[SOLVED] M.2 NVMe SSD doesn't work in M2P slot on Z390 AORUS Master?

[htradne]

I've built a new PC with the following hardware so far:

Mobo: Z390 AORUS Master
SSD: Samsung 970 Evo Plus SSD 512GB M.2 NVMe
RAM: 32GB DDR4
BIOS: ver F11c (Dec 2019)

According to the Samsung website the M2 drive is supposed to be PCIe. I tried installing the drive in the M2P slot but the BIOS didn't recognize it. I found posts here and on the Gigabyte forums talking about this issue. I tried most of what was suggested My BIOS version didn't have some of the parameters as described so rather than playing around with things I know nothing about I only tried changing the following:

Switched CSM Support to disabled (no effect) then back to enabled (no effect)
Changed Storage Boot Option from UEFI to Legacy (no effect)
Changed Other PCI Devcies from UEFI to Legacy (no effect then switched it back to UEFI)
Changed Windows 8/10 Features to Other OS (no effect then switched it back)

I believe the only change I have set now is Storage Boot Option to Legacy.

After all that I moved the M2 to the M2A slot and the BIOS now recognizes it. According to the manual the drive needs to be PCIe type to work in M2P and as I mentioned above the Samsung website does state that my drive is PCIe. I really wanted to use the M2P slot so I don't lose a SATA port (I have no plans to use the PCIEX4 slot).

Any ideas as to why this drive won't work in M2P?

 

[Ralston18]

Do you have the motherboard's User Manual?

I found the following link:

https://download.gigabyte.com/FileList/Manual/mb_manual_z390-aorus-master_1001_190219_e.pdf

Verify that the manual matches your motherboard.

Refer to Section 1-9 starting on physically numbered Page 33, Step 13 that extends into Page 34.

The installation must follow the motherboard's specifications and requirements.

 

[htradne]

I was able to solve this problem myself with help from someone on the Gigabyte forum, but I'll post the solution here in case someone else comes along later with the same problem. I've seen this same issue discussed in various places including reddit, Tom's Hardware, the Gigabyte forum and a couple misc forums so I'm clearly not the only one to come across it.

For me, the M2 drive was never recognized in the M2P slot while it was out of the box unformatted and installed as the only drive (new build). Temporarily moving the drive to the M2A slot allowed the BIOS to recognize it. From there I installed Win10 with updates then moved it back to the M2P slot at which point the BIOS recognizes it as the boot drive.

Putting it in M2P while not using the PCIEX4 slot allows it's use without taking up a SATA port. Leaving it in M2A (or M2M) would use up a SATA port.