Both my PCs are older Builds. One I keep upgrading and then I send the upgraded parts to my second. They both have boards with the X58 chipset, one an Intel MB and the other an EVGA MB.
My back up PC had 6GB of DDR3 RAM in it. I have not used the PC for quite some time and when I fired it up I noticed that it was only using 3.99GB of 6GB installed. I naturally assumed that I had a bad stick so I ordered a new set of the same RAM.
Today I installed the new RAM and got the same 6GB Installed 4.99 usable
Just for shits and giggles I installed the other three sticks now it says 12GB installed 7.99 usable
I have tried just about everything I can think of including changing Bios settings and still no luck.
There is a lot of BS on the net about possible reasons and fixes for this issue but they all have 1 thing in common, they are all on X58 Chip MBs