On the Emulation of TU58s

[Chuck Guzis]

On 06/16/2015 01:54 PM, Brent Hilpert wrote:

> Once ran across a Honeywell drive (7-track) that had a 'vacuum
> capstan'. The capstan wheel had a vacuum path through the axle and
> then transferred the vacuum out to holes around the perimeter. So
> rather than a pinch roller or rubber frictional surface on the
> capstan to grip the tape, it was a vacuum holding the tape to the
> smooth metal surface of the rotating capstan.  Or was this common on
> higher-end vac-column drives?

Two counter-rotating capstans on the CDC 60x, 65x, 66x drives at least. 
  The vacuum/pressure was switched by means of a voice-coil valve.  IBM 
seemed wedded to the pinch-roller model.

I can recall having a discussion about who had the "sloppy write/careful 
read" versus the "careful write/sloppy read" technology, but don't 
recall who claimed which.  I do remember hours spent with various tapes, 
developer (e.g. Magna-see) and a loupe looking at patterns on problem tapes.

--Chuck