I have a problem with a motherboard PDSGE. The motheboard's bios version is 1.0b and doesn't recognize all the ram installed. I have installed 8Gb of ram and it recognizes only 4GB. I tried to install 1Gb module and 2Gb module (on different slots) but it recognizes maximum 4Gb.
Please update your BIOS to revision 1.0c, it will correct your problem.