42,300 Transistor Megaprocessor Is Complete

As it turns out, the answer is not 42, it’s 42.3 — thousand. That’s how many discrete transistors spread across the 30 m2 room housing this massive computation machine. [James Newman’s] Megaprocessor, a seriously enlarged version of a microprocessor, is a project we’ve been following with awe as it took shape over the last couple of years.

[James] documented his work in great detail, and by doing so, took us on a journey through the inner workings of microprocessors. His monumental machine is now finished, and it’s the ultimate answer to how a processor – and pretty much everything that contains a processor – works.

8 bytes of Megaprocessor RAM (ca. 200 x 200 mm)

Everyone of the ~42,300 transistors were hand-soldered to one of the massive PCBs, which look more like interactive circuit diagrams than actual circuit boards. This incredible amount of discrete transistors makes up the thousands of logic gates that eventually form the Megaprocessor’s registers, its arithmetic logic unit, its sequence control and also: its 256 bytes of RAM. Each logic gate displays the current IO state through LEDs, which also turns the RAM into a gigantic LED wall on which you can play Tetris.
Despite its complexity, the Megaprocessor is pretty much self-documenting. [James] mounted all PCBs on large frames, which add up to a 10m long and 2m tall “computation display”. Detailed diagrams show the information flow between the functional blocks – and through the room. At full throttle, it runs at about 8 kHz clock frequency, but to follow the execution of a single instruction you can just turn it down to 1 Hz, or even stop the processor to study its state.

[James] wasn’t always sure how many transistors the build would eventually require since it was hard to predict how many 8 Byte RAM cells – which consist of 766 transistors and 64 LEDs each – a single human can solder before the madness kicks in. It has not been easy, it has not been cheap — but it’s an idea that haunted [James] for more than a decade now, and it’s amazing to see it finished. Enjoy the video where [James] takes you on a tour through the machine:

It seems that building discrete processors is all the rage this days. Just a couple of months ago we got a good look at a 6502 processor faithfully recreated with individual transistors.

83 thoughts on “42,300 Transistor Megaprocessor Is Complete

          1. Anyway, jokes are like any other hack–it’s the effort that counts. You get to criticize after you’ve made a better one yourself. :-)

          1. I just reverse-searched that image and am laughing my ass off!
            I should pay my cable bill the same way. :D
            Best 7 legged spider drawing ever!

    1. I hope he gets sponsorship to take this thing on the road. People need to see this in person. The biggest failing of technology is the abstract nature of ever smaller devices. Although still beyond comprehension for most people, seeing the huge build, and being talked through the overarching use of each module of the machine will help people relate to the computers that run their lives.

      1. I think if we could get these in schools/universities they would make one of the best teaching aids ever. It’s all very well teaching the fundamentals and having the students visualise what is going on in their heads but with this you can see exactly how things work.
        I love this and wish I could go and see it and have a little play around.

          1. Yeah I agree sadly but even if a smaller more mass production friendly version was too offshoot it would be great. failing that I hope he takes it out on the road and shows as many people who are learning as possible.

          2. The choice of hand-soldered through-hole is a bit insane, especially if you want more than one.

            If it were re-designed to use super-cheap surface-mount transistors (e.g. 2N7002) then it could be mass-produced in China quite affordably. And by affordable, I mean there’s still about $400 of transistors in it plus $1k in PCBs and $1k in assembly costs and and … maybe $5-10k all up instead of the $60k this guy spent.

        1. I dunno, as a teaching aid. You don’t need to understand every transistor in a CPU. You just need to learn that so many transistors make a gate, or a RAM element. Then cobble some gates into a full adder and some other components. Then go up from there. Modularity, keeping things on different levels of abstraction, is how we manage to invent things like that in the first place. Single-transistor level is just for people debugging or optimising 8-bit processors in the 1970s. Even then I’m sure most of the design was done on higher levels of abstraction.

      2. Does he need sponsorship to do that? I’m thinking it could be easily installed in a converted (and well cleaned) horse trailer and powered by an off the shelf backup generator. Both could probably be obtained cheap at an auction.

        Ok, that isn’t exactly in the price level most of us consider spending just to show off a build but considering what he has already spent it isn’t really that much. Anyway, then it would be a simple matter of parking it in a maker faire parking lot and opening the door.

        1. Because of it’s relatively flat shape, I would suggest hinging it so that all the panels fold into one flat rectangle. Some wheels on the bottom of each panel would assist setup and perhaps a caddy to get it through doorways and hallways – depending on it’s size.

  1. Spending over USD 50000 on a hobby project sounded a bit over the top to me until I realized that spread out over three years is “only” about 1500 per month which is a bit more reasonable. But my wife would still kick my ass if I spent that much… I guess this guy is either single or have a *very* understanding partner.

    1. I can promise you that this guy is single. He has no time for a woman when all he is doing is blowing money and being tied up in a super-nerd hobby project.

      Pretty sweet build though.

        1. Yah. Another person commented about taking it on the road. I commented that he should permanently mount it in a trailer. I didn’t say it there but that was a dual-purpose suggestion.

      1. I would not assume such things to quickly. There are a lot of tech savvy girls (and guys) out there that would enjoy having their…. registers poked or their… bits shifted..

      1. Agree That kind of burn rate is unusual for someone in that age group. Most would still be paying off student loans or mortgages.

        $50K when invested for 10 years – assuming 6% return rate, 2% inflation rate
        Gets $40K worth of return (before inflation) and $73K total (investment+return) after adjusted for inflation.

  2. Really really inspiring! Love the memory wall.
    All those leds! Great visualization of the inner workings.
    Don’t let me near that room… I wouldn’t be able to leave on my own power. ;)

    1. +1
      Needs a second megaprocessor somewhere else in the building so that he can play Tetris with another person. Would need some giant modem panels on the wall I think. ;)

  3. “But I still managed to get maybe a dozen or so transistors in backwards across the project. And I find them really difficult to spot. See how you get on. ” – http://www.megaprocessor.com/GBU_build_faults.html
    This is what hacking is about, the hours you spend going back over things to find its your own simple human error, the head-bashing and ability to collect have the stories like ‘I spent 2 days going around in circles until I found I had [xxxx]’, but thats how we learn, and that is why this project is a master of hackery. Great job and great for sharing sorts of insights like ‘If I had my time again what would I do ?’….

  4. I am sure that lots of us have considered doing exactly what he has done.

    I think this is indeed a great build and his insight into CPU design now is fantastic!

    Maybe London science museum would be a good place to keep it so that that lots of people can enjoy looking at it and learning from it?

    1. Perhaps he could rent it out as a feature from time to time – for museums and educational facilities.

      As it *is* unique – it would present unique opportunities in the education sector. Really, the way a CPU works hasn’t changes that much at a transistor level.

  5. This is a museum piece. It is the ideal initial display in a computer museum. What is a computer? Hopefully someone will buy it at an appropriate price and place it in a museum. Those of us who understand the inner workings tend to underestimate how opaque the verbal descriptions are to most people.

    Of course, I prefer the discrete 6502. But that’s because it was the first processor I studied in detail. Which was lucky, as it was far more elegant than most of its contemporaries.

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