Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!cs.utexas.edu!tut.cis.ohio-state.edu!purdue!haven!umd5!hans
From: hans@umd5.umd.edu (Hans Breitenlohner)
Newsgroups: comp.sys.atari.8bit
Subject: Re: Densities and their Interactions
Keywords: 1050 US Doubler Enhanced Density Double Density
Message-ID: <5079@umd5.umd.edu>
Date: 7 Jul 89 23:53:41 GMT
References: <8057@bsu-cs.bsu.edu>
Reply-To: hans@umd5.umd.edu (Hans Breitenlohner)
Organization: University of Maryland, College Park
Lines: 18


The following information is based on disassembly of the Indus GT ROMs.
It is, of course, in no way related to the intenals of the US doubler,
but may help to shed some light on the situation.

The Indus accepts two format commands.  The '"' command (x'22') always 
formats in "enhanced" density.  The '!' command (x'21') formats based on
the current density.  If the current density is single, it formats in
single density.  If the current density is double, it formats in double
density, and if the current density is "enhanced", it formats in
SINGLE density.  
The current density is determined at power-up by checking the disk in the
drive (configuration switch if no disk is inserted), and changed by
configuration commands, format commands, or by sensing the format of
the disk when the first read/write operation after a disk change is
performed.

hans