Watch a Computer Made Out of Dominoes Do Basic Math | Hacker News Reader

Watch a Computer Made Out of Dominoes Do Basic Math

thescienceexplorer.com

142 pointsColinWright22 comments

If you are interested in non-electronic digital computers you might want to check out this previous discussion:(https://news.ycombinator.com/item?id=7824588)

If you are particularly interested in domino logic and adders, baddox posted this video (https://www.youtube.com/watch?v=SudixyugiX4), petercooper posted this one (https://www.youtube.com/watch?v=lNuPy-r1GuQ) by Matt Parker (the same guy in this video) and I documented a 2-bit build I did (http://imgur.com/a/qq7Kl).

There's actually a style of digital circuit design called "domino logic": https://en.wikipedia.org/wiki/Domino_logic

The mathematician who set this up also wrote a popular maths book called "Things To Make And Do In The Fourth Dimension". It is by Matt Parker.

I read that a few months ago and was incredibly upset when I turned to the last page.

Such a fun read, requires no more than early college math (maybe not even that), but dives deep into some really, really interesting and quirky problems.

Can't recommend it enough.

I'm confused. Would the same book with the last page removed be recommendable?

Yep :) I was disappointed because it was the last page "Oh no, it's over!"

I'll tell Matt - he'll be pleased.

He is known sometimes, when walking past book shops, to see if there are copies of his book. If there are he sometimes surreptitiously signs a few and puts them back on the shelf.

If ever I write a book I'd find that a very tempting thing to do. I have published (note that I am the publisher, not the author) and am tempted to get the author to sign some of them that we place in shops, just because.

It's not a technical technology book - in case you're interested: http://williamsonfineart.co.uk/BridgesOfDee.html

I was slightly hoping that it would be this: https://davidlazar.github.io/PCPL/

Nice. It is unfortunate, though, that every logic gate can be used at most once.

Nice idea for the next project: a robot that puts down domino blocks based on a specification.

An automatically resettable version of this, with configurable inputs, would be super awesome for a science/computer museum.

This is fascinating because it's such a relatable physical demonstration of real physical CPU concepts such as overclocking, die size, voltage, reliability, tunneling/leakage, architecture, multiple cores, etc.

For any kid out there who's thinking "why can't they just make CPUs faster", this is a great way of explaining why. It's hard, and as you push the limits, reliability goes down. So the challenge is in keeping reliability high enough to be acceptable, and performance increased.

While I was watching that some time ago I was wondering what it would take to optimize this and make it still work with the same underlying principles. It occurred to me that falling dominoes are just transmitting a mechanical signal, that is ultimately "sound", thus phonons.

So I thought : can you make a computer that would use phonons inside tiny metal wires instead of electrons?

See, for example, this form of memory:

https://en.wikipedia.org/wiki/Delay_line_memory

> Delay line memory is a form of computer memory, now obsolete, that was used on some of the earliest digital computers. Like many modern forms of electronic computer memory, delay line memory was a refreshable memory, but as opposed to modern random-access memory, delay line memory was sequential-access.

> Analog delay line technology had been used since the 1920s to delay the propagation of analog signals. When a delay line is used as a memory device, an amplifier and a pulse shaper are connected between the output of the delay line and the input. The memory capacity is determined by dividing the time taken to transmit one bit into the time it takes for data to circulate through the delay line. Early delay-line memory systems had capacities of a few thousand bits, with recirculation times measured in microseconds. To read or write a particular bit stored in such a memory, it is necessary to wait for that bit to circulate through the delay line into the electronics. The delay to read or write any particular bit is no longer than the recirculation time.

I recently stumbled upon a good video showing some old delay line memory: https://www.youtube.com/watch?v=N9cUbYII5RY

good explanation of earlier version https://youtu.be/Yc945sNB0uA?t=102

Mercury was something used for this, but I have always liked this little tidbit of information:

> (Alan Turing proposed the use of gin as an ultrasonic delay medium, claiming that it had the necessary acoustic properties.[3])

I used to do the same thing in my youth. The dominos have a rather low reliability and I'd always run out before I could set up a useful circuit. Resetting your design to test it with different inputs can make the whole thing a real test of patience. Now days when I want to make esoteric computers I simply play minecraft.

This was lifted from Numberphile. That's the place to go for cool videos like this.

Ingenious. I wonder if they found serious race condition issues.

They had a current leak in the demo

Where can I buy cheap dominoes just to make these ladders?

Memserizing! Getting timing right must be hard. It's a one time use computer though :)

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