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The Tube Computer

thetubecomputer.com

232 pointselvis7063 comments

Brilliant! and warming. ( literally and figuratively. )

"My family was homeless when I was born. But my parents found work, the council found us a flat, and 20 years later my dad was the managing director of a very large engineering firm, and my parents built a fabulous home.

To cut a long story short, much later my parents had a few personal problems, and sadly my mum finally killed herself. I don’t think you ever get over it, you really just learn to live with it.

My life then went a bit pear shaped. I trusted bad people and guess what, really bad things happened. Very kind friends managed to put me back on my feet, and then, at 55, I met Judy and her family, and we’ve had the most wonderful 15 years together.

So please, what ever happens, please don’t give up."

I'd really love to know more about him. That seems super interesting. Also to see this level of creativity after retirement is encouraging.

In my experience, it's more common than we suspect. I've met quite a few people in their 60s with fascinating hobbies. Some of it boils down to the fact that they had many decades to get good - and with career in the rearview mirror and adult children, they have a lot more time, too.

But it's also true that with age, you lose the drive to get praise from strangers - so at best, you get a text website viewed by hundreds, not a series of TikTok or YouTube videos viewed by millions. And sometimes, not even that website.

When that person dies and leaves behind a man-sized vacuum tube computer, or a collection of vintage calculators, or something of that sort... the heirs usually don't have the willpower to carry on, and because the stuff is impossible to sell, it's often destined for the dump. Maybe a couple of years in a storage unit before that.

It's even worse with digital assets. Who's gonna renew that hobby domain or pay that hosting bill? I've seen some really valuable online resources disappear after the author died.

> Who's gonna renew that hobby domain or pay that hosting bill? I've seen some really valuable online resources disappear after the author died.

This is why the Internet Archive is so important.

Eh, kinda. It technically preserves content, but it has almost zero discoverability. The site disappears from Google & co, so unless you come across a dead link in some old HN or Reddit thread, you won't even know it's there.

Yep. It helps IA that there are people keeping track of old URLs and making sure that they get added to the store.

One thing they've added to their extension lately is a count of how many times a page/site has been saved. If one finds a great resource with a no- or low-count, it can be added at your request; sometimes it will ask if you want to save the page.

I didn't say it's sufficient, but without the preservation that the Internet Archive does, we'd be completely lost.

I have come across some wealth of deeply technical information by entering dead links on still live pages in the wayback machine, and then following crosslinks from there to further old sites. I shudder to think what would have been if I hadn't found the dead links in those cases, and I'm sure I still missed a lot because I didn't know it was there. So yes, this is a very real problem.

"so at best, you get a text website viewed by hundreds, not a series of ... videos viewed by millions."

As my music-maker friend once put it, "it's not so important much how many like it, but who likes it."

Or put a couple million into your stinky living computer museum!

From down the tubes to a much more solid state of existence...bravo!

From the website: The person who built this appears to be (at least) 70 years old. Amazing!

> My family was homeless when I was born. But my parents found work, the council found us a flat, and 20 years later my dad was the managing director of a very large engineering firm, and my parents built a fabulous home.

> To cut a long story short, much later my parents had a few personal problems, and sadly my mum finally killed herself. I don’t think you ever get over it, you really just learn to live with it.

> My life then went a bit pear shaped. I trusted bad people and guess what, really bad things happened. Very kind friends managed to put me back on my feet, and then, at 55, I met Judy and her family, and we’ve had the most wonderful 15 years together.

> So please, what ever happens, please don’t give up.

For a long time I've been thinking about building one based on relays. The problem is that I would need a lot of relays just to achieve anything very simple. My solution: think about the simplest computer architecture I could come up with, and the simplest one was a NAND computer. In this architecture, the program is a simple loop with instructions all in the same format: input addess 1, input address 2, output address. The only supported instruction simply writes at the output address the result of a NAND operation of the input addresses.

Since any circuit can be built using only NAND's, this computer can simulate any circuit, including the circuit of a Turing complete CPU. It certainly would be very slow, but relatively simple to build. I still have to think about a good type of memory for this machine. Maybe one day I'll take the courage to build it.

For something simpler than the computer described in the article, you might be interested in Usagi Electric's UE-1 vacuum tube computer. Construction is nearing completion, and it's documented on Youtube:

https://www.youtube.com/playlist?list=PLnw98JPyObn0v-98gRV9P...

This is a 1-bit design based on the Motorola MC14500B:

https://en.wikipedia.org/wiki/Motorola_MC14500B

Code executes directly from a literal loop of paper tape, so the clock speed is very slow. I expect this design would also work with relay logic.

Yes, code executes directly from a literal loop of paper tape, and more specifically, there is only one loop (the paper tape loop), and every instructions executes at every iteration.

Yet it can do what any other computer can do (in terms of computation, not I/O), because not every instruction has to actually effectively do something in each iteration, and it is a cornerstone of theoretical computer science that you can transform every program into one represented in an academic language called "WHILE", which is restricted to exactly that principle: It only consists of a single outer WHILE loop, and then inside the loop you have a bunch of conditions.

That’s how tom7’s printable executable [1] works!

[1]: https://youtube.com/watch?v=LA_DrBwkiJA

The problem with ultra low gate counts is always memory. No matter how simple your CPU is, you still need at least thousands of discrete components for it to do anything useful, unless you resort to something like Williams tubes or delay lines. (Torsion wire delay line is probably the most practical form of memory for a computer like this)

You can build an interesting CPU core out of whatever, and then connect it to a silicon SRAM chip, and still say you built an interesting CPU core out of whatever.

Or if you can get your hands on magnetic core memory, that might be neat

There's a Brainfuck relay computer: https://hackaday.io/project/18599-brainfuckpc-relay-computer

Its author is now building a rack-mounted vacuum-tube based computer: https://www.youtube.com/watch?v=2HAf52AKt7Q

I started designing this, designed one using transistors instead, and built half of that.

But I think you can built an 8-bit relay version of my 16-bit transistor CPU core with on the order of 400 DPDT relays, which is on the order of $1000, plus a comparably big bag of diodes, which is much less than $1000. This includes registers (10 of them), control and sequencing logic (including a diode microcode matrix), but not RAM, which you wouldn't want to make from relays. (To make an 8-bit version you'd probably have to add another 3 upper address registers, to still have 16-bit addresses.)

Yup, having an emulator for another, more complex architecture running on the very simple architecture is common amongst projects like this. Linux on Intel 4004 does exactly this: https://dmitry.gr/?r=05.Projects&proj=35.+Linux4004

And its predecessor project(s) do as well.

Usagi's UE-1 was already mentioned as another vacuum tube computer. It indeed just runs instructions in a loop, and runs every instruction in each loop (but not every instruction is always effective).

> For a long time I've been thinking about building one based on relays.

When I was in 7th grade, around 55 years ago, I used a relay to make what was, both literally and figuratively, a 2-bit computer. Got an A+ on the math class project though! :)

http://nandgame.com might help with that

https://youtu.be/RfXrT619jBw?si=yWZO9S-PgLs_9DJd He made a bigger one a few years later..

Bit of an aside but I wonder how far tube technology might have advanced, without semiconductors intervening. In the late 1950s and early 1960s, GE, IBM, and RCA, probably other companies, were working on "integrated tubes" with many components in a single envelope, as well as techniques for easier and more automated manufacture. For example, introduced in 1959: https://upload.wikimedia.org/wikipedia/commons/b/ba/Nuvistor...

> Bit of an aside but I wonder how far tube technology might have advanced, without semiconductors intervening.

There were Compactrons. There were subminiature vacuum tubes.[1]

A one piece printed circuit board of glass, with multiple tubes, might be possible. A glass plate made with lots of recesses, electrodes and wiring created by photo-etching like printed circuit boards, a glass plate on top, pumped down to vacuum and sealed. A low-density integrated tube.

That's what a plasma panel display is. It's an integrated array of neon lamps. In a vacuum fluorescent display, each illuminated element is a triode vacuum tube. So it's quite possible to fabricate a big array of tubes.

Maybe something like a ball grid array would work for external connections.

Probably could have been done if necessary. Density probably would have maxed out around the density of elements on on the most dense vacuum fluorescent displays. Maybe devices at 1mm scale, or 1,000,000 nm. Good enough for mainframes and minicomputers, but not microprocessors.

[1] https://archive.org/details/The_MIT_Museum_The_Subminiature_...

Would tube reliability have limited how much you could scale it up? As far as I know, tubes have a limited lifetime and burn out eventually. If you have a million or a billion of them, they might fail so fast that your computer simply doesn't work.

I don't know whether reliability is a solvable problem. Tube-based devices were once very common, so that suggests it would have been solved if it could have been.

Tubes have a limited lifetime, but high-reliability, long-life tubes were developed specifically for digital circuits.

One such development was a change in alloys for the filaments. It turns out that the filaments were made from a tungsten alloy containing silicon, and the silicon evaporates and is deposited on the cathode. The cathode has a special coating to help it emit electrons, and the silicon deposits would interfere. From what I can tell, the alloy for filaments had silicon in to make it easier to draw through the dies necessary to construct the filament in the first place, so there is some tradeoff between the lifetime of the tools used to make the tubes and the lifetime of the tubes themselves.

This is not entirely unlike the problems faced by semiconductor manufacturers—problems with impurities, solid state chemistry, and vapor deposition. I can imagine an alternate timeline with extremely long-lived vacuum tube circuits.

I recently read up on "zone melting" which was developed to purify germanium - but of course this same method can be used for other materials. Interesting that Hamming of Hamming codes fame gave encouragement to the developer of this materials process: https://fs.blog/great-talks/richard-hamming-your-research/ (search for Bill Pfann)

Say a CPU was made the size and shape of a plasma TV. You wouldn't have to run it all at once. You could make many CPUs or logic blocks and re-route traffic to hitherto unused blocks when a fault was detected.

Oof. I don't know much about tubes, do they always fail in ways that are reliable to detect? (E.g. I can imagine that detecting a burned out heater is easy, but I don't know what other common failure modes there are.) And even then there's a lot of effort to just make the system "switch over"... and a lot of extra real estate with technology that was already constrained by the minimum size bound of the tubes.

I was thinking pretty high level stuff, like running a quorum of CPUs or something. But it could also be a manual thing with switches on a panel. :)

> Vacuum Tubes require high voltages to work efficiently and are not for the faint hearted.

People used to build vacuum tube circuits on breadboards at home back in the 1950s. They seem pretty frightening by today’s standards, but they’re a lot like big, hot, high-voltage, low-current transistors. The low-power tubes used for signals are not that hot, just kind of warm.

I’m not really criticizing here, I just want people to think of vacuum tubes as accessible to people with any kind of electronics background, and just more inconvenient than transistors.

Most people will get frightened by a medium-high or high voltage, but low voltage at high currents needs care too, a small short circuit could mean a huge fire. When I was studying we had to disassemble a decomissioned tube computer, the tubes were the sub-miniature type, the double triodes were just a bit bigger than a incandscennt christmas tree light bulb.

Plate voltages can exceed the skin breakdown voltage of ~450V, which potentially makes them more dangerous than a domestic mains supply.

Start with 150 V instead.

You probably don’t need voltages that high. DIYers can stick with 200 V or something reasonable. The remaining people who deal with 450 V are probably servicing guitar amps.

Plate voltages can exceed much more than 450 V. The 811A is rated for 1500 V of plate voltage. But the same is true for transistors—you can find transistors with similar voltage ratings.

Wonderful project. I learned vacuum and solid-state electronics in parallel so I'm familiar with tube electronics. My fascination with valves go back to my early childhood when I used to move our console-type radio from the wall and touch the grid-1 spigot connection which would make a loud humming sound much to the horror and chagrin of my parents.

One of the problems I've witnessed with training in electronics these days is how little time is devoted to vacuum tube electronics. Perhaps that's a necessity given constraints of course time etc. but without an understanding of how vacuum tubes work an important part of one's understanding of the subject is missing.

Vacuum tube technology is still a vitally important part of both electronics and of physics experimentation. For instance, magnetrons (microwave ovens, radar, etc.), klystrons, TWTs (travelling wave tubes), high power transmitting tubes (TV, FM) all rely on vacuum tech. So too do PMTs (photomultipliers) and imaging devices such as vidicons and orthicons. In physics, understanding thermionic emission is essential to understanding thermodynamics, so too cold cathode emission and related tech such as vacuum deposition, etc. Even electron microscopes and similar instrumentation relies on vacuum technologies.

Unfortunately, now since the widespread adoption of semiconductor electronics much of that vacuum tech tends to be rather specialized so those who've an interest in learning the subject don't get any hands-on experience at an early age.

What's great about this project is that it brings vacuum technology to the fore where it can be not only seen but also demonstrated.

Learning the transfer characteristics of thermionic diodes and triodes is an excellent way to gain such experience. And to begin one doesn't have to go to such lengths as this amazing project, starting with a single tube superregenerative FM receiver is a good place to start.

Tommy Flowers (https://en.wikipedia.org/wiki/Tommy_Flowers) knew a thing or two about valves (and how reliable they were if not switched off!). We have him (amongst many others) to thank for the success of Bletchley Park.

Fuses help with the "bang", as do using 5U4 or other vacuum tube diodes in the power supply, which limit current. I've learned not to be absolutely frightened of B+ at 200-300 volts, though I definitely respect it. Once you get above 500 volts, and an amp... the danger is very real, and the fear returns, in spades.

That being said, the biasing voltages get crazy too, leading to the big boy voltages.

300v b+ combined with 200v c- means that you're at 500v of potential if you short the wrong bits that are probably right next to eachother.

Exactly why I keep wooden chopsticks in my amp repair kit. But the voltage is moot without the amperage to back it up, and most power transformers will happily supply it in heaps.

"The basic, domestic quality thermionic tubes have codes for a projected life span of either 1500 (6Н3П-Е) or only 500 hours (6Н3П). Many were used and then stored for over 50 years, quality stamps may have been accidentally altered, so life expectancy may be questionable, both for the tubes and for me!"

I love the idea of an expiration date, or at least an ever-present need for repair. It emphasizes the idea that the computer is a machine, subject to the constraints of the physical world. There's something charming about that.

I restore a lot of 50s era tube radio equipment. The tubes are suprisingly robust!

I'm surprised at how many times _resistors_ go bad, and of course we all know that capacitors fail. But more often than not, all the tubes in a typical 5 tube AM radio I find are working.

Radio Shacks¹ used to have a tube tester machine in them.² I was always impressed that there was such a finite universe of tubes that a single machine could test all of them.

⸻

1. For the kids, this was a store that sold various electric gizmos including radios and circuit components, then later computer and televisions.

2. I think they may have also been present in hardware stores as well.

There was a tube tester in our town's main pharmacy.

So in principle you could pull the main tubes from (say) your TV and have at it.

I remember tube testers at grocery stores when I was a kid. I'd go with my dad to test tubes from our TV set, and buy replacements for burned out ones.

There's a HeathKit one up on Ebay now: 'Heathkit TC-3 Tube Tester'

And future proof! Made me question my sanity for a moment.

It's possible to build a switch so that these 62NP tubes are interchangeable with 12AX7 (or ECC83).

Instructions in this thread:

https://www.diyaudio.com/community/threads/6n2p-ev-vs-12ax7....

Pins 9 and 5 of the tube socket must be galvanically disconnected from the PCB. The switch is then interposed there.

I build Vacuum tube audio amplifiers, mostly Push-Pull class A's with EL84s. This is next level. Absolutely awesome!!

Ooh those must sound glorious! I've never played through one, but have been close to Vox AC30 guitar amps cranked up loud!

For non-musician HN'ers, if you've heard Brian May with Queen, that's the sound of overdriven Class A EL84s!

> They can switch several hundred million times a second, and in the 1950s they were combined with germanium diodes as the basis for many incredible computer designs.

Whoa, I didn't know they could switch that fast! Because afaik vacuum tube computers were measured in thousands of mathematical operations per second

I guess it’s highly dependent on the type of the tube. The documentation [1] for the 6N3P (the one Mike uses) talks about input resistance at 100 MHz, so the tube must handle at least as much.

[1]: https://www.istok2.com/data/575/

Keep in mind that's in relation to amplifying analogue frequencies around 100MHz. It doesn't necessarily mean you can make digital logic that runs at 100MHz

>using 18 bit instructions, it could be rented for $12,000 a month.

Release of the IBM700 utilized 6N3P diodes, that tend to burn out due to voltage alterations, until the 7000 series, with System 360 was transistorised.

> The IBM700 series was the most successful 1950s computer system. ... Able to handle 36 bit words using 18 bit instructions, it could be rented for $12,000 a month.

That's cheaper than an AWS p4d.24xlarge.

Not if you scale those dollars to 2024 Buck$. Back then, $12,000 was a lot of money. You could rent a whole office building, yearly, for that (actually, you could probably buy it, outright).

These days, there are flats in NY and SF that go for more than that.

Apparently 12,000 dollars in 1959 even is over $100,000 today: https://measuringworth.com/dollarvaluetoday/?amount=12000&fr...

“So please, what ever happens, please don’t give up.”

Love that - thank you!

How long before an audio manufacturer will implement some kind of DSP on this thing and marketing it as having "tube warmth"?

So, if this became sufficiently popular to a degree in which many more units like these were produced and released, and it was decided that they all should be connected somehow, in a sort of inter-network...

...it would finally be a series of tubes.

>They can switch several hundred million times a second

Huh. Wasn't expecting that.

Plus, we get free time travel to boot! Great project, I love it.

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