Hello, I just bought a set of Geil PC300 DDR 512x2 matched sticks of ram. Installed it in Slot 3 of my Powermac G5 REV A. Dual 2.0 I'v got another set of Geil 256x2 in slot two( no problems ) and the originals 256x2 in slot 1. Setup: 4) empty 3) 512 geil 2) 256 geil 1) 256 original 1) 256 original 2) 256 geil 3) 256 geil 4) empty No matter what slot I put the 512'a in OSX will not recogize it's there. In the profiler and under about this mac it still says I've only got 1g of ram whe obviously 2g are installed. I tried returning the sticks for new ones and the same still happened. I tried putting them in the different orders but still not seeing it. The 256 geil sticks work fine. Whats wrong?