3GB of RAM showing up as 2GB

Last year I built a Core i7 920 system based on the ASUS P6T Deluxe motherboard. I have 3x1GB of DDR3 (triple-channel configuration), but only 2GB is being reported by: Windows XP, CPU-Z, the BIOS. Is this a hardware problem, or is the third gigabyte of RAM being reserved by the system for video card-related stuff? The video card has 512MB of RAM.

I realize that 32-bit Windows XP is not the ideal operating system for more than 2GB of RAM, but from what I've read it should be reporting at least 2.5GB.

Scott

Posted 2009-05-03T18:34:39.450

Reputation: 1 143

Answers

If the BIOS is reporting 2Gb, then it's a hardware or BIOS problem, nothing to do with XP.

First thing I'd do is try the RAM two sticks at a time to see whether they're all good. Second thing would be checking if a BIOS upgrade is available.

chaos

Posted 2009-05-03T18:34:39.450

Reputation: 1 599

41/ press the sticks down firmly, to make sure they are properly installed. 2/ get 1 stick at a time to show up, by removing them all, and trying one by one. It's usually the simplest things, hence 1. – Alister Bulman – 2009-05-03T19:22:30.550

You can also try a memtest to check if everything is okay – setatakahashi – 2009-05-07T12:04:55.483

1This answer was the closest to being correct, so points to you. I ran CPU-Z and it reported that Slot C1 was empty, so I opened the case, reseated the stick, and it's now coming up as 2.99 GB in WinXP and 3 GB in the BIOS. – Scott – 2009-05-29T03:06:48.530

Double check what the BIOS is reporting. I suspect that your memory is actually there, but remapped over the 4GB limit: a 32bit OS will be able to see only 2GB, the BIOS should report the correct amount of memory though.

Your memory map might something like:

0-2GB physical memory
2-4GB hole for MMIO
4-5GB physical memory

My P5B-E does the exact same thing, but I'm running a 64bit OS...

Luca Tettamanti

Posted 2009-05-03T18:34:39.450

Reputation:

I have used a XP Machine (32 bit) with 4 GB so i know that it supoprts upto 4 GB. since you are saying that BIOS is also reporting it as 2 GB , this should be a hardware problem, you probably need to test the slots or do some switching of the RAM modules to identify the faulty one.

Dinesh Manne

Posted 2009-05-03T18:34:39.450

Reputation: 1 079

In the bios, there should be a setting for dual or triple channel memory.

Ryaner

Posted 2009-05-03T18:34:39.450

Reputation: 161

Sounds like he's probably using it, from his question. – chaos – 2009-05-03T18:50:20.083

2With these boards, you can put in the 3 sticks of ram, leave it defaulting to dual channel and it will boot fine, just picking up 2 of the 3 sticks. – None – 2009-05-04T08:30:01.873

There is no BIOS setting; it's automatic. – Scott – 2009-05-29T03:04:44.540

Try enabling the /3GB switch in your boot.ini.

http://support.microsoft.com/kb/833721

Sören Kuklau

Posted 2009-05-03T18:34:39.450

Reputation: 201

4The /3GB switch is for Virtual Address Space for applications,not Physical Memory. If the Bios is not recognizing the memory, there is no point looking for it at OS level – None – 2009-05-03T18:40:55.207