Bletchley Park to restore 112-byte* '50s Brit nuke computer
'Computing equivalent of raising the Mary Rose'
In a project described as "the computing equivalent of the raising of the Mary Rose", engineers at Bletchley Park intend to restore a 1950s-era computer - featuring a magnificent 112.5 bytes of memory* - to working order.
The machine in question was built at the Atomic Energy Research Establishment at Harwell in Oxfordshire. It was designed in 1949 to automate the job of a human calculating team, whose work was apparently so boring that mistakes became unacceptably frequent.
The Harwell computer wasn't intended to perform calculations faster than a human, just more reliably. Human mathematicians armed with mechanical calculators were well able to keep pace with it for half an hour or so, but would then have to give up as the machine plodded on remorselessly.
Kevin Murrell of the National Museum of Computing at Bletchley Park, where the vintage machine will be restored, says "promises for reliability over speed were certainly met – it was definitely the tortoise in the tortoise and the hare fable".
Apparently the old box worked mainly using electromechanical relays, but also featured 900 gas-filled tubes which could each hold a single bit of information* in memory. Paper tape was used both for input and for program storage.
The Harwell machine ran from 1951-57 at the atom lab, which at the time was claimed by the government to be working solely on peaceful uses of nuclear power - though in fact there were also links to the national weapons programme. Official untruthfulness around the subject was a major factor in the birth of the anti-nuclear movement and associated fear of all nuclear technology, a phenomenon which persists to this day.
After retiring from nuclear work, the computer was offered as a prize to the college which could make best use of it. The then Wolverhampton and Staffordshire Technical College (later Wolverhampton University) won and renamed the machine WITCH (Wolverhampton Instrument for Teaching Computing from Harwell). It was used to teach computing students until 1973.
After its second retirement the WITCH was stored at the Birmingham city museums' collections centre until being acquired for restoration this year by the National Museum of Computing. It arrives at Bletchley Park today, and the team there anticipate having it running at full tortoise-like poke in a year's time.
“The team are eager to start the restoration work,” enthuses Murrell. “It’s the computing equivalent of the raising of the Mary Rose and they are up to challenge!"
The ex-WITCH will sit alongside the already rebuilt Colossus cipher-cracking machine of World War Two fame, and the museum says that once running it will be "the oldest original functioning electronic stored program computer in the world". The current title holder is the Pegasus at London's Science Museum, of 1956 vintage**. ®
*Bletchley Park have been in touch to say that in fact the numbers stored by the "Dekatron"/"Decatron" gas-filled things in the WITCH are decimal numbers, not binary, so our extrapolation to bytes is wrong. More detail in the comments.
**The Colossus doesn't count, as it is only an "electronic programmable computer" - the world's first.
"The Colossus does not count"
The reason that the Colossus does not count as the world's oldest working computer
is simply that the machine on display at Bletchley Park is only about 10 years old.
There are other replicas and rebuilds of early machines around such as
the Manchester Baby, the Atanasoff machine and the Zeus Z3, the WITCH
however is original and is, AFAIK, the 3rd oldest surviving computer, the
oldest being Australia's CSIRAC and the 2nd oldest the Pilot ACE in the
London Science Museum.
The main problem with decatrons was comparatively slow switching, the ones used in WITCH are HivAC GC10B's - they glow purple - some high speed (and high voltage) ones are used in the multiplication and division unit, these have a pinkish glow.
It was a most impressive sight at night !
A really neat side effect of the use of decatrons was that you could see exactly what number was in every memory location simply by standing in front of the machine and looking at it -
great for programme debugging.
You could also stand in front of the multiplication/division unit and watch it doing long multiplication and long division step by step.
Tubes and Valves - Transistors Yuuuuukkk
Valves or Tubes in the U.S are very very easy to get. One previous poster thinks they have gone out of fashion. The fact is they are better than the modern equivalent in many cases. Langrex down in Croydon still have and buy in stock from all over the world. Many shortwave transmission station use valves and being a radion amateur myself still use them.
Apart from dropping them on the floor they are a lot more rugged electrically speaking as they physically move electrons through a near vacuum, with a few gasses as opposed to a solid substrate.
Listen to any valve radio and then listen to its modern equivalent. Modern ones just just rubbish by comparison.
Going back to an article done by the late Paul Young for Everyday Electronics in the 80's, when he was lucky enough to meet the boss of Sony (I think), even the boss (in Japanese) agreed.
Why do you think places like Maplin sell a Valve Amplifier kit ?
Good luck to those at Bletchley - Keep up the good work !
What I'd give for a job at Bletchley Park. I have always been involved with computers and now work for myself but I have always loved the historical side as Microsoft have made computers so boringly predictable
Anyone from Bletchley park reading this get in touch.
Re: More Pedantry
>> The fact that our American cousins call everything a tube does not mean that we call everything a valve.
Next you will be telling me that I am wrong when I say "sise doesn't matter".