http://msdn.microsoft.com/en-us/library/aa366778%28VS.85%29.aspx
Physical Memory Limits: Windows 8
The following table specifies the limits on physical memory for Windows 8.
| Version | Limit on X86 | Limit on X64 |
|---|---|---|
| Windows 8 Enterprise |
4 GB
|
512 GB
|
| Windows 8 Professional |
4 GB
|
512 GB
|
| Windows 8 |
4 GB
|
128 GB
|
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
|
