I just built new PC based on Asus Z87-Plus motherboard and in BIOS boot menu I now have my removable devices listed twice – once as a device itself and once with "UEFI: " prefix.
It looks like this for Blu-ray drive on SATA port 5:
P5: PIONEER BD-RW BDR-208M (3523 MB)
UEFI: PIONEER BD-RW BDR-208M (3523 MB)
USB flash drives are similarly listed twice.
Hard drives are only listed once as non-UEFI.
What are the implications of picking UEFI boot option vs non-UEFI? Why aren't hard drives available in boot menu with UEFI option?
Best Answer
The non-UEFI option will boot the device in the legacy BIOS mode. If you have a Win7/8 DVD it can be booted in either BIOS or UEFI mode. If you have a GPT partitioned boot drive then you need to install Windows in UEFI mode.
Once you install an OS in BIOS or UEFI mode, to switch modes you'll need to reinstall the OS (with Windows at least), so guess for hard drives only the mode the OS is installed in is shown.
Dynamically selecting modes is thus generally useful only for USB or DVD drives.