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

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