Dave said:
Partially true. If it's patched correctly, you can use 3 Gigs of RAM.
If unpatched, the limit is 2 Gigs.
If you get a 64-bit Version, yes. But, that would assume that all of
your current software will run on 64-bit OS, without modification.
Then there is the question of, what kind of software are you running
that can benefit from MORE than 2 Gigs of RAM?
You probably don't need to do anything, as far as RAM goes. -Dave
Based on reviews on the Newegg site, for the WinXP x64 they're selling,
not everyone is happy using that version of the OS. You can have more
trouble finding drivers for it and the like. So it may not represent
good value, as an upgrade from the x32 version. A 64 bit version of
Vista, or Windows 7 when it comes out, may work out a bit better.
(Windows 7 was offered for download, and you could have used that
to test out what a 64 bit OS is like, for free.)
There is a setting in WinXP, that controls the split between
user and kernel space. With no modifications, a single program can
use up to 2GB of memory. If you run several programs, you can use
up whatever memory remains. With "/3GB" and a program with the
"large address aware" flag set, a single program can use up to 3GB.
http://www.microsoft.com/whdc/system/platform/server/PAE/PAEmem.mspx
The maximum total memory available, is limited by address space on
WinXP x32. There is 4GB of address space, and some address space must
be provided for PCI bus, AGP bus, or PCI Express bus. On some
machines, you'd install 4GB of RAM, and see a report of "3.5GB free".
On others, this number drops, as the hardware uses more of those
resources. On a machine with two Nvidia 512MB video cards in SLI,
the reported free memory could be as low as 2.75GB. (On a machine
like that, it may make more sense to install 3GB of physical memory,
and only lose access to 0.25GB of it.)
So the hardware installed in the WinXP x32 machine, can have an
impact on the free memory reported, because the machine has run
out of address space to use it all. Using a 64 bit OS can make
a difference, or perhaps a server OS, where the PAE facility still
works as intended. On WinXP x32, PAE is hijacked for other purposes.
"Memory Limits"
http://msdn.microsoft.com/en-us/library/aa366778(VS.85).aspx
Paul