The TIM-8 Is The Smallest 8-bit Relay Computer Ever

Who wouldn’t want to build a computer out of relays? We do, but we’ve got too many projects on our plate already. It looks like [rory] has his priorities in order because his build is one of the most amazing we’ve ever seen.

We’ve seen [Harry Porter]’s amazing relay computer and we’re familiar with [Konrad Zuse]’s WWII era endeavours. Relay computers aren’t exactly uncommon, but [rory] built the TIM-8, that may be the smallest 8-bit relay computer ever. The total relay count in the TIM-8 is 152 compared to [Harry Porter]’s 415 relays. This isn’t a fair comparison because [Harry]’s uses 4-pole relays, while the TIM-8 uses 1-pole relays, making the [rory]’s project 8 times smaller than [Harry]’s.

There are a couple of neat features that makes the TIM-8 really exceptional. Programs for the TIM-8 are written in a text editor on [rory]’s desktop,  then compiled and printed onto receipt paper. The TIM-8 has a few phototransistors to read the bands of white and black printed on the paper. [rory] has come a long way from a three bit adder made with relays and light bulbs.

Check out a ton of videos after the break. There’s a few demos of programs running off of receipt tape, calculating the Fibonacci sequence, and playing ‘Mary Had a Little Lamb’ on the relay sound card. Thanks to [J. Peterson] for sending this one in.





20 thoughts on “The TIM-8 Is The Smallest 8-bit Relay Computer Ever

  1. Aside from the wow factor of someone doing design at the bit-level using relays, this device has the one thing that always makes computers cool. Awesome sound effects. Nothing like the clatter of relays and hum of motors to let you know something is happening. Job well done.

  2. …I refuse to use a RAM chip for memory, because it’s a RELAY computer, not a relay-with-several-million-transistors-thrown-in-because-I’m-to-lazy-to-do-it-properly computer.

    My feelings exactly!

    1. I was worried about that too, but it stays surprisingly cool actually. The only bit that gets hot are the register’s which are regularly on for long periods of time, and turned out to be 6 volt relays rather than 12 volt ones. But this even they only get slightly warm to the touch.

    2. No, because they also are much larger than transistors, and are excellent heat sinks themselves. That’s why Rory had no issues. Now if he was to try to switch anywhere near the kinds of currents that the relays could safely switch, then maybe we’d have a problem.

  3. Very cool. I wonder how much power all those relays must consume? The needle on his meter dances all over the place.

    Wish his tape feed motor was a bit quieter so I could enjoy all those relays going off.

    1. Capacitors or paired(6V) or quaded(12V) coin cells could make the relays run a lot more stable and make less demands on the power supply. The coin cells would not be as fast at responding as capacitors, though. The back RF must be incredible but unless you’re going for higher frequencies, this is acceptable for a technology demo.

  4. So many cool things here. Not only has he built a programable relay computer but he’s got his own sound card and peripherals. Very cool project and I agree with the postings above. Part of the cool factor is the sound of clicking relay : )

  5. Thank you so much for publishing this! My website view counter just exploded yesterday, and I traced the source back here :P I’ve be trying so hard to get the TIM project out there, and you’ve done an amazing job! Thank you again :)

    1. Hey Rory, think that’s impressive? There’s a way to make a computer using just a cassette tape and just a few relays. It’s called the 2,3 Turing machine and Wolfram goes over it quite a bit. Not that I’d want to wait for the thing to finish the calculation! (Adding 2 16-bit unsigned integers without carry would take quite a while)

      There’s a reason that no one has seriously been building one of those. Unlike your machine that actually has some efficiency, a 2,3 Turing machine would need many, many machine cycles just to finish one ‘instruction’ in the conventional sense of the word for assembly programmers. Also, no one has actually proven universality AFAIK. It would essentially involve making a translator for an existing CPU.

      For those unfamiliar with the s,c terminology, it works like this. You have a machine that can have 2 possible ‘states’ and 3 possible ‘colors’. Another name for states that assembly programmers might be familiar with is possible values in register memory. In this case, you would have a 1-bit register. The colors are your I/O values. So this Turing machine would have trinary(also called ternary or 3-state) I/O. Given a set of rules for these 6 combinations of inputs, it’s actually supposed to be possible to write run any program so long as you have a long enough tape and the patience to wait. The ruleset is very strict, as well.

      I’d be curious as to how someone would read and write 3-state values to a tape. Or in fact, any arbitary non-binary value. Probably some kind of angle encoding? 0/120/240-degree constellations like an analog phase modulation I guess. AM or FM methods would probably work, too.

      Thanks for sharing this project with us – I’ve been interested in minimal computers for years now!

    2. Hmm, I could have sworn 2,3 was not proven, yet. It turns out that someone won the prize in 2007, although there’s still some controversy over the validity of the proof – doesn’t help that Wolfram’s other theories hinge on it and he went around the prize board. I read the 2006 edition of the book, sigh…

  6. Well. If something upsets every transistor out there, people like you will save society!

    Using a basic building block different than the standard to make a computer is very cool! Gets us technical people back to our roots, reminds us how magical our modern devices really are and how much goes on in the smallest of chips!

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