Question Can't boot after BIOS changes, removing CMOS battery doesn't fix it

Apr 23, 2022
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I recently got a new GPU (RTX 3080) and wanted to enable resizable bar, since this GPU supports it. I booted into the BIOS, and flipped on reBAR support. When exiting the BIOS, it asked me to save the listed changes. This list also included enabling fast boot and moving to or from UEFI (can't really member which one). I assumed these were requirements for reBAR, and saved & exited.
Now, when trying to boot, the fans and RGB turn on, but the screen remains black. Trying to mash delete for the BIOS leads to the same result. On the motherboard, the LED for an error with the boot drive is on. I tried removing the CMOS battery for a few seconds with the power unplugged, but nothing changed.
Any idea how to fix this?

Specs:
MoBo: MSI z370 gaming pro carbon ac
GPU: MSI RTX3080 ventus 3x plus oc edition
CPU: intel core i7 (i think 9700k, can't boot to double check)
 
Apr 23, 2022
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Hey there,

When resetting CMOS, you normally have to switch a jumper first, take the battery out, wait 30 seconds, replace jumper, reinsert battery. Check your mobo manual to be exactly, sure. Then try again.
Thank you, that worked!
Do you possibly also know if I messed something up when enabling reBAR so I could do that properly now?
 

keith12

Illustrious
Thank you, that worked!
Do you possibly also know if I messed something up when enabling reBAR so I could do that properly now?
You're welcome! No probs. Glad it worked.

In terms of rebar, yes, it should just be a matter of simply turning the option on in the bios, save & exit.

If you find the settings don't stay upon reboot, then you might need to replace the CMOS battery. But given the reset has worked, so should rebar now.
 

keith12

Illustrious
Also, just a note:

Some MSI mobo's can have issue with RTX 3080's. Have you experienced any stuttering in game whilst playing.? If you have, you might consider a bios update, as this will solve this issue. If you don't' have issues, you can skip the bios update if there are no other problems.
 
Apr 23, 2022
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I had to update the BIOS to get rebar support for the mobo anyways.
I also went and tried to enable rebar again, but it did change the same settings together with it again, so I exited without saving..
 

keith12

Illustrious
I had to update the BIOS to get rebar support for the mobo anyways.
I also went and tried to enable rebar again, but it did change the same settings together with it again, so I exited without saving..
I can't be certain, as MSI's website doesn't specify (or at least I couldn't see it!), but it appears that only 11th/10th Gen Intel support rebar. I think your Coffee Lake CPU might not be officially supported.

I note a post on this reddit here: Resizable Bar support for 9700k? : intel (reddit.com)

that if you disable CSM, and enable rebar it will then work with the 9700k. Hope this helps :)
 
Apr 23, 2022
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All the steps they mention there (switching off CSM, enable 4G decoding) are the things the BIOS switches automatically when I enable rebar. I'll try doing them one by one instead of all at once to see if a specific step causes the same problem again, but that will have to wait until I have some time to tinker. Thanks for your time and help :)
 

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