A 3D Printed, Electromechanical Computer

If you had a machine that could print complex mechanical parts in an hour or so, what would you do? [Chris] is doing the coolest thing we can imagine and is building an electromechanical computer from 3D printed parts.

You may remember [Chris] from his efforts to getting his tiny, 1/10th scale Cray-1 supercomputer up and running. Even though he has the OS on a disk, actually booting the machine is a bit of a problem; much the same as his electromechanical computer project. Late last year we saw [Chris] building a few gears for his computer, but now he’s got a punch card reader that looks very much like a Jacquard loom.

Even though the computer doesn’t actually do anything yet, it’s amazing to think that [Chris] is building out of plastic that will run computer programs. You can check out the video of [Chris]’ video of his punch card reader after the break.

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Making Punch Card Programming A Snap

About thirty years ago [H. P. Friedrichs] pulled off a hack that greatly improved the process of programming with punch cards. At the time, his school had just two IBM 029 keypunch machines. One of them is shown in the upper right and it uses a keyboard to choose which parts of each card should be punched out. This was time-consuming, and one misplaced keystroke could ruin the card that you were working on. Since you had to sit at the machine and type in your source code these machines were almost always in use.

But wait, the school acquired a dozen of the TRS-80 computers seen in the lower left. They were meant to be used when teaching BASIC, but [HPF] hatched a plan to put them to task for punch card generation. He built his own interface hardware that connected to the expansion port of the new hardware. Using his custom interface a student could create a virtual card deck that could be rearranged and revised to correct mistakes in the source code. The hardware then allows the virtual deck to be dumped in to the punching machine. This broke the bottleneck caused by students sitting at the punch card terminal.

We think that [HPF] sent in this project after seeing the antiquated hardware from that 1970’s calculator. These hacks of yore are a blast to revisit so don’t be afraid to tip us off if you know of a juicy one.