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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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...

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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.

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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.

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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!

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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.

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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.

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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.

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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.

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Re: Completely and utterly bonkers

Imagine if he'd used valves...

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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 :-)

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Pint

AN OUTRAGEOUS ERROR!!

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

The 'k' in kHz should be lowercase.

Thanks.

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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!

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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

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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.

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Re: AN OUTRAGEOUS ERROR!!

It was bitflip, ociffer.

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Beat the clock

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

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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.

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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.

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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.

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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.

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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.

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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 .

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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. )

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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.

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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.

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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.

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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....

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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.

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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).

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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

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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.

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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.

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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.

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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.

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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

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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)

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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.

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Re: Ladybird?

Project Books published by the Dairy Industry Council.

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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!)

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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?

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Pint

Where do I donate some transistors?

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

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Anonymous Coward

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

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Windows

Sponsorship...

Or sponsor a gate or two?

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Re: Sponsorship...

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

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

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Go

Hand Made Vacuum Tubes by Claude Paillard

No need for silicon! (Except in the glass, of course.)

https://www.youtube.com/watch?v=EzyXMEpq4qw

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Re: Hand Made Vacuum Tubes by Claude Paillard

Thank you. That was 12 minutes well spent.

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Re: Get some Silicon and get doping

Great suggestion. With a bit of care, he may even be able to put more than one transistor on the same piece of silicon, and save on all that tedious wiring interconnect. Perhaps he could use some sort of photographic system so that the repeating units don't have to be drawn by hand.

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Re: Hand Made Vacuum Tubes by Claude Paillard

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

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