Memory size support for Window 2003 and Window 2008

I have serveral HP proliant server that could support up to 32Gb of memory. Those servers are installed with Window 2003 32 bits, 64 bits and Window 2008 64 bits.

Under these stitution, can my Window servers performance for those 32 bits OS, by adding the /3GB in my boot.ini. Can I say that only 64 bit OS could be benefit from adding memory over 4GB ?

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Shreedhar EtteCommented:

Refer this article:

Hope this helps,
AXISHKAuthor Commented:

I still get confused. 32-bit According to the table, Window should be limited to 4Gb of memory. But there is also a statement says that "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."

So, does it mean that it is possible for 32bit OS to access memory over 4GB ?

Thank again.

Yes, according to the link provided. (an extension of the link provided by shreedhar)

* Direct quote from the above link.

Physical Address Extension (PAE) is a processor feature that enables x86 processors to access more than 4 GB of physical memory on capable versions of Windows. Certain 32-bit versions of Windows Server running on x86-based systems can use PAE to access up to 64 GB or 128 GB of physical memory, depending on the physical address size of the processor.
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AXISHKAuthor Commented:
PAE does not change the amount of virtual address space available to a process. Each process running in 32-bit Windows is still limited to a 4 GB virtual address space.

So, under which stituation should this be benefit ?

Most modern 32 bit processors have a 36 bit physical address bus so can access up to 32GB of RAM. PAE makes this possible, but you must be using an OS that permits over 4GB RAM. With Windows 2003 that means Enterprise or Datacenter editions. Others are limited to 4GB of RAM by licensing restrictions. There is no legal way around this.

In any 32 bit OS each process has a fixed 4GB address space, completely independent of RAM size. Of this 4GB, the lower 2GB is private to each process, while the upper 2GB is shared by all processes and is used by the system. Note that this 2GB system address space does not mean that 2GB RAM is reserved for the system. RAM is allocated to the system and user processes according to need, not some fixed ratio. Because each process has a private 2GB address space (not shared), potential RAM usage can be many GB.

The /3GB has almost nothing to do with RAM usage. It changes the virtual address space division to 3GB per process with 1GB for system use. Again, this is virtual address space, not RAM. The larger virtual address space does help some applications. But there is a price to be paid. The restricted system address space has some serious implications. This severely limits the system cache which will usually reduce overall performance. System RAM will be limited to 16GB maximum, often less. Be sure to understand the implications before using.
Darius GhassemCommented:
Here is where the confusing part comes into play you can't use the PAE switch but you OS will only see 4GB you will not be able to view anymore then 4GB without using the PAE the system could hold 1GB of memory so your system would actually only see 3GB this is why the PAE is important to use. No matter what your Standard system is still limited to 4 GB of viewable RAM. Now in a Enterprise edition for 32-bit you are still limited to 32-bit limits but the OS can see more memory and allocated using the 32-bit limits.
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