January 19, 2012, 4:46 PM — If you have used a PC during the last three decades or so, you should be familiar with the PC's Basic Input / Outpit System, or BIOS. The fact that it has been around for so long should also be all the indication you need that it has outlived its usefulness. UEFI is poised to replace it, and take our PC experience to the next level.
The BIOS provides the core functionality for the motherboard itself that enables the hardware to function, and provides the jumpstart for the system before the actual operating system boot process begins. It is essentially the operating system for the motherboard, and your operating system of choice runs on top of it.
If you've ever needed to switch the order that devices boot up -- like to boot from a USB device instead of the internal hard drive -- you have most likely experienced the joy of racing to hit 'F1' or 'DEL' or whatever key is designated on your system to enter the cryptic BIOS setup before the OS starts booting.
The problems with BIOS are many, though. The antiquated system operates in a mere 1,024 kilobytes of space, can only work with hard drives up to 2.2 terabytes, and is simply not engineered to deal with the technology of today...never mind tomorrow.
So, now we have Unified Extensible Firmware Interface (UEFI). UEFI doesn't truly replace BIOS, because some form of basic IO system is still necessary just to kickstart the motherboard. UEFI is stored in the /EFI/ director in non-volatile memory, and runs between the PC hardware and firmware, and the operating system.
UEFI provides a number of advantages, though, over the traditional BIOS. For starters, UEFI is capable of addressing hard drives with capacities up to 9.4 zettabytes. Yes, zetabytes. By some estimates, that's roughly three times more than all of the information on the entire Internet right now, so it should be sufficient for the foreseeable future.
UEFI is more like a mini operating system of its own. Instead of the rudimentary 8-bit text-based menus of BIOS, UEFI provide access to the full hardware of the PC, including the Ethernet adapter, Wi-Fi network, USB ports, Bluetooth connectivity, audio system, and graphics card. UEFI is a much richer and more capable platform than BIOS.
UEFI initializes hardware faster for a more "instant on" experience, and it allows for security and authentication before the operating system is booted. UEFI can also connect to a network. That means that even a PC that can't boot into the operating system could be remotely accessed for troubleshooting and maintenance.