The original motivation for EFI came during early development of the first Intel–HP Itanium systems in the mid-1990s. UEFI is independent of platform and programming language, but C is used for the reference implementation TianoCore EDKII. In 2005, UEFI deprecated EFI 1.10 (the final release of EFI). Some of the EFI's practices and data formats mirror those of Microsoft Windows. Intel developed the original Extensible Firmware Interface ( EFI) specifications. UEFI replaces the BIOS which was present in the boot ROM of all personal computers that are IBM PC-compatible, although it can provide backwards compatibility with the BIOS using CSM booting. Examples of firmware that implement these specifications are AMI Aptio, Phoenix SecureCore, TianoCore EDK II and InsydeH2O. They define the architecture of the platform firmware used for booting and its interface for interaction with the operating system. UEFI ( Unified Extensible Firmware Interface) is a set of specifications written by the UEFI Forum. They can use different I/O protocols, but SPI is the most common. The UEFI implementation is usually stored on a NOR-based EEPROM that is located on the mainboard.

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