Help needed identifying old MFM drives from the excavation

Martin Peters martin at
Mon Dec 14 04:55:06 CST 2020

Fred Cisin via cctalk:
> The Seagates were commodity drives, used in almost everything.
> Number is approximately the unformatted capacity.
> ST506 was 5MB formatted (305 Cyl x 2 heads) ;

The ST-506 had 2 platters, 4 heads. Mechanically the ST-506 and the
ST-412 are mostly the same. The track-to-track-distance and the position
of the inner and outer track differ.

> ST412 added buffered seek, was 10MB formatted (306 cyl x 4 heads).

Yes, but there are later versions auf the ST-506 with microcontroller on
it. Don't know if they already allowed buffered seek, but I think so.


Martin Peters
martin at

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