Path: utzoo!utgpu!news-server.csri.toronto.edu!mailrus!cs.utexas.edu!uunet!motcid!derosa
From: derosa@motcid.UUCP (John DeRosa)
Newsgroups: comp.sys.mac.misc
Subject: Re: Formatting 800k as HD ?!?
Message-ID: <3290@crystal9.UUCP>
Date: 30 May 90 16:44:17 GMT
Organization: Motorola Inc., Cellular Infrastructure Div., Arlington Heights, IL
Lines: 47

One small piece of information.  I have seen in various
Macintosh Catalogs a device that very cleanly punches the HD
square hole in a DSDD disk.  Budgetbytes I believe.

Also, someone made a comparison about traffic lanes and wide
cars.  I think that the analogy is wrong.  The media (i.e. iron-oxide
particles on a plastic plater) in the disk is homogeneous
(i.e. the iron-oxide particles are not layed down in "lanes" but
are completely uniform across the plater).  Actually, iron-
oxide is too simple of a term, most magnetic media is
formed with a "soup" of ingredients including other ferris-
oxides and rare earths (thus the different settings on your
tape player for tape bias).  For the purposes of this 
discussion, we will use iron-oxide.  (historical note: the
first tape recorders used a steel wire and were called
"wire recorders.  How's that for basic magnetics?).

The formatting process is what causes the "lanes" to be 
created on the disk.  This is not a physical process (i.e.
grooves are not dug into the iron-oxide) but an electrical 
process whereby the random magnetic ordering of the 
iron-oxide is changed into constant magnetic "lanes".
Therefore formatting a DSDD disk as HD just creates 
different magnetic "lanes", smaller and closer together
in the case of HD formatting.

There in lies the problem.  DSDD disks use a different 
"grade" of iron-oxide that HD disks.  HD disks (because
the magnetic lanes are closer together) uses a finer
and better quality of iron-oxide in the manufacturing 
process.  Also the HD drives use a lower magnetic 
field in the read/write head to prevent problems
between adjacent "lanes".

BUT....who is to say that the manufacturers are not
just producing one type of (higher grade) disk and 
putting SSDD, DSDD or HD on the outside casing?  This
would save them money in the long run.  Therefore 
you could format DSDD as HD and live happily ever
after.  Isn't circular logic wonderful?
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
=    John DeRosa, Motorola, Inc, Cellular Infrastructure Division           =
=                   e-mail: ...uunet!motcid!derosaj                         =
=                Applelink: N1111                                           =
= I do not hold by employer responsible for any information in this message =
=      nor am I responsible for anything my employer may do or say.         =
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=