
Watch a Computer Made Out of Dominoes Do Basic Math - ColinWright
http://thescienceexplorer.com/technology/watch-computer-made-out-dominoes-do-basic-math
======
chas
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](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](https://www.youtube.com/watch?v=SudixyugiX4)),
petercooper posted this one
([https://www.youtube.com/watch?v=lNuPy-r1GuQ](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](http://imgur.com/a/qq7Kl)).

~~~
p1esk
There's actually a style of digital circuit design called "domino logic":
[https://en.wikipedia.org/wiki/Domino_logic](https://en.wikipedia.org/wiki/Domino_logic)

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Phithagoras
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.

~~~
prezjordan
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.

~~~
mac01021
I'm confused. Would the same book with the last page removed be recommendable?

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

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14113
I was slightly hoping that it would be this:
[https://davidlazar.github.io/PCPL/](https://davidlazar.github.io/PCPL/)

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amelius
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.

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

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shurcooL
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.

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grondilu
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?

~~~
DanBC
See, for example, this form of memory:

[https://en.wikipedia.org/wiki/Delay_line_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.

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

~~~
TrevorJ
good explanation of earlier version
[https://youtu.be/Yc945sNB0uA?t=102](https://youtu.be/Yc945sNB0uA?t=102)

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IIAOPSW
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.

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

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

~~~
kzrdude
They had a current leak in the demo

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

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

