Pinout for SED9421

[Tony Duell]

> >In particular, we gave up on Micropolis because of their stubborn
> >insistence on using a leadscrew positioner, long after almost everyone else
> >went to the faster taut-band.  I still have a 96 tpi Micropolis drive that

Is the difference in inertia between the band and the leadscrew really 
that significant?  I always thought the taught band was indroduced for 
cheapness...

And many of the better 3.5" drives went back to a leadscrew mechancism. I 
particularly like the Sony ones where you can remove the head carriage 
and the stepper/mount assembly and put them back without upsetting the 
alignment.

> >employs buffered seek (goes not ready while seeking).  It also mounts the
> >drive electronics board and the positioner on the movable part of the disk
> >clamping assembly.  Only the drive motor and tach circuit is mounted on the
> >stationary drive frame.
> 
> The disk that Shugart used while innovative was really bad for repeatability 
> of position and slooowwww. 

It was, of course, also used on the Apple Disk // (which was based on a 
Shugart mechanism). I found it to be a disgusting design to be honest, 
really unreliable.

-tony