I have recently built my own pc but I am having RAM issues. I have 4x4GB sticks and windows detects 16GB but says only 7.9GB is useable. I have tested all RAM and they all work. If I put 1 RAM stick into slots 1 or 2 (DIMM_A1 or DIMM_A2) the PC will start but if I place RAM in either of the last 2 slots the pc will not start. I rechecked the compatability of the ram with my mobo and it is not in the list. Could this be causing the problem?