Powering up a module from the IBM 604: an electronic calculator from 1948

https://www.righto.com/2026/06/ibm-604-thyraton-tube-module.html

by elpocko • 2 months ago

92 29 2 months ago

kens7• 2 months ago

Author here for your vacuum tube questions...

Have you ever run into that method (discrete module+components) in non-IBM configurations? What abut non-computing configs? I've never seen it before.

kens7• 2 months ago

I powered up the module independently, powering a light bulb, so it's a non-computing configuration. (I'm not sure if that's what you're asking.)

kens7• 2 months ago

Univac had similar single-tube modules (but without the handle), as well as multiple-tube modules. See this video: https://www.youtube.com/watch?v=NVbjXHR6WAY The BRLESC computer used printed-circuit boards that had components and a single tube (parallel to the surface). I have a Burroughs module with 8 tubes.

analog31• 2 months ago

Philbrick op amp K2-W was an analog circuit with two dual-triode tubes on top of circuitry, with an octal plug at the bottom. I have one with data sheet but have never fired it up.

fredoralive• 2 months ago

Roughly how many varieties of module were used for a full 604 system?

I suspect quite a few as other "modular" systems in the transistor era like the later IBM Standard Modular System and DEC Flip-Chips ended up with plethora of specialised modules, but I'd be interested if that growth had already begun in the tube era.

kens7• 2 months ago

I don't have the information for the 604, but the 605 used about 36 different types of tube modules. IBM couldn't resist making different types of modules; the 650 had sixteen types of cathode followers alone.

andrehacker• 2 months ago

No vacuum tube questions.

Fantastic deep dive as always, thanks for doing such stellar work!

On that note, any chance we might get a teardown/history of Cray architectures in the future? Specifically the Cray-1 and 2?

To throw a more serious challenge your way: How about a write-up on the original Frank Rosenblatt Perceptron? I know finding an original Mark-1 part would be close to impossible but it blows my mind that they were successfully doing real-time visual classification in 1957 with an electro-mechanical machine (potentiometers and motors) using a 20x20 "video" feed with some learning algorithm that was not based on backprop.

somat• 1 month ago

With regards to the more advanced tubes (tetrodes, pentodes, etc) Was there any experimentation with integrated circuits before transistors took over? Put 10 tubes in the same enclosure, 100.

I am imagining something like a vacuum florescent display but with logic instead of display elements.

avian• 1 month ago

I think solid state technology came too soon for the miniaturization of vacuum tube technology to be fully explored. Ken mentions in one of his older posts that even in these old tube-based IBM computers a lot of digital logic was in fact already done with semiconductor diodes, not vacuum tubes. Optimizations like the nuvistors never took off because semiconductors were already more economic.

I guess you could do a whole circuit on photo-etched or stamped sheet metal inside a glass envelope in a similar process that VFDs, although I don't know how you would implement cathode heating. It would be an interesting exercise to think where that could lead you, but I think modern VFDs date much later, when semiconductors already wholly replaced tubes in digital logic.

What fails in a tube is usually the heater filament, which is a wear part with a limited life. Where some (very) expensive tubes did go is to have replaceable heaters - so not more but less integration.

labcomputer• 1 month ago

I think the Compactron is what you’re looking for: https://en.wikipedia.org/wiki/Compactron

Retro_Dev• 2 months ago

No questions, but I really enjoyed the article - thank you for sharing. It amazes me how few vacuum tubes these early computers use, compared to the billions and trillions of mosfet transistors used in modern devices.

kens7• 2 months ago

One way they get away with using relatively few tubes is that most of the Boolean logic is done with semiconductor (germanium) diodes, using tubes to amplify the results.

summa_tech2• 1 month ago

Tubes can also just be very _clever_ in a way that transistors generally are not. For instance, counting tubes that would contain a decimal counter in a single glass bubble (that's quite a few transistors even in TTL, and about twice as many in CMOS). Multiple approaches to building such tubes existed. This is one:

https://lampes-et-tubes.info/cd/cd053.php?l=e

Or the complicated and impressive storage tubes, that would fit 16 kbits of RAM in a single CRT:

https://lampes-et-tubes.info/sc/sc022.php?l=e

By the way, this website is one of my favorite finds on the Internet and very long-running.

userbinator2• 2 months ago

The 604 isn't really a "computer", but more like an ALU hardwired to some I/O.

rahen• 2 months ago

The Gamma 3, which competed with the 604, only had about 400 tubes as far as I remember: https://en.wikipedia.org/wiki/Bull_Gamma_3

Both the 604 and the G3 were bit serial to save components.

Animats• 2 months ago

That's a machine from IBM's 600 line, cost-effective business machines that did automated arithmetic. The IBM 601 (1931) read and punched punch cards, multiplying fields as set by a plugboard. It was entirely mechanical. The IBM 602 (1946) was similar, and could divide. The IBM 602A ("a 602 that worked" 1948) was in wide use into the early 1970s.

IBM had been working on electronic arithmetic prior to WWII, and the IBM 603 Electronic Multiplier (1946) was IBM's first deployed product with large numbers of tubes. It was built to find out if tube machines could be successfully deployed in a business environment and used commercially without constant tending by skilled technicians. That was the commercial limitation - the ENIAC and UNIVAC sized machines required large numbers of on-site techs to keep the hardware going. The 603 didn't. All IBM machines at the time were rented by IBM, and rental included on-site servicing by IBM Customer Engineers in white shirts and ties. IBM had to keep the servicing cost down. IBM was only willing to deploy tubes if the operating and maintenance costs were acceptable.

The 604 was a more commercial version of the 603. The 603 looked like a very large suitcase built of black perforated metal. The 604 looked like IBM's other tabulating machines and had better access to the components. This was the first high-volume product with tubes.

None of these machines had much memory. Just a few registers. There were no good memory devices yet suitable for field deployment. They were all programmed with plugboards. Everybody involved knew they needed better programmability, and there was an effort at Columbia University in the 1930s to do that. It involved Eckert and Mauchley, who went on to design the ENIAC and the UNIVAC I. But there was no good place to put the program.

The memory problem persisted for years. Williams tubes were unreliable. Acoustic delay lines had temperature stability problems. Rotating drums could work at a commercial price point. The IBM 650 (1953) was IBM's first real business computer, with drum main memory and all-electronic computation. Knuth's first book is dedicated to the IBM 650.

This side of computing gets less attention in histories, which tend to focus on the military machines. But this was the side that shipped in volume and made real money. It came from the engineers with relays and clutches in Endicott and the accountants at Armonk, who had to develop something IBM Sales could sell to large and medium sized businesses. No need for Turing, von Neumann, etc.

The IBM 1401 (1959) ended the 600 line. At last, all-transistor, all core memory, in a reliable box that could be deployed to customer sites. It's a very strange machine, with variable-length everything, but it works well. Then, of course came the IBM System/360, which standardized architecture for decades to come.

kens7• 2 months ago

Nice summary! For anyone interested in these systems, the book "IBM's Early Computers" provides a detailed history.

userbinator2• 2 months ago

They were all programmed with plugboards.

Arguably, that is the ROM.

dare944• 2 months ago

Arguably more like soft wired CPU logic, since the contents of the plugboards were not uniformly addressable words.

WarOnPrivacy2• 2 months ago

I haven't seen a tube deployment like that before - where the tube is combined with it's supporting components into one module - and that module plugs into a tube socket.

It's clever. It should reduce time for some repairs.

Gibbon1• 1 month ago

If they're the same you can swap them and see if the problem changes. Otherwise swap in known good ones till to works.

Old bus based systems you did that too. I remember once sending a dozen cards to a customer who had an intermittent issue.

jsrcout• 2 months ago

1948 was an interesting time for computing.

Not a commonly seen statement :-)

ChocMontePy• 2 months ago

My favorite part was a footnote: Footnote 2 specifically. I'd always wondered how plugboards worked and the footnote and the linked pdf gave me some sort of idea.

hilbert422• 1 month ago

I still have well over a dozen of those IBM modules together with their paperwork and circuit diagrams (somewhere in my miles of files).

They've been getting in the way and I've been meaning to chuck them away on many an occasion but something inside me has stopped me doing so because of their possible historical value.

Shirriff's blog has reinforced my thinking, they'll just have to clutter up my place for a little longer methinks.

kens7• 1 month ago

I'd be interested in scanning the drawings if they aren't already scanned. If you want to get rid of the modules, I can set you up with a museum.

hilbert422• 1 month ago

I've not scanned them, I'd have to find them first and that's not easy at moment because they're among tens of thousands of docs that need sorting (I rarely chuck out docs like that).

How I came by them was by accident when I was helping a guy who was a worse (indiscriminate) hoarder than I am move his tooling and machining factory. He hoarded anything technical, especially electronics stuff.

He didn't know what the circuits were but I did. Despite having little interest in either the modules or circuits instinct made me rescue them (it's a fluke they weren't scrapped). Reason: I once recall hundreds of these modules flooding onto the auction market and no one wanting them except for the tubes so I assumed everyone who'd be interested was already in the know.

The circuits (if I recall correctly—the factory move was in 2012) were together in a big folder a bit too big to scan on a quarto/A4 scanner.

Incidentally, there were stacks of old IBM computer racks that IBM historical people had rescued earlier (presumably the modules were from the same computer) but the modules and circuits surfaced later and never ended up with the rest of the hardware.

I'd be very surprised if others don't possess copies of those folders of circuits (computer historical societies etc.) as at one time those modules were so ubiquitous.

Seeing there's interest I'll hone in on them as I sort through the files (I know roughly what room they're in). The moment I find them I'll put them on line.

In the meantime I'd urge you to seek out copies of those circuit folders. IBM documented everything so well, their manuals were masterpieces of documentation in their own right (unlike the terrible situation of today where tech info on products is as scarce as hen's teeth).

Re museum, I'm in Australia so I'll seek out the mob who took the racks and try to mate the modules with the rest of the H/W. Thanks for the offer.

Powering up a module from the IBM 604: an electronic calculator from 1948

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