Hello I have the late 2005 Dual 2.3 GHz Powermac G5. It can take 16GB of PC2-4200 DDR2 SDRAM. This is what the crucial memory advisor says: However, the Apple website says it takes PC2-4200. OK, I understand that both 6400 and 5300 are backward compatible (meaning that they will fit in a PC2-4200 slot but only operate at the max speed of the system), so my question is: Is Crucial just trying to up-sell me the more expensive RAM or does my system actually support PC-5300/PC-6400 speeds? I have read that Apple's maximum RAM specifications often reflect for the memory available at that time, and when faster RAM is available the documentation is not updated. Hope this isn't a stupid question. Thanks!