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The Unified Extensible Firmware Interface (UEFI) is a software technology that prepares a computer to boot into an operating system after it is turned on. It has been marketed as a replacement for the Basic Input Output System (BIOS), a technology first developed for the original IBM® PC. The program was designed to overcome some of the weaknesses of BIOS, such as speed and hardware limitations. Intel® introduced the technology in 2003 and later transferred authority to an industry trade group that has slowly been gaining support for the standard in consumer PCs.
Most computer users have probably noticed that, no matter how much faster the microchips inside their systems get, virtually all PCs have a delay between the time the power button is pressed and when the operating system is ready. During this period, specialized software communicates with electronic code called firmware found in hardware devices. The software looks for new hardware components, inspects and prepares existing components for booting to an operating system, and selects a drive or network location from which to boot. Historically, this role has been filled by BIOS software, but the newer UEFI standard was intended to supplant it.
The BIOS is one of the oldest vestiges of the original IBM® PC, and limitations in its basic design have kept many PCs from booting faster than they potentially could, with delays of up to 30 seconds or more before an operating system begins to load. Unlike the hardware inside computers, the BIOS did not change much after its introduction in the early 1980s. The system was tweaked to support newer hardware, but it still faced problems and limited speed because of its heritage. For example, the BIOS was designed for 16-bit processors rather than the 32 or 64-bit chips found in more modern computers.
Compared to the BIOS, UEFI has many advantages. It was meant to be platform independent, meaning it isn’t locked into a specific computer architecture and could potentially be used on other types of hardware, like tablets. Boot-up times could be shortened to just a few seconds, and applications and drivers can even be created to run in the environment before an operating system loads. An application that mimics the traditional behavior of BIOS can also be created to enable backwards-compatibility. The maximum size of a hard drive that can be used for booting also rose from about 2 terabytes (TB) under BIOS to 9.4 zettabytes (ZB).
UEFI was initially released as the Extensible Firmware Interface or EFI, a technology developed by Intel® for use with their high-end Itanium® line of 64-bit processors, which were incompatible with the BIOS standard. In 2005, Intel® relinquished control of EFI to the Unified EFI Forum, an industry group composed of multiple companies. The forum renamed the standard and promoted industry adoption in desktop computers and other devices.