Memory Limits for Windows Releases/OS

Physical Memory Limits: Windows 7

The following table specifies the limits on physical memory for Windows 7.

Version	Limit on X86	Limit on X64
Windows 7 Ultimate	4 GB	192 GB
Windows 7 Enterprise	4 GB	192 GB
Windows 7 Professional	4 GB	192 GB
Windows 7 Home Premium	4 GB	16 GB
Windows 7 Home Basic	4 GB	8 GB
Windows 7 Starter	2 GB	N/A

Physical Memory Limits: Windows Server 2008 R2

The following table specifies the limits on physical memory for Windows Server 2008 R2. Windows Server 2008 R2 is available only in 64-bit editions.

Version	Limit on X64	Limit on IA64
Windows Server 2008 R2 Datacenter	2 TB
Windows Server 2008 R2 Enterprise	2 TB
Windows Server 2008 R2 for Itanium-Based Systems		2 TB
Windows Server 2008 R2 Foundation	8 GB
Windows Server 2008 R2 Standard	32 GB
Windows HPC Server 2008 R2	128 GB
Windows Web Server 2008 R2	32 GB

Physical Memory Limits: Windows Server 2008

The following table specifies the limits on physical memory for Windows Server 2008. Limits greater than 4 GB for 32-bit Windows assume thatPAE is enabled.

Version	Limit on X86	Limit on X64	Limit on IA64
Windows Server 2008 Datacenter	64 GB	1 TB
Windows Server 2008 Enterprise	64 GB	1 TB
Windows Server 2008 HPC Edition		128 GB
Windows Server 2008 Standard	4 GB	32 GB
Windows Server 2008 for Itanium-Based Systems			2 TB
Windows Small Business Server 2008	4 GB	32 GB
Windows Web Server 2008	4 GB	32 GB

Physical Memory Limits: Windows Vista

The following table specifies the limits on physical memory for Windows Vista.

Version	Limit on X86	Limit on X64
Windows Vista Ultimate	4 GB	128 GB
Windows Vista Enterprise	4 GB	128 GB
Windows Vista Business	4 GB	128 GB
Windows Vista Home Premium	4 GB	16 GB
Windows Vista Home Basic	4 GB	8 GB
Windows Vista Starter	1 GB

Physical Memory Limits: Windows Home Server

Windows Home Server is available only in a 32-bit edition. The physical memory limit is 4 GB.

Physical Memory Limits: Windows Server 2003 R2

The following table specifies the limits on physical memory for Windows Server 2003 R2. Limits over 4 GB for 32-bit Windows assume that PAE is enabled.

Version	Limit on X86	Limit on X64
Windows Server 2003 R2 Datacenter Edition	64 GB (16 GB with 4GT)	1 TB
Windows Server 2003 R2 Enterprise Edition	64 GB (16 GB with 4GT)	1 TB
Windows Server 2003 R2 Standard Edition	4 GB	32 GB

Physical Memory Limits: Windows Server 2003 with Service Pack 2 (SP2)

The following table specifies the limits on physical memory for Windows Server 2003 with Service Pack 2 (SP2). Limits over 4 GB for 32-bit Windows assume that PAE is enabled.

Version	Limit on X86	Limit on X64	Limit on IA64
Windows Server 2003 with Service Pack 2 (SP2), Datacenter Edition	64 GB (16 GB with 4GT)	1 TB	2 TB
Windows Server 2003 with Service Pack 2 (SP2), Enterprise Edition	64 GB (16 GB with 4GT)	1 TB	2 TB
Windows Server 2003 with Service Pack 2 (SP2), Standard Edition	4 GB	32 GB

Physical Memory Limits: Windows Server 2003 with Service Pack 1 (SP1)

The following table specifies the limits on physical memory for Windows Server 2003 with Service Pack 1 (SP1). Limits over 4 GB for 32-bit Windows assume that PAE is enabled.

Version	Limit on X86	Limit on X64	Limit on IA64
Windows Server 2003 with Service Pack 1 (SP1), Datacenter Edition	64 GB (16 GB with 4GT)	X64 1 TB	1 TB
Windows Server 2003 with Service Pack 1 (SP1), Enterprise Edition	64 GB (16 GB with 4GT)	X64 1 TB	1 TB
Windows Server 2003 with Service Pack 1 (SP1), Standard Edition	4 GB	32 GB

Physical Memory Limits: Windows Server 2003

The following table specifies the limits on physical memory for Windows Server 2003. Limits over 4 GB for 32-bit Windows assume that PAE is enabled.

Version	Limit on X86	Limit on IA64
Windows Server 2003, Datacenter Edition	64 GB (16 GB with 4GT)	512 GB
Windows Server 2003, Enterprise Edition	64 GB (16 GB with 4GT)	512 GB
Windows Server 2003, Standard Edition	4 GB
Windows Server 2003, Web Edition	2 GB
Windows Small Business Server 2003	4 GB
Windows Compute Cluster Server 2003		32 GB
Windows Storage Server 2003, Enterprise Edition	8 GB
Windows Storage Server 2003	4 GB

Physical Memory Limits: Windows XP

The following table specifies the limits on physical memory for Windows XP.

Version	Limit on X86	Limit on X64	Limit on IA64
Windows XP	4 GB	128 GB	128 GB (not supported)
Windows XP Starter Edition	512 MB	N/A	N/A

Physical Memory Limits: Windows Embedded

The following table specifies the limits on physical memory for Windows Embedded.

Version	Limit on X86	Limit on X64
Windows XP Embedded	4 GB
Windows Embedded Standard 2009	4 GB
Windows Embedded Standard 7	4 GB	192 GB

How graphics cards and other devices affect memory limits

Devices have to map their memory below 4 GB for compatibility with non-PAE-aware Windows releases. Therefore, if the system has 4GB of RAM, some of it is either disabled or is remapped above 4GB by the BIOS. If the memory is remapped, X64 Windows can use this memory. X86 client versions of Windows don’t support physical memory above the 4GB mark, so they can’t access these remapped regions. Any X64 Windows or X86 Server release can.

X86 client versions with PAE enabled do have a usable 37-bit (128 GB) physical address space. The limit that these versions impose is the highest permitted physical RAM address, not the size of the IO space. That means PAE-aware drivers can actually use physical space above 4 GB if they want. For example, drivers could map the "lost" memory regions located above 4 GB and expose this memory as a RAM disk.