These systems have a total of 8 Slots and can be upgraded to 8GB's total. When upgrading the Power Mac G5 you must install the memory in identicle pairs. Each kit below contains two modules. APPLE Part# M9652G/A compatible 512MB PC3200 DDR KIT (2X256MB) $59.99 APPLE Part# M9653G/A Compatible 1GB PC3200 DDR DIMM KIT (2X512MB) $90.00 APPLE Part# M9654G/A Compatible 2GB PC3200 DDR DIMM KIT (2X1GB) $140.00