An historical nit about FDDs

William Donzelli wdonzelli at
Thu Jul 12 10:48:39 CDT 2018

> 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.

Someone asked (you?) on one of my Youtube videos for more detail about
the 23FD's stepping method, so I made a video covering the finer


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