This topic describes memory limits for supported Windows releases:
Limits on memory and address space vary by platform, operating system, and by whether the
IMAGE_FILE_LARGE_ADDRESS_AWARE value of the
LOADED_IMAGE structure and
4-gigabyte tuning (4GT) are in use.
IMAGE_FILE_LARGE_ADDRESS_AWARE is set or cleared by using the
/LARGEADDRESSAWARE linker
option.
4-gigabyte tuning (4GT), also known as application memory tuning, or the /3GB switch, is a technology (only
applicable to 32 bit systems) that alters the amount of virtual address space available to user mode applications.
Enabling this technology reduces the overall size of the system virtual address space and therefore system
resource maximums. For more information, see
What is 4GT.
Limits on physical memory for 32-bit platforms also depend on the
Physical Address Extension (PAE), which allows
32-bit Windows systems to use more than 4 GB of physical memory.
Memory and Address Space Limits
The following table specifies the limits on memory and address space for supported releases of Windows. Unless
otherwise noted, the limits in this table apply to all supported releases.
| Memory type | Limit in on X86 | Limit in 64-bit Windows |
|---|
User-mode virtual address space for each 32-bit process
|
2 GB
Up to 3 GB with IMAGE_FILE_LARGE_ADDRESS_AWARE and 4GT
|
2 GB with IMAGE_FILE_LARGE_ADDRESS_AWARE cleared (default)
4 GB with IMAGE_FILE_LARGE_ADDRESS_AWARE set
|
User-mode virtual address space for each 64-bit process
|
Not applicable
|
With IMAGE_FILE_LARGE_ADDRESS_AWARE set (default):
x64: 8 TB
Intel Itanium-based systems: 7 TB
2 GB with IMAGE_FILE_LARGE_ADDRESS_AWARE cleared
|
Kernel-mode virtual address space
|
2 GB
From 1 GB to a maximum of 2 GB with 4GT
|
8 TB
|
Paged pool
|
Limited by available kernel-mode virtual address space or the
PagedPoolLimit registry key value.
Windows Vista and above: Limited only by kernel mode virtual address space. Starting with Windows Vista with Service Pack 1 (SP1), the
paged pool can also be limited by the
PagedPoolLimit registry key
value.
Windows Home Server and Windows Server 2003: 530 MB
Windows XP: 490 MB
|
128 GB
Windows Server 2003 and Windows XP: Up to 128 GB depending on configuration and RAM.
|
Nonpaged pool
|
Limited by available kernel-mode virtual address space, the
NonPagedPoolLimit registry
key value, or physical memory.
Windows Vista: Limited only by kernel mode virtual address space and physical memory. Starting with
Windows Vista with SP1, the nonpaged pool can also be limited by the
NonPagedPoolLimit
registry key value.
Windows Home Server, Windows Server 2003, and Windows XP: 256 MB, or 128 MB with 4GT.
|
75% of RAM up to a maximum of 128 GB
Windows Vista: 40% of RAM up to a maximum of 128 GB.
Windows Server 2003 and Windows XP: Up to 128 GB depending on configuration and RAM.
|
System cache virtual address space (physical size limited only by physical memory)
|
Limited by available kernel-mode virtual address space or the
SystemCacheLimit registry
key value.
Windows Vista: Limited only by kernel mode virtual address space. Starting with
Windows Vista with SP1, system cache virtual address space can also be limited by the
SystemCacheLimit
registry key value.
Windows Home Server, Windows Server 2003, and Windows XP: 860 MB with
LargeSystemCache
registry key set and without 4GT; up to 448 MB with 4GT.
|
Always 1 TB regardless of physical RAM
Windows Server 2003 and Windows XP: Up to 1 TB depending on configuration and RAM.
|
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 that
PAE 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.
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