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STRIX X670E-A // Missing PCIe Lanes on M.2_2 after cold boot (reduced speed)

Level 7

Hi everybody,

I seem to have a problem with my second M.2 drive slot (M.2_2).

After a cold boot (several hours of shutdown) the drive installed in the M.2_2 slot sometimes runs only with x2 or even x1 speed instead of the x4 which it is supposed to do. After a reboot (hot boot) the system recognizes the drive with the full speed (x4). The reboot fix is 100% reproducible. Also a boot directly after shutdown gives me full speed. The M.2_1 drive always runs with x4 no issues there.
I'm running the newest BIOS 1807 on my ASUS ROG STRIX X670E-A GAMING WIFI.

Installed are:
- AMD Ryzen 7 7800X3D
- 64 GB RAM (2x32 GB CMK64GX5M2B5200C40)
- 4 SATA devices (2x HDD, 1x SSD, DVD drive)
- M.2_1: Samsung SSD 970 EVO 1TB
- M.2_2: Samsung SSD 970 EVO Plus 2TB
- MSI RTX 3080 Gaming Z Trio LHR

So far I tried the following BIOS settings with no success:
- Setting the PCIe Connection of the M.2 drives to Gen3 with the hope to force a correct recognition of the lanes.
- Disabling Fast Boot and force a Normal Boot
- I'm currently testing a 5 sec POST Delay instead of the standard 3 sec in order to give the system time to "wake up"

I hope you guys might have a fix or an idea what I have missed so far and can resolve this problem.


Level 9

A lot of people are having problems with either M.2 slots having reduced performance or even sometimes missing, or PCIe slot for the GPU having reduced performance (either PCIe lanes or PCIe version/speed). You can find a beta bios on this website that is supposed to fix some of that (unknown if it does), but I don't want to encourage anyone to install beta BIOS on their PC because of the potential for bugs.

Yes, it looks like that. For me it's the GPU missing lanes. I wonder how this problem can pop up so inconsistently: in my case the number of lanes changes per boot & related which BIOS version is installed on the board. Others report no problems, and again others report a different pattern of missing lanes or missing lanes for the M.2 slots, like Thallios here.

And it seems to be not easy to reproduce. Makes me think that interactions with some stochasticity between motherboard  and other hardware might be in play (for example with the socket/connections, CPU (e.g. a somewhat unstable I/O die), or NVME and GPU firmware timing misalignments or whatever). I hope ASUS, AMD and the other manufacturers can sort this out, so AM5 becomes a mature platform.

I got a message back from ASUS Support. They told me that my case was escalated to Tier 2 and the development department to adress this issue in the next BIOS release. Let's hope for the best.

Level 7

It seems the issue is BIOS related as you said.
Bios Version 1709 works just fine

Level 7

I'd keep an eye on whatever drive is vanishing because technically that's also a symptom of a dying nand chip or controller.

Chances are it's fine but you never know.