Sorry, that was a bit confusing. Typically, you'll only be worried about two parts: the controller and whatever device you have hooked up to it. So you can run a SATA I (1.5Gb) drive on a SATA II/III port (99% of the time), but you won't see any benefit over running it on a SATA I port. Conversely, you can run a SATA III drive on an old port, but you'll be severely limited by the bus.