I just installed xp64 on a new system with an AMD 64bit processor with 4 gigs
of matched dual channel memory. Both the bios and Windows report having just
under 3 gigs of memory. Can anyone tell me why?

Have you looked in your motherboard manual for a possible explanation or the
board's website?
I have a P4P800 which says that with 4GB installed the machine will report
under 4 GB of installed memory because of resources taken by the chipset
which I assume might mean address space. However, they say just a little bit
is lost, you seem to have lost a lot.

Could be you have a bad stick or it isn't 100% compatible with your system.
I believe a dual-channel system will revert to single channel if it doesn't
have matching sticks and if one is bad then it wouldn't think it had
matching.

Try them one at a time to see if they all work and try runnng a diagnostic
like Memtest+ to see what it finds.

Billh

"Mikalele" <Mikalele@discussions.microsoft.com> wrote in message
news:21BC0B1F-D796-482A-8D42-38297BFEA166@microsoft.com...
>I just installed xp64 on a new system with an AMD 64bit processor with 4
>gigs
> of matched dual channel memory. Both the bios and Windows report having
> just
> under 3 gigs of memory. Can anyone tell me why?

In news:21BC0B1F-D796-482A-8D42-38297BFEA166@microsoft.com,
Mikalele <Mikalele@discussions.microsoft.com> had this to say:

My reply is at the bottom of your sent message:

> I just installed xp64 on a new system with an AMD 64bit processor
> with 4 gigs of matched dual channel memory. Both the bios and Windows
> report having just under 3 gigs of memory. Can anyone tell me why?


I can't say for certain but it's worth noting that this applies to server
systems. I haven't broken the 3 GB barrier yet - and have found that 2 GB
suits all my needs so I actually have spare sticks kicking about - so I'm
not 100% certain this applies to you.

Not All Physical Memory May Be Reported By The Operating System:
http://support.microsoft.com/kb/555458/en-us?spid=3208

I'd take a look at that and consider giving Option A a short if B is not an
option you can consider. The depth of the reasons behind it far exceeds my
ability to comprehend so, if that's the problem, a firmware upgrade is your
best choice. Flashing your BIOS would be the most logical first step
assuming such is available and you have a reason behind it. If you can get
by with 3 GB then so be it. I only recommend BIOS flashes (mostly because I
am old-ish I suppose and remember the problems of yesteryear) when it's
going to add either a feature or functionality that you absolutely can not
live without.

--
Galen - MS MVP - Windows (Shell/User & IE)
http://dts-l.org/

"A man should keep his little brain attic stocked with all the
furniture that he is likely to use, and the rest he can put away in the
lumber-room of his library where he can get it if he wants it."

Sherlock Holmes

Thanks for the suggestions. As it turned out I had to first update the
chipset drivers and then update the bios. Now the bios and Windows see all 4
gigs of RAM. The mainboard is an ASUS A8N-E.