[SOLVED] Disabling CSM makes M.2 boot drive unavailable ?

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Jarmil

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Feb 20, 2016
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Hello All,

Operated this build for a couple of years before recently upgrading my gpu to the 6700xt, and was hoping to enable SAM. Updated the BIOS on my mobo successfully. In the BIOS I am able to enable both Above 4g and RBar support. As I understand it, I also need to disable CSM support. However, when I do, and save and exit, I get the BIOS screen again and notice that my NVMe boot drive is not listed. If I just enable CSM again I can boot to Windows as normal, but no SAM support.

Am I missing something simple, or is SAM just not compatible with my setup?

MB: Gigabyte X570 Aorus Ultra BIOS F35
Mem: 16 GB 3200
CPU: Ryzen 7 3700X
GPU: Sapphire Nitro+ 6700XT
SSD: Sabrent Rocket NVMe 4.0 1TB (only drive on my system)
OS: Windows 10 64 bit

Appreciate the feedback in advance!
 
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Jarmil

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Feb 20, 2016
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drea.drechsler said:
Disabling CSM means it will operate in UEFI mode which requires the system drive to be prepared in GPT partitioning scheme. If that wasn't done when the OS was installed it has to be converted...not always easily done.

https://www.windowscentral.com/how-convert-mbr-disk-gpt-move-bios-uefi-windows-10
Click to expand...
Thank you for the analysis! It looks like you are spot on. Brief review of the link you provided, and a couple of the diagnostic steps, and I can see that my drive is not set up in GPT. I don't even recall getting an option during first set up, but may just have been my ignorance on the differences. I'm going to review in more detail and maybe do a little soul searching before tackling this conversion however. Looks a bit daunting for sure...

Much appreciated!
 
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drea.drechsler

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Oct 16, 2017
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Jarmil said:
... I don't even recall getting an option during first set up, but may just have been my ignorance on the differences. ...
Click to expand...
I'm not really certain how that happens either as every time I've installed Win10 it set up the system drive in GPT scheme. It may be that if the BIOS is set up with CSM (compatibility support mode) enabled at the time the OS is installed it defaults to MBR, or maybe if your drive was previously configured in MBR the Win10 install defaulted that way.

I'm not sure but I think Win11 setup requires the system be running in EFI mode (CSM disabled) and it will configure the system drive in GPT partitioning scheme.
 
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Jarmil

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Feb 20, 2016
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I went all new at that time to keep from dragging old baggage along; new mobo, NVMe, new Windows 10 install. Guess that's my concern with trying to convert...not knowing what might not be compatible after the fact. I don't have a burning desire to go to Windows 11, but updater does tell me my machine is NOT compatible, so understand why that is now. Better knowledge now than I had then...

I'm leaning toward a good back-up of data and giving it a try (glutton for punishment I guess). Will update if I go this route.
 
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drea.drechsler

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Oct 16, 2017
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Jarmil said:
...
I'm leaning toward a good back-up of data and giving it a try (glutton for punishment I guess). Will update if I go this route.
Click to expand...
I've never used it but from those that have it seems very reliable. It will either refuse to run at all...if things aren't set up right...or just works. And knowing how MS works it should be a fairly robust process so if it crashes out for any reason you'll still have a useable system...or at the very least recoverable data. They have a lot of experience in this sort of thing considering the many OS updates and upgrades they've been pushing at us for these past years since Win10 launched.
 
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