I recently upgraded to AM5 and bought the MSI MPG B650 CARBON WIFI mobo, and almost immediately started to have M.2 related issues (not recognised).
My two SSDs:
- 1. Crucial P5 Plus - boot drive with Win11 - in M2_4
2. WD Black SN850X - non-boot drive, only for games - in M2_1
This mobo has four M2 slots. If you wonder why I'm not using M2_2 and M2_3, it's because these slots share bandwidth with the main (!) PCIe x16 slot (the graphics card), lowering it to x8 instead of x16. This is highlighted even in the user manual multiple times. This is not ideal IMHO, and pretty much makes those two M2 slots useless (to me). However, M2_4 is still Gen 4, and although it comes from the chipset, it doesn't share bandwidth with other stuff. And M2_1 is coming from the CPU, and it's Gen 5 capable (not that I'm interested in Gen 5 atm).
I also have two SATA HDDs.
Interesting thing is, my Crucial M.2 drive (in M2_4) is ALWAYS recognised, but sometimes the WD SN850X (in M2_1) is not recognised, and needs a reboot.
A recommendation, which mentions going into the BIOS and manually setting the SSD Gens for your M.2 drives from Auto to the actual Gen, improved the situation.
I'm using BIOS 7D74v19 (latest non-beta BIOS).
Most people who have M.2 problems mostly mention Samsung or WD drives. I wonder what would happen if I would replace my WD drive with something else, e.g. the Crucial T500 (which is similar to the WD SN850X in speed) ?