"Anno v. Heimburg" wrote in message
...
Generally, if the PC recognizes the RAM, it should be able to use it.

Well, yes an no. Windows XP in its standard incarnation is able to manage
up
to 4GB of RAM, however, it will assign a maximum of only 2GB to a single
application. So, if you only run one memory-hungry app at a time, more
than
2GB won't do much for you.

That's not true, for a couple of reasons.

First, there is a way to configure Windows to allow processes to use 3GB of
virtual address space, rather than just 2GB. This is done with a switch in
the boot.ini file (and may only be available on the server editions of
Windows...I don't recall if they added it to XP).

Secondly, the 2GB (or 3GB if enabled) per process limit is for the processes
*virtual* address space. It has little to do with the physical RAM in the
computer. It's true that any individual process still won't be able to
access all 3GB or 4GB of RAM if that's what you have installed; they will be
limited to 2GB. But a) in reality no process is ever going to be using a
full 2GB of *physical* RAM even if they have completely allocated their 2GB
quota of *virtual* memory, and b) the full amount of physical RAM is usable
by all the processes combined. So you could have three different processes,
all of which want 1GB of RAM, and they could all theoretically have all of
their data resident in physical RAM if 3GB or more of RAM is installed.

Of course, even there you run into the fact that lots of other processes
need some of their data resident in physical RAM in order to work as well.
The 1GB x 3 scenario is simply theoretical. But the fact is that having
more physical RAM can always provide a benefit, assuming you've got enough
processes to take advantage of it. You don't even need all of those
processes to be memory hungry. You just need enough other processes
competing with one memory hungry process (and Windows certainly has plenty
of other processes)...lower-footprint processes can all share what's left
over after the memory hungry process gets its chunk.

It's sort of like having multiple CPUs (multi-core, multi-package, whatever)
when you're playing a video game that has only one thread (which is nearly
all the video games so far). Sure, the one process that the game is in
doesn't get to directly take advantage of the extra CPUs, but because of the
extra CPU all the other processes on the computer don't wind up competing
with the game for one of the CPUs, and the game can still run somewhat
faster.

The bottom line: because of the fact that Windows has lots of processes that
generally have nothing to do with whatever your one (or few) memory-hungry
process is doing, having more than 2GB (or 3GB as appropriate) of physical
RAM can still be very useful, as it allows that one memory-hungry process to
not have to compete with all the other processes for the same physical RAM.

Pete