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 …

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

re: hydraulic computers, there was MONIAC but I'm not sure if it counts as hydraulic (involving water pressure in some useful way) or a computer in the usual sense.

What prompted me to reply, though, was that I just recently came across the idea of a hydraulic ram pump. Sounds like it would make an excellent component in this speculative machine.

Now you've got me thinking about powering stuff with water in Minecraft :(

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Gosh. Well done thet man! Although if I'd had the knowhow and wherewithal, I'd have gone for replicating a 6502, always prefered the instruction set for them over the 8080. Less transistors to connect up, too, apparently (I'm astonished the 6502 used so few - I honestly thought it was more like an order of magnitude more than that!).

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Looking at that table the 6502 was something of a wonder of efficiency, makes ARM look hefty..

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The finished circuitry, when mounted on a wall of boards, will measure 14 metres long and 2 metres high (46ft by 6.6ft), will weigh about a half-ton, and will consume 500W.

So a bit like my old XT then?

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As the current owner of a PC XT, I can confirm that this is indeed the case.

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Facepalm

Each transistor acts like a digital switch, and can be chained together to form huge decision-making circuits that execute software, instruction by instruction.

Wow, amazing. So that's how they do it is it?

I always thought it was done by little Elves, or something.

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Unhappy

Okay.

To all the downvoters of my comment above, do you really need to be told that a transistor is a digital switch? on an El Reg Forum?

That was the point of my post.

I'm in awe of the Prof, and think it's a great (if bonkers) project.

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Digital switch?

Um, aren't most switches digital? Do you mean electronic?

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To all the downvoters of my comment above, do you really need to be told that a transistor is a digital switch? on an El Reg Forum?

That's entirely possible. There's lots of people in tech who don't understand the basic tech. For most, the operational theory behind the processor is the FM* Theory of Operation.

* aka: Freakin' Magic

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What! I thought it was done by elves.

Does that mean I didn't need to pour the biscuits and milk into the laptop after all?

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To all the downvoters of my comment above, do you really need to be told that a transistor is a digital switch?

No, I don't need to be told that. You think that a transistor is a digital switch. I know that it isn't. You can wire them into an arrangement where their gain is high enough that it makes no difference and the resulting system behaviour is very digital, but that is in circuit. In isolation there are no ifs or buts, a transistor is an analog device.

I did look into doing something similar to this a few years ago and it got much further than a thumbnail sketch. The goals were slightly different - this was a 38.4kHz 12-bitter with a few niceties (e.g. hardware multiply and divide) and a few oddities (hardware assisted garbage collection). It was a lot simpler than this, estimated at 3,500 transistors and perhaps 3ftx2ftx18" in size, but no integrated circuits anywhere - not even memory. Most of that reduction in complexity was down to the use of threshold logic gates which are a slightly quirky semi-analog system - digital inputs, digital outputs, but internally the processing is very analog in nature which allows for a much richer set of functions than pure Boolean logic. This approach was common for research systems in the 60s to reduce the complexity of the systems by exploiting that very analog nature of transistors.

Utmost respect for the guy though because I know precisely what is involved. My project didn't get further than design, a few test assemblies, and a software emulator and assembler before the transistor I had based it around (BF199) went out of production. They were less than 3p each in quantity and when I saw the cheapest through hole alternative was £1.50 the entire thing went on the back burner.

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"To all the downvoters of my comment above, do you really need to be told that a transistor is a digital switch?"

As the refined chap said , that is far from the case - thats why there are big ones with big heat sinks attached in your amplifier.

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"That's entirely possible. There's lots of people in tech who don't understand the basic tech."

Any of them will be used to abuse by now.

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"To all the downvoters of my comment above, do you really need to be told that a transistor is a digital switch? on an El Reg Forum?

I didn't downvote you (I don't use the up/down vote thingies, because I am over 12 years old) but my memory of college fiddling with transistors and doing calculations about how to bias the base so that it operated in the "knee" part of the accompanying datasheet graph made them work in a very analogue way as they were transitioning. Hence the analogue output of a transistor amplifier. They can work as a switch, but there is more to a transistor than the behaviour of a relay.

Of course, this makes no difference the way that transistors are being used for this project.

After I left college and fell into the world of hardware development, I found that using transistors in projects was done using shortcuts and I didn't have to think about all that NPN PNP shit ever again.

Off the top of my head, did silicon bias at 0.7V, germanium at 0.5V? It''s been 25 years since I did hardware, little has been retained.

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"do you really need to be told that a transistor is a digital switch?"

Article said "acts like a digital switch". Which is correct in the current context. Saying that it *is* a switch sounds like an universal claim.

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I've met computer science graduates who don't understand the connection between writing a value to an output port:

*port=0x3c

and (say) light number 3 going to brightness level 12/16.

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Anonymous Coward

Individual transistors and LEDs - sure - but hand made wiring looms? I'd at least have gone for some PCBs for the backplane (with hand made looms linking the PCBs together). Density of components looks low enough that even one sided PCBs would work with small hand soldered bridges to jump wires.

Fair play indeed - more patience than I have ...

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If you look at his website, where the pictures are bigger, you'll see there are PCBs for the modules, mostly linked together via ribbon cable terminated with IDC connectors.

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Boffin

Kudos and beer

That's most impressive. I designed and built a sort-of hybrid 8080/6502 from discrete TTL, so just eight bits, and even that took four Eurocards (and several months of simulation beforehand).

Now if only one of the chip makers had got around to doing a 74HC ALU chip...

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Re: Kudos and beer

They did, the 74181.

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Re: Kudos and beer

Yah. But it only appears to be still available in the hot'n'hungry 'LS181 version. :(

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Re: Kudos and beer

If you're still interested LittleDiode claim to have some of the HC variety in stock.

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Thumb Up

Re: Kudos and beer

Seems someone else had similar ideas. An internet connected machine made from 74 series.

http://www.homebrewcpu.com

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Re: Kudos and beer

Quite obtainable.

https://octopart.com/search?q=74HC181

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Re: Kudos and beer

End of life or what? Looks like LittleDiode's rip-off prices for the UK... thanks, guys. Time to replace the huge proms that emulate an ALU.

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Re: Kudos and beer

Yes, TI 74LS181 seems to be the only 181 still in production. If you wanted industrial quantities of HC181, then it's a bit tough, there are only leftovers.

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Tip of the hat

I am always amazed at the dedication some people put into their hobby projects.

And I agree with the other posting - THIS is the kind of thing that should be taught about in school.

I don't envy him when it comes to troubleshooting it though. Ouch.

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Re: Tip of the hat

"And I agree with the other posting - THIS is the kind of thing that should be taught about in school."

OK TonyJ and anyone, what is the THIS that you want teaching?

I'm serious.

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Re: what is the THIS that you want teaching?

How computers work, as opposed to how to use them.

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Re: Tip of the hat

"OK TonyJ and anyone, what is the THIS that you want teaching?"

The underlying architecture of what drives a computer.

How the core components from a transistor upwards come together to make a gate. How gates come together to build logic. How... and so on.

In other words, it's all well and good showing kids how to use PowerPoint, but let's start by showing them how the actual computer works.

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Coat

Re: Tip of the hat

In other words, it's all well and good showing kids how to use PowerPoint, but let's start by showing them how the actual computer works.

Using animated powerpoint naturally

Mines the one with a wire-wrap tool in the pocket (yes I have one from the days of actually wiring up computer backplanes)

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Re: what is the THIS that you want teaching?

"How computers work, as opposed to how to use them."

OK, so are we taking an historical/hardware approach or building up from logic (and/or/not and Boolean algebra, leading to shift registers, half adders &c) or from the conceptual side (Von Neumann machine/Turing computability which rests on the 'diagonal proof' and its generalisation) or through programming (variables, assignment, loops, subroutines/functions then into more abstract areas) or all of those?

Could take a bit of time (and need some serious skills). Best of luck. One tiny activity I use sometimes: take an 8 by 8 grid of squares on squared paper. Draw a resonably complex shape (each square is either black or white).

Now devise a way of sending the shape to someone else using an sms message. Document the method for reconstructing the shape.

Now find a method that will work for a shape drawn on a 16 by 16 grid, and then a 32 by 32 grid &c.

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Re: what is the THIS that you want teaching?

It would be an exception for computers if we were to start teaching how they work.

I don't believe that as part of the standard syllabus we are teaching how anything works to GCSE level apart from maybe light bulb filaments.

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If possible I would also have opted to replicate suitable chip based registers with an option to swap them in/out as necessary during fault finding.

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Next project

Imagine the handwired Smartphone.

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It's so beautiful!

And something that I've always wanted to do myself.

A work of art of that quality deserves to be in a museum for all to see.

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but can it run crysis?

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In ASCII mode, yes.

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... on an ASR33 at 110 baud.

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Actually yes, if you give it access to a large enough persistent data store and spent the time writing a PC emulator for it.

The speed wouldn't be much to write home about - we'd be talking about one frame every few thousand years I reckon - and there'd be no visual display on a monitor. But yes, in principle, it could.

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A strange game

The only winning move is not to play. How about a nice game of chess?

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Re: A strange game

It will run a text version of Crysis:

You are flying through the alien caverns

Your nanosuit is configured to maximum speed

You see a button.

What wouldst thou do?

=>

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Really?

Some people have far too much spare time and money on their hands!

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Re: Really?

One of the nastier side-effects of having enough capital infrastructure to escape subsistence farming.

In the old times, one would take to the Mayflower in protest and sail west.

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Meh

Re: Really?

"Some people have far too much spare time and money on their hands!"

Yes, and spend them on Sky TV and paying for footy millionaire's cars.

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Unhappy

Re: Really?

It always amazes me that some people allegedly don't have to spend 25 hours out of 24 simply to ensure their continued existence. It must surely be a wonderful feeling.

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MJI
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Re: Really?

Have you ever thought about thaving a hobby or two?

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Some day, all computers will be made like this. This miniaturisation thing has had its day. Long live the 2N2222!

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3,500 LEDs

It's a real computer - it has Blinkenlights!

But he really ought to be winding his own Core memory.

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