Intel I5 2500K
GA-Z77X-D3H Rev 1.0
MSI Nvidia Geforce 970
Running any overclock with the original bios resulted in unstable booting, a little confusing as there are zero issues in stress tests or usage. I have not been able to cause any stability or benchmark failures and temperatures never go too high. I mostly resolved this issue with an update to the F16 bios, believe the F9 addition of "Improve CPU stability" helped but it is still present, about 1 in 40 boots.
However adding a Geforce 970 caused issues. From what I can understand, if the boot fails and it goes to the backup BIOS it cannot even get to BIOS due to a compatibility issue solved in F14 Improve VGA compatibility. It actually displays the BIOS logo but will sit there ignoring keyboard for two minutes before going to a black screen. I have to remove the GPU entirely to get into BIOS and then save and exit, reboot with it back in and everything is fine.
So I thought I could fix this updating the backup BIOS but it doesn't want to exist! The motherboard itself proudly displays the dual bios logo but it is totally absent in BIOS and Q Flash. Following tutorials has not helped, using a PS2 Microsoft Basic Keyboard with ALT-F12 does not get me backup bios update.
For now I have disabled any overclock in the hope of totally stable booting but with a CPu as easily overclockable as the 2500K this is a waste!