20 Oct
2005
20 Oct
'05
11:23 p.m.
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:
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
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