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From: harmon@abvax.icd.ab.com (Larry Harmon)
Newsgroups: comp.sys.m6809
Subject: Re: What is Coco II / III
Message-ID: <29@abvax.icd.ab.com>
Date: Tue, 11-Aug-87 12:28:23 EDT
Article-I.D.: abvax.29
Posted: Tue Aug 11 12:28:23 1987
Date-Received: Fri, 14-Aug-87 04:44:09 EDT
References: <1646@korppi.tut.fi>
Organization: Allen-Bradley Company, Inc; Industrial Computer Division, Highland Heights, OH
Lines: 26
Summary: Dragon 64 is an enhansed CoCo II


	The Tano Dragon is basically an enhansed CoCo II.  The enhansements
include the addition of a hardware uart (6551) located at $FF10 and a parallel
printer interface using the keyboard PIA (6821).  The two units are so close
that the CoCo II firmware will run in the Dragon with 2 minor modifications.
The modifications are required because the powerup routine sloppily addresses
the PIA at $FF00 by one of it's mirror addresses ($ff1c) which conflicts
with the Dragon's 6551 uart.  All of the CoCo II expansion interfaces will work
with the Dragon.

	I have successfully used a J & R electronics 256k ram disk with the
Dragon.  This interface replaces plugs into the 6883 SAM chip socket and thus
doesn't take up an expansion slot.  I believe a 512k ram disk is also available.

Note:  because the Dragon has the additional uart the 6809 bus is loaded more
and use of Y cables should be avoided.  The Tandy Multi-pac interface may be
used however, the Dragon needs to be raised up about an inch to mate with
the MPI.  A couple magazines work nicely.

	I have used the Dragon with Tandy OS9 level I and found it to be a good
system (until I got a CoCo III).  The additional Serial and Printer ports may
be used with drivers found on the Compuserve OS9 group to provide a complete
computer system with only the addition of a disk interfacs.  The uart is even
connected to the 6809 interrupt line unlike the Tandy RS232 pac.

						Larry Harmon