I don't believe those were the earliest of the 5-1/4" types. The early
SA-400's I remember used a lead screw just like the 8" drives, but that was
too costly for the competition that followed. When Apple started buying
"partial" drive mechanisms in order to implement their more software-driven
approach, with the idea of saving a few bucks . . . multiplied by a milion
or two drives . . . other manufacturers including SIEMENS and BASF, among
others, tried a two-phase stepper on a helically-tracked drive wheel as
opposed to the stepper driving a lead screw. Most makers later went to a
band-actuator system using a small stepper.
Since the business of designing floppy and hard disk controllers was my long
suit back then, I had several of nearly every type of FDD and HDD lying
around the shop, and there were LOTS. By the time IBM got into the game,
the positioning mechanism contest was pretty well settled. Apple drives
used a form of GCR on their drives, the heads of which were positioned with
a software timed DC motor, while nearly everyone else used FM or MFM on
drives which used steppers driving band actuators. Once the volume was up,
the cost wasn't that much greater, while the precision and accuracy were
quite a bit greater. I don't even remember what the nature of the physical
linkage between the motor an the head positoner was, since I stayed away
from them. I still have an Apple drive somewhere. I suppose I could look .
. .
Of course, Apple's orientation toward YOUR data was that nobody really cared
if you had to punt and hit the reset button just because the FDD wouldn't
read the floppy it wrote just a few minutes before . . . After all, if you
were serious, you didn't use an Apple. If you were serious it's for sure
you had some 8" drives for the data you wanted to keep.
Dick
-----Original Message-----
From: James Willing <jimw_at_agora.rdrop.com>
To: Discussion re-collecting of classic computers
<classiccmp_at_u.washington.edu>
Date: Wednesday, April 07, 1999 1:57 PM
Subject: Re: Heatkit 5 1/4 floppies
>On Wed, 7 Apr 1999, Jeffrey l Kaneko wrote:
>
>> These were in common use on Z89's and Z-90's. Heathkit used drives made
>> by
>> Tandon and Siemens. The Siemens drives were kinda unique: It used a
>> disk with a spiral groove for the head positioner.
>
>Hmmm... hardly that unique it would seem... The Shugart SA-400 series
>drives used that same positioning systems (first?).
>
>-jim
>---
>jimw_at_agora.rdrop.com
>The Computer Garage - http://www.rdrop.com/~jimw
>Computer Garage Fax - (503) 646-0174
>
Received on Wed Apr 07 1999 - 17:44:24 BST