Physical Address Extension (PAE) overview
Updated: January 21, 2005
Applies To: Windows Server 2003, Windows Server 2003 R2, Windows Server 2003 with SP1, Windows Server 2003 with SP2
Physical Address Extension (PAE) X86 overview
Physical Address Extension (PAE) X86 allows software using the Address Windowing Extensions (AWE) API set and running on a computer with an Intel Pentium Pro processor or later, and more than 4 gigabytes (GB) of physical memory to map more physical memory into the application's virtual address space.
Applications not using the AWE API set can also benefit from PAE X86 because the operating system uses the larger physical memory to reduce paging and thus increase performance. This can also benefit consolidation servers hosting multiple applications.
Applications that manipulate large amounts of data achieve better performance by keeping data in memory instead of on disk. For example, PAE X86 can significantly improve the performance of the following types of applications:
Databases, such as Microsoft SQL/E 7.0 or later.
Scientific and engineering applications, such as computational fluid dynamics.
Statistical analysis applications that do extensive data mining.
Updates to PAE X86
The following updates have been made to support the addition of Data Execution Prevention (DEP), which is also known as no-execute page protection:
PAE is automatically enabled on computers running Windows Server 2003 with Service Pack 1 (SP1) and Windows XP with Service Pack 2 (SP2) when DEP is enabled on a computer with a processor that supports the no-execute page protection feature.
When PAE mode is enabled on Windows Server 2003, Standard Edition with SP1 and Windows XP with SP2, physical address space is limited to 4 GB. Limiting physical address space to 4 GB helps prevent driver compatibility issues with PAE mode.
Only specific hardware will support PAE X86, therefore, this feature is not enabled upon initial installation of the operating system. For more information on what hardware supports PAE X86, refer to the hardware compatibility information for products in the Windows Server 2003 family, which you can find by clicking the appropriate link in Support resources. For more information about how to enable PAE X86, see Enable Physical Address Extension (PAE).
This topic does not apply to Windows Server 2003, Web Edition.