Thank you so much everyone, this is something I've worked on for a few years on and off -- I posted about it here in a Show HN a few hours ago [0]
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!
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 :)
well the fact that you can wire the Rotary Switch to power and the thing physically rotates --- that's definitely Haptic Feedback that i dont ever recall seeing in a computer. lol.
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.
The Rotary Switch - which is both input and output in the real Minivac - is absolutely wild yeah.
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. :-)
Interesting: the entry for the Apollo Guidance Computer (AGC) indicates it used integrated circuits—I had remembered hearing it used RTL (resistor-transistor logic).
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.).
In particular, the IBM 1401 (two of them actually) that you can see demonstrated at the Computer History Museum in Mountain View are transistor-based and were very successful computers.
When you attach a name as inventor of something, it sounds as if the whole concept was borne by them, which is not true. All "inventors" and "great leaders" are only carriers of incremental change, which sometimes marks a milestone for a series of changes done by their predecessors or the context.
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.
There are many cases when the incremental change that is due to an individual inventor is very clearly defined, so it is known precisely which is the contribution beyond what was inherited from the predecessors.
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.
Very cool. I've been sketching out a relay computer myself. Mostly unbuilt but I have tested a variety of circuits implementing gates, latches, oscillators, flip flops, counters, registers all using only SPST reed relays.
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.
Oscillator can go high, but real logic is complex and requires realiability. and the fact that cheap relays are absolute crap with a ton toff spread between 3ms to 18ms! The actual clock frequency you can hope for is around 10-15 hz :(
It's almost hard to believe this is possible now in a modern web browser. It's a really sublime thing and I'm glad someone figured out a way to do this. I remember Web 1.0 before the days of JavaScript and P.H.P. allowed interactive websites... Indeed, it's entirely different now.
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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!
[0] https://news.ycombinator.com/item?id=45945762
[1] https://spinningnumbers.org/a/circuit-sandbox.html
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-/
[1] https://www.instagram.com/reel/C6qqCdhJbM2/
[2] https://www.youtube.com/watch?v=ue-1JoJQaEgm
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...
https://computerhistory.org/exhibits/ibm1401/
(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.
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