Here are two posts from two different forums by a wise poster that might work to go back to an older bios:
"The newer round of bios' have to be flashed with @bios.
The problem is, if you don't like it or it causes problems like it did for me you have to take steps to get rid of it. For some reason after a while I was unable to boot into Windows on the new bios so I could not use @bios to change it.
I had flashed the new F9 to the main bios on my UD5H, and I left F8 on my backup. So what I did was boot up with the backup bios and hit Ctrl + F10, and this "swapped" the main and backup bios. Then all I had to do was throw the bios switch back to the main bios, boot up, and hit Alt + F10 and this overwrote the "bad" F9 bios with a copy of the F8 bios. Now if the system needs a fresh copy of a known good bios the F9 will no longer be there.
Make sense? lol.
It's strange that the F9 worked well for a few days but suddenly it went south. Oh well, F8 works fine for me."
"Actually, I had to revert all the way back to F8 mod BIOS on my Z87 UD5H. Suddenly I could not boot all the way into Windows no matter what I did. I've been a few rounds with this in the past so I knew the easiest fix was to just not use the F9 bios.
So.....I found out something.
Bear in mind that the newest F9 BIOS had to be flashed with @bios -since Qflash wouldn't work for the "new" bios- and in my case I had flashed F9 as the main bios.
So happens I had F8 as the back up bios.
With the bios switch in the backup position, I booted up and hit Ctrl + F10, and this swapped the main bios to the backup, and the backup to the main. Yep, didn't know it worked that way with Z87.
Then all I had to do to flash over the new F9 -remember I had to use @bios to flash it- was boot up in the main bios and hit Alt + F10, and that copied the F8 main bios to the backup and overwrote the "bad" F9 bios.
Clear as mud? lol. "