Question B450 MSI. changes bios setting and PC will not boot win 10

Dec 28, 2022
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System: r2600, msi carbon ac mobo, rx570

Was doing some overclocking of the CPU ... When this happened...or perhaps the quirck was there in the first place I don't know
PC will boot to win10 wit bios defaults but change something in bios and it won't anymore. (It boot loops back into bios and in bios the changes are still present)

Some trouble shooting lead me to believe that enabling rebar somehow messes it up. But it used to be no problem to change that.. ( it's part of the things I want to change in bios to enable SAM with modded AMD driver)

Did jbat, did CMOS battery, flashed multiple different bios (now back on the latest), reinstalled windows., Reinstalled chipset drivers

what I noticed is that when its in this mode of not accepting changes that the hdd partitions to boot from are gone in the quick boot menu. Which is peculiar but could explain why it won't boot, not sure why it does that though. Restoring bios defaults save reboot will make the system boot windows although the problem persists, ....reverting the last change that made it 'flip' manually doesn't help. Although it seems that bios is completely functional otherwise (changes stay, if I increase CPU clock the auto core voltage has increased on the next run for example)
 
Dec 28, 2022
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So I tried again to change the settings of the bios one by one but left resisable BAR till the very end. It seems I can actually change everything except reBar...

And when i do that the system reacts as above...after setting save

-system bootloops back into bios.
  • can verify now that my ssd (win install) disappears from the boot menu. When the system was behaving normally the Kingston ssd was there, now it's not.
  • where it says 'boot mode select' in bios is also greyed out where first I had options

It's quite annoying and I don't see what rebar has to do with the SSD or how I caused this by doing a simple overclock on the cpu. (Which i can still do btw and the CPU adjusts its parameters and no crash) only weirdness happens when i activate rebar, which I could always do and that setting had been activated on my system for months
 
Dec 28, 2022
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I found this:

"PSA: If you enable Resize BAR support & it only reboots to the bios every time and no longer boots to the OS, see below.
Your OS partition is MBR, which requires the use of CSM (compatibility support module) to boot from it, rather than the modern GPT layout. When you enable resize bar, it disables CSM, since they're incompatible, causing it to boot back to the bios on reboot.

Go to the boot tab and enable CSM and you will be able to boot normally again but no resize bar yet. You'll have to convert your OS partition to GPT and then disable CSM again for it to be able to function with the resize BAR ability"
 
Dec 28, 2022
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So I need to get my os on gpt.... It seems that I'm in legacy mode while reinstalling window recently and then you get a mbr instead of gpt partition.

I think what I did is just select the USB with win10 instead of uefi usb win 10
 
Dec 28, 2022
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Is there a question here? Maybe I've missed it...but this link may prove useful:

https://learn.microsoft.com/en-us/windows/deployment/mbr-to-gpt
Not really, the question was in the op and the last comment was more a conclusion I arrived at. I reinstalled so the disk had a gpt partition to begin with ( didn't know that I had to choose the usb with uefi prefix to do that or that it made a diff)

Anyway did that instead of bothering with converting mbr to gpt on what was a fresh install anyway. Now the bios works as it supposed to.
 
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