Hello,
For those of you that have the dreaded "black-screen" upon bootup after exiting the BIOS, well, there's a simple trick I discovered with the Z7S that works for me.

I have a HP P800 and Dell Perc 5i Raid controllers, with the HD4870X2 Gfx card, and sometimes it doesn't give the POST code after doing BIOS changes and restarting.

It would just spin the fans up, that's it, no video or POST.

While it's in that state, press the "Del" key, and keep it in for 5-15 seconds, board should reset BIOS defaults and POST.

Please let me know if this works for you guys with "BIOS" issues.

Best regards,
MrBean