Processor and memory capabilities of Windows XP Professional x64 Edition and of the x64-based versions of Windows Server 2003 (888732)

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The number of processors and the amount of physical RAM that are supported

The following table compares the number of processors and the amount of physical RAM that are supported by the x64-based versions of Windows Server 2003 and by Windows XP Professional x64 Edition to those that are supported by the 32-bit versions.

Operating system	Number of processors	Physical RAM
Microsoft Windows Server 2003, Standard Edition	4	4 gigabytes (GB)
Microsoft Windows Server 2003, Standard x64 Edition	4	32 GB
Microsoft Windows Server 2003, Enterprise Edition	8	64 GB
Microsoft Windows Server 2003, Enterprise x64 Edition	8	1 terabyte
Microsoft Windows Server 2003, Datacenter Edition	32	128 GB
Microsoft Windows Server 2003, Datacenter x64 Edition	32	1 terabyte
Microsoft Windows XP Professional	2	4 GB
Microsoft Windows XP Professional x64 Edition	2	128 GB

Memory allocation settings

The following table compares the memory allocation settings that are supported by the x64-based versions of Windows Server 2003 and Windows XP Professional x64 Edition to those that are supported by the 32-bit versions.

Memory allocation settings	32-bit versions	x64-based versions
Total amount of virtual address space	4 GB	16 terabytes
Amount of virtual address space per 32-bit process	2 GB (3 GB if the /3GB switch is added to the Boot.ini file)	2 GB (4 GB if the /LARGEADDRESSAWARE option is used)
Amount of virtual address space for the 64-bit processes	Not applicable	8 terabytes
Amount of paged pool memory	470 megabytes (MB)	128 GB
Amount of non-paged pool memory	256 MB	128 GB
Size of system cache	1 GB	1 terabyte

For more information about the x64-based versions of Windows Server 2003, visit the following Microsoft Web site: For more information about Windows XP Professional x64 Edition, visit the following Microsoft Web site:

Technical support for Windows x64 editions

Your hardware manufacturer provides technical support and assistance for Microsoft Windows x64 editions. Your hardware manufacturer provides support because a Windows x64 edition was included with your hardware. Your hardware manufacturer might have customized the Windows x64 edition installation with unique components. Unique components might include specific device drivers or might include optional settings to maximize the performance of the hardware. Microsoft will provide reasonable-effort assistance if you need technical help with your Windows x64 edition. However, you might have to contact your manufacturer directly. Your manufacturer is best qualified to support the software that your manufacturer installed on the hardware.

For product information about Microsoft Windows XP Professional x64 Edition, visit the following Microsoft Web site: For product information about Microsoft Windows Server 2003 x64 editions, visit the following Microsoft Web site: