On Sun, Jan 05, 2014 at 12:28:52PM -0800, Chuck Guzis wrote:
[...]
Shugart could have handled the motor issue by using
two pins on the interface
(one to turn the spindle motor on; the other to turn it off), conditioned on
drive select--a trivial modification.
The Amiga had a rather neat approach to this: each drive contained a latch
which sampled the motor line when its drive select line became active, thus
allowing each drive's motor to be controlled independently. It also retained
the four drive select lines.