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From: hans@umd5 (Hans Breitenlohner)
Newsgroups: comp.sys.atari.8bit
Subject: Re: questions
Message-ID: <1385@umd5>
Date: Fri, 5-Dec-86 18:47:15 EST
Article-I.D.: umd5.1385
Posted: Fri Dec  5 18:47:15 1986
Date-Received: Fri, 5-Dec-86 22:49:37 EST
References: <7117@topaz.RUTGERS.EDU> <468@inuxm.UUCP> <434@rayssd.RAY.COM>
Reply-To: hans@umd5.umd.edu (Hans Breitenlohner)
Distribution: net
Organization: University of Maryland, College Park
Lines: 21

In article <434@rayssd.RAY.COM> cc@rayssd.RAY.COM (Charles R Coday) writes:
>
>	I have used Dos 2.0 (unmodified) with double density drives thru
>an ATR8000 in the double density mode.  Most of the double density drives
>and their mods will automatically switch to the correct density upon
>boot-up.  Atari Dos 2.0 gets notified of the appropriate density and then
>has no problem.  Mydos, though, will additionally handle the situation
>where you want to switch disks of different density where Atari Dos 2.0
>fails.  Bill Wilkinson of OSS (and an author of Atari Dos 2.0) published a
>book called Inside Atari Dos containing the Dos SOURCE code and
>explanations of how it can handle double density drives.  So, just put a
>double density disk in and boot-up!

I don't think you are quite right about this.  There is no code in Dos 2.0
to treat the first three sectors of the disk specially (i.e. 128 instead of
256 bytes), so any function which writes these (format, write Dos files, etc.)
will fail.  Perhaps the ATR 8000 compensates for this, and allows you to write
these sectors either way, but I am sure a regular disk drive will not do this.

It does seem like a crying shame, since someone certainly went to a lot of 
trouble to put 95% or more of the code for double density support into Dos 2.0.