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Moving the pagefile to RAM is a ridiculous notion Just turn it off and by more RAM. :)

No matter how much RAM you have, you want the system to be able to use it efficiently. Having no paging file at all forces the operating system to use RAM inefficiently for two reasons. First, it can't make pages discardable, even if they haven't been either accessed or modified in a very long time, which forces the disk cache to be smaller. Second, it has to reserve physical RAM to back allocations that are very unlikely to ever require it (for example, a private, modifiable file mapping), leading to a case where you can have plenty of free physical RAM and yet allocations are refused to avoid overcommitting.

Consider, for example, if a program makes a writable, private memory mapping of a 4GB file. The OS has to reserve 4GB of RAM for this mapping, because the program could conceivably modify every byte and there's no place but RAM to store it. So immediately, 4GB of RAM is basically wasted (it can be used to cache clean disk pages, but that's about it).

Moving the pagefile to RAM is a ridiculous notion Just turn it off and by more RAM.

No matter how much RAM you have, you want the system to be able to use it efficiently. Having no paging file at all forces the operating system to use RAM inefficiently for two reasons. First, it can't make pages discardable, even if they haven't been either accessed or modified in a very long time, which forces the disk cache to be smaller. Second, it has to reserve physical RAM to back allocations that are very unlikely to ever require it (for example, a private, modifiable file mapping), leading to a case where you can have plenty of free physical RAM and yet allocations are refused to avoid overcommitting.

Consider, for example, if a program makes a writable, private memory mapping of a 4GB file. The OS has to reserve 4GB of RAM for this mapping, because the program could conceivably modify every byte and there's no place but RAM to store it. So immediately, 4GB of RAM is basically wasted (it can be used to cache clean disk pages, but that's about it).

Xeon could access a total of 8GB RAM, 64GB of Physical Space with HDD included (pagefile again). (This ^ covers PAE,-more to come with links added).

Xeon could access a total of 32GB RAM, 64GB of Physical Space with HDD included (pagefile again). (This ^ covers PAE,-more to come with links added).

I don't want to write a technical document on platform ardchectrure to put my point across, so if you don't mind, please undelete my answer. Then I can put these links up.

Edit: Ok here is one to start, I'll add more through edit if I can..Thanks. I will try to post in an order which gives a sort of crash course on architectural limits at the basic level.

^This is important to know, OS is limited by CPU because only the CPU can access REAL physical addresses where physical pages are kept.

If the screenshots are messed up it's my browser. Could someone tidy them up please. thx

The bottom line is really not that complicated. For the last 15 or so years many end users have been given the impression a pagefile is some integral part of the Operating System, it is not. It never has been. This misconception is partly fuelled by corporations like Intel and Microsoft.

RAM is a fast storage device, the Hard Drive is a slower storage device, so essentially RAM is level 1 cache, the Hard Drive is Level 2 (disregarding CPU cache for this analogy). Both can be accessed by the CPU.

If not enough RAM is available for the CPU to store the pages it needs to, the HDD can be used as an overflow. If there is plenty of RAM, then the PF is redundant.

Up until Core 2, Intel processors had a 32pin DRAM bus, and 32 registers meaning the CPU had access to 4GB of RAM, and 4GB of HDD space (pagefile). This is an architectural hardware limitation, not a Windows limitation.

The total available for processes was 3.5GB, because a page table takes up 512MB. Which is why 3.5GB shows up in Windows with Intel CPU's (up until Core 2). Add a GPU and even less is available.

Xeon could access a total of 8GB RAM, 64GB of Physical Space with HDD included (pagefile again). (This ^ covers PAE,-more to come with links added).

http://www.windowsdevcenter.com/pub/a/windows/2004/04/27/pagefile.html

3rd screenshot source: System V Application Binary Interface AMD64 Architecture Processor Supplement Draft Version 0.99.7

I intend to continue improving this answer and adding source material and relevant info. I'd like to achieve a balance between not enough information and too much technical information. Suggestions are welcomed. Please don't downvote just because it may not be written so well.