[SOLVED] Turning CSM off makes my BIOS not recognize any of my SSDs

Oct 13, 2020
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I have a Samsung 850 EVO and a 860 QVO. The first is in MBR, the other in GPT. When i tried turning CSM off, the PC rebooted into the BIOS and none of the 2 SSDs was shown as connected, the only recognized storage device was a USB stick. Is there some compatibility issue with these SSDs or is there something that should be installed on them for them to work with CSM off?
The mobo is an Asus Prime B-450M-A with a Ryzen 3600.
 
Show the screenshot first.
If GPT drive contains windows partition, then you can possibly make it UEFI bootable by creating bootloader partition manually.
If MBR drive contains windows partition, then you can convert your system to UEFI bootable with mbr2gpt utility (assuming you have windows 10 and not windows 7).
 
Reactions: Teknoman2
Oct 13, 2020
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In order to enable smart access memory you need CSM off. I know that SAM is not available in this motherboard but i just wanted to see how it all works in case i upgrade to something compatible and i noticed that my SSDs are not recognized. In case of an upgrade i don't plan to just throw away 2 perfectly working SSDs for something that could be a non issue that i simply don't know how to work around so i came to ask.
 
Is there some compatibility issue with these SSDs or is there something that should be installed on them for them to work with CSM off?
If windows is installed in legacy mode and you turn off csm, system becomes unbootable.
UEFI only mode (disabled CSM) needs UEFI bootable device.
MBR partitioned drive is not UEFI bootable.
Your GPT partitioned drive doesn't contain bootloader, so it's not UEFI bootable either.

Can you show screenshot from Disk Management?
(upload to imgur.com and post link)
 
Oct 13, 2020
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What about the USB stick? Among other things it contains the windows installation files, is MBR and its the only thing shown. Considering that the PC didn't boot from it to take me to windows installation i guess it doesn't work either with CSM off. Is there a way to turn it into GPT without losing the files? If not, how to make an empty stick GPT and put the windows install files in that?
 
Show the screenshot first.
If GPT drive contains windows partition, then you can possibly make it UEFI bootable by creating bootloader partition manually.
If MBR drive contains windows partition, then you can convert your system to UEFI bootable with mbr2gpt utility (assuming you have windows 10 and not windows 7).
 
Reactions: Teknoman2
Oct 13, 2020
63
11
45
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The disk on which i have windows is MBR and the other that has all the games is GPT. The USB stick is also MBR.
I tried the mbr2gpt /validate on the windows disk and it passed but the USB stick wont validate, too old i guess.
Anyway, thanks for the pointers, now that i know what i'm looking for i'll be able to google a solution when i need to... Maybe make a partition on the GPT SSD and put the windows installation files there
 
Last edited:
Oct 13, 2020
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I didn't see your request on the first post and was wondering what screenshot you meant. Now it would be obsolete as i used the mbr2gpt utility successfully but here you are

Windows is on the 850EVO
 

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