NANDputer Is Mostly Wiring

We would wager that by weight this project is mostly wiring. We might go as far as betting that the wire outweighs the rest of the components 2 to 1. We’ll keep our fingers crossed that there’s never a loose connection, but for now it seems that [Kevin Horton’s] NAND-based computer project is up and running. Very nearly ever part of the build is based on NAND gates, which is why the point-to-point wiring is so crazy. There is one peripheral board which uses some non-NAND components, but he eventually plans on replacing that to make the system…. pure?

Now get ready for the crazy part. This is just one half of the program counter! There’s another board that looks just like it. The two join at least a half-dozen other boards of similar size and complexity to make a functioning computer. Crazy! The post shares a ton of details, but you can also just skip down after the break to see a video of it running a program.

If you’re wondering how a NAND-based computer works you should make your way through this online course.

[Thanks Jeroen]

24 thoughts on “NANDputer Is Mostly Wiring

  1. This is really impressive, Kevin! I see comments are closed on your website, but I would be interested in learning more about your design. For example, how did you build your flip-flops with only NAND gates? I’ve tried this, and while the basic types work, the more complex (and useful) ones like J-K and D are much harder.

    1. Hello Lee,
      Back in ancient times there were no libraries and you had to submit custom chip designs [at least for some vendors] in NAND gates. It seemed like as many were used for inverters as were used as gates. One advantage[?] of designing your own flops is that you can add only the features that you need. You can lookup an old TI SSI part like SN7470 [gated JK] and they will show the logic equivalent in gates. The simple way is to design logic to replace each gate. It takes 6 NAND gates to do a simple 4 input AND gate.

      1. That’s a good idea, MelllowFellow! My data books aren’t old enough to show the internal schematics, but I’ve seen that in really old ones. I’ll see if I can find one. My thought was to build something a bit less ambitious than this project; a digital clock with only gates.

          1. Ren: Pull out that box, and finish it up! We’d love to see it, and it will inspire others. :-) Don’t worry about a monitor program; there are literally dozens of them already written for the 8080. EPROM burners are cheap and easy to find. Even a hand wirewrapping tool is faster than soldering.

            Mikrysoft: Thanks for the tip. An old TI data book had just what I needed (internal schematics of real J-K and D flip-flops).

  2. I worked on something like this a few years ago for the open logic completion, tho not nearly this complex. I had the pure 7400 quad-NAND mindset like him and boy was it a nightmare! Excellent build and interesting read.

  3. Simply beautiful :) Nice job on everything! You have waaaaay more patience than myself. Keep up the good work and best of luck with the final project. I will definitely be looking for it on HaD :)

  4. I remember working on computers consisting of a dozen boards, all of which were the size of a laptop and mostly covered on one side with 7400 series chips and the other side completely covered in blue wire-wrapped spikes ;-)

    Talk about sucking power!

  5. I once started to wire wrap a small 8080 board, processor, ROM, RAM, 7-segment LEDs, serial chip. About 1/3 of the wiring was done, an engineer asked me what “monitor” program I was going to use, and how was I going to burn it into the EPROM. Huh? Whazzat?
    It is still sitting in a box in the garage…
    But if I should happen to find a cheap, working wire-wrap gun…

  6. Whats the chances of getting all meta on the nand concept, this guys a sadist for the wiring involved, so you print a pcb, which means lots of cad time ‘wiring’ it up. Could you write a script to do the pcb layout, automatically like?

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