i875p Canterwood does not see 4GB RAM - Sees 3GB RAM

This is very frustrating and I'm feeling a little cheated here...
Please anyone give me a real answer.

I've built a Photoshop workstation based on the P4C800-E Deluxe. I
have 4GB of Dual-Channel PC3200 by Micron/Infineon.

When I put in one stick the MB shows ~1GB, 2 sticks ~2GB, 3 sticks
~3GB, but 4 sticks is ~3GB not ~4GB. Asus says this is "normal" and
happens on other chipsets by Via and SiS, but I just can't take that
for a real answer.

I've swapped the sticks around to no avail. Doesn't matter if I have
2 sticks in Dual or Single-Channel mode, they still POST at ~2GB so I
can't blame it on the Dual-Channel Mode.

I know there's *some* overhead for AGP aperture and MCH 1.4, etc. but
that does not account for the failure to utilize over 1GB of fine RAM!

I've read the MCH whitepapers in Intel's site, but they don't account
for this much loss.

I'm on the latest BIOS, have tried APIC and no APIC, MCH 1.1 and 1.4.

Arrrgghhhh! What is going on? Intel is no help, and ASUS claims a
note from their "engineers" explains it all, "this is normal," but
also says some people have reported utilizing 3.8GB. How?

Anyone know the real story?

 

I bet if you remove your AGP video card and use a PCI video card,
more of the memory will be available. The tough part will be getting
Windows to recognize the extra memory you are working so hard to
free up. (I wish I knew of a software utility that can display
the memory map for a system - the info you need to debug the problem
would be found in the Northbridge control registers, but I don't know
how to get at that info.)

Daytripper gave me this reference before:
http://support.microsoft.com/default.aspx?scid=kb;en-us;268363

This article references a /3GB flag for booting:
http://support.microsoft.com/default.aspx?scid=kb;en-us;283037

Paul

 

There is a lot more 'overhead', than just the AGP aperture. Basically every
PCI card and controller will be using some addresses at the top of the
memory. Looking at device manager, and the 'memory range' for cards, will
give an idea of just how much is involved. For instance, on the 'AGP' video
card, it is typical to see perhaps three seperate memory ranges in use. One
is down 'low', and corresponds to the normal EGA/VGA addresses in the base
memory, and then a couple in high memory as well. On a modern card, expect
perhaps about 140MB in total for the video card alone!. Then add other
devices (RAID controllers have a BIOS, network cards, a window into memory,
etc. etc..). Typically, you will be lucky to get away with less than 0.5GB
to 0.7GB being used by the cards. It is common to be able to use more RAM
area, on motherboards designed for 'server' applications. Using a PC video
card, and some more careful mapping of the addresses given to devices (and
not having things like built in sound, which again use memory areas), brings
the useage down significantly, also many of these when switched to fully
32bit mode, disable the low memory addresses, and gain back the area here.
Be aware, that the normal releases of Windows, themselves place limits on
the RAM available to programs, so the gain beyond about 3.2GB, is little,
unless you are using a custom modified OS. The amounts useable on boards
have declined over the last few years, with increasing numbers of devices
mapped into the upper memory 'as standard'. So the presence of multiple
PCI-PCI bridges, USB controllers, sound cards etc. etc., have all eroded the
maximum useable RAM...
Now your problem goes a little 'beyond' this. I'd have certainly expected
you to see perhaps 3.3, to 3.5GB available. It may be as simple as a limit
in the BIOS's ability to 'report' memory. If you run a memory diagnostic
tool like Memtest86, what does it report?.

Best Wishes

 

How much memory does the BIOS System Information show? Have you tried
running Memtest86+, if so how much memory does is show? How much Total
Physical Memory does Windows Task Manager show?