An Arduino Enhances This 7400 CPU

How quickly could you make an entire computer from 74 series logic, from scratch? [Richard Grafton had only 30 days until the UK’s Retro Computer Festival and set out to design and build his Cambridge-1 computer in that time. The result is a machine spread across several breadboards, with neatly placed wiring and unexpectedly an Arduino Micro sitting in the corner. Isn’t the little Italian board a cheat? Not so, he says, because instead of being part of the computer itself it serves as a program loader to make putting software onto the machine from a PC as easy as possible.

The machine itself is simple enough, a 4-bit design with 8-bit data and address busses. There are only 16 instructions, and the clock speed is a relatively pedestrian 40Hz. This does, however, allow the many blinkenlights to show the machine’s state in a more visible manner. There’s a video which we’ve placed below the break, and if you have further questions you might like to look at the GitHub repository.

We like the Cambridge-1, and we see no problem with the Arduino being part of it. It doesn’t take away from the 74-driven nature of the machine. Instead, it enhances the usefulness of the device by facilitating coding on it. We’ve had huge quantities of TTL computers here over the years so it’s difficult to pick one to send you towards, however you may want to consider the 7400 as the original in the series.

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