Have 2 x512M modules installed Size: 512 MB Type: DDR SDRAM Speed: PC3200U-30330 And was thinking about going to 2 x 1G. I see it's DDR but when i look around - DDR2 is less than half the price of DDR So although i know it's unlikely - wanted to check if there was any compatibility between the G5 ALS and DDR2 memory? ------------------------ This from crucial uk would suggest not Generally speaking, motherboards are built to support only one type of memory. You cannot mix and match SDRAM, DDR, DDR2, or DDR3 memory on the same motherboard in any system. They will not function and will not even fit in the same sockets. Found on ebay some suggestions that 'high density' memory doesn't work in Macs - sounds like i need to be careful what i get - any suggestions here?