Gigatron – A TTL Microcomputer

I became aware of the Gigatron project through a thread in the VzEkC-Forum. The Gigatron is a computer based purely on TTL components that works entirely without a CPU. The blocks of a CPU are simulated using TTL chips. Very interesting!

The Gerber files for the project are freely available, further, very detailed information is available on the project website. The appropriate software is available on Github.

Thankfully, there was a bulk order for the circuit boards in the forum. I used Mouser to procure components, as a shopping cart that matches the project is stored there.

What particularly impressed me is the detailed and lovingly made manual, which describes the structure of the system in a way that is easy to understand, even for beginners. Even short introductions to electronics, soldering and explanations of the required components are included. The entire structure, including the test procedures, is described in detail and illustrated - very nice!

Assembly Part 1

After I had laid out all the components of the BOM, I started.

First came the 0.1uF blocking capacitors. One can imagine that a computer based purely on TTL components would require quite a few of them - a total of 40 must be installed. It is advisable not to assemble all of them in one go - otherwise it will be much too tight to be able to solder properly. Spread it over three runs.

Next came the power supply. A USB power supply is used as input. A so-called supervisory circuit sits on the board - in addition to a fuse, a capacitor for smoothing, a power LED - which waits after the supply voltage has been applied (approx. 350 ms) until it has stabilized and then the system's program counter set to NULL.

Then it was the turn of the clock generation. This consists of a 6.25 MHz crystal, a 74HCT04, and a few capacitors and resistors.

The next step (part 2 of the report) continues with the 40 sockets for the ICs. By the way, I decided to socket all ICs, not just the RAM and EPROM - but I won't do that until tomorrow.

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