Harry Porter's relay computer is a loud, clunky, heavy thing of beauty.
While the rest of the world may be focusing on miniaturization, Harry Porter is headed in the opposite direction. A professor in computer sciences, Porter has a strong interest in showing just exactly how these systems work. To that end, he's built a very impressive relay computer, which occupies a place (make that a big place) of honor on his living room wall.
Harry proudly displaying his relay computer.
Porter's relay computer consists of four physical units: arithmetic logic, register, program control, and a sequencer unit. Each is housed in a nice wooden frame with a glass front for display. Everything is organized logically and LEDs are in place so you can actually see the data flow through the system while the 415 total relays emit a familiar and satisfying cacophony. You can see and hear it in the video below.
The specs, taken from Harry's documentation, are as follows:
Data Bus (8 bits)
Address Bus (16 bits)
All relays are identical (Four-Pole-Double-Throw, 12 Volts)
Max Power Consumption: Estimated 12 Amps @ 13.5 Volts (160 Watts)
Porter completed the computer in 2007. When I asked him if it still worked, he replied "Yes, it is still functional. But it doesn't get much use. I tend to read email on my iPad instead," which is completely understandable. It now waits on standby, ready to be powered on if an excuse presents itself.
Registers and switches.
Click the image above to view the entire slideshow of 17 images.
Programming is quite an arduous task that involves first selecting an address, then using switches to select the byte you wish to enter and then push that into the memory. Repeat this process over and over until you're ready to begin your computation. There are a few sample programs documented on Porter's site that demonstrate how the machine does simple addition, subtraction, and multiplication.
Harry has done a fantastic job of documenting the build. He shares not only a wonderful set of pictures of the process, but also PowerPoint presentations, schematics, and a 60-minute detailed breakdown of the relay computer's design.
I've been following passionate people doing home projects for years and years. This was one I saw a long time ago that I thought really deserved some fresh attention. There's just something so satisfying about hearing those mechanical switches clicking and clacking, I'm glad my laptop doesn't do that, but I kind of wish something in my house did!
Oh man, my co workers would kill me. I get aggressive with mechanical keyboards. By the end of a long sentence I'm furiously pounding on it just for the satisfaction of the RATA-TAT-TAT. You don't even want to see me use a typewriter with a manual carriage return.
I need to stay away from those for everyone's sake.
A long time ago I had a pre-PC keyboard, I'm thinking it was from Burroughs, that had fairly mushy (no snap-action) keys. They actually built in a small solenoid in it to give you a nice loud click for audible feedback, and a little vibration for tactile feedback, on each keypress.
Someone gave me one of those the other day...can't be that old as it has a PS2 connector. It was too nice to chuck, but if anyone wants it, let me know...you pay postage from Aussie (and they're not light!) I'd love to see it go to a good home.
@Joe....nope, you're the man. SMS me your email address on 0428 425 099 and I'll get in touch (don't like posting my address directly). I can probably get it to Sydney for you to pick up (I'm in sunny Bathurst). Wife will be happy....something going out of the house instead of coming into it!
I always loved the sound of a keypunch. I had a friend who called them "pea-kunch machines" because that's the sound they make: p-kunch, p-kunch, p-kunch followed by the satisfying hiss and klunk-klunk as the card is released and a new one loaded.
Eniac moved to Aberdeen, MD. after it was born, same as me! It lived at the BRL, where dad worked from the late 40s to the late 70s. I was a lucky little kid.
Ironically, we didn't get our own computer at home (a tragically tiny VIC, initially) until about 1980, although there were programmable TI 58s rattling around the house occasionally, which I learned to program for lack of anything better.
I learned to etch PCBs so I could expand the pitiful memory on that little VIC. Pitiful by today's standards, but relatively lavish compared to a TI58.
Max obviously has not seen this yet....eat ya heart out Max!!! A serious labour of love though. I see he uses a 32K x 8 static ram chip for memory....cheating really, though it's excusable - if he did that with relays it would take up his whole lounge room. Pity he did not use ferrite core memory or something else from a bygone era for that.
This reminds me of the "BiTran 6" computer I used at Penn Technicial School. It used 7400 logic chips but was programed using binary. I remember for my senior project I programmed it to solve the quadratic equation. The good old days ....
... and sell T-shirts that say "I'm living in the past, man". Or better yet, pocket protectors. Maybe we could join forces with the Society for Creative Anachronism and have mock sword fights with slide rules -- or use the giant ones as battering rams.
First, thanks for putting "clicks and clacks" in the headline. It's hard for me to resist any story with that! I LOVE this project. It is not just a great demonstration of how a computer works, but it is true kinetic art. It belongs in a museum like the Smithsonian, which I'm relatively sure would love it.
(I recently visited the Smithsonian and, to my astonishment, there was a gasoline-powered Pennsylvania-branded lawnmower that was the very same model I used to cut my family's lawn when I was about 12. First, I thought: "Why is the Smithsonian showing some dumb old lawnmower?" My second though: "Man, I must be geting old."
My first run-in with a computer was visiting my father's bank around 1960s where there was a monster tube-driven computer printing out punch-card checks in a vast refrigerated room. It was loud and printed out another check every couple of seconds, which was amazing back then. But that wouldn't be nearly as cool to see in the museum as this wall-hanger.
Personally, I am very grateful that I'm old enough to have come of age at the beginning of the microcomputer revolution and enjoyed the exciting "barnstorming" days before the "suits" took over. Now it's all DRM and patent infringement lawsuits. But there's still plenty of fun to be had in embedded design where you can still program at the bare metal, and in open source hardware and software where there's so little money to be made that the patent extortion entities find better targets.
I did a FORTRAN course once and you had to punch your cards out on the machine, then take them down to the computer centre (you learned to use 2 elastic bands the first time they fell apart :-) and they'd run it and you'd collect your printed output later. Along with the wrath of the operators if you had an endless loop that chewed up valuable computer time.....
I take it you are talking about something like this:
Yep, that's a drum card. Wikipedia calls them "program cards", but we never called them that because usually your whole deck of cards was a program. Its main use was for setting tab stops, so you'd have one card for Fortran and another card for assembly language (tab stops for opcode, operands, and comments). But it could also automatically skip columns, duplicate a column from the previous card, and automatically shift to numeric so you wouldn't have to hold down the numeric key when entering data.
If you were entering fixed-format data such as " .word 12345,67012,45670, ..." you could have the drum card automatically copy the ".word" and commas, skip to the correct columns, and shift to numeric so all you had to key in was the numeric values. This was a very fast way to enter a lot of numbers, and I've yet to see a screen-based editor with similar capability.
Doubt it was exactly the same course, but I think in that era most computers were shared with punched card input. It was lots of fun. I'd just discovered biorhythms (remember them?) and as an (unofficial) exercise wrote a Fortran program to print them out. Obviously doing graphs on text-based printouts wasn't that easy, but I got it working pretty well. I was tweaking something and did the (for me) inevitable - forgot to close a loop. When I went to get my printout (which was usually about 3 or 4 sheets) I had half a ream of fan fold 132-column paper waiting for me with my biorhythms for the next 50 years...and a VERY stern talking to from the head operator (especially as it wasn't set classwork). If nothing else it taught me to check my loops VERY carefully in future.
@Betajet...Drum Cards...was reading more about these... seems they would enable you to put your statement numbers, contents etc in the right columns, and also limit what you could type in them......am I right? The machine I used was used by a number of different users for different purposes and I don't think had a drum card used....but I could be wrong. I can see it would be really useful if you were only entering (eg) Fortran statements.
Me, too, David. But just barely. I used them in a statistics class at UCSD back in '72. I remember we had to wait to do our class work at night because the serious engineering students had claim to the big computer during the day. My relatively simple statistics problem took about an hour to run. Today, we could all probably get a lot more done sharing a smartphone. ;-)
Speaking of punch cards....some San Francisco trivia; I once heard the four Embarcadero Center office buildings were designed to look like punch cards standing on end. I think of that every day as my ferry pulls into the embarcadero.
A couple of years ago I was talking to a Russian (now working for an Israeli company) who had worked on a pneumatic computer used to control a Russian nuclear power station. It was the size of a supercomputer, and was all built with pneumatic logic gates and ran off air pumped in by a huge set of fans which were so noisy that the operators had to wear ear protection.
Given the low reliability of the hardware the whole machine used redundant and error-correcting logic (3-way majority voting on *everything* IIRC, gate-level and module-level) such that failed modules could be hot-swapped *while the control program was running* with no effect.
Why do this? Bacause nothing is more rad-hard if something goes horribly wrong than a computer which doesn't use electronics, only AC power...
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