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Gigatron! The TTL computer as a kit

A project log for Gigatron TTL microcomputer

"Just because", a microcomputer that runs without a microprocessor

Marcel van KervinckMarcel van Kervinck 12/06/2017 at 21:032 Comments

Some months ago my good friend Walter has silently joined the project. The reason is that I receive a lot of enthusiasm whenever I show this to friends, to the point where one is already seriously trying to write a chess program for it. So we decided to take this one step further and upgrade this to a build-it-yourself soldering kit. Today we received the first samples for the enclosure, custom designed for this computer.

With a new phase comes a new name. Neither of us really liked the "Chipper" working title I used before, so the kit version will be known as the "Gigatron TTL microcomputer".  I couldn't possibly do this all by myself, so I'm super happy that Walter has stepped in. 

This retro-computer is something to build, play with but also look at, so we plan to offer it as complete as possible, except for the soldering you will have to do yourself. So it will include all the 74xx-TTL chips, RAM, ROM, sockets, capacitors, diodes, resistors, LEDs, supervisory circuit, jacks, a game controller, a nice mahogany coloured wooden enclosure with plexiglass viewing window, one or two built-in video games and a mini-USB cable for power. Not all details are finalised yet: the photo is a prototype and we will still change some things we don't like. We think we can target the 150-180 euro price range (hopefully below 200 dollars), provided there is sufficient interest. For reference, getting to the first PCB version set me back north of 500 euros, that is where I stopped counting, and that excludes the oscilloscope you need when designing something like this from scratch. And did I mention the 800 hours of research, trial and error? This is still just a private hobby project, so this kit will be something we will literally do from our living rooms. We figure that if we do a few dozen units that would push the prices down a lot and at the same time not take too much risk.

Of course a kit isn't the same as a one-off project, and Walter has worked tirelessly on morphing the project towards something that can be reliably soldered together in 3 to 4 hours. All components are now through-hole components and sourced from proper sources (not scavenged from e-bay). Walter has written a supercool manual that includes intermediate tests, a circuit diagram and even soldering instructions and tips for novices. Although there are 144 components on the board (many capacitors and diodes), I feel it will still be a beginner's level kit because of the spacing and all through-hole components. All you need is a soldering iron, solder, a multimeter, some pliers and a rainy Sunday afternoon. If you can make Oscar's PiDP-8, then you can make this also.

For those interested in this kit, you can subscribe to our mailing list. We will use this mailinglist only to announce when we are comfortable to accept orders, know the exact pricing and have some kits ready to ship. Subscribing to the mailing list doesn't imply any obligation to buy: it is just a way to keep informed of when we are ready and you can easily delist as well. We expect we will be ready near the end of January. It will then also be clear what the final kit looks like, what the built-in software can do, etc.

For those interested in this kit, check out our website: gigatron.io

Discussions

Justin Davis wrote 01/24/2018 at 20:36 point

I have a suggestion for the kit if it's not too late:  considering your problems with the EEPROM socket wearing out, you could use an edge connector instead and have plug-in cartridges with an EEPROM on it.  I'm thinking Atari 2600-style.

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Marcel van Kervinck wrote 04/08/2018 at 23:52 point

The connection problems were on the breadboard prototype and there I fixed it with wire-wrap sockets. See https://hackaday.io/project/20781-gigatron-ttl-microcomputer/log/62437-wire-wrap-sockets-meet-solderless-breadboard 

The kit uses double leaf spring sockets for the ceramic 27C1024 EPROM chip. We switched to those for the larger capacity and improved retro experience.

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