PC floppy cable twists...

[Allison]

>
>Subject: Re: PC floppy cable twists...
>   From: "Chuck Guzis" <cclist at sydex.com>
>   Date: Thu, 20 Oct 2005 14:53:41 -0700
>     To: cctalk at classiccmp.org
>
>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...
>
>Cheers,
>Chuck

Once upon a time drive need time to spin up before you loaded the head 
and read it. As drives improved that time shortend and the motors went 
to brushless where relibility didn't degrade with stops and starts 
(brush motors this is a relability/wear issue). So having seperate motor
enables allowed one to spin the drives and then allow a 10sec (or longer)
timeout after last access before they would stop.

Allison