What you are seeing is the amount memory available for user programs.
There are two of you using the computer; you and the computer.
The max address range for x86 is 4GB. The upper addresses are used by the
system and hardware buffering. When you have 4GB that range is hidden from
user programs to prevent user programs from writing there.
When you have less than 4GB installed, say 2GB, the system area addresses
are offset into the user area by the memory manager, but by that time the
available user addresses have already been determined so you see the full
2GB of ram installed. The memory manager then marks the offset addresses to
prevent user programs from writing there.
The bottom line is that the full 4GB is in use; by you and the computer.
Vista SP1 will change what is reported on the system properties page and you
will see 4GB where you are now seeing 3.325 GB. That is just a change from
reporting the memory available for user programs to reporting the physical
ram installed. The change will not make any more memory available to user
programs. The change in what is reported is being made because the number
now being reported is so widely misunderstood that MS has given up on its
usefulness. The change is not a "fix" but a change in reporting.
I prefer the present method of reporting because it tells me something
useful; how much memory I can use. Reporting installed ram may be more
understandable to a lot of folks but then they are going to wonder why they
can't seem to use all that memory. It's a devil's choice for MS on which to
report, but I wonder why they simply don't report both on the system
properties page.
