A Single Board Computer, With Vacuum Tubes

We have occasionally featured vacuum tube computers here at Hackaday and we’ve brought you many single board computers, but until now it’s probable we haven’t brought you a machine that combined both of these things. Now thanks to [Usagi Electric] we can see just such a board, in the form of his UE-0.1, a roughly 260 by 210 mm PCB with 24 6AU6 pentodes on board that implements a simple one-bit CPU.

The architecture starts with the MC14500B 1-bit microcontroller, which was the subject of a previous vacuum tube computer. People found the unusual architecture difficult to understand, so this board is an even simpler take. It doesn’t have all the features of the Motorola original but it is (just) enough to be a CPU.

The tubes are arranged in groups of four with heaters in series from a 24 V supply, while the inputs and clock come in the form of on-board suitably retro-looking switches. The final touch is a VFD of the type used in bar graphs, were used to show the state of the various bits. It’s a fully working computer in the simplest sense, and definitely worth a look in the video below the break.

It would be interesting to see whether the tube count could be reduced further, or is this a record. The number of physical devices could be cut by using tubes with more than one device in them such as double-triodes, but perhaps that would be cheating.

Meanwhile, if you think vacuum computing is all about the old stuff, perhaps you should look at the state of the art.

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Too Cool For 8-bit Retro? Try 1-bit Gaming

While the world has been racing for higher and higher bit counts for CPUs, there are always those that buck the trend. Consider the venerable Motorola MC14500B, a 1-bit CPU, no kidding. [Usagi Electric] built up a computer based on one of these chips using a breadboard but has since pulled it apart to use the breadboard for other things. So this time, he’s made a permanent version on a PCB and created a simple game to show it off. You can see the result in the video below.

Well, the chip had one bit in the datapath. It did not have any memory, but it did have a way to feed it 4-bit instructions, and, as you might guess, there were 16 possibilities for instructions. The chip was meant to replace industrial controllers where even a PLC might be overkill, and apparently, it did see some use in the real world.

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Single Bit Computer From Vacuum Tubes

Culminating a year-long project, [Usagi Electric] aka [David] has just wrapped up his single-bit vacuum tube computer. It is based on the Motorola MC14500 1-bit industrial controller, but since [David] changed the basic logic unit into an arithmetic-logic unit, he’s dubbing it the UE14500. Built on a wooden panel about 2.5 x 3 rabbit lengths excluding power supply. [David] admits he has cheated a little bit, in that he’s using two silicon diodes instead of a 6AL5 dual diode tube in his universal NOR gate on which the computer is based — but in his defense he notes that plenty of vacuum tube computers of the era used silicon diodes.

The tube he uses in the NOR gates is the 6AU6 miniature pentode, which he selected because of its availability, price, and suitability for low voltage. [David] runs this computer with two power supplies of +24 and -12 VDC, rather than the hundreds of volts typically used in vacuum tube designs. The modules are constructed on single-sided copper-clad PCB panels etched using a milling machine. The video below the break wraps up the 22-part series, where he fixes a few power supply issues and builds a remote front panel for I/O, and gives a demo of the computer in operation. Alas, this only completes one fourth of the project, as there are three more building blocks to build before the whole system is complete — Program Control (magnetic tape), RAM Memory bank, and a serial input/output module. We look forward to seeing the whole system up and running in the future.

We just wrote about the MC14500 a few days ago, and we’ve also covered [David]’s vacuum tube implementation of a 555 timer among other of his vacuum tube projects, several of which are featured on his Hackaday.io page.

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One Bit CPU Runs At A Blistering 60Hz

If you really think hard about it, a CPU is just a very general-purpose state machine. Well, most CPUs are, anyway. The MC14500 is a one-bit computer that has only 16 instructions and was meant to serve in simple tasks where a big CPU wouldn’t work for space, power, or budget reasons. However, [Laughton] took the idea one step further and created a single-bit computer with no real instructions to control a printing press. The finished machine uses a clever format in an EEPROM to drive an endless program.

Honestly, we’d say this is more of a state machine, but we like the idea of it being a minimal CPU which is also true. The design uses the EEPROM in an odd way. Each CPU address really addresses a block of four bytes. The byte that gets processed depends on the current phase and the status of the one-bit flag register.

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Gorgeous Perfboard Build Puts 1-Bit Controller Back To Work

Eight-bit computers are all the retro rage these days, with people rushing to build computers either from chips like the 6502 or the Z80, or even recreating these chips from a collection of TTL logic chips. And while we respect and covet those builds immensely, 8-bit computers aren’t the only game going on. To wit we present this lovely single-board computer sporting a 1-bit CPU.

The machine, which creator [Simon Boak] cheekily dubs “the world’s least-powerful computer,” is based on the Motorola MC14500B, a chip from the 1970s that was aimed at the industrial controls market. There, the chip’s limited instruction set and narrow bus width were not as limiting as they would be in a general-purpose computer. In fact, since the chip requires an external program counter, it offers a great degree of design flexibility. [Simon] chose a 4-bit address space, but with a little wizardry he was able to get eight bits of input in the form of DIP switches and eight bits of output LEDs. It’s not good for much past making lights blink, but it does that with nary an Arduino in view — although it does sport a couple of 555s.

[Simon]’s goal for the build was simply to build cool from an unusual chip, and we think he succeeded. In fact, we can’t recall seeing a neater perfboard build — it’s almost to the level of circuit sculpture. We especially like the hybrid solder and wirewrap construction. We’ve seen builds based on this chip before, but never one so neat and attractive.

[via r/electronics]

What Everyone Else Did With Eight Bits, The Germans Did With Only One

In the 1980s there was an impetus for the first time for young people to be equipped with computer literacy. A variety of different educational programmes were launched, typically involving a collaboration between a computer manufacturer and a broadcaster, and featuring BASIC programming on one of the 8-bit home computers of the day. One such educational scheme was a bit different though, the German broadcaster WDR produced an educational series using a modular computer featuring an unusual 1-bit processor that was programmed in hexadecimal machine code. [Jens Christian Restemeier] has produced a replica of this machine, that is as close to the original as he can make it. (Video, in German, embedded below.)

The computer is called the WDR-1, and had its origin in a kit machine before it was taken up by the broadcaster. The unusual 1-bit processor is a Motorola MC14500, which was produced from 1977 onwards for industrial control applications. He takes the viewer in the video below the break through the machine’s parts, explaining the purpose of each daughter card and the motherboard. Lacking an original to copy he instead worked from photographs to replicate the chip placements of the original, substituting pin headers for the unusual sockets used on the 1980s machines. Take a look at his video, below the break.

More information on the WDR-1 can be found online in German (Google translate link). Meanwhile we’ve featured the MC14500 before, in a small embedded computer.

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Building An Industrial Control Unit With An Industrial Control Unit

Back in the 70s, industrial control was done with either relays and ladder logic or new programmable logic controllers. These devices turned switches on and off, moved stuff around a factory, and kept the entire operation running smoothly. In the late 70s, Motorola came out with an Industrial Control Unit stuffed into a tiny chip. The chip – the MC14500 – fascinated [Nicola]. He finally got around to building an ICU out of this chip, and although this was the standard way of doing things 30 years ago, it’s still an interesting build.

[Nicola]’s ICU is extremely simple, just eight relays, eight inputs, the MC14500, a clock, and some ROM. After wiring up the circuit, [Nicola] wrote a compiler, although this chip is so simple manually writing opcodes to a ROM wouldn’t be out of the question.

To demonstrate his ICU, [Nicola] connected up an on/off switch, a start button, and a stop button. The outputs are a yellow, green, and red lamp. It’s a simple task for even a relay-based control scheme, but [Nicola]’s board does everything without a hitch.

If you’re looking for something a little more complex, we saw the MC14500 being used as an almost-CPU last year.

Video below.

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