Windows XP 64-bit Edition - Definition and Overview

Windows XP Professional x64 Edition is a release of Windows XP designed for 64-bit systems. There are two versions of Microsoft Windows XP Professional x64 Edition available:

• Microsoft Windows XP 64-bit Edition: For use on Intel's IA64 architecture, as implemented by the Intel Itanium product line.
• Microsoft Windows XP Professional x64 Edition: For use on the AMD64 architecture, as implemented by the AMD Opteron and Athlon 64 products.

Compatibility with 32-bit Applications

Windows XP 64-bit Edition includes a technology named WOW64. This technology allows for 32-bit applications using the IA32 instruction set to be executed on Windows XP 64-bit Edition. On all Windows XP 64-bit Edition implementations, WOW64 includes:

• Wow64.dll: Provides core emulation services such as data type conversion and an interface to the Windows NT kernel.
• Wow64win.dll: Provides a wrapper for Win32k.sys.

On the AMD64 architecture, hardware support for 32-bit execution is used. However, on the IA64 architecture, WOW64 additionally includes:

• Wow64cpu.dll: Provides for software emulation of the IA-32 instruction set.

The WOW64 subsystem redirects the following services when dealing with 32-bit applications:

• Windows Registry: 32-bit applications see a different version of the registry to ensure compatibility between DLL and COM object registrations in 32 and 64-bit modes. WOW64 further provides a registry reflector that intelligently incorporates safe parts of the 32-bit registry tree with the main (64-bit) registry.

• File System Redirection: The directory "%systemroot%\System32" is used by the 64-bit operating system for DLL files. WOW64 transparently redirects 32-bit requests for this directory to the "%systemroot%\SysWOW64" directory, where 32-bit DLLs are stored.

Windows XP Professional x64 Edition does not support the execution of 16-bit Windows or DOS code.

Links

• Microsoft.com - Windows XP Professional x64 Edition Home Page (http://www.microsoft.com/windowsxp/64bit/default.mspx)
• PlanetAMD64.com - Forums, 64bit Software Database, 64bit Driver Database, 64bit News (http://www.planetamd64.com)

Drivers

• ATi.com - ATI Display 64bit Driver (http://www.ati.com/support/drivers/winxp/radeon-xp64.html?type=xp64&prodType=graphic&prod=productsXP64driver&submit.x=14&submit.y=10)
• Nvidia.com - Nvidia Display 64bit Driver (http://www.nvidia.com/object/winxp64_57.30)