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Path: utzoo!utcs!mnetor!seismo!hao!hull
From: hull@hao.UUCP
Newsgroups: net.micro.amiga
Subject: Re: single sided disks
Message-ID: <154@hao.UUCP>
Date: Sat, 19-Jul-86 14:37:57 EDT
Article-I.D.: hao.154
Posted: Sat Jul 19 14:37:57 1986
Date-Received: Sat, 19-Jul-86 22:26:09 EDT
References: <252@pttesac.UUCP>
Organization: High Altitude Obs./NCAR Boulder, CO
Lines: 38
Keywords: disks single sided
Summary: disk polishing


The situation you cite is only one of many possible scenarios.  There are
several contributors to the cost of disk manufacturing, and the media may
be less expensive than test equipment and test time.  Some manufacturers
try to save money on the quantity of plastic used to make the case.  This
can result in admission of a greater quantity of dust through a poor fit
half-to-half.  Keeping in mind that there is a large unsealed gap at the
drive spindle in almost all disks, gaps around the edges may be critical
only in certain environments where the edges are more exposed to dust and
moisture than the sides.

So as it is, some manufacturers use the same process for both sides and
only format one side for test.  You have a high probability of getting a
good double sided disk at single sided disk prices.

Others process both sides to the point they are assured that the unused
side will not damage a two-head drive, polish the good side, then test.
The amount of polish on the unused side then can vary from so little that
loose oxide will foul your head to the point you will need to clean it,
to a situation in which the disk will appear to read and write ok when
new, but then begins to "forget" data not re-written frequently (as loose
bits of oxide containing information are rubbed away).  You can inspect
new disks visually by opening the trap door and examining the image of
a bright object with sharp edges (a light bulb at a distance of 10 feet
will do) reflected off the surface.  Compare the two sides.  Remember to
look at the surface as though it was the mirror of a cosmetic compact
(gawd, am I so old that I have to explain what that is?), concentrating
on the appearance of the far object rather than the surface itself.
Minor distortion of the image is not a problem; however, a cloudy, fuzzy,
or indistinct image is an indication of an incomplete polish.  To get an
idea of what's tolerable, inspect a known reliable disk you've used for
a while (a Workbench disk, for instance).  Don't breathe on the disk; be
careful not to get eyelashes, nose hairs, bougars, or spit balls in the
open trap door ;-)
								Howard Hull
[If yet unproven concepts are outlawed in the range of discussion...
                   ...Then only the deranged will discuss yet unproven concepts]
	{ucbvax!hplabs | decvax!noao | mcvax!seismo | ihnp4!seismo} !hao!hull