Which file does UEFI look for when booting a 32bit system?

Which file does UEFI look for when booting a 32bit system?

• \EFI\boot\bootx86.efi
•  \EFI\boot\bootia32.efi
• The Master Boot Record (MBR)
• \EFI\boot\boot_x86.exe

EXPLANATION

The Unified Extensible Firmware Interface looks for FAT32 media containing a folder named \EFI\boot which contains boot executables.
The boot filename depends on the architecture being booted and files for multiple architectures may be present. See the source for more info

SOURCE

http://www.uefi.org/sites/default/files/resources/UEFI%20Spec%202_6.pdf