Path: utzoo!utgpu!news-server.csri.toronto.edu!mailrus!cs.utexas.edu!usc!jarthur!mwilkins
From: mwilkins@jarthur.Claremont.EDU (Mark Wilkins)
Newsgroups: comp.sys.mac.misc
Subject: Re: Formatting 800k as HD ?!?
Message-ID: <7309@jarthur.Claremont.EDU>
Date: 29 May 90 03:04:38 GMT
References: <35018215MES@MSU> <21943@dartvax.Dartmouth.EDU> <10957@pucc.Princeton.EDU> <9546.2652d2ce@amherst.bitnet> <34@hite386.UUCP> <30281@cup.portal.com>
Organization: Harvey Mudd College, Claremont, CA 91711
Lines: 48

In article <30281@cup.portal.com> Lou@cup.portal.com (William Joseph Marriott) writes:
>1. Single-sided diskettes should be formatted at single-sided. Double-sided
>diskettes should be formatted as double-sided. High-Density disks should be
>formatted at high density. Mac disks should be formatted on a Mac. PC disks
>should be formatted on a PC, or on an FDHD Mac running Apple File Exchange.

[stuff deleted]

> 
>3. You can use tape and certain kinds of hardware to format a high-density
>disk as 800K or 400K. Even if this operation seems to work, the disk will
>behave unreliably, and will ruined for high-density use. To put things in
>English terms, imagine diskettes are like multi-lane highways, and that
>your data is represented by different colored cars. An 800K disk has wide
>lanes and large cars, so fewer cars can fit on the highway at any time. An
>HD disk has very narrow lanes and tiny cars. Now,if you try to format an
>HD disk as 800K, you wind up putting wide cars on narrow lanes. The effect is
>that it is not always clear which lane a given car is in. Imagine the traffic
>problems that would ensue if no matter what you did, you would always have
>part of you car in someone else's lane. Imagine how flaky your disk will
>behave if you format it for a different density.



  Alright, two questions.

 1) If formatting a DS/DD disk is so dangerous at high density, why don't
ANY of the drives in the PC clone world check for the presence or absence of
the hole used to indicate them?

 2) Given (1), why is it that there have been no similar discussions of disk
failure in the PC clone world, even among people who routinely buy DS/DD
disks and format them at 1.4MB just because they've never been told any
differently?

  Note that the Apple 1.4 MB low-level encoding scheme is identical to that
of an IBM PC floppy, but the hardware is much different.  If there is an
answer to (2), it probably has to do with that.

  I agree with your statement 2 that mutilating a disk is a recipe for
disaster.  However, nobody who advocates Apple's party line has ever
given me an answer to these two objections.

  By the way, if you have any references to publicly available articles in
engineering journals or the like which support Apple's official statements
on the matter, I'm curious.

-- Mark Wilkins