. I have a high-quality power supply from Seasonic.

[Korth]

Any way you can test your card in someone else's machine or borrow their card to test in yours? To confirm/deny hardware fault before digging into firmware/drivers/etc.

ROG CROSSHAIR VI HERO user manual, if you need it. I assume you're plugging the card into PCIE_X16/X8_1 and that PCIE_X8_2 is empty.

There's apparently a x8 restriction if the board identifies Athlon instead of Ryzen ... possibly you need to apply some kind of firmware/microcode update to get the mobo to recognize the Ryzen, possibly the CPU isn't properly seated. Though I'd focus on the GPU card before taking everything else apart, lol ... still, wiggling the RAM only takes couple seconds, quickly confirm it's not part of the problem, lol.