Microsoft KB Archive/303956

= Description of Extensible Firmware Interface =

Article ID: 303956

Article Last Modified on 12/1/2007

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APPLIES TO


 * Microsoft Windows XP Professional x64 Edition

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This article was previously published under Q303956





SUMMARY
This article describes Extensibile Firmware Interface.



MORE INFORMATION
The Extensibile Firmware Interface specification defines a model for the interface between operating systems and platform firmware. The interface consists of data tables that contain platform-related information and boot and runtime service calls that are available to the operating system and its loader. Together, these provide a standard environment for booting an operating system and running pre-boot programs. Microsoft supports Extensibile Firmware Interface as the only firmware interface to boot Windows XP. Because the 64-bit version of Windows will not boot with BIOS or with System Abstraction Layer (SAL) alone, Extensibile Firmware Interface is a requirement for all Intel Itanium-based systems to boot Windows.

The IA-64 architecture defines the following three firmware layers:
 * Processor Abstraction Layer
 * System Abstraction Layer
 * Extensibile Firmware Interface

The Processor Abstraction Layer, System Abstraction Layer and Extensibile Firmware Interface layers work together to provide processor and system initialization for an operating system boot. Processor Abstraction Layer and System Abstraction Layer provide machine check abort handling and other processor and system functions which would vary from implementation to implementation.

The System Abstraction Layer is a firmware layer that isolates the operating system and other higher-level software from implementation differences in the platform, while the Processor Abstraction Layer is the firmware layer that abstracts the processor implementation.

For additional information please see the following Knowledge Base articles:

294780 Determining Firmware Version of Itanium-Based Workstation

303971 What is NVRAM and why does the Itanium use it?

For more information about the Extensibile Firmware Interface, Processor Abstraction Layer, and System Abstraction Layer, please see the following Intel and Microsoft Web sites:

http://developer.intel.com/technology/efi

Microsoft provides third-party contact information to help you find technical support. This contact information may change without notice. Microsoft does not guarantee the accuracy of this third-party contact information.

http://www.microsoft.com/resources/documentation/windows/xp/all/proddocs/en-us/extensible_firmware_interface.mspx?mfr=true

The third-party products that are discussed in this article are manufactured by companies that are independent of Microsoft. Microsoft makes no warranty, implied or otherwise, regarding the performance or reliability of these products.

Additional query words: efi pal sal

Keywords: kbenv kbinfo KB303956

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