back to article This whopping 16-bit computer processor is being built by hand, transistor by transistor

A bloke in Cambridge, UK, is building a computer processor using 14,000 individual transistors and 3,500 LEDs – all by hand, piece by piece. James Newman said his Mega Processor relies almost entirely on the hand-soldered components, and will ultimately demonstrate how data travels through and is processed in a simple CPU core …

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  1. Steve Crook
    Thumb Up

    Completely and utterly bonkers

    But I hope he manages to complete it and find a home for it because it'll be a wonderful achievement.

    I'm assuming it'll go abroad because that's where most great British technology ends up...

    1. Martin Taylor 1

      Re: Completely and utterly bonkers

      Doesn't have to go abroad, bring it to the Museum of Computing in Swindon if they have space (it's almost abroad, I guess, from a Cambridge perspective). It may not be truly a museum piece yet, but it's undeniably a brilliant educational tool.

      We have good beer, too.

      1. Spiracle

        Re: Completely and utterly bonkers

        If they'll take it in at the Cambridge museum he'll be able to throw a couple of spools of solder into his bike basket and cycle down to finish (or, more likely, mend) it.

        1. TRT Silver badge

          Re: Completely and utterly bonkers

          It could also find a home as the set of some homage Sci-Fi production, along the lines of Space:1999. Now that was a computer with a lot of lights!

          1. Anonymous Custard Silver badge
            Thumb Up

            Re: Completely and utterly bonkers

            Given some of the stuff they put in there, he could probably get a room in the Tate Modern for it for a while too.

            Wonderful stuff anyway, hope it doesn't drive him too crazy getting it finished and debugged.

      2. This post has been deleted by its author

    2. Steve Crook

      Re: Completely and utterly bonkers

      If you haven't, go and look at the WEB site for the project. It's fascinating, board construction, component layout, testing, managing connections. Amazing breadth of skills the man has.

      From his site:

      "I spent a bit of time trying to work out how to do the 7-segment display using discrete transistors but the answer is vast. Really, really big. It would have near doubled the size of the thing and the circuitry for the display would have obscured the circuitry for the processor which would have undermined what I was trying to do. As its only for debug and not proper function I went for chips. This is definitely NOT cheating, it is just for debug. It is irritating though."

      And

      "The RAM's turning out to be quite sizable. A square inch per bit ! I'm hoping to do 64 bytes, but that translates to the best part of two square metres."

      Really, I had to laugh. Sizeable? Not half it isn't.

      1. bonkers

        Re: Completely and utterly bonkers

        As the final arbiter of all things Bonkers, I approve, wholeheartedly.

        I actually know the guy, we discussed this in the kitchen at work just a few months ago.

        I suggested he use these new "chip" things you can get.

        1. TRT Silver badge

          Re: Completely and utterly bonkers

          Imagine if he'd used valves...

          1. Roq D. Kasba

            Re: Completely and utterly bonkers

            Seems to me this would be a great project to distribute between many enthusiasts - lots of similar modules, so publish the schematics and a bill of parts, enthuse a bunch of others, and spend the time integrating :-)

          2. Fatman
            Joke

            Re: Completely and utterly bonkers

            Imagine if he'd used valves...

            There are several examples of those monstrosities around.

            Here is a list:

            https://en.wikipedia.org/wiki/List_of_vacuum_tube_computers

            1. metasonix

              Re: Completely and utterly bonkers

              >There are several examples of those monstrosities around.

              None of which are actually functioning today. The Computer History Museum in California has a number of historic tube computers which would be a nightmare to restore to working order. Most of them used magnetic drum memories, guaranteed to be nonfunctional and almost impossible to repair. The only tube computer that is functional today is the Colossus replica at Bletchley Park, and it's not even a "general purpose" computing device.

              1. Phil Endecott Silver badge

                Re: Completely and utterly bonkers

                > None of which are actually functioning today.

                The Manchesterr "Baby" replica in the museum of science and industry is functional. Or was last time I visited.

              2. Chemist

                Re: Completely and utterly bonkers

                "None of which are actually functioning today"

                AFAIK the replica of the Manchester 'Baby' is around and ran in 1998. I was taught physics by a chapvwho worked on the original and had a photo of himself, stripped to the waist, working in basement surrounded by racking

      2. Phil O'Sophical Silver badge

        Re: Completely and utterly bonkers

        The RAM's turning out to be quite sizable. A square inch per bit !

        Sounds like he's using static RAM, maybe he should have tried a dynamic RAM design? With decent capacitor sizes he wouldn't have too fast a refresh cycle...

        I suppose core memory would be better still, if he's into knitting!

        1. elDog Silver badge

          Re: Completely and utterly bonkers

          The hum from those cores would be amazing. And to replace a burnt-out one? I remember the days when we "programmers" would write a loop to flip a bit on and off and get that one core very toasty red.

    3. Fortycoats

      Re: Completely and utterly bonkers

      Of course it's completely bonkers. It even has an "Igor" (4th module from the left in that basic mock-up diagram). No mad-scientist project is complete without an Igor.

      Yeth, marthter......

      Well done that man. Hope it works out.

    4. JeffyPoooh Silver badge
      Pint

      AN OUTRAGEOUS ERROR!!

      "...20,000 instructions per second from a 20KHz clock."

      The 'k' in kHz should be lowercase.

      Thanks.

      1. zhveurnq

        Re: AN OUTRAGEOUS ERROR!!

        It was bitflip, ociffer.

      2. Daniel von Asmuth Bronze badge

        Beat the clock

        I wonder what's keeping him from increasing the clock speed.

        1. Phil O'Sophical Silver badge

          Re: Beat the clock

          I wonder what's keeping him from increasing the clock speed.

          Propagation delays across those square metres of panels, I'd guess.

          1. adam 40

            Re: Beat the clock

            It's only 14m long. Assuming 0.7c because of the dielectric of the wires that would be 66.6ns propagation delay end-end. So you could run is under 15MHz, say 1MHz should be do-able.

            With the current speed it still beats the 1957 all-valve DASK.

            1. Charles Manning

              Re: Beat the clock

              It's the capacitance, not the length.

              Those wires act as huge capacitors which need to charge and discharge on each cycle to allow the signal to stabilise.

              1. Nigel 11

                Re: Beat the clock

                Those wires act as huge capacitors which need to charge and discharge on each cycle to allow the signal to stabilise.

                Not huge.

                The general rule for a signal to settle on a plain old wire is something like six times longer than the speed of light along the wire. (Or two to-and-fro bounces at 0.7c)

                I've often wondered what is the optimum design for a discrete-transistor computer. Minimise the transistor count, build as small as possible, and clock as fast as possible, or go for wider buses and more transistors clocking more slowly? (Of course in the early days they went for small component counts, because transistors - germanium alloy junction ones - were significantly expensive, and suffered thermal runaway at fairly low temperatures so cooling really mattered. )

            2. ChrisBedford

              Re: Beat the clock

              "It's only 14m long. Assuming 0.7c because of the dielectric of the wires that would be 66.6ns propagation delay end-end. So you could run it under 15MHz, say 1MHz should be do-able"

              Yeaaahhhh... I only know a tiny little bit about RF, so I might be talking complete rubbish here, but wouldn't there be radiation issues? I seem to remember that one of the constraints on the original IBM PC (4.77 MHz) was that pushing the clock any higher led to disproportionately high energy losses to radiation (and of course interference with your transistor radio!), and that on a printed circuit board of much less than 2 sq ft. I imagine that a 14m long assembly with lots of interconnecting cable and hand-soldered assemblies might have a slightly worse problem with that.

              1. Nigel 11

                Re: Beat the clock

                Take a look at a photo of an old enough computer that the CPU consisted of a large number of logic modules connected with a wire-wrapped backplane (for example Google "Images PDP-8 Backplane). You'll soon deduce that the interference problem is not insurmountable. It was not negligible, though!

                The routing of wires within the backplane was a black art. Some were artificially lengthened so as to introduce deliberate signal delays. Others took non-parallel routes from A to B to reduce crosstalk - interference is by far the greatest between closely parallel wires. The general term was "random-wired". It was most definitely not a good idea for structure in the circuit schematics to be explicit in the physical arrangement of wires in the backplane.

          2. Andrew Torrance

            Re: Beat the clock

            My final year university project was something similar , building a bit sliced processor . The limiting factor on speed for us was the capacitance and length of the cabling . I expect it will be similar for this guy .

            1. Michael H.F. Wilkinson Silver badge
              Pint

              Re: Beat the clock

              Maybe he is initially being conservative. I bet there is some room for overclocking this BRILLIANT piece of work that I am certainly going to feature in next year's "Introduction to Computing Science" course that I teach.

              1. Simon Harris Silver badge

                Re: Beat the clock

                He found out that a state transition takes about 1uS to propagate through a gate, and to work right through an adder was about 40uS (change on the LSB through to carry out) - it's this that sets the maximum clock frequency.

        2. picturethis
          Mushroom

          Re: Beat the clock

          To some degree it not just the length of the wires, but the differences in length wrt the frequency being used.

          I sure hope he's keeping the length of the wires (as appropriate) the same to each (and within) similar functional banks of transistors, otherwise the differing propagation delays will be madness to try to debug. This is normally done at chip layout and PCB layout. Clocking in incorrect bits (on some lines) and not others would surely lead to a long stay at a mental institution.

          Slowing down the frequency until it worked might be practical, but with a little attention to the lengths, he might find that he could run at a much higher frequency. Overclock - baby....

      3. Old Handle
        Joke

        Re: AN OUTRAGEOUS ERROR!!

        You're not familiar with Kelvin-Hertz? It's a measure of how much a computer heats up per cycle. Although at 20 Kelvin-Hertz this design does seem fairly impractical.

      4. jeffdyer

        Re: AN OUTRAGEOUS ERROR!!

        kHz or KHz is valid, after all, little "m" means "milli", big "M" means "mega", as kilo = 1000, it is a multiplier and can be K. But from wikipedia:

        * The engineer's society, IEEE, and most other sources prefer "kHz" to "KHz." This apparently makes it less likely that users will confuse "kilo" (decimal 1,000) with the computer "K" (1,024).

  2. Hans Neeson-Bumpsadese Silver badge
    Thumb Up

    Yes!

    In a world where school "IT" lessons revolve around how to use PowerPoint, *this* is exactly what we should be doing to show kids how proper IT works.

    1. Terry 6 Silver badge

      Re: Yes!

      Absolutely,

      I'm no fan of "coding" in schools.

      Which seems to be pretty pointless for most kids.

      But if we're showing the kids what is actually under the bonnet and then letting them try to make it do something there's a chance that some ( the right ones ) will be inspired to really get involved.

      1. hplasm Silver badge
        Thumb Up

        Re: Yes!

        I seem to remember a ladybird book ( I think) with a computer made from wood and OC71 germanium transistors, and some dairy/milk Co series* of many-how to booklets that did the same sort of thing.

        Where are these sort of things now...?

        *can't find them on Goog - they were thin, square and white, with blue titles etc.

        1. Hans Neeson-Bumpsadese Silver badge

          Re: Ladybird?

          Are you sure it was Ladybird. The content sounds like the sort of thing that used to be in MacMillan books (squarish format, white cover with thin orange/red border).

          Either that, or something out of Professor Branestawm perhaps

          1. J.G.Harston Silver badge

            Re: Ladybird?

            Project Books published by the Dairy Industry Council.

        2. Charles Manning

          Re: Yes!

          Was the wood + gerrmanium transistors not a book on radio? I have a copy of one of those.

          The "computer" I remember from one of these books was nothing more than a continuity-based wire game thing that buzzed or lit up when you connected 2 + 2 = to 4.

      2. Tocsin

        Re: Yes!

        Our maths teacher did this to us in 1971 - built on vero boards, 16x 8bit memory, accumulator, command register, counter and a few gates... after one or two attempts to do other things, I spent a (mostly) enjoyable career in IT ;)

        (I still have the manual!)

    2. Sgt_Oddball Silver badge

      Re: Yes!

      If it helps I remember managing to make a desk calculator (not this beasty but still) getting binary to work on a hardware level is not easy but really fun (for the geeky types anyways)

  3. Anonymous Coward
    Anonymous Coward

    Awesome! I cannot approve more of this project - what a geek, utterly awesome!

    Cambridge Uni: He mentions space is a problem for the final CPU, please promise this guy a room for a few months to demo the finished CPU - knowing this will surely aid his motivation.

    Funding: How much is this all costing? Where do I donate some transistors?

    1. A Non e-mouse Silver badge
      Pint

      Where do I donate some transistors?

      Transistors? Give the bloke beer. And lots of it.

      1. Anonymous Coward
        Anonymous Coward

        Maybe best to save the beer for when he's finished. :-)

    2. keithpeter
      Windows

      Sponsorship...

      Or sponsor a gate or two?

      1. TRT Silver badge

        Re: Sponsorship...

        They'll name them after you. I hear Bill has a few already.

  4. TedF

    The Fellow is a fraud! Commercially made transistors? Pah! Get some Silicon and get doping...

    1. This post has been deleted by its author

      1. James Cane

        Re: Hand Made Vacuum Tubes by Claude Paillard

        Thank you. That was 12 minutes well spent.

        1. Martin-73 Silver badge

          Re: Hand Made Vacuum Tubes by Claude Paillard

          Seen this video dozens of times. It's worth the 17 minutes every time. More wine!

      2. Nigel 11

        If you really want to go off-piste ...

        A technology that existed in Babbage's time, but of which Babbage was unaware, is hydraulic logic. It's possible to create a bistable out of fluid (air) being pumped through an appropriately shaped cavity, and to switch it between its two stable states using pipework connected to the output of others. Logic gates are also feasible.

        Anyone fancy building the world's first (?) hydraulic programmable computer?

        Or even a simulation thereof, just to hear what it might sound like while it is computing.

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