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EDSAC computer to be rebuilt at Bletchley Park

  • Tape printer
  • Construction
  • The team
  • EDSAC
  • Sir Maurice Wilkes

By Nicole Kobie

Posted on 13 Jan 2011 at 17:18

The first working stored-program computer is set to be rebuilt at Bletchley Park.

The Electronic Delay Storage Automatic Calculator (EDSAC) was built at Cambridge University by a team led by computing pioneer Sir Maurice Wilkes.

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It ran its first programme in 1949 and its success lead to the creation of the first business computer, the LEO.

The EDSAC was two metres high and its 3,000 vacuum tubes took up four metres of floor space. It could perform 650 instructions per second and all data input was via paper tape.

It used mercury-filled tubes for memory, but in the interests of safety, the replica will use an alternative non-toxic substance.

"Recreating a fully-functioning EDSAC computer is quite a challenge, but our experience in rebuilding the Colossus computer gives us confidence and insight," said Kevin Murrell, a director and trustee of The National Museum of Computing.

The replica of the EDSAC was commissioned by the Computer Conservation Society, part of the BCS, and will be built over the next four years at Bletchley Park, home to the National Museum of Computing, where visitors can watch the work as it happens.

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User comments

mercury tubes

the mercury tubes were in fact delay lines. The ones in the leo computers had an adjustable paddle in the middle to stop oscillation.

Just a small observation- there may be quite a lot of information out there which may be prevented from coming to light by an overly complicated registration process. (we are talking very old and wrinkly)

By ronwh on 13 Jan 2011

We are NOT Americans!

I thought the EDSAC had about 3000 valves in its construction, not something I've never heard of called 'vacuum tubes'. It was a British computer and its constructors were British (like I thought PC Pro is, but obviously I'm mistaken).
Are you sure Bletchly Park is in England, or is it North Carolina?

By JohnMalcolm1961 on 13 Jan 2011

Old & wrinkly?

Hey, hey! I worked as a computer operator (one of 3 shifts of 8 people) on a LEO installation at Reynold's Chains in Wythenshawe, near Manchester, in 1971.

And I *still* managed to register for the PC Pro website ...

By mikelaye on 13 Jan 2011

Old & wrinkly?

Hey, hey! I worked as a computer operator (one of 3 shifts of 8 people) on a LEO installation at Reynold's Chains in Wythenshawe, near Manchester, in 1971.

And I *still* managed to register for the PC Pro website ...

By mikelaye on 13 Jan 2011

First? Stored Program computer

I thought that honour went to the Manchester Mark 1 (Baby).
At least that is what my comp sci lecturers told me when I was at Manchester (England!) in 1979 - I don't think they were biased (there's a joke in there for old electronics techs) :)

By gfmoore on 14 Jan 2011

school visit to LEO computers Queensgate London

When I was 13 we were taken to visit LEO. At lunch I suggested that it would be great if all the computers could be joined together to make one big one. Stupid boy. What a stupid thing to say.

By jobsworth on 14 Jan 2011

queensway not queensgate

moderator please edit post

By jobsworth on 14 Jan 2011

Wot no cardigan?

Bill Renwick must have been a real boffin as he was allowed to work without wearing a suit tie and cardigan.

By milliganp on 14 Jan 2011

build a modern work-alike first

it would be instructional and relatively quick and inexpensive to build a functionally equivalent machine using, for instance, discrete transistors or transistor arrays. This box could be used to verify operation of the tube/valve version. In fact, it would make sense to build 2 or 3 them since component costs are low.

By gregben on 14 Jan 2011

@JohnMalcolm1961: You're correct, but the "vacuum tubes" were the glass envelopes that the "valves" were contained in. Can't have valves without a vacuum.

By PeterCapek on 14 Jan 2011

LEO Computers

Mike Laye might like to visit the LEO Computers web site at www.leo-computers.org.uk LEO 1 went live 60 years ago this November.

By leo2man on 30 Sep 2011

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