The simplest of calculating logic is based on a half-adder, from which a full adder with carry can be built. These are then chained together in modern computers to implement a full 32 or 64 bit addition. There have been some interesting ventures in to computing based on biological processes, but now a team has built three and four bit adders entirely of dominoes:
https://www.youtube.com/watch?v=OpLU__bhu2w
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(Score: 5, Interesting) by francois.barbier on Sunday April 06 2014, @11:59AM
Another interesting mechanical one: Marble adding machine [youtube.com]
(Score: 1) by b on Sunday April 06 2014, @03:38PM
(Score: 2) by maxwell demon on Sunday April 06 2014, @05:08PM
OK, so who now builds the marble computer controlled Lego domino computer builder?
The Tao of math: The numbers you can count are not the real numbers.
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(Score: 5, Informative) by VLM on Sunday April 06 2014, @12:42PM
You can do a decent full adder with two relays
http://www.electronixandmore.com/projects/relaycom puter/index.html [electronixandmore.com]
As you can see its all in the logic level specs, some making it more difficult, some less.
Starting from something like that design I eventually built up a pretty decent bit slice ALU design using about two dozen relays per bit to provide microcontroller CPU level functionality. Not quite a bitslice 68000 or pdp11 but it was more capable than a 1802 or arguably a 6502. Less than a Z80 probably.
At a Chinese import cost, I could implement 16 of those giving me a 16 bit CPU for well under a kilobuck, which is an affordable project. Obviously it would take an entire winter to wire and test, so it sounds expensive, but on an hourly basis its much cheaper than golf or watching movies or pretty much anything other than reading library books.
Anyway much like the linked article I felt static ram for memory would be cheating and given the costs of latching relays, making memory out of relays is simply not affordable. So I never went forward with the project.
Early computers were always like that. Making an adder sounds hard to a modern, but according to moderns, memory is cheap so don't even think about memory. However, the ratio of whats hard and easy is actually the other way around. Memory is much harder than a simple CPU. The hard part is affording/building enough memory to do something "interesting" not a simple adder which is like two relays per bit. Then you add two relays (or more) per buffer/latch and you'll need quite a few, and more than 1 or 2 relays per bit of RAM plus a latching relay for the bit itself, and suddenly that "2 relays per bit adder" starts looking like the cheap part of the project.
There's scalability to large sizes but the learning experience is there's scalability to small sizes... so dynamic memory, perhaps based on electrolytic capacitors, doesn't scale to less than a K or so, because of the cost of the substantial switchgear required to implement refresh, what amounts to sense amps, etc.
I was considering making some classic DTL flipflops to use as static ram for my relay based computer. Done in SMD for size and also its easier to build with SMD than surface mount (once you know how...) I could fit quite a few K of memory in a shoebox, relatively cheaply. That rapidly turns into a fan-in/fan-out puzzle to be solved in the circuitry connected to the FFs. Maybe some other decade. I was going to use optoisolators to connect the DTL memory to the relay based CPU. That of course rapidly degenerates into why not build an entire CPU using discrete transistors and DTL logic.
As an example of a dedicated application specific large DTL system, I have no connection with these guys at all, other than admiring their product from a distance:
http://www.transistorclock.com/ [transistorclock.com]
Eventually all these discussions degenerate to reimplementing IBM's century old unit record equipment, poorly. Which would be kind of fun, assuming a source of punchcards. Which leads to weird ideas involving commercially available "index cards / note cards" and lots of metalworking and hacking around.
(Score: 4, Funny) by Dunbal on Sunday April 06 2014, @02:26PM
Gives a whole new meaning to the RunOnce registry key.
(Score: 4, Interesting) by bugamn on Sunday April 06 2014, @02:29PM
At about 7 minutes into the movie he starts showing how to implement dominoes logic gates.
It seems that one of the biggest problems in this implementation is adjusting the circuit so the timing is right.
I just wish they had a page with photos of the circuit and explanations.
(Score: 3, Informative) by mrcoolbp on Sunday April 06 2014, @03:30PM
Here is the biocomputers article [wikipedia.org] that was in the original submission.
(Score:1^½, Radical)
(Score: 1) by cubancigar11 on Sunday April 06 2014, @06:59PM
This is pretty neet. Even after the problem they had on day 2 it is so much cool and you can see a lot of kids get a lot excited about binary math. I think, mission accomplished!
(Score: 0) by fishybell on Sunday April 06 2014, @07:30PM
A computer is only a computer if it computes correctly. The answer to 9 + 3 is not 30.
(Score: 4, Funny) by maxwell demon on Sunday April 06 2014, @07:52PM
So you say computers with certain Pentium processors were no computers?
The Tao of math: The numbers you can count are not the real numbers.
(Score: 1, Offtopic) by mendax on Sunday April 06 2014, @09:10PM
And I always thought that an adder was a snake. And there is that pesky Blackadder.
Go ahead, mod me down!
It's really quite a simple choice: Life, Death, or Los Angeles.
(Score: 2) by jimshatt on Sunday April 06 2014, @09:18PM
(Score: 1) by ChocolateTeacup on Monday April 07 2014, @07:37AM
in the classical sense. But a lot easier to troubleshoot than squinting at a 'scope.
BTW, Anyone remember modelling logic in Life?
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