On Sun, 29 Jun 2003 14:47:39 -0400, Roger Turk wrote:
> IIRC, the necessity of low level formating was because of the positioning
> motor on the HD's reading arm. With MFM and RLL drives, after a while the
> arm would not align with the cylinders and a low level format had to be done
> to realign the cylinders with the read head.
I was led to believe it was due to the track and sector markers "fading"
in time, as these are not ever re-written during the normal life of the
disk.
> With the advent of stepper(?) motors, the alignment problems went away and
> low level formating wasn't necessary, and as Bastaain demonstrated, even
> dangerous.
No I think the alignment problems were worse with the stepper motors, as
they could only move in discrete steps from one track to the next. Any
wear in the drive between the motor and the head arm would tend to cause
mis-alignment of the head.
Later drives all use "voice coil" positioning of the heads which is a
continuous positioning system and AFAIK it uses a dynamic feedback system
to keep the head aligned with the position that gives optimum readability
of the track.
from Greg Mayman, in Adelaide, South Australia
Home of the Bay to Birwood Vintage and Classic motor runs
http://www.baytobirdwood.com.au
Visit me at http://homepages.picknowl.com.au/greg_mayman/default.htm
-- Arachne V1.71;UE01, NON-COMMERCIAL copy, http://arachne.cz/
