Path: utzoo!utgpu!news-server.csri.toronto.edu!bonnie.concordia.ca!ccu.umanitoba.ca!herald.usask.ca!regina!hercules!cazabon
From: cazabon@hercules (Charles Cazabon (186-003-526))
Newsgroups: comp.sys.amiga.emulations
Subject: Re: Question about Cross-Dos
Message-ID: <507@regina.uregina.ca>
Date: 12 Jun 91 05:28:28 GMT
References: <1991Jun11.215637.563@wpi.WPI.EDU> <1991Jun12.001931.3711@ucselx.sdsu.edu>
Sender: news@regina.uregina.ca
Reply-To: cazabon@hercules.uregina.ca (Charles Cazabon (186-003-526))
Organization: University of Regina, Regina, Saskatchewan
Lines: 44

In article <1991Jun12.001931.3711@ucselx.sdsu.edu> civir1070@ucsvax.sdsu.edu writes:
:In article <1991Jun11.215637.563@wpi.WPI.EDU>, amartin@wpi.WPI.EDU (Allen R Martin) writes...
:> 
:>	Will Cross-Dos work with an AE high density drive to read IBM
:>high density disks?  I don't see any reason why it shouldn't but I was 
:>just wondering if anyone has had any experience with this.
:> 
:>			Allen Martin
:>			amartin@wpi.wpi.edu
:
:No.  Consultron (CrossDos) syss that it will not work.  The AE drive will
:read standart, 720k disks, just like an Amiga drive, but it won't read
:the 1.44 meg IBM.  Consultron said it was because of the way they get 1.52
:megs on a floppy was "signifigantly" different from the way big blue does
:it. Hmmm.  I really wish I could use 1.44 megs disks.
:
Applied Engineering boobed when they desgined their high density drive.
The way an IBM gets 1.44 megs onto a 3.5 inch disk is to slow it down to
half the speed of a 720 K disk (rotational speed, not transfer speed).
That way, they get 18 sectors per track instead of 9, and voila, twice the
storage.

The Amiga puts 11 sectors per track on a 720K disk instead of 9, but it can
read 9 sector per track formats.

To read 1.44 disks, you would need to slow our drives to half their speed,
and then squeeze 22 Amiga sectors on each track, to enable you to read
IBM 18 sector per track format.

Applied Engineering got unreliable reads at that speed, so they didn't slow
it quite that much, and only got 19 secotors per track.  Hence, 1.52 megs
per disks.  However, also, it will not read the 1.44 disks because of the
difference in speed.    

Commodore's high density drive (standard equipment on the 3000UX) manages
to get the reliable reads at that speed, and so can read 1.44 IBM disks,
and also, as a bonus, you get the AmigaDos 1.76 megs/disk format.

AE knew that CBM had to provide 1.44 disk compatibility to comply with
UNIX SVR4 standards; they should have provided for it.


--Chuck Cazabon, cazabon@hercules.cc.uregina.ca
* My Opinions Are Not My Own...Feel Free To Plagiarize