MOBO: ASUS M5A99X EVO R2.0
Something weird happened this morning when I turned on my PC, and I've never had any issues with this board until now. When I powered on - it goes into BIOS screen without prompt or any user input. All boot options are gone, save for a few UEFI boot options of USB drives I have plugged in.
Looking through the BIOS: under SATA config - All my HDDs/SSDs I have installed are recognized there. However, Under the "Boot" tab, the only options for Boot Order are the UEFI choices for a couple USB drives -- nothing else. Also, the BBS boot configuration, which is usually right underneath the boot order options, is gone in it's entirety! It's not even greyed out or anything, it's simply not there at all!
At first (after the WTF!?) I started through some troubleshooting. I thought maybe it could not be detecting a CPU fan (oh noes! did my H90 pump die!?) -- but no, all fans are accounted for in their places within the BIOS. After that I thought maybe the USB drives are conflicting somehow so I unplugged everything non-essential and rebooted... same thing. Now I'm starting to sweat it a little more.
I decided to shut it down, turn off the PSU switch, and let it flush all supplemental power and hopefully reset itself. When I powered back on - it booted normally and right into Win 8.1. I looked through the ASUS AI Suite utility's sensor apps and everything, and for whatever reason my fan profiles in fanXpert had disappeared. Great! I set them up again. At this point I decided to shut down normally from Windows. Upon reboot -- oh noes again! Right back into the BIOS with no prompts or inputs.
Luckily it just so happens that there was a BIOS update that was newer than I was using, but it seems minor and the only additions to the changelog are compatibility fixes with some external USB devices. I decided to flash it and update the BIOS. Went smoothly with no issues and instead of restoring the previous settings after the flash I went ahead and did a fresh, virgin setup of the BIOS and got everything set back up again. Seems to be running like new again (i've only had the board for a few months, and like I said I've never had any problems with it before now). I've rebooted several times and i have not run into this issue again, yet.
I'm unsure what to expect. If this were the late 90's I would hazard a guess that the CMOS battery was going out or something along those lines, but to be honest I don't even know if modern motherboards use that stuff anymore. Does anyone have any suggestions as to what happened, or maybe have run into this issue before themselves?
Thanks guys & gals - any help is welcome.