Gigantic ball-manipulating binary computer

The folks at Evil Mad Scientist Labs just put up a post on the giant mechanical binary computer they brought to last month’s Maker Faire.

As a faithful reproduction of the Digi-Comp II from the 1960s, every operation is powered by balls falling onto levers. Unlike the original, the larger version is powered by billiard balls instead of half-inch marbles. The Digi-Comp II is able to count, add, subtract, multiply, divide, get the 1s or 2s complement and zero all of it’s bits. With a 7-bit accumulator, the Digi-Comp II is able to calculate anything where the result is less than 127, so we wouldn’t recommend doing your taxes on it. In the demo video, it took the Digi-Comp II about two minutes and twenty seconds to multiply 3 by 13. We’re not going to venture a guess on the equivalent seconds per cycle for an electronic calculator, but it’s an impressive build

The Digi-Comp II is a great way to show the process of binary arithmetic in a computer and we were wondering why there aren’t any educational toys like the Digi-Comp II out today. A site linked from the build page tells us there will be kits available this summer, we’re hoping the kit doesn’t fill the bed of a pickup truck.

Check out the video after the break for the multiplication demo.


  1. abobymouse says:

    It’s not analogue computer, surely? It’s implementing digital logic.

    It’s really cool; I love stuff like this. It’s a nicer analogy for teaching logic than lightbulbs.

  2. adam outler says:

    That’s a hardcore implementation of mechanical digital logic

  3. Hirudinea says:

    After reading the title I was disapointed it wasn’t a sex machine, but after watching the video I was amazed, I want one, hell I want the toy, why don’t they make toys like this anymore, really nice. Ok, now where’s the sex machine?

  4. Alex Parting says:

    Amazing that in the past something with the selling points “has flip flops” was considered a toy. Kids these days are stupid.

  5. IceBrain says:

    @Alex: there are still geek toys, they just don’t have the same success as other genres, and I bet that was true back then too.

  6. localroger says:

    I want a Turing complete computer that works like this.

  7. vasskk says:


  8. anti-fanboi says:


    IceBrain: you’d lose. Gen Y is characterised for it’s almost non-existent attention span, over abundance of apathy and affinity for “ooOOoo shiny”.

  9. Blastar says:

    The Girl could use some makeup. I know, she probably WANTS to look that way (Geeky), but I think that her face is screaming for some.. -at least basic- makeup.

  10. bootnecklad says:

    Some one finally did it! Now I want one, maybe two! Imagine the possibilities! Faster calculations!

    @anti-fanboi: That is totally not true, I’ll have you kno – ooOOooo a butterfly! *chases butterfly*

  11. Blue Footed Booby says:

    Every generation has proclaimed the next generation to be dumber, more apathetic, and less aware of the world. The world is constantly changing, but hardly anyone actually guesses correctly as to where that change is headed.
    Remember: history repeats itself not when people forget history, but when they become convinced that they understand better than those who came before and can’t possibly make the same mistakes.

    And for the record, the only studies I’ve seen show the opposite: kids these days are much more likely to be tolerant of differences, and more likely to have an interest in the rest of the world (whether this interest results in understanding is a separate question).

    Also, cool project.

  12. So tilting this at a larger angle would be like over-clocking the machine?

  13. Hungry_Myst says:

    Your sexism is astounding.

    • Hiatus138 says:


      Thank’s for that (setting the dumbass straight)
      Never fails, any mention of a female engineer or hacker quickly degenerates into “id do her lol”
      You like women engineers? How about making them feel welcomed and appreciated! Then maybe we’ll get more of them!

  14. Miroslav says:

    Amazingly smart and funny.

  15. tulcod says:

    gcat122: welcome to pipelining.

    • gcat122 says:

      Exactly. Well close. Not as well separated as fetch, execute, store. But it makes for a good bit ripple race. Overclocking without bouncing the ball off the hypertilted table. I want to hear the video without the balls clacking. I wish I could find my digicomp 2.

  16. kernelcode says:

    Has anyone read Makers? (Cory Doctorow)
    This reminds me of Lester’s Barbie-head computer

  17. kim says:

    I believe the androgeny is intentional. Is the girl the one with or without the ponytail?

  18. DarkFader says:

    it’s digital! it’s binary! it’s serial! it’s slow! it’s cool though.

  19. Elias says:

    Holy freaking sheet. I’ve watched this once, a month ago, then I’ve been so amazed by it I’ve been searching it for DAYS. Seriously, I’ve spent at least 20 hours googling. You definitely can’t find this on google if you don’t specify “site:hackaday”, which is a pity because I wonder how many cool things Google is still hiding from me. :(

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