The 64-bit versions of Microsoft Windows Server 2003 and of Microsoft
Windows XP use the Microsoft Windows-32-on-Windows-64 (WOW64) subsystem
to run 32-bit programs without modifications.
The WOW64 subsystem creates a 32-bit environment on the x64-based
versions of Windows Server 2003 and of Windows XP Professional x64 Edition.
Some 32-bit programs may run slower on these operating systems than they would
on 32-bit versions of Windows Server 2003 and of Windows XP. For example, a
32-bit program might run slower on Windows XP Professional x64 Edition than it
would on Microsoft Windows XP Professional. Alternatively, some 32-bit programs
that require lots of memory may exhibit increased performance on the x64-based
versions of Windows Server 2003 and of Windows XP Professional x64 Edition.
This performance increase occurs because the x64-based versions of Windows
Server 2003 and of Windows XP Professional x64 Edition support more physical
memory than the 32-bit versions of Windows Server 2003 and of Windows XP
Professional.
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