The bios setup screen in some motherboards has an option to enable UEFI. For example:
http://forums.evga.com/FindPost/2024096
As I understand it, UEFI enables quick boot in windows 8 but has little benefit for win7. How does the selection of BIOS vs UEFI impact the use of AHCI vs RAID, if any? Certainly, when modding the OROM and the driver of an x79 chipset, unintended consequences can be disheartening. Does anyone have experience with the behavior of RAID under an OS installed under a traditional bios vs UEFI?
Besides the boot time there are no remarkable differences while working.
The only difference is, that you can enter the RAID Utility from within the BIOS, if you are running an OS in UEFI mode. Since the RAID Utility of an UEFI mode OS installation is part of the BIOS, the RAID configuration has not to be initialized separately.
With UEFI, you may boot from drives greater than 2TB (which is a big laugh, because it uses a smaller UEFI partition to boot your x>2TB HDD).
In addition, you get a new "platform", because BIOS is more than 20 years old.
You get an EFI shell as well, but not every manufacturer gives you access to it. It is like CMD within Windows, but with different commands.
Modules / OROMs / etc. are stored in another way. AND you may load them by shell … if you know the commands … (i don’t!) 
and so on …
Sincerely
IDDQD