On 07/11/2018 11:12 AM, Tom Gardner via cctalk wrote: > Anyone know where the Step/Direction version of the FDD interface > originated. > > So far as near as I can tell the earliest FDDs (IBM 23FD Minnow and Memorex > 650/651) used Step In/Step Out. The IBM 33FD Igar used direct control of the > motor. > > The earliest Step/Direction FDD I can find is the Shugart 800 which first > shipped in September 1973.
Shugart is probably it, unless there's a hard drive interface that precedes it. Mostly a minimal bit of logical difference between the Step in/Step out and Step/Direction. One can be converted to the other rather easily. --Chuck
