PC floppy cable twists...

Chuck Guzis cclist at sydex.com
Thu Oct 20 16:53:41 CDT 2005

On 10/20/2005 at 4:14 PM Michael B. Brutman wrote:

>With all of those pins on the interface, why wouldn't the motors be 
>independently controlled?  That seems like a waste on any system, never 
>mind the wear and tear on the drives & inserted floppies.

But there really aren't any unused pins.  Remember that all of the
odd-numbered pins are grounded, so that leaves only 16 for signals.  Pin 2
was originally reserved for "reduced write current" signalling (or "density
select').  Pin 4 was  for "Head load" and was a spare only on some drives
that didn't have that feature and pin 34 was used for disk change/ready.
There really aren't any spares.

Besides, with a "head load" facility, who needed to control the motors
individually?  But the PC didn't use a drive with a head load facility...


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