For example, it is also impossible to span volumes when an OEM-specific partition is logically between two spanned data partitions. The SAL is a firmware layer provided by OEMs. SAL abstracts the uniqueness of a particular platform by providing a consistent interface to a higher level of the software stack to discover and control an Itanium-based system. SAL exports its components and their associated access details to the operating system through EFI using the SAL System Table. A partition is a contiguous space of storage on a physical or logical disk that functions as though it were a physically separate disk.
Partitions are visible to the system firmware and the installed operating system.
Access to a partition is controlled by the system firmware and the operating system that is currently active. For 64-bit Windows, bootable hard drives must be partitioned using the GPT mechanism defined in EFI 1.0. GPT complements the older MBR partitioning scheme that has been common to PCs. Chapter 16 of the EFI specification defines the GPT format. Additional guidelines for implementing GPT support for Itanium-based systems is defined in Hardware Design Guide Version 3.0 for Microsoft Windows 2000 Server, coauthored by Intel Corporation and Microsoft Corporation.