Upper memory limit

[Matthew Wettergreen]

I am running a dual 1.13GHz Pentium III with 4Gb of RAM.
Windows XP only recognizes 3.59Gb. I need this much
memory because of the taxing CAD processes I do. I have
never been able to get any one program to use more than
1.5Gb of RAM before the program crashes. My page file is
set at several Gb and has never been hit. My Questions
are:

1) Why won't my computer utilize all of the memory that
it has available?
2) Why is there a limit on the amount of memory that a
program can handle before it crashes?
3) Is there a way to get my computer to use all of the
possible memory?

Thanks for the help in advance,
Matthew

 

[David Jones]

Because of the way 32-bit memory management works in
Windows, each process only has access to 2 GB of RAM
(with 2 GB handled by the OS for kernel-mode and
system "memory"), and depending on how the program is
allocating that RAM, it may not even be able to use all 2
GB.

This is each process, if you have multiple processes at
once, each one gets 2 GB for what's called "user mode".

The crashing is impossible to diagnose without knowing
exactly what they do and debugging the application
itself, a well developed application should not be
crashing in this instance.

It's up to the application to handle a lot of this stuff,
there are various 'hacks' to allow additional memory to
be used, but they must be developed into the application
itself, the end user can't affect it.

You're actually a prime example of someone who would
probably benefit by switching to a 64-bit workstation
like the Itanium2 or the forthcoming Opteron and other
AMD-64 chips. 64-bit processors do not have this 4 GB
limit and can access huge amounts of RAM without needing
to go through all this.