This may not be a mobo issue but wasn't sure where to post.

I just recently went from 2GB of RAM to 4GB of ram. I had a pair of Corsair Dominator 2GB kit 800 4-4-4-12 which spit out memory errors under mem test so I RMA'ed.

In the meantime I bought a cheapie 2GB Patriot kit 800 4-4-4-12 while my RAM was in transit (2 weeks). Turns out the Patriot memory ROCKS!

Anyways, I got my Corsair memory back and plugged it in by itself ran mem test no errors %100 ok, so I then plugged in my extra 2GB Patriot RAM.

The boot up shows 4GB in bios. But, Windows XP and Vista 32 U, both show 2.25GB?????

CpuZ shows 4 modules, but Sisoft Sandra and Everest both show 2.25GB??

Mem performance has gone down slightly but othewise the system is stable and fast as before???

Anyone else run into this? thanks in advance

Its a problem with 32bit operating systems. They can only address a total of i think 4gb of memory, that includes cache and everything else. So you will only be able to access so much of your actual RAM, only way to alleviate this problem is to get a 64bit os. This dilemma is widespread and very known and a quick google search will turn you up many similar situations.

Sadly, working as designed.

You will need 64-bit Vista or something along those lines to address your issue. Basically Windows needs to reserve space under 4gb for logical use by drivers and will simply not use that physical RAM.

In most cases 3.0-3.5gb of RAM is available.
(I see 3.5gb on my system)

However, when SLI is implemented, most folks report drops in available RAM to as low as you are reporting. This is likely due to some odd games that SLI is doing with its drivers.

At this point you are most likely best off by just using 2gb since.

thanks man, I thought it might be something like that but I "assumed" XP and Vista were advanced enough to manage much more ram than that...,

Ok, no big, I'll pull out the Patriots go with just 2GB, bummer. I'm not ready to mess with 64bit.

thanks again all...

I did some research on this 'problem'.

The problem is not that Vista and XP are not advanced enough. It is a physical limitation of the 32 bit operating system.

ANY 32 Bit OS, whether it be MAC OSX or any of the various flavors of Linux, can only address a maximum of 4GB, 64Bit OS's have a similar limit, but only reach it at 128GB!

Read here for a better explanation: 32-bit/64-bit Explained

Actually it is a limit in the OS itself.

Some 32-Bit Operating systems can handle more than 4gb of RAM.
Even some versions of Windows.

http://www.microsoft.com/whdc/syst [...] ae_os.mspx

Example - Windows Server 2003 SP1 32-Bit Edition can address up to 64Gb of memory.

Microsoft has made a concious decision to not include this support in their desktop operating systems. In fact, they actually removed some PAE support from XP going from SP1 to SP2.

With XP SP1, you could enable PAE support and the drivers would use ram pointers above 4gb and hence allow you to use all 4gb of memory.

The long and short still is that the average home user will need Vista-64.

I'd like to add a question to that. I want to go (in the next 12 months, so no rush) from 2GB to 4GB memory on my Asus P5B Deluxe. I have dual-boot WXP Home 32-bit and Vista Home Premium 64-bit.

If I put on the "memory remapping" in my Bios to be able to use my whole 4GB under Vista (as I've read I don't know where), will that cause problem for WXP?

Is there a guide anywhere about that?

Thanks.

P.S.: It's true that the 4GB limit is true for all 32-bit OS.

Who knows. (Well somebody may :> )

Just test to find out.
Much may depend on your hardware, drivers, etc.. etc...
Some may handle it better than others.