Maximum RAM limit in Windows XP / Vista

The maximum RAM supported in Windows XP (4GB) has become a subject to lot of discussions. The reason for this limit is address-apace limit in 32-bit operating systems. Even though it is said to be 4GB of maximum, you won’t actually get 4GB, because of part of address-space is used to PCI devices, Graphics card, etc. So it is only 3.23GB is shown in System Properties.

What about Maximum RAM limit in Windows Vista

Does Vista resolve the problem? Even though Windows Vista consumes lot of RAM compare to earlier operating systems, the maximum limit of RAM supported in Vista is also 4GB.

But some people may feel it is not enough 4GB of RAM, if they are used to run couple of VPCs in their workstation. The most suggested solution for this issue is move into 64-bit operating systems, which is not a practical option for most of us. (Because you need hardware upgrade too)

The other solution (for me the best solution) is to use a server operating system. Windows Server 2003, Enterprise Edition supports 32GB of RAM. Windows Server 2003 Service Pack 2 (SP2), Enterprise Edition supports 64GB of RAM. Please note that it is only Enterprise Edition supports this amount.

These operating systems support Intel-provided memory address extension called PAE (Physical Address Extension) to overcome address-space limit. Support for PAE is provided under Windows 2000 and 32-bit versions of Windows XP and Windows Server 2003. 64-bit versions of Windows do not support PAE.


shane said...

Windows 2003 Enterprise edition, as you mentioned, achieves the 64GB limit using PAE. Although PAE is an alternative, its not a magic bullet.
Extracted from wikipedia:
"The operating system uses page tables to map this 4 GiB address space onto the 64 GiB of total memory, and the map is usually different for each process. In this way the extra memory is useful even though no single regular application can access it all simultaneously."

I'm guessing that VPCs would get any real benifit from PAE since its still limited by the 4 gig limit.
I think you are still better off investing in an 64bit configuration. Plus you get the added benifit of the new processors having hardware virtualization which significatly improves your VPC performance as well.

Prasad Sampath Wickramasinghe said...

Yap. You are correct. But my situation was different. I recently upgraded my machine to Core 2 Duo 2.66GHz with 4GB RAM, and to upgrade RAM to 8GB in mind. I didn’t go for 64-bit because of fear of software compatibility.

When I configured my machine I came to know that Xp, Vista has this limit. So the solution I found out is this