28 Feb
2015
28 Feb
'15
4 p.m.
----- Original Message -----
From: "Eric Smith" <spacewar at gmail.com>
To: "General Discussion: On-Topic and Off-Topic
Posts" <cctalk at classiccmp.org>
Sent: Saturday, February 28, 2015 5:56 PM
Subject: Re: 3.5" floppy failure mode? Hub not
attched to media.
On Sat, Feb 28, 2015 at 11:14 AM, Mike Stein
<mhs.stein at gmail.com> wrote:
...
I knew they had two steppers but didn't know that
they could actually step every sector if
necessary.
I'm convinced; pretty impressive, especially if it
was implemented on a 3.5" drive.
How much did these drives cost?
Thanks!
m
Are you saying that it actually stepped in and
out
during a rotation to follow the eccentricity?
Yes, it did fully closed-loop servo positioning,
with embedded servo
bursts in all inter-sector gaps. That's why they
have not one, but TWO
stepper motors for positioning, with a
mechanical adder mechanism.
The coarse positioning stepper doesn't have the
resolution needed for
track following.
This can also be seen in their US patent
4,630,145: