toddpw@tybalt.caltech.edu (Todd P. Whitesel) (01/22/90)
w0033@desire.wright.edu writes: >I was unable to find any technical data on how individual drives are accessed >through the smartport. Maybe it's some sort of company secret or something. >I suspect that there are a couple select lines which go high or low to tell >which drive is expected to respond, but I really don't know. I could guess how >I would do it, but of coourse it would all be conjecture. I have heard that the >drive port itself can handle 128 drives with up to 4 Gig per drive, but the >current GS software and other hardware have a problem with this. I would guess >that ideally someone could design a hard drive that plugs right into the disk >port on a chain. The 128 drive smartport is a packet-based protocol that is pretty bizarre and is explained in reasonable detail in the //gs firmware and hardware reference manuals (what you need would be in the firmware manual). Accessing "dumb" drives (no CPU, i.e. Disk ][ and Apple 3.5) is accomplished by playing with the IWM registers or softswitches. Some juicy info on the IWM registers may be found in the Mac Family Hardware Reference. However, the UniDisk and the Smartport Hard drive (forget the letters, but yes there actually was one, it was 20 megs I believe) communicate by using the packet protocol which is very much like a slow, serial SCSI in operation but entirely different in implementation. I think Apple would have gone with SmartPort and tried to speed it up if SCSI hadn't been served to them by the standards committee. Todd Whitesel toddpw @ tybalt.caltech.edu