M.2_2 Slot Always Runs at 1x on STRIX Z790-E GAMING WIFI

[crymsonsunset]

Problem
The M.2_2 slot only runs at x1 (single PCIe lane) no matter how the system is configured, even with the graphics slot set to x8. Note that I'm running 2 SSDs, one in M.2_2 and one in M.2_5. I've tried swapping the drives, but the drive installed in M.2_2 always runs at x1. Has anyone else encountered this problem? Is there a solution?

Configuration

• STRIX Z790-E GAMING WIFI, BIOS 0813
  
• I9-13900K
  
• Arctic Liquid Freezer II 360
  
• RTX 3080 Ti
  
• 32GB G.Skill DDR5-6000 (F5-6000J3038F16G)
  
• Samsung 990 PRO 2TB -> M.2_2 -> Always runs at x1
  
• Samsung 990 PRO 2TB -> M.2_5 -> Always runs at x4
  

[JohnAb]

Never heard that one before. But, ME firmware not matching the BIOS can cause NVME problems (sometimes causing a slot not to work at all). Just thought I'd also ask if your ME firmware matches your BIOS. Have a look on your support page and if you have the latest BIOS it will also say what firmware you should be on.

It's a longshot, but otherwise I'm thinking drivers or a strange BIOS config. What happens if you reset the BIOS to defaults?

[crymsonsunset]

JohnAb wrote:
Never heard that one before. But, ME firmware not matching the BIOS can cause NVME problems (sometimes causing a slot not to work at all). Just thought I'd also ask if your ME firmware matches your BIOS. Have a look on your support page and if you have the latest BIOS it will also say what firmware you should be on.

It's a longshot, but otherwise I'm thinking drivers or a strange BIOS config. What happens if you reset the BIOS to defaults?

BIOS versions 0813 and 0703 with optimized settings both behave this way. I'll try reflashing the ME firmware and see what happens. Good suggestion. I don't think it is driver-related (running the standard MS storage driver in Windows 11, FWIW) because BIOS itself reports the link speed as x1 and both HWiNFO and Samsung Magician report the same. Benchmarks confirm that performance on the drive in the M.2_2 slot is dramatically below expectations for the drive - and dramatically below performance of the same drive installed in the M.2_5 slot.

[JohnAb]

OK, the next idea is to disable all power settings that you can find, both in Windows and in the BIOS. It's just another guess I'm afraid, unless there is a hardware related issue. Even that seems unlikely though, unless a motherboard trace has been damaged? Otherwise I would have thought that the slot would not work at all. I'll continue to have a think but this seems like a tough one!

Do you have any other PCIe devices plugged in? I'm assuming you have a GPU, but anything else that might be stealing lanes due to a weird fault? No, I think not, that's a stupid idea. Hmmm. Do you have all slot speeds set to auto? I remember that it's possible to select x3, but I don't think x1 is an option.

[crymsonsunset]

SOLVED

TLDR; There was a single hair - one of mine, I believe - in the CPU socket. I removed it, and the problem disappeared.

JohnAb - appreciate your help. While the root cause didn't turn out to be any of our guesses, your comment about motherboard traces potentially being damaged got me thinking. I was pretty careful during the build. I didn't think I damaged anything, but I wondered if maybe there was a problem in the way the CPU was seated in the socket. I decided to reseat it. When I took the CPU out and looked at the socket with a magnifying glass, I discovered a fine hair running across many pins. Kind of amazing that the system worked at all. Not only was it working, but aside from the PCIe problem, it was running exceptionally well. Crazy.

Now - I suppose I can't PROVE that the hair was the culprit and that just reseating the CPU was the fix, but I feel pretty comfortable working on that assumption. 😄

[JohnAb]

That's great. I didn't think it would have been the CPU personally, but it just goes to show, you never know! Anyway, great job in finding the cause and yes, I think as assumptions go, you can say that's a pretty solid one!

Great job and now you can enjoy both 990 Pros 🙂

It's funny isn't it, in the past I have sometimes suggested looking for dust and debris under the CPU, but when I fail to think of it, that turns out to be the reason 🙂 🙂 🙂 Suppose there could have also been something in the M.2 connector - I failed to think of that as well lol