The biggest unlock was finding Willy McAllister's excellent Circuit Sandbox [1], which provides the Minivac Simulator's underlying electrical math. I tried so many approaches to simulate electricity (a doomed DIY approach, Falstad, Spice...) but Circuit Sandbox's DC analysis did the job perfectly.
Ping me for questions, and would love to read your feedback!
Feature request: I was wanting for a bit more sound… I mean, when I see "relay computer", I'm heading there for lots of soft clicks.
I totally feel you - the one reservation is that I’m using (gasp) not the original Minivac Relay sound. I need to go to a Computer Museum that will let me record one to offer a more authentic simulated experience.
So tldr - let me get a clean real sound and then we can come back to this question :)
that manual is wild too. entire section on games.
reminds me a lot of those old radioshack "build your own circuit" boards. the wires to components especially but also the manual, the way it just builds up dozens of examples from simple to complex, so if you really wanted to, a child could work their way through it slowly and understand everything.
looks like the inflation adjusted cost would be around 900 bucks today.
One of the crucial things I didn't get to yet is making that wheel controllable - some circuits in the manuals do require you to turn it. That's high in the todo list (with mobile support).
I also really want to share all of the videos I've been collecting of similar "wheels" - in (modern-ish) elevators [0] and light shows [1]... And also pinball machines! [2]
Re: RadioShack boards, I did have the "300 in 1" kit growing up, so yes... it's full circle for me. :-)
[0] https://www.instagram.com/reel/C3dk5GkJni6/ and https://www.instagram.com/reel/CzuHXKRpuN-/
https://www.computerhistory.org/timeline/computers/
It looks like transistorized computers were dominant at the point when integrated circuits were introduced.
It turns out both are true [1]. The "integrated circuits" were sort of "flat-packs" of RTL circuits. I had forgotten that early IC's were not quite what we envision today. Regardless I suppose ICs were RTL before they were TTL (before they were CMOS, etc.).
[1] https://en.wikipedia.org/wiki/Apollo_Guidance_Computer#Logic...
(are those knife switches in the upper right?)
Steam engine concepts were already there before Jame Watt, logic by electrical circuits was already there before Shannon. People provide incremental guidance for the change, like river banks do to the flow of the river. No single part of the river brought the river upto that point.
For that incremental change, the name of its inventor is appropriate.
However, you are right that too frequently people fail to distinguish what was new and what was old in an invention, and they misleadingly attach the name of the inventor/discoverer to the entire big system or theory, not to the small features that are truly new.
The inventors or discoverers are frequently guilty of this themselves, by failing to properly acknowledge their sources and by making exaggerated patent claims, which nowadays are too frequently accepted by patent offices that do not perform an adequate search of prior art.
I'm fixated on speed. I connected some reed relays in a 3 stage ring oscillator and it ran at 1.8 kHz. That has me thinking that with a pipeline 100 instructions a second might be attainable. Reed relay logic seems to be fast enough for a UART at 50 baud. Teletype interactivity is a stretch goal.
My program counter is also 12 bits! And I've also been using Digital to simulate parts of it. Great tool for that.
The current design is RISC-like with a 12 bit word requiring 4 cycles for most instructions. I have an old version of the design specified in gate level Verilog. I should publish that. Though I'm forever tinkering with the control such that it'll probably never be done. Karnaugh maps are like Sudoku.
The Enigma-cracking Bombe (on display at the extraordinary Bletchley Museum of Computing) also used relays
https://www.tnmoc.org/bh-10-bombe-description
And the Z3 as well!
It was a hybrid electronic-relay computer, containing more than twenty thousand electromechanical relays and more than ten thousand vacuum tubes.
This is likely the biggest and most complex relay computer ever made, though its main arithmetic part and its fastest registers were made with vacuum tubes, for increased speed in comparison with a pure relay computer.
1) Are any of them for sale? :)
2) Would you be open to recording a clean sound of one of its relays turning on and off? And helping me figure out some specifics about the motor wheel (its speed and whether it experiences any speed up)
Thank you! My email is:
hi at greg.technology
If anything though, I want to go build a physical relay computer mechanism myself now (if even just a 4-bit adder or something).
[0] https://minivac.greg.technology/manuals/1961-minivac601-book...
