Robert: The short answer is that the SATA card takes over the function of the IDE controller, which you then don't need any more. The longer explanation is that the Serial ATA ("SATA") disk interface has two advantages over the Parallel ATA ("PATA" or "IDE") disk interface in the Powermac. The first is speed; SATA 1 is three times as fast as IDE, and SATA 2 six times. That's not the whole story, of course; the rest of the system has to be able to keep up with that rate, and you probably won't see any increase in speed with SATA 2 over SATA 1. But I sure see an increase with SATA 1 over IDE, especially given that the Powermac IDE controller isn't that fast even as IDE controllers go. The second advantage is that there is no 128 GB address space limit on a SATA card as there is on the Powermac IDE controller. So you can use (today) 1.5 TB drives, and see all of that space. There are hacks to get around this limit on the IDE controller, but none for speed. The SATA card simply plugs into any open PCI card slot, and has SATA connectors to hook up compatible hard drives. You cannot connect your old PATA drives to a SATA card, so you'd have to replace them. OWC carries SATA cards that will support both 2 and 4 drives per card. So you can see that you can add a LOT of new drive space if you need and want to. That being said, you can use both PATA and SATA drives in the same machine. The limitation becomes the power supply, its capacity, and the number of power supply connectors available for more drives. My G4 has physical space for four drives, but only three power supply leads. There are adapters available for this function, as long as there's enough current available for all the stuff in your system. And of course, every time you access a PATA drive in a mixed system, you sloooooowww down. So right now in my system, I've removed my PATA drives, and replaced them with a single 160 GB SATA, which can be had fairly inexpensively. For me, it's been a great upgrade. - Michael B. in Cincinnati