my Z87X UD3H doesn't recognize my G710 keyboard on boot most of the time, neither my older G15, neither are my mouse, it was impossible to me to get into the BIOS until I had to borrow to my friend a serial keyboard. The problem is not always there, sometime it working, and lately, the workaround I found is to reset the CMOS with the screwdriver to make it working again and reload my profile. But as soon I boot into windows later, the problem persist later if I have to go in the BIOS again.
I'm not strictly speaking from BIOS accessibility, sometime when I want to get in safe mode it not possible neither so the problem really reside outside the OS.