1) The 4GB limit, is a "RAM license" limit.
2) The later service packs of WinXP x32, come with PAE enabled.
PAE must be enabled, to support the NoExecute (NX) feature.
PAE is not being enabled from a customer-centric viewpoint,
to
enable large memory usage. It's for NX instead.
(It allows marking pages as not executable.)
3) As proof of this, try installing this RAMdisk.
http://memory.dataram.com/products-and-services/software/ramdisk
This RAMDisk wouldn't be able to access memory above 4GB,
unless a PAE page table setup was in place.
The experiment I've done is:
1) Install 6GB of memory on P5E Deluxe.
2) Operating system used is WinXP Pro x32 SP3.
PAE is enabled by the OS (I didn't need to modify boot.ini).
3) When configuring the RAMDisk, it would install a 2GB
RAMDisk (using memory above 4GB). This can't be
accessed without PAE, as far as I know. And that
memory can't be used by programs. The reason the
RAMDisk can do it, is the RAMDisk lives in "driver land"
and the rules there differ.
The result of my experiment is, "3GB available" in the OS
itself, 2GB used by the RAMDisk, and 1GB remains inaccessible.
That means, my x32 computer was using *5GB* of RAM during the
test
which lasted four days.
Even though the missing 1GB is probably lifted above the 4GB
mark, the RAMDisk won't use it.
Benchmarking the 2GB RAMDisk, is shown in this picture. I
wish I'd kept a picture of Task Manager, with everything
showing.
http://img196.imageshack.us/img196/8694/hdtunedataram2gbabove.gif
Background info:
http://en.wikipedia.org/wiki/Physical_Address_Extension
http://en.wikipedia.org/wiki/3_GB_barrier
The memory license is for physical memory, and if you have
a swap file, then more than 4GB worth of programs can be
loaded. As long as the larger programs aren't resident, you
might still have some performance.
As a further experiment, I used the 2GB RAMDisk as a swap
file for the 3GB OS, and it was as smooth as silk, when
filled past the usual 3GB limit. The only problem is,
while that RAMDisk program is good, it still isn't
bulletproof. I no longer use that configuration,
because of detected anomalies (two problems in
four days testing). But if you wish to use that
RAMDisk for ordinary storage, it seems to be a lot
better than the last time I tested it. It crashed
pretty well immediately, the first time I ran it.
The recent versions are much better. Whoever wrote
that thing, knows a lot.