Question UEFI board lists BIOS as legacy in summery?

olblindman

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Mar 22, 2014
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My ASUS motherboard (ROG Maximus hero XII) uses UEFI, and my boot drive is GPT, but my system summery lists my BIOS mode as legacy. WHY is that, and can I set it to UEFI without a clean install?
 
Look for a setting to disable CSM mode.

CSM is "Compatibility Support Mode" which makes UEFI boot the system as legacy BIOS does, using the MBR. Disabling it forces it into UEFI mode and it uses the EFI partition. You may have the boot drive in GPT but if Windows was installed wrong it might not have created the EFI partition and won't be able to boot. You can always go back into BIOS and re-enable CSM mode in that case.
 
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olblindman

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Is there any way (other than disabling CSM) to determine if windows installed an EFI partition? Although I have built many systems, I am always leery of BIOS/UEFI, having had 1 PC take a dive after a change in settings (although it may have been coincidental) And, if it did not install EFI, will I need to do a clean install of windows? I am asking this because Win 11 will require a secure boot setting (as well as TPM 2.0), and Legacy does not allow for that.

Thanks for the quick reply, BTW
 
WHY is that, and can I set it to UEFI without a clean install?
Show screenshots.
Include Disk Management screenshot also.
(upload images to imgur.com and post link)

And, if it did not install EFI, will I need to do a clean install of windows?
Depends on current partition configuration.
It might be as easy as creating bootloader partition manually and/or using mbr2gpt utility.
But need to see Disk Management screenshot first.
 
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Zerk2012

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Is there any way (other than disabling CSM) to determine if windows installed an EFI partition? Although I have built many systems, I am always leery of BIOS/UEFI, having had 1 PC take a dive after a change in settings (although it may have been coincidental) And, if it did not install EFI, will I need to do a clean install of windows? I am asking this because Win 11 will require a secure boot setting (as well as TPM 2.0), and Legacy does not allow for that.

Thanks for the quick reply, BTW
Don't stress over windows 11 W10 is supposed to be supported for 5 more years and their no telling what will change with W11 by then.
 
Is there any way (other than disabling CSM) to determine if windows installed an EFI partition? Although I have built many systems, I am always leery of BIOS/UEFI, having had 1 PC take a dive after a change in settings (although it may have been coincidental) And, if it did not install EFI, will I need to do a clean install of windows? I am asking this because Win 11 will require a secure boot setting (as well as TPM 2.0), and Legacy does not allow for that.

Thanks for the quick reply, BTW
Don't be afraid of UEFI. It's been around a long time and is well proven. It's also the only way to have a truly secure system free (mostly) of threats from ransomware. And even if not going to Win11 it's good to secure your system as the threats are getting ever greater with state-sponsored hackers making concentrated efforts to compromise as many computers as possible in order to disrupt economies.

You can look for the EFI partition in Disk Manager; probably around 100MB, no drive letter assigned, called "EFI System Partition". If it's there then you should be able to disable CSM.

Even if it doesn't work then I'd suggest doing a clean install of Windows. It's not really as hard as it sounds and often fixes a lot of things you just put up with. There are ways to fix it, of course, but probably a bit difficult.
 

olblindman

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My apologies, my SSD is set at MBR...… I guess I will do the conversion to GPT and then set the BIOS to UEFI....I could swear I did that when I built this rig. O Well. Thanks all for the replies! Shame to waste UEFI when the Mobo is designed for it!
 

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