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Information - Duet

LanguagePublisher[no publisher]
DeveloperDistributorAtari World
Box / InstructionsEnglish, GermanSoftware

Alich, Andreas

LicensePD / Freeware / Shareware
SerialST TypeST, STe, TT, Falcon030 / 0.5MB
ResolutionLow / Medium / High / VGA / RGBNumber of Disks1 / Double-Sided
Dumpdownload atari Duet Download / STMIDIYes

Instructions - Duet

Duet 1.00 

German text file translated to English by
Leslie Hartmier (leslieh@warpcon.ersys.edmonton.ab.ca)

English translation edited by
Denesh Bhabuta (dbhabuta@cix.compulink.co.uk) and
Andreas Alich (Andreas_Alich@wue.maus.de)

*** Please read the file REGISTER.TXT ***

2 May 1995

This text file has been translated to English by someone other than
the author, and as such, may or may not contain errors (I'd like to
think that it is completely correct, but I've never actually studied
German, and have relied on RufTrade (a new and wonderful shareware
German to English translator program (yes, I've sent my money in!),
and my dictionary)). I have tested the instructions, and most of the
rest (I couldn't make any of the errors occur), and it seems to be
okay. This English text file is now part of the Duet package, with the
exclusive permission of the author. Pay the shareware fee for this if
you use it.  It is a wonderful program, and I'm not keen on
programmers for my machine of choice taking off for greener pastures.
This programmer has a very open mind it seems where the shareware fees
come in, so at least send him something! 
Anyway, it seems to be more or less right, so I hope it helps you
install this program, and possibly understand it a little better.


I make no warranty that the information in this text file will work,
or that it won't do anything nasty. Neither Leslieh Hartmier, Denesh
Bhabuta, or Andreas Alich will be held responsible for any damage that
may be caused to your system, bike, or sanity, by the use of this
software. The software has been tested as much as possible and has
been stable on our systems.

Leslie Hartmier (the name is German, the person is not!)


Duet (c) 1994 by Andreas Alich
(Yet Another Net for Ataris)

Andreas Alich
Rittergasse 4
D-97070 Wrzburg

Account Number: 5102900
Bank Code: BLZ 790 500 00
Bank: St„dtische Sparkasse Wrzburg

MausNet: Andreas Alich @ Wš
Internet: Andreas_alich@wue.Maus.De

Copyright (c) 1994 by Andreas Alich. All rights reserved.

Duet is Shareware, ie. it may not be copied, used or passed along for
commercial purposes, but may be distributed freely and only in
unchanged form. The free distribution over mail-boxes is allowed and
desired. This program can only be included in magazine coverdisks with 
the exclusive permission of the author. You may even approach Denesh 
Bhabuta, who will contact me. Duet may be included on CD-ROM 

If you use Duet regularly, you are asked to send me the amount of
money that you feel the program is worth.  There is no minimum or
maximum; that is up to you to decide.  If you have no money, perhaps
you could send me a few nice words on a beautiful postcard. More
details in the text file REGISTER.TXT. Please read the file.

If enough people use shareware regularly, do not pay for it,
(surprise!) and it becomes apparent that there is no market for
shareware in the Atari world, the platform will die. It is necessary
for everyone to show interest in good shareware programs by
registering. If you are one of the unpaid shareware users, keep in
mind that if you don't support the platform of shareware, the platform
will dry up and leave you with a severely crippled system. It's up to

Shareware offers the opportunity to test a program before you decide
to buy it. The shareware price pays for the most current version,
which may be the one that is already possessed and/or used. If you are
not content with the currently available version of the program, it is
not a bad idea to make the author aware of errors and suggestions, and
if still interested in the program, wait upon the answer of the
author. However, even if one is not completely satisfied with the
program, if you use the program regularly, the shareware fee still
applies. If the program doesn't please you, you don't need to use it.


You use Duet at your own risk.  I undertake no responsibility for any
damage, whether through legitimate or unintentional use of Duet. Duet
works for me with no trouble at all.  If this is valid for any other
computer configuration, I have no idea (having only a limited computer
zoo, I can only test certain configurations).  Anyone who wants to use
Duet should, at least for the time being, read through the entire text.

The Aim and Object of Duet

Duet allows the connection of two TOS-based computers
(ST/STE/TT/Falcon etc..) over the MIDI, LAN or serial interfaces, the
purpose of which is to allow each computer to use the other's drives
(floppy and hard disk). Apart from that, one printer can be used by
both computers.

How Duet Works

Duet is a terminate and stay resident program. This means that it is
loaded into the system, and remains dormant until called upon.
Externally, it is like Big Net.
Duet works at the BIOS level. On the one hand it needs regular BIOS-calls
to work ('normal' TOS versions DO call the BIOS regularly). On the
other hand, the drives of the other computer are available via the
BIOS plane as well. This offers some advantages, but also at least one
major disadvantage, that those of you might have guessed - if both
machines are writing to the same partition at the same time, (this is
not a problem if both system are left in the 'Read-Only' state) there
is a very good possibility that the partition will have its FAT
destroyed, effectively erasing all of the files! The 'Read/Write'
state should only really be used if there is absolutely no way that
both computers will be accessing the same partition simulataneously.


First, you have to decide what interface you want to make the
connection on. In the case of a 'normal' ST, MIDI is the fastest
interface (this offers 31,250 baud). If you have a computer with faster
interfaces such as a TT connecting with an ST (its serial interface in
the original state maximum 19,200 Baud), you might consider, with a
little work, a faster serial interface could be installed, and this
interface could be used.  To this purpose, I recommend Harun
Scheutzow's RSVE or Stephan Skrodzki's RS_Speed. With it (and the
suitable drivers) you can obtain with an 8 MHz ST with a TT over the
serial interface a (Bit-)transmission speed of 57,600 baud. You can
also use the LAN interface if both computers have them. Unfortunately,
the program for using the Falcon's LAN interface does not function
correctly; without doing tests on a Falcon, it seems unlikely to work.
Harun Scheutzow's ST_ESCC is not, at present, supported, due to the
fact that I do not have information on the heightened abilities of
the 85C230.

Once you have decided on the interface you'll be using, the interface
should normally be the same on both computers.  With the MIDI
interface, the MIDI OUT on one computer must be plugged into the MIDI
IN, and the opposite is also necessary to make the network ring. With
a serial connection, in each case TxD must be connected to RxD of the
other computer using a null modem. Handshaking is not necessary. You
can not connect the MIDI with LAN, but you can for example, connect a
TTs Modem 2 with another TTs Serial 2.

You must use the correct driver for the chosen interface. With a
'normal' ST one can, admittedly, using corresponding hardware (see
above) reach a transmission speed of 57,600 Baud. However, the
'normal' ST cannot actually receive the characters at that speed, even
if RSVE or RS_Speed can (at maximum capacity the computer would have
to be able to use data at 5,760 bytes per second). A 'normal' ST can
use data at a maximum of about 4,000 bytes per second. So, to use a
faster computer with a slower computer at the connection speed of
57,600 baud, the faster computer must insert a break between two
characters. To serve this purpose, the faster computer must use one of
the special drivers, the programs that contain a 'D' (as in "delay")
on the end of the name (e.g. DUET_S2D.PRG). These drivers activate the
normally unused Timer A of the MFP.

Program name | driver for
DUETLANF.PRG | LAN-interface of the Falcon (*)
DUETLANT.PRG | LAN-interface of the TT/Mega STE
DUET_M.PRG   | 'normal' serial interface (MODEM 1 of the TT/Mega STE)
DUET_M2.PRG  | MODEM 2 of the TT/Mega STE
DUET_M2D.PRG | MODEM 2 of the TT/Mega STE with break insertion
DUET_MF.PRG  | serial interface of the Falcon
DUET_MFD.PRG | serial interface of the Falcon with break insertion
DUET_S2.PRG  | SERIAL 2 of the TT/Mega STE
DUET_S2D.PRG | SERIAL 2 of the TT/Mega STE with break insertion

(*) this driver did not function when tested, but may do so in the
future hopefully.

Once you have selected the appropriate driver, you must insert it into
your AUTO folder. DUETCONF.PRG and DUETCONF.INF must also be added to
the AUTO folder.

DUETCONF.PRG must come after the driver in the AUTO folder, using an
AUTO folder order changer to change the physical sequence if necessary.


The configuration for the selected port is set as a result (at present
exclusively) of having DUETCONF.PRG in the AUTO folder.

The default DUETCONF.INF is fine, but you may if you wish, personalise
it, using a text editor. The DUETCONF.INF file is explained below.

Blank lines and lines that start with a '#' (without quotation marks)
are ignored.
Lines, that start with the keywords
        -TIMEOUT or
are read and determine the settings of Duet.

The value after CPS decides, using the drivers with break insertion (D
on the end of the name) what the maximum character per second transfer
rate is. This value should be set to a value less than one-tenth of
the baudrate (SPEED). The transmission of a byte requires ten bits.
Connecting a ST to a TT via the serial interface at 57,600 baud, a value
of 4000 (which is the maximum that the ST can handle, and
only if you don't move the mouse!) or less for the TT is sensible.

The value after CPS decides, using the drivers with break insertion (D
on the end of the name) what the maximum character per second transfer
rate is. This value should be set to one-tenth of the baudrate
(SPEED). The transmission of a byte requires ten bits. Connecting a ST
to a TT via the serial interface at 57,600 baud, the CPS is set to a
maximum of 4,000 cps (which is the maximum that the ST can handle, and
only if you don't move the mouse!).

DRIVE can be entered more than once. Each 'DRIVE' line installs a
new drive at one computer, allowing this computer to access a drive
of the other computer via this drive as its own. The first character
after 'DRIVE' declares the new drive. The second character states
which drive of the other computer is accessible via this drive.
The line 'DRIVE N C' mounts drive N, aliasing it as the other computer's
drive C (ie, makes drive C on the other computer available on this 
computer as drive N).

NETPRN must NOT be set on both computers. Only one DUETCONF.INF may
contain it! The computer which has NETPRN set sends data for the parallel
interface to the other computer. The other computer sends this data to its
parallel interface.

The value after SPEED decides (except for the driver for the MIDI
interface) baud rate. This must be set on both computers to be the
same baud rate.

Driver    | possible values for SPEED
 DUETLANF | 19200, 38400, 57600, 115200, 125000, 229500
 DUETLANT | 19200, 38400, 57600, 115200, 125000, 229500
 DUET_M   | 19200, 38400, 57600, 115200 (*)
 DUET_M2  | 19200, 38400, 62500, 76800, 125000, 153600
 DUET_M2D | 19200, 38400, 62500, 76800, 125000, 153600
 DUET_MF  | 19200, 38400, 62500, 76800, 125000, 153600
 DUET_MFD | 19200, 38400, 62500, 76800, 125000, 153600
 DUET_S2  | 19200, 38400, 57600, 115200, 125000, 229500
 DUET_S2D | 19200, 38400, 57600, 115200, 125000, 229500

(*) without hardware modification, this interface only supports a
maximum transmission rate of 19,200 baud.  The higher transmission
rates are only possible using the hardware modifications RSVE or

The value after STATE sets the read/write status of the netted drives.
Possible values are 0 for 'Read-Only' and 1 for 'Read/Write'.
Normally, 'Read-Only' (0) should be chosen. 'Read/Write' allows drive
modification access (saving, erasing, defragmenting, etc.) to the
drives of the other computer. Only one computer should be activated
for r/w if you know exactly what you're doing.  If both computers
simultaneously write to the same partition, this can erase everything
on the partition (through destruction of the FAT)!

The value following TIMEOUT decides the time in seconds that the
computer will wait before giving an error message, in the case that
the other computer does not answer.

XSPEED is something for specialists or those for whom SPEED is not
sufficient. Depending on the driver there are the following two (MFP)
or three (SCC) parameters.  The parameters being:

1st parameter: prescale/clock mode: 1: 1:4
                                    2: 1:10
                                    3: 1:16
                                    4: 1:50
                                    5: 1:64
                                    6: 1:100
                                    7: 1:200
2nd parameter: counter

1st parameter: flow phase: 0: RTxC
                           1: TRxC
                           2: BRG with RTxC as source
                           3: BRG with PCLK as source
2nd parameter: prescale/clock mode:   0: 1:1
                                      1: 1:16
                                      2: 1:32
                                      3: 1:64
3rd parameter: counter

Operating system requirements

It should be possible for any computer with any TOS version to access
another computer's drives using this program.

In order to divert printer output to the other computer, however, will
require a minimum of TOS 1.02.  (To be more accurate: the xcon vectors)

Using one of the serial interfaces or LAN interface you have to be
aware of the fact that transmission parameters (transmission rate and
protocol) can become disrupted through CPX modules and other programs,
as can the XBIOS.Rsconf() call, in the case that the active TOS
version does not support XBIOS.Bconmap(), which to my knowledge are
all TOS versions up to and including TOS 1.04.  TOS 2.06 and 3.06 do
not seem to cause any problems whatsoever. On older TOS versions,
either be sure that the MODEM.CPX is not active, or that it is at the
same parameter as Duet has (existing baud rate, 8N1) set the
communication setting to!

Duet cannot protect itself from any other programs that have a direct
interface to the existing hardware to access or change parameters. If
such a program changes a parameter, the communciation will no longer
work, nor will it be able to be restarted without rebooting the

If one of the drivers that performs break insertions has been
installed, no other program may use Timer A of the MFP. Delay drivers
do not really insert breaks. They are driven by Timer A-interrupt
instead of Transmit interrupt, i.e. they do not send the next
character as soon as the transmission register is empty but as soon as
the next Timer A-interrupt occurs (and the transmission register is


If the computer crashes when it is accessing the other computer's
drive, it may be that the maximum sectorsize of the other computer is
larger than the maximum sectorsize of the computer accessing it.  The
solution to this problem is that the hard drive drivers of both
computers must be configured correspondingly (that is, the same or
greater for the crashing computer!)

Moving the mouse a good deal can interfere with high transmission
rates. If there is any possibility that this is likely to happen, it
might be a good idea not to move the mouse of the slower computer at
all, or as little as possible.

Occasionally, the system may appear to freeze due to mouse movements.
This then, may cause the other computer to report that the other
computer isn't answering, and will no longer allow the connection to
continue. Most of the time, though, it will be possible to remove the
'blockage', by using the net in the opposite direction, e.g. by
accessing the frozen computer's drives via the file selector from the
other computer. It is necessary to make sure that an access really
happens since directories are possibly already buffered by caches!

Sometimes, due to a GEMDOS not noticing a media change after an
alteration of a drive, the directory does not get updated. If this is
the case, simply pressing the ESC key should rectify the situation.
Another option is the program DUETCHG.PRG. This forces the operating
system to ignore the rest of the drive's/drives' information, and
removes the media change from the network altogether.


The future of Duet depends, in large part on your interest and your
reactions. If I receive no reactions or input, that will show the lack
of interest, and there will be no more work put in to this.

If you have error messages, comments and/or suggestions, you may reach
me at the above address.  If you do not have an E-mail address, but
want an answer, please include return postage. Alternatively, you may
reach Denesh Bhabuta who provides UK support for this program. Details
are in the file REGISTER.TXT

Final Comments

At this point I would like to thank Christoph Zwerschke
(Christoph_Zwerschke@KA.maus.de) for his LED-Panel and the brilliant
Debugging-Byte in it, which has helped me with this development very
much. Christoph has also written a program VGA-Simulator, which allows
you to have VGA resolutions on a TT connected to a TT High Resolution
monitor. Please register for the VGA Simulator if you are using it, as
it is a program in a million!

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