The /3GB switch, is so the ~3GB free that WinXP reports, can be used
by one single program. I have a 4GB machine here, and to use 3GB of RAM
requires me to use two or more programs. I have no single program
here, which is LARGEADDRESSAWARE and also has a hunger for RAM.
If I had a LARGEADDRESSAWARE program here, and I set the /3GB switch,
then that program could grow to fill 3GB.
The problem with memory hoisting, is when you install 4GB physical RAM,
the first 3GB are linearly mapped, and the fourth gigabyte is lifted
to between the 4GB and 5GB mark. Something like that. Even the RAMDisk
program, doesn't like that particular segment of RAM, and the RAMDisk
will use
RAM either below (AWE) or above (PAE) that mark. I don't know what is magic
about the 4GB to 5GB area. If you watch a modern version of memtest86+
testing RAM, it exhibits the same strange behavior. Segments above 4GB
being tested 2GB at a time, while one segment seems to be 1GB in size.
And perhaps that 1GB segment, is the 4GB to 5Gb area.
PAE is enabled on WinXP, at least for SP3. That's done so they could
fit the No Execute function for malware hardening. So the PAE part
of the solution is there, that would allow more memory in a 32 bit OS.
PAE would not allow a single program to use all the memory either.
There would still be a 4GB virtual address space available to each
process, which bounds how much RAM it could use. If PAE made 64GB
available to me, I'd need more than 16 programs to use it all.
A 32 bit copy of Photoshop, could not use the entire 64GB. Only
a small portion.
The article here, the author of this article, hacks Vista x32, so that
it will use 8GB of RAM. You would need to find the WinXP equivalent of
this, to test out the idea (I'm pretty sure, it's not as easy as the
Vista case). At least we know Win98 is not a candidate,
as Win98 falls apart if offered too much RAM.
http://www.geoffchappell.com/notes/windows/license/memory.htm
OK, here's a hint for WinXP. No idea if this is stable or not.
http://superuser.com/questions/292207/is-there-any-way-to-use-memory-above-3-25gb-using-windows-xp
"I have heard tales that it's possible to break this barrier in
32bit XP, but it requires much more than a simple registry edit.
IIRC, the limit is compiled into the operating system directly.
To get around it, you have to find a specific .dll file from a
32bit Server 2003 machine and use it to replace the equivalent
file on your Windows XP machine. For this to work, the file has
to be modified so that XP won't reject it and you have to use
volume shadow copy to get it to replace the existing file. I don't
remember and can't find the link now for which file you need or
how to modify it. After this is accomplished, you should be able
to make the same settings to 32bit XP that you can to Server 2003
to allow the higher memory cap. Of course, such a change is highly
unsupported and violates your license agreement."
HTH,
Paul