"Roger Hamlett" said:
This is normal.
Unfortunately, unless you are running a machine with addressing extensions
enabled, your total memory 'space' addressable by the processor, is 4GB.
The AGP card itself, will map into a huge slice of this, the BIOS, another
large slice, and most I/O cards/devices will also grab big pieces of the
memory area. This is why many boards implement one of the address
extension schemes, which reduces this problem. If your board offers an
address extension mode in the BIOS, try enabling this (you may also have
to modify the XP boot). If not, then there is nothing that can be done,
except to minimise the number of added cards/devices.
The difference can be large. On a machine with two video cards, I have
seen the useable memory change from 3.1GB, to 3.8GB, by enabling these
extensions. Generally though, chipsets aimed at the 'user', rather than
'workstation/server' markets, do not implement such extensions (assuming
that people will probably not try to use 4GB of RAM).
Best Wishes
To add to Roger's info, there is this Intel doc on the Asus site,
and it contains Intel's explanation of the 4GB issues.
http://dlsvr01.asus.com/pub/ASUS/mb/4GB_Rev1.pdf
The 945P chipset doesn't support memory remapping AFAIK. So
chapter 4 of the Intel document won't apply to your board.
If you look for a motherboard like a P5WD2 Premium (955 based),
which lists support for 8GB of memory, it should have a memory
remapping function in the BIOS. One problem with the "memory remapping"
or "memory hoisting" function, is that Asus doesn't always document
the setting in the initial manual, so that makes it difficult to
prove that such a setting exists. (On one of the Asus AMD
motherboards, the code was only added to the BIOS, in the fifth
BIOS release. Such late delivery of features makes it difficult
to be sure what you are getting!) But the combination of memory
remapping, plus an OS that properly supports 4 or more GB
of remapped memory, would be a step in the right direction.
I suspect very few users get this working right, as I've never
seen a "success" posting from any user who has asked this
question. Maybe some day we'll get a little useful feedback.
HTH,
Paul