Reinventing The Harwell Dekatron

A huge number of modern replicas of retro computers pass our screens here at Hackaday, and among them are an astonishing variety of technologies. Those who weren’t lucky enough to be present in the days when the building blocks of computing were coming together may have missed out on understanding gate-level operation of a computer. Put your super-powerful and super-complex systems-on-chip aside sometime and dig into the details of their distant ancestors.

Most such machines follow a very conventional architecture, so it is something of a surprise to find a project recreating a modern version of something far more obscure. The Harwell Dekatron, also known as the WITCH, can be found at the National Museum Of Computing in Bletchley, UK, and [David Anders] is building a modern all-electronic replica of it.

The original machine is currently the world’s oldest working digital computer, a hybrid electromechanical computer built at the start of the 1950s  to perform calculations for British nuclear scientists. It was retired by the end of that decade and found its way — via a technical college, a museum, and a period of storage in a council archive — to Bletchley where it was restored to working order by 2012. Its special feature is the use of dekatron discharge tubes as memory, allowing an instant visual display of its working as it happens.

[David]’s replica uses modern logic chips to replicate the building blocks of the Harwell Dekatron, and his write-up is as fascinating for that as it is for his study of the real thing in the museum. We ran into [Dave] showing off this project at the Hackaday Dallas event last year and are excited to learn of the advancements since then from his Hackaday.io page. He’s put his research and designs on GitHub, and a series of YouTube videos, the introduction to which we’ve put below the break.

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Colossus: Face To Face With The First Electronic Computer

When the story of an invention is repeated as Received Opinion for the younger generation it is so often presented as a single one-off event, with a named inventor. Before the event there was no invention, then as if by magic it was there. That apple falling on Isaac Newton’s head, or Archimedes overflowing his bath, you’ve heard the stories. The inventor’s name will sometimes differ depending on which country you are in when you hear the story, which provides an insight into the flaws in the simple invention tales. The truth is in so many cases an invention does not have a single Eureka moment, instead the named inventor builds on the work of so many others who have gone before and is the lucky engineer or scientist whose ideas result in the magic breakthrough before anyone else’s.

The history of computing is no exception, with many steps along the path that has given us the devices we rely on for so much today. Blaise Pascal’s 17th century French mechanical calculator, Charles Babbage and Ada, Countess Lovelace’s work in 19th century Britain, Herman Hollerith’s American tabulators at the end of that century, or Konrad Zuse’s work in prewar Germany represent just a few of them.

So if we are to search for an inventor in this field we have to be a little more specific than “Who invented the first computer?”, because there are so many candidates. If we restrict the question to “Who invented the first programmable electronic digital computer?” we have a much simpler answer, because we have ample evidence of the machine in question. The Received Opinion answer is therefore “The first programmable electronic digital computer was Colossus, invented at Bletchley Park in World War Two by Alan Turing to break the Nazi Enigma codes, and it was kept secret until the 1970s”.

It’s such a temptingly perfect soundbite laden with pluck and derring-do that could so easily be taken from a 1950s Eagle comic, isn’t it. Unfortunately it contains such significant untruths as to be rendered useless. Colossus is the computer you are looking for, it was developed in World War Two and kept secret for many years afterwards, but the rest of the Received Opinion answer is false. It wasn’t invented at Bletchley, its job was not the Enigma work, and most surprisingly Alan Turing’s direct involvement was only peripheral. The real story is much more interesting.

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Hackaday Links: July 5, 2015

It’s the fifth of July. What should that mean? Videos on YouTube of quadcopters flying into fireworks displays. Surprisingly, there are none. If you find one, put it up in the comments.

The original PlayStation was a Nintendo/Sony collaboration. This week, some random dude found a prototype in his attic. People were offering him tens of thousands of dollars on the reddit thread, while smarter people said he should lend it to MAME and homebrewer/reverse engineer groups. This was called out as a fake by [Vadu Amka], one of the Internet’s highly skilled console modders. This statement was sort of semi retracted. There’s a lot of bromide staining on that Nintendo PlayStation, though, and if it’s a fake, the faker deserves thousands of dollars. Now just dump the ROMs and reverse engineer the thing.

Remember BattleBots? It’s back. These are my impressions of the first two episodes: Flamethrowers are relatively common now, ‘parasitic bots’ – small, auxilliary bots fighting alongside the ‘main’ bot are now allowed. KOs only count for the ‘main’ bot. Give it a few more seasons and every bot will be a wedge. One of the hosts is an UFC fighter, which is weird, but not as weird as actually knowing some of the people competing.

Ceci n’est pas un Arduino, which means it’s from the SRL camp. No, wait. It’s a crowdfunding campaign for AS200 Industries in Providence, RI.

Wanna look incredibly sketchy? Weld (or braze, or solder) your keys to a screwdriver.

The UK’s National Museum of Computing  is looking for some people to help maintain 80 BBC Micros. The museum has a ‘classroom’ of BBC micro computers still in operation. Caps dry out, switching power supplies fail, and over the years these computers start to die. If you have the skills and want to volunteer, give it a shot.

USA-made Arduinos are now shipping. That’s the Massimo Arduino, by the way.

Win $1000 for pressing a buttonWe’re gauranteed to give away a thousand dollar gift card for the Hackaday store next Wednesday to someone who has participated in the latest round of community voting for the Hackaday Prize.