My 2008 Mac Pro was limping along with the supplied 2GB of RAM, so I bought a couple more 1GB sticks. I know for sure that the sticks and the risers were pushed all the way in. But System Profiler still showed 2GB, instead of the 4GB installed. I downloaded the tech manual for the system and found that one of the original Apple-supplied sticks had gone bad.
So I bought another 2GB. This time around there were no LEDs lit on either riser, but the system still insists it has only 2GB installed! I put two modules on each riser (but I also tried putting all four on one riser), and they are the same brand as the ones supplied by Apple. The System Profiler report is only registering the module installed in the first slot of each riser—according to the tech manual, if the risers were bad, then all four LEDs would be solid red.
