Large Systems + WITCH
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When computers were few but big!
In the largest gallery in the museum, you can see just how big those early systems really were. There's the Harwell Dekatron aka WITCH computer from the early 1950s, three Elliotts from the 60s, PDP-11s from the 1970s and more. Most of them are either being restored or actually working.
Whenever families with children visit, they are always amazed just how big the systems from the 50s, 60s and 70s really were. Their only knowledge of computing might be the PC or laptop they have at home, or the iPod and mp3 player in their pocket (which has many times more processing power than all the systems on display). We have also had many complimentary comments from those of yesteryear who actually worked on or maintained the systems on display, and are often amazed that we have them working.
Harwell Dekatron computer aka WITCH
The world's oldest original working digital computer
In 1949 plans were drawn up for a machine to automate the tedious work performed by teams of bright young graduates using mechanical calculators. Simplicity, reliability and unattended operation were the design priorities. Speed was of a lower priority.
This pioneering computer first ran in 1951 and by 1952 was using 738 Dekatron tubes for program and data storage, relays for sequence control and valve-based electronics for calculations.
It was used at Harwell until 1957, when it was won by Wolverhampton and Staffordshire Technical College (later becoming Wolverhampton University) in a competition for colleges to see who could make best use of it. It then became known as the WITCH (Wolverhampton Instrument for Teaching Computation from Harwell), and was used in computer education right up until 1973.
After a period on display at Birmingham Museum of Science and Industry, the computer was disassembled and stored at Birmingham City Council Museums’ Collection Centre.
In 2009 the machine was spotted dismantled in storage by TNMOC volunteers and a plan was made to bring it to TNMOC for restoration in full public view. Here is a BBC video of the WITCH arriving at TNMOC in September 2009. When restoration is complete, it will be the oldest original working digital computer in the world.
A tortoise not a hare The Harwell computer was pitched against a human mathematician to check the machine’s operation. The human kept pace for 30 minutes, but then retired exhausted as the machine carried on remorselessly. The computer once ran unattended for ten days over a Christmas/New Year holiday period.
You can follow the technical story of how the Harwell Dekatron / WITCH computer was restored here.
Because of its age, we can't always guarantee that the Harwell Dekatron will be working when you visit, but you'd be unlucky if it wasn't!
The Reboot - 1 minute version
The Reboot - 21 minute version
Elliott 803B from around 1962
This is a fully functioning machine which, when it was donated to the museum, had spent about 15 years in a farm barn. The restoration was lead by John Sinclair, and the machine has been running with little need for attention for many years. It has recently had two upgrades: The addition of a Calcomp drum plotter and some additional input/output features. As well as the system on display here at TNMOC, John has also restored and maintained an 803B system for the Science Museum in London.
As with any good system we have it working hard each Saturday. Members of the project team keep their programming skills sharp by developing programs for the 803 using the original software tools. These programs play music, draw graphs or solve mathematical problems. One recent program calculates the cost of a shopping list in pounds, shillings and pence (£sd, the UK's currency pre-decimalisation in 1971). This is a far cry from its original use for planning bakery delivery routes or accounting, but it does allow the system to be shown working and in doing so ensures its continued operation.
Three Elliott machines from the 800 and 900 series are on display at TNMOC.
The PDP-11, first launched by Digital Equipment Corporation in 1970, was one of the most popular mini-computers in the world throughout the 1970s and 1980s. Models were still being made in 1990.
The first PDP-11 machines were transistorised, but by the end of the line the whole machine would fit on a chip. They could be configured as a system as small as a paperback book and built into a machine or be a huge multi-user system. PDP-11 systems could be found being used to run experiments in university laboratories, controlling production equipment in factories, and even on US Navy warships.
It was widely copied, particularly behind the Iron Curtain. One the first official versions of UNIX ran on PDP-11 machines.
In the Museum is the IRIS Air Traffic Control System and the Blacknest PDP-11 designed to distinguish seismic events from nuclear explosions.
And there's more...