I have currently a dual G4 and a MacBook sporting between them 4 processors. I do get all 4 rendering and the amazing thing is that the MacBook is almost as fast as the G4 even thou it is moving the data through my Airport network. Pretty cool stuff. I don't have access to ether a Quad G5 or one of those MacPro desktops to test Carrara in. But I am sure you would get all four cores showing up.