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]
I love the 555 with supporting passives all on one chip socket
Yeah – that’s pretty good: you can change the period and pulse width without breaking out the soldering iron.
Love this part. I have several of them, plus the support chips. I had a friend that worked for a bio-medical company when they first came out, and he and I built up a MC14500B, switches, LEDs and a few other things on some of whatever that white board with the holes that always get reamed out and have nice intermittent connections. I also have a couple of the original red data books for this part.
I remember several years after we built that board this commercial for Honeywell or somebody like that, and they have this PCB 3D rotating onto the screen, proclaiming how the thermostat is computer controlled, and LO! you could read the MC14500B and the Motorola logo as it rotated by.
I build all my stuff with wire wrap and stweezer , and when Radio Shack out of business sale, I bought up every wire wrap wire, white red blue …. it is hard to trace a circuit when all the wires are the same color
Kudos to the builder!! Over clock it and see what happens
Think I got a few of these in a grab bag of CMOS and TTL from back in the day when hamfests were allowed, you know, 5 years ago back in 2019. ;-) … Anyhoo, will have to bookmark this to come back to when I need more insight in what to do with them. I think I pulled a basic datasheet that left me more confused than informed, i.e. cryptic pinout, hairy timing diagrams etc.
The 14500 has the wonderful attribute that the time it takes to execute a loop is independent of which way the branch instructions go. Means you can use the loop time as a constant for things like traffic lights and such.
I always wanted to build one and saw this as an option https://www.youtube.com/watch?v=5KeHVW0NO6M. But I got infected by Burkhard’s TPS/MyCo featured here a few times bug and there you have a 4 bit processor and are able to start programming / executing on paper only even – and just released it as workbook. On the MyCo TPS facebook site you can actually start programming using coins, pebbles or similar – Covid times need some distraction …
https://www.amazon.co.uk/gp/product/B08MN15NMQ/ref=dbs_a_def_rwt_bibl_vppi_i26
Now THERE’s a CPU that can be implemented in relays without requiring five packing cases to put it in. (https://hackaday.com/2020/10/23/relay-computer-consumes-six-years-and-4-5-suitcases/)
i like buttons, mechanic screen (like a Moon Nasa computer), or flight cocpit design switch.
make it and put to tinde, and add wifi for input output.
for example small program
while true
do
send wifi message
sleep
done
Does anybody know the part number of those square pushbuttons ?
They’re just an eBay special, but if you search for “transparent cap tactile switch” you’ll find them on eBay and Alliexpress
Excellent. Thanks.
We used these in the electronics module of my physics degree, fun little thing to program.
The board looks indeed lovely.
It’s a wonderful tribute to the MC14500B, I think.
By the way, remember this chip from the German magazine “CQ DL” or “Funkamateur”. If memory serves, in the late 80s/early 90s, it was used for an educational computer.
Also, if memory serves, the MC14500B was used for generating morse code. Among other things. Spraking under correction, though.
That’s truly a beautiful build! I might have to admit that I never produced a perfboard build that look even nearly as neat as this.
I can’t help but to mention the WDR-1 computer. A very similar thing, an educational project from the early 80s:
https://hackaday.com/2020/02/01/what-everyone-else-did-with-eight-bits-the-germans-did-with-only-one/
There is even an educational TV program about it. They explain the hardware the programming basics. All six episodes are available on youtube. In episode 6 they use the 14500 for industrial control applications: https://youtu.be/tshgyhyCK9U?t=327
episode 1: https://www.youtube.com/watch?v=iGVIs3Aczog
You don’t have to understand German to enjoy the show. The setting! The presentation! The outfits! And make sure not to miss the title sequence – 80s at its best.