The Atari 8-bit network interface
By Harry Reminder 

Hello guys, this is my first article for MyAtari magazine. Subject is a peripheral that is able to connect two or more Atari 8-bit computers for data exchange. This network interface is plugged via a SIO cable (standard cable for the Atari 8-bit computer's serial data bus) to the computer. A simple two-way cable provides the connection to the other interfaces, which are connected as a bus. I don't think there was a device like that produced by Atari itself and I haven't seen something like it anywhere else.

The Atari 8-bit network interface was Jiri Bernasek's idea. He is Czech and I know him only from articles he published in the ABBUC magazines. Last year he wrote about a network game programmed by himself. He used the hardware already working with an older game to connect the computers. He drew a circuit diagram of the network interface so anyone could build the hardware at home. But until the annual general meeting of the ABBUC club in 2000 there were no new built units available.

Fortunately someone borrowed Jiri's complete personal set of interfaces for the Unconventional 2000. We installed it on four computer systems so we could play his game at the ABBUC club meeting. Some people wanted to have such an interface but nobody was selling it. I looked at the little piece of hardware and thought it would not be difficult to build it even in a bigger quantity. Later I discussed it with my friends and then decided to construct the hardware (based on Jiri's schematics) and distribute it like the other hardware of the RAF. I requested and received the written permission of Jiri to do this.

Additionally I thought, if the hardware is available this will be a base for more software development. Now we plan to start a programming competition in the club and I hope people will create something. Perhaps it can become a standard for networking with 8-bit Ataris.

Although I am manufacturing and distributing the interface, I haven't written any software for it. I don't know the software routines for handling the data on the network, they should be requested from Jiri.

The game Jiri wrote is called Multi Dash and it is freeware. It could be described as a kind of multi-player Boulder Dash. Up to eight players can collect gems, stones and bombs. The bombs are good for blowing up walls or destroying other players. Collected items and certain actions score points. There are also computer-controlled opponents who can kill you or other players. The one surviving the longest time and gathering most points will win.

One of the computers acts as the server. It loads the program from disk and all the other computers boot via the network, so only one disk needed. There is also the option to send messages from one system to the others. The program is on the ABBUC Special Magazine Disk #27 and includes a circuit diagram of the hardware and a description of how to use it. At the Atariada 2000 in Prostejov (Czech Republic) it was presented the first time. Later at the Unconventional 2000 in Lengenfeld (Germany) with Jiri himself, at the ABBUC annual general meeting 2000 in Herten (Germany) where it won the 1st prize at the BOS (Best of Show) event and finally at the Atari 8-bit fair in Schreiersgrün (Germany) together with the new hardware of 2001 by the RAF.

The program Maze of Agdagon is on ABBUC Magazine Disk #50. This game is a 3D labyrinth game for up to eight players. Like Multi Dash you have to collect items and destroy other players with bombs. The most important thing is to survive. The program is written by the guys of the Agdagon Group, USA. It is shareware and was published in 1993. It was presented with the earlier network interface hardware at the Atariada 1999 in Prostejov (Czech Republic) and later in 2001 at the Atari 8-bit fair with the new hardware.

The interface circuit is quite simple. The two separate signals from the SIO bus are joined together by transistor stages to a single data line. So it is possible to use a simple cable to get the computers connected. A shielded cable is recommended, a coaxial type will be the best. It works with a cable length of up to 20 meters. The protocol of the data transfer has to take in account that there can only be one transmitter at a time on the line.

In February this year I started to design the layout of the PCB (printed circuit board) for the network interface. For this I used professional CAD software to get the wires, connectors and components onto a small board. Its dimensions are about 50 x 50 mm (2 x 2 inches). For the network media I chose cinch cables (cable with RCA connectors) as they are commonly used in the audio world, and that's one of my favourite hobbies.

The SIO connectors have become rare and expensive. Therefore I used single metallic pins soldered on the board to make the connection to a SIO-cable (every user should own one). But also it is possible to assemble a SIO connector (male) on the board instead of the pins. This is better but has its price.

I produce the interfaces by myself. Cutting, drilling and assembling of the boards is completely manual. Altogether it takes several hours to build one interface. I haven't found a suitable case for them, so they only get a protection plate on the solder side. All those extras increase the price. So I offer as standard a simple version. If someone wants a SIO connector, a case or other extras I can build it to order.

Maybe I will offer a complete kit for hobbyists later, with a lower price. Certainly every interface will be tested. All the ones I manufactured worked first-time.

In March I showed the first interfaces to my friends at the RAF. We decided to present them at the Atari 8-bit spring fair in Schreiersgrün (Germany) at the end of the month. By this time I had built eight interfaces and I could sell them all there. This was a successful debut of the new hardware.

The price for one network interface is 10 Euro (standard version). The cinch cable is extra and costs 1 Euro (5 meters) or 2 Euro (10 meters). The package and shipping is extra and depends on type of payment, size and location. Order can be done via e-mail or internet.