The Unified EFI (UEFI) specification (previously known as the EFI specification) defines a similar interface between an operating system and platform firmware. UEFI is independent of the processor architecture and it
The interface consists of data tables that contain platform-related information, boot service calls, and runtime service calls that are available to the operating system and its loader. These provide a standard environment for booting an operating system and running pre-boot applications.
The UEFI specification was primarily intended for the next generation of IA architecture-based computers, and is an outgrowth of the "Intel® Boot Initiative" (IBI) program that began in 1998. Intel's original version of this specification was publicly named EFI ending with the EFI 1.10 version. In 2005 The Unified EFI Forum was formed as an industry-wide organization to promote adoption and continue the development of the EFI specification. Using the EFI 1.10 specification as the starting point, this industry group released the follow on specifications renamed Unified EFI. The current version of the UEFI Specification can be found at the UEFI web site.
UEFI (Unified Extensible Firmware Interface) will be a specification detailing an interface that helps hand off control of the system for the pre-boot environment (i.e.: after the system is powered on, but before the operating system starts) to an operating system, such as Windows* or Linux*. UEFI will provide a clean interface between operating systems and platform firmware at boot time, and will support an architecture-independent mechanism for initializing add-in cards.
While UEFI uses a different interface for "boot services" and "runtime services", some platform firmware must perform the functions BIOS uses for system configuration (a.k.a. "Power On Self Test" or "POST") and Setup. UEFI does not specify how POST & Setup are implemented.
UEFI is an interface. It can be implemented on top of a traditional BIOS (in which case it supplants the traditional "INT" entry points into BIOS) or on top of non-BIOS implementations.
Platforms using the existing EFI 1.10 specification are already in the market place. Platforms using the UEFI specification will enter the market as the specification is being developed by the Forum.
Interesting! Isn't it! Let's wait and watch!