Floppy Drive operation (was Re: Heatkit 5 1/4 floppies)

From: Chuck McManis <cmcmanis_at_mcmanis.com>
Date: Thu Apr 8 15:57:19 1999

At 11:50 AM 4/8/99 -0600, Someone wrote:
>8" drives typically spun all the time, as their motors were AC types. If
>your 5-1/4" drive spins all the time, something's wrong.

As in any good discussion this information is insufficient and perhaps a
bit misleading.

It is true, the most 8" drives ran the motor all the time *AND* they
"loaded" the heads when they read or wrote. The only time the drive
suffered wear was when the heads were loaded. On some old IBM 8" drives
from a 370 I believe there was a counter that counted seconds of "head
loaded" time. When it got to about 28 hrs (over 99,999 seconds) the drive
was supposed to be returned to have the heads refurbished.

Early 5.25" drives were similar, but "cheap" 5.25" drives figured they
could get away with leaving the heads on the drives and then just spinning
the motor when they were reading or writing. This gives a cheaper mechanism
at the cost of slower access times. The "high end" TEAC drives continued to
keep the motor running and only load the heads on reads and writes.

The defining characteristic of "floppy" disks is head/media contact.
Designed to operate in this way made them a good compromise between the low
cost of tape and the random access of disks. I believe I even have an early
IBM POPs manual that refers to them as DiscTape rather than a "Floppy Disc"

--Chuck
Received on Thu Apr 08 1999 - 15:57:19 BST