Hi there, I've got a Mac Pro (2x2.8 Quad Core) Early 2008. The computer came with 2GB of RAM (2x1GB). Last year I bought an extra 4GB (2x2GB) from Crucial and installed them without any problem. I just got 8GB (2x4GB) and I thought I was installing the chips properly, but OSX only shows that I have 10GB installed. My configuration is as follows: Riser A: DIMM 1: 1GB DIMM 2: 1GB DIMM 3: 4GB DIMM 4: 4GB RISER B: DIMM 1: 2GB DIMM 2: 2GB DIMM 3: EMPTY DIMM 4: EMPTY Anyone have any suggestions? Thank you!