MacBook Pro Boot Mode

OSX system requires EFI to boot, EFI is the product of the BIOS upgrade, and now most motherboards do not have this thing, so to install OSX must be simulated EFI.

The Apple Computer is powered by EFI, with no bios, and the only boot option that can be set is boot.
The following startup key combinations can be used on Intel-based MAC computers
Press and hold the C key at startup-boot from a bootable CD or DVD disc, such as a randomly attached MAC OS X installation disc.
Press and hold the D key at startup--If you insert installation DVD 1, the Apple Hardware Test (AHT) is started.
Press and hold the OPTION-COMMAND-P-R key until you hear two beeps-press and hold the option key when the NVRAM starts-boot into startup Manager, you can choose to start from a Mac OS X volume. Note: Press and hold the N key to display the first bootable network volume.
Press and hold the Eject, F12 key, or hold down the mouse button (/trackpad)-to eject all mobile media, such as a disc.
Hold N at startup--attempt to boot from a compatible network server (NetBoot).
Press and hold the T key at startup-starts as FireWire target disk mode.
Hold down the Shift key at startup-boot to Safe mode and temporarily close the login entry.
Press and hold the COMMAND-V key at startup--boot to Verbose mode.
Press and hold the Command-s key at startup--starts as single-user mode.
Press and hold the Option-n key at startup--starts with the default boot image from the NetBoot server.

MacBook Pro Boot Mode