Question M.2 SSD NVME only Shows in CSM

[Murkxx2]

I just built a new system and I’m having a hard time with my M.2 storage drive, Samsung 990 Pro, not showing up in my Boot Options and Boot Sequence/Priority on my Motherboard.

System specs are as follows:
Windows 11 Home
AMD Ryzen 7 9800X3D
Gigabyte x870E Aorus Elite Wifi7
Gigabyte Windforce 5080 SSF OC 16GB
G Skillz 32GB DDR5-6000mhz RAM
OS SSD- Crucial T700 Gen5 NVME M.2 2TB
Storage SSD- Samsung 990 Pro Gen4 NVME M.2 4TB
MSI MEG Ai1300w PSU ATX 3.1 80+ Plat
Artic Freezer III 360mm CPU Liquid Cooler
Fractal North XL Case

Things that I know:

The Samsung 990 Pro is being detected by the MB in Periphelas and in the NVME configuration.

The drive is installed in the M.2D slot on the MB, which is a Gen4 slot. This is so the GPU is receiving all channels in the PCIE1 Gen 5.0 x16 slot. If I install the SSD in any other storage slot, the GPU will then split channels and go to an x8x8 channel (which I do not want.)

Windows 11 is successfully installed and boots fine on the other OS-SSD. The OS-SSD also shows in the boot option, priority, and sequence.

Both SSDs have been health tested to factor out any damage or faulty drives. Both are 100% healthy according to CrystalDisk Info scans and also DiskManagement in Windows.

The Samsung 990 pro has been initialized and shows up in Windows 11, and is usable.

The drive has been taken out and reinstalled to rule out a faulty connection.

Turning ON CSM support shows the Samsung 990 as a bootable device, and also in the boot options/priority.

Turning OFF CSM support does not show the Samsung 990 as a bootable device anymore. It is not in the boot sequence, priority, or options.

I really do not want to use CSM support.

So the question is- How do I get my Samsung 990 pro to show up as a bootable drive on my MB without enabling the CSM support?

Any help is appreciated- thank you!

 

[Lutfij]

Welcome to the forums, newcomer!

What BIOS version are you on for your motherboard? For the sake of relevance, while you're not in CSM, does the suspect SSD show up when dropped into any other M.2 slot, regardless of what lanes are allocated to the discrete GPU?

Speaking of GPU's, remove the discrete card and work off the iGPU.

 

[Murkxx2]

Thank you for the quick reply!

I have tried this on 2 different motherboard BIOS updates . This is a Rev 1.1 board as well for clarity.

F3h - Dec 03, 24
F3 (current)- Feb 05, 25

I do see a new MB BIOS update showing for Feb 07, 25 called F4a.

Should I update the MB to the newest version before anything else?

 

[SkyNetRising]

I just built a new system and I’m having a hard time with my M.2 storage drive,
Samsung 990 Pro, not showing up in my Boot Options and Boot Sequence/Priority on my Motherboard.

That is normal behavior.
In UEFI mode only UEFI bootable drives will appear in Boot options.

UEFI bootable drive contains bootloader partition.
If your drive doesn't contain UEFI bootloader, then it will not appear in boot options.

In legacy/CSM mode all detected drives are shown in boot priority settings (even if they are not bootable).

So the question is- How do I get my Samsung 990 pro to show up as a bootable drive on my MB without enabling the CSM support?

Install windows on it with no other drive connected.

 

[Murkxx2]

That is normal behavior.
In UEFI mode only UEFI bootable drives will appear in Boot options.

UEFI bootable drive contains bootloader partition.
If your drive doesn't contain UEFI bootloader, then it will not appear in boot options.

In legacy/CSM mode all detected drives are shown in boot priority settings (even if they are not bootable).

Install windows on it with no other drive connected.

I do not want to install windows on this drive. This is a storage drive.

I tried removing the storage SSD and reinstalled windows 11 on the OS SSD. Still having the same issue.

 

[USAFRet]

So the question is- How do I get my Samsung 990 pro to show up as a bootable drive on my MB without enabling the CSM support?

In UEFI, you can't.

Only a drive that is bootable will show in the boot menu.

 

[SkyNetRising]

I do not want to install windows on this drive. This is a storage drive.

Then there's no need to boot from the drive, if it is just a storage drive.
Storage drive will NEVER appear in UEFI only mode boot priority.

Purpose of boot priority list is - to choose drive to boot from.
If you're not booting from the drive, then it doesn't need to be in boot priority.
That's how it works in UEFI mode.

 

[Murkxx2]

Then there's no need to boot from the drive, if it is just a storage drive.
Storage drive will NEVER appear in UEFI only mode boot priority.

Well then…

Thank you for this information, I was unaware. I thought each drive installed was always meant to show in the boot priority/options.

So by this clarification, it’s perfectly fine for my storage drive to NOT show up as a bootable drive in my BIOS? I don’t have to worry about losing any data on this drive because of this? That’s really what I was worried about because it was “working” but not showing in the boot sequence- so I thought something was off.

 

[SkyNetRising]

I thought each drive installed was always meant to show in the boot priority/options.

That was so in legacy/CSM boot mode.
Not in UEFI boot mode anymore.

it’s perfectly fine for my storage drive to NOT show up as a bootable drive in my BIOS?
I don’t have to worry about losing any data on this drive because of this?

Yes. That's how it works in UEFI only mode.

 

[Murkxx2]

Well this is solved then and I learned something today thanks to you guys & Tom’s Hardware!

Thank you all for your input and infinite wisdom!!!!!