A Description of Nonvolatile RAM on Itanium-Based Computers (303971)

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NVRAM is a generic term for any read/write data storage system that does not lose data when the power to the computer is turned off.

On Intel Itanium processors, NVRAM is part of the Extensible Firmware Interface (EFI). The NVRAM stores the Boot menu, the Boot Option Maintenance menu, and internal EFI commands. The Boot menu can include Windows XP or Windows .NET for Itanium-based computers, operating system loader options, and bootable devices, such as, a CD-ROM, a hard disk, the Pre-Boot Execution Environment (PXE), and the EFI shell. The Boot menu is very similar to the 32-bit Windows Boot.ini Boot menu.

NOTE: Neither Windows XP nor Windows .NET for Itanium-based Systems contain a Boot.ini file.

On current Intel Itanium-based computers, the total NVRAM storage size is 64 kilobytes (KB) for all system, boot manager, and shell NVRAM variables. Each program that implements NVRAM needs to identify its variables with a globally unique identifier (GUID). Each shell, boot manager, and Setup program can only have access to its NVRAM variables. This access can be obtained by providing the correct GUID for access to its NVRAM variable. For more information about EFI specifications, refer to the following Microsoft and Intel Web sites: 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.

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.