I upgraded my G4 Mirror Drive system to a new(ish) G5 2Ghz DP system, which sadly has nothing but PCI-X slots. Other than possible server stuff, what can you do with them? I was annoyed when I realized it... I had a PCI card in my G4 with four USB2.0 ports and was hoping to migrate it to the G5 but, apparently not. Unless there is a 'trick' to make it work... like making the 9600Pro work in my old G4 using tape and covering up pins etc.