Power Mac G5 memory slots accept only 184-pin dual inline memory modules (DIMMs). The memory must be DDR SDRAM at a speed rating of PC 2700 (333 MHz) for the 1.6 GHz model or PC 3200 (400 MHz) for all three models. Something to remember here is that DDR SDRAM DIMMs must be installed in matched pairs. “Matched” in this context means that the two DIMMs have the same capacity and speed. A valid pair would be two 512 MB PC2700 DIMMs for a 1.6 GHz G5, for example. Plus, G5s are not as forgiving as the G4 or G3 Macs were regarding RAM, you can only use the RAM intended for the computer as described above, slower RAM (for example, PC2100) will not work. As always, call your Sweetwater Sales Engineer who can help you get the right RAM for your computer.