I heard the SP3 for xp can allocate more than 2gb of ram...

[Flammable]

Is it true? the beta is apparently out for selected people

 

[pm]

Not that it says here:
http://neosmart.net/blog/2007/...sed-analysis-included/

 

[stash]

You question is a bit vauge. XP can already allocate up to 3GB of virtual memory per process if you use the /3GB boot.ini switch AND the process is marked largeaddressaware.

Otherwise is is still 2GB per process on x86.

 

[Jiggz]

Originally posted by: stash
You question is a bit vauge. XP can already allocate up to 3GB of virtual memory per process if you use the /3GB boot.ini switch AND the process is marked largeaddressaware.

Otherwise is is still 2GB per process on x86.

Are we talking about Virtual Memory (Paging File) or System Ram? If we are talking about VM, then the limit is 4Gb per disk (including logical). So if you have one hdd with 3 partitions, then you can have a maximum of 3 paging files at 4GB each or a total of 12GB.

If we are talking about System Ram (which I believe the OP was asking), the limit is 4GB. This is shown by the computation 2^32 = approx 4.295 billion bytes or approx 4GB. This ram is divided into two usage by the OS, 2 GB for kernel and the other 2GB for application.

The /3GB switch is used to change the allocation of the application memory from 2GB to 3GB while at the same time reducing the Kernel memory to 1 GB. Depending on your system usage, this can be either good or bad, but definitely bad for terminal servers.

The OS cannot report all physical rams above the 4Gb limit. In addition, with some rams used for I/O mapping, the reported rams usually falls in the range of 3.2~3.6 GB.

I have XP Pro 32bit with 4GB of physical ram and the reported rams is 3.6GB. And I don't use the /3GB swtich.

As for the original question of SP3 addressing more than 2GB of ram, YES, Windows has been able to address more than 2GB since W2K, WinNT and later. On the contradictory, Win95 and other versions of this platform were limited to 2Gb.

 

[stash]

If we are talking about VM, then the limit is 4Gb per disk (including logical). So if you have one hdd with 3 partitions, then you can have a maximum of 3 paging files at 4GB each or a total of 12GB.

I'm talking about VM. You aren't however You're talking about page files.

This ram is divided into two usage by the OS, 2 GB for kernel and the other 2GB for application

No.

The /3GB switch is used to change the allocation of the application memory from 2GB to 3GB while at the same time reducing the Kernel memory to 1 GB. Depending on your system usage, this can be either good or bad, but definitely bad for terminal servers.

Yes as I posted above. However, simply editing the boot.ini to include the 3GB switch does nothing unless you have apps that are marked largeaddressaware. If you don't have any apps like that, all you are doing is starving the kernel of VM (potentially). All user mode processes not marked largeaddressaware will still get 2GB of VM (per process).

I have XP Pro 32bit with 4GB of physical ram and the reported rams is 3.6GB. And I don't use the /3GB swtich.

The 3GB switch has nothing to do with this.

 

[Jiggz]

This ram is divided into two usage by the OS, 2 GB for kernel and the other 2GB for application

No.

Uuh???

 

[stash]

RAM is not virtual memory. VM uses RAM of course, but the way you described it above is not correct.

If we are talking about System Ram (which I believe the OP was asking), the limit is 4GB. This is shown by the computation 2^32 = approx 4.295 billion bytes or approx 4GB. This ram is divided into two usage by the OS, 2 GB for kernel and the other 2GB for application.

It is true that the limit for physical memory on XP and Vista x86 is 4GB. It is also true that the limit of virtual memory on x86 is 4GB. However physical RAM and virtual memory are not the same thing. If you have 1GB of physical RAM, the OS still gets 2GB VM by default and each usermode process gets 2GB VM by default. Same goes for any amount of RAM you have. Every usermode process runing on the system has a 2GB VM address space.

If you are running an x86 Windows OS that supports PAE (like Server 2003 Enterprise), you can access more than 4GB of physical RAM, but the VM address space remains at 4GB. The only way to get more than 4GB VM address space is to run a 64 bit OS.

 

[Canterwood]

Why is PAE enabled on XP SP2 when the OS is being limited from using 4gb of ram?

I understand why it has been crippled due to buggy drivers, but not why PAE wasn't just switched off instead.

 

[VirtualLarry]

Because the PAE extra level of page tables are needed for NX bit support (Hardware Data Execution Protection), AFAIK.

 

[stash]

Yep PAE is on for DEP/NX support.