The Extensible Firmware Interface (EFI) is an updated BIOS specification developed by Intel. Designed for use with trusted computing, it allows vendors to create drivers which cannot be reverse engineering. It also allows operating systems to run in a sandbox (security), delegating networking and memory management to the firmware. Hardware access is converted to calls to the EFI drivers. The EFI BIOS is used to select the operating system, replacing boot loaders.

EFI got its start with Intel s IA-64 server architecture but has been migrating into the standard desktop market on some of Intel s newer chipsets. It has been touted as a badly needed update to the original IBM PC BIOS, which has not changed significantly since its release in 1981. Though the traditional PC BIOS has been extended with some new features, notably the Advanced Configuration and Power Management Interface (Advanced Configuration and Power Interface) and System Management BIOS (SMBIOS), its fundamental functionality, structure, and design has remained the same. Rather than toss these extensions aside, EFI is slated to incorporate both ACPI and SMBIOS functionality which should help keep development costs and OS compatibility issues to a minimum.

Ideally, the EFI development model will extend the concept of hardware drivers to the lowest level of the PC structure. Currently all motherboard device initialization is done through a BIOS designed by a BIOS vendor. With the EFI model, however, manufacturers of motherboard hardware will be free to write their own hardware drivers, akin to how companies write OS device drivers for their products. Among other things, this frees EFI to initialize all hardware before turning control over to the operating system. This feature could be used, for example, to allow the PC to connect to the Internet and retrieve drivers before an OS is even installed.

Another advance EFI will allow is for the Central processing unit to power up to a fully functional state. Under the traditional PC BIOS, to maintain backwards compatibility, the CPU must power on in a degraded condition and must wait before it can operate at full capacity.

EFI also provides for a small Operating_system_shell. Rather than booting directly into a full OS, the EFI end user can boot to EFI shell. The EFI shell is an optional intermediate step in the booting process which can be used to run utilities and the like. EFI shell capabilities are very nearly that of MS-DOS 3.2, but with access to the entire map of installed memory. In that sense, it is similar to Open Firmware, the hardware-independent firmware used in PowerPC-based Apple Macintosh computers.

Unlike traditional BIOS, further extensions to EFI capabilities can come from virtually any non-volatile storage device. For example, an Original equipment manufacturer can sell systems with hidden EFI partitions which can add to the basic functionality of the standard EFI stored on the motherboard s flash ROM. The unlimited extensions possible in EFI suggest that a traditional OS may no longer be necessary.

Though EFI was initially developed by Intel, its apparent intention is to release at least one open-source form of the standard. This may provide the impetus for EFI to become the de facto standard in the general PC market. EFI mandates the File Allocation Table, a familiar standard. Using EFI, disk partitions are not Master boot record, but instead GUID Partition Table.

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