Is the 2.75GB showing in BIOS or Windows*?
Memory channels usually affect the speed but not the capacity. You may also want to verify the memory compatibility or check if all the memory sticks and slots are working properly.
In the BIOS, with 4GB installed, I see the following:
Base Memory 640K
Extended Memory 3405824K
Total Memory 3406848K
My understanding is that dual channel takes whatever memory is installed and cuts the useful amount available in half and utilizes the available memory to increase speed and performance -- whatever that is for memory.
How might I test memory slots or the memory?
Ok, you read my mind in regards of the processor.
Do you have an option in BIOS called Memory Hole Remapping?
In the BIOS I saw,
Memory Hole at 15M-16M [disabled]
I enabled it and CentOS would not boot up, "Error 28: Selected item cannot fit into memory". I was able to boot into XP Pro, but I stll saw 2.67 GB showing as useful in My Computer.
It the BIOS I also see,
DRAM Timing Selectable [BySPD <or> manual]
There are a series of options available that are greyed out unless "manual" is selected.
So, leaving aside the operating systems, there is no change in the memory reading from BIOS with Memory Hole Remapping disabled/enabled?
The second setting gives you the option to use the memory with SPD (auto) values or to configure it manually. This should not affect the capacity.
I believe this is related to the BIOS somehow, did you try contacting the motherboard manufacturer?
One of the first things I did was try to see if the BIOS had an upgrade, but the BIOS has the last posted upgrade that I can find, R1.28VH.
I am basing my problem on the fact that I see only 2.67 GB available in my 64bit install of Linux CentOS. I think that XP Pro is not capable of using 4GB of memory and so seeing that amount available in XP Pro is not the source of my concern. I was expecting the 64 bit Linux to use all 4GB even if XP Pro would not. Is it possible that the 64 bit Linux is just not using the memory and the motherboard is not at fault at all?