The BIOS that was on the motherboard at purchase.

"Support Intel 3rd generation 22nm E1 stepping CPU (Ivy Bridge). Improve power on issue. Update ME/CPU code."

"Improve USB3.0 compatibility."

"UEFI BIOS. When updating from legacy to UEFI, use only the utility attached to your BIOS file."

How to flash non-UEFI BIOS via Q-Flash.