[SOLVED] UEFI and CMS and booting USB

[txbdan]

I guess i'm a little out of the loop. I got a prebuilt PC from Microcenter. Asrock X570 Pro4 mobo, 3700X, RTX3070. First computer i haven't built myself, but its been about six years. This all started as i try to boot a USB stick to run memtest86.

If i run msifno32, i see the system BIOS is in "UEFI" mode. I also saw in the BIOS that CMS is on. I can see my USB device is the BIOS, its an option in the boot-to menu, but it doesn't boot. It jsut says "insert device and press a key" or something like that. I tried every USB port on the computer.

I googled a bit and some people say you need to turn CMS ON in order to boot. Well mine is already on. I tried to turn it off and everything in Windows seems fine, but USB is no longer a bootable option in the BIOS.

What exactly is UEFI and CMS and what is their effect on booting USB devices? How does this all fit together? How should my system be setup and secondarily, how can i boot this dumb USB stick?

Thanks

Update: found a good link: https://pcrepair2000.co.uk/blogs/uefi-mbr-bios-boot-table.html

 

[kerberos_20]

CSM is old bios emulator, to run old hardware which doesnt supports UEFI, and to boot legacy operating systems aswell (like windows 7)
if you turn off CSM and USB doesnt boot, then that USB device doesnt have UEFI boot data

if it doesnt booth with or without CSM, then that USB device is not bootable
https://www.memtest86.com/downloads/memtest86-usb.zip
run that imageUSB and write that image to your usb stick
it should boot on both UEFI and CSM

 

[txbdan]

CSM is old bios emulator, to run old hardware which doesnt supports UEFI, and to boot legacy operating systems aswell (like windows 7)
if you turn off CSM and USB doesnt boot, then that USB device doesnt have UEFI boot data

if it doesnt booth with or without CSM, then that USB device is not bootable
https://www.memtest86.com/downloads/memtest86-usb.zip
run that imageUSB and write that image to your usb stick
it should boot on both UEFI and CSM

Yeh, that's exactly what I'm doing, using their tool to write the memtest86 image. It's not booting in either mode. Hrmm. I'll try to something bootable USB image to sanity check.