This is copy/pasted verbatim from my post on the superuser board on StackExchange: https://superuser.com/questions/1620978/computer-stuck-in-pre-bios-boot-loop-double-boot

Update 3: I can't get anything to display on screen since replacing the CMOS battery (first update). I have tried multiple monitors with multiple connection types (HDMI and VGA), but nothing displays on screen. When the mobo is set to dual BIOS, I get the boot loop. When it is set to single BIOS, it powers on without resetting, but NEVER displays. It doesn't seem to matter which setting the BIOS switch is in (default or backup), nor what I have attached (drives, GPU, RAM, fans, etc.)

Update 2: This is my motherboard: https://www.gigabyte.com/Motherboard/GA-Z97X-UD5H-rev-10/support#support-manual When switching from the default dual BIOS to single BIOS (hardware switch), the double boot stops. However, it does not load a BIOS screen.

Update 1: Still double booting after replacing CMOS battery.


----------


My desktop is stuck in a pre-bios boot loop, by which I mean it powers on, but then turns off and back on before getting to the bios screen. If this is not the correct place to post this issue, I would appreciate advice on where a better place would be.

Most forumns seem to suggest that this is a hardware issue, so I've been attempting some hardware troubleshooting to try to identify if the issue is PSU, Mobo, or other.

 1. I disconnected everything from my motherboard except my CPU and one stick of RAM and it booted fine (by which I mean it got to the BIOS screen...obviously it didn't get further as there was no drive for which to load an OS).
 2. I added each of the other 3 sticks of RAM, one by one, and it continued to boot fine.
 3. I then added the SSD that has my OS...back to the boot loop. So it must be my SSD, right? Well I continued to test hardware and things got confusing.
 4. So I disconnected this SSD and tried a different SSD. Worked fine.
 5. Added a HDD. Worked Fine.
 6. Plugged case USB ports into motherboard and tried to boot from recovery flash drive...boot loop. Undo. Still works fine.
 7. Added another HDD...back to the boot loop. Okay, so what are the chances that 2 of my drives FAILED simultaneously? (Maybe quite high...but I assumed not.)
 8. So I tried just my OS SSD again, and it booted fine. Weird.
 9. Then just the HDD that seemed to cause an issue in step 6. Again booted fine.
 10. Played around with many combinations of these 4 drives, sometimes encountering the boot loop, but typically booting. Tried to see if one of the SATA ports was bad, but many combinations seemed to show this couldn't be it. On multiple boots, the OS was never able to find the step 4 SSD (not the one that seemed to cause an issue). So I removed this entirely and was able to boot CONSISTENTLY.
 11. So I presumably have a bad SSD. But this shouldn't explain the issue, as it happened when this drive was never connected.
 12. Time to put the GPU back in...boot loop.
 13. Take the GPU out and make sure it still works...NOPE, boot loop.
 14. Disconnect everything again to make sure I can boot in the way I was able to in steps 1 and 2...nope, boot loop.

So my guess is that this is somehow an issue with my motherboard. If I can get it booting again from step 1, I'll attempt various combinations of drives and GPU to see if I can pinpoint anything, but it seems to be the case that the issue is independent of which specific things are connected. I would greatly appreciate advice on how to identify/fix the issue.