Windows XP 64-Bit Edition

Windows XP 64-Bit Edition
	Version of Microsoft Windows
OS family	Windows NT
Version	5.1, 5.2
Architecture	IA-64
Release date	2001-10-25
Support end	2005-06-30
Based on
	Windows XP Professional (Version 2002); Windows Server 2003 (Version 2003)

Windows XP 64-Bit Edition or Windows XP 64-Bit Edition for Itanium Systems is an edition of Windows XP designed for Itanium processors. Two versions of this edition were released; one that uses the original Windows XP codebase and another that uses the Windows Server 2003 codebase. Both editions were discontinued in January 2005 after HP, the last distributor of Itanium workstations, ended sales for their Itanium-based workstations in September 2004.

History[edit | edit source]

Plans to port Windows to a 64-bit processor date back to the late 1990s, where Microsoft planned to port Windows 2000 to the upcoming Intel Itanium architecture and produce a 64-bit version for the DEC Alpha AXP64. Early Itanium work was done on simulators, but even after the AXP64 version of Windows was cancelled, development continued for a while on AXP64 since no IA-64 hardware was available. Upon the availability of the first IA-64 machines, development shifted to such machines. In 2000, Microsoft canceled the IA-64 port of Windows 2000 in favor of Whistler in the face of continued delays of delivering production IA-64 workstations.

Version 2002[edit | edit source]

The initial release of the 64-Bit Edition shipped on 25 October 2001 simultaneously with Windows XP for x86 machines. It was notable for lack of certain features, unlike in the x86 edition, such as Windows Media Player, NetMeeting, visual styles, and support for 16-bit applications.

A compatibility layer called WoW64 allowed the execution of applications compiled for x86 versions of Windows. This compatibility layer used an on-chip decoder integrated into the Itanium processor. However compared to natively compiled software, this decoder was deemed to be extremely slow compared to IA-64 binaries and was later replaced with a faster software translation layer.

Only Service Pack 1 was released for this edition of Windows XP, despite Service Pack 2 for Windows XP x86 being released before the announcement to end support for the IA-64 editions.

Version 2003[edit | edit source]

The second release of Windows XP 64-Bit Edition, Version 2003, was released on 28 March 2003. It adds support for Itanium 2 processors and is based on the Windows Server 2003 codebase. Unlike x86 versions of Windows XP, it didn't have the Luna theme and was still missing several features compared to the x86 versions of Windows XP.

Since the decision to end support for this version of Windows was made during the development of Service Pack 1, only pre-release builds up to build 3790.1260 can be installed. All later builds can only be installed on Windows Server 2003 and will fail with an error message when attempting to install them on version 2003. It is however possible to install both RTM versions of Service Pack 1 and Service Pack 2 for Windows Server 2003 with a workaround.