Photos: Secrets of early computing revealed by rediscovered EDSAC documents

When volunteers began rebuilding one of the world's first fully operational general-purpose computers they had to painstakingly piece together the inner workings of the 65-year-old machine.

The original EDSAC - the Electronic Delay Storage Automatic Calculator - was built immediately after World War II at the University of Cambridge, where it aided research into areas including genetics, meteorology and X-ray crystallography. The machine's design was later used to create LEO, the world's first business computer.

With the historic EDSAC scrapped decades ago, the 20 volunteers recreating the computer had to scrape together information about the machine. For guidance the team consulted documents held by individuals and in libraries at the University of Cambridge, and examined the one surviving chassis used in the EDSAC.

Now the team working out of Bletchley Park in England, home to the famous World War II codebreakers that included father of computing Alan Turing, have had confirmation the rebuild is on the right track after stumbling across diagrams of the original machine.

The 19 detailed circuit diagrams, which came to light more than 60 years after they were drawn up, were delivered to the team by chance.

For decades the drawings sat in the home of John Loker, who worked as an engineer in the maths lab at the University of Cambridge and came across the diagrams in 1959, just after EDSAC had been decommissioned.

"In a corridor there was a lot of stuff piled up ready to be thrown away, but amongst it I spotted a roll of circuit diagrams for EDSAC. I'm a collector, so I couldn't resist the urge to rescue them," he said.

"It wasn't until I visited TNMOC [The National Museum of Computing at Bletchley Park] recently and learned about the EDSAC Project that I remembered I had the diagrams at home, so I retrieved them and gave them to the project."

Many of the diagrams, which date from between 1949 and 1953, were drawn after EDSAC had been constructed and are thought to have been an aid in refining the original machine and in designing its successor. They are believed to have been part of a much larger set of at least 150 drawings and are in remarkably good condition.

Andrew Herbert, leader of the EDSAC Project rebuild, said: "Thankfully, the documents confirm that the reconstruction we are building is basically correct, but they are giving us some fascinating insights about how EDSAC was built and show that we are very much in tune with the original engineers: both teams have been exercised by the same concerns.

"Importantly, the drawings clearly show that the aim of EDSAC's designer, Sir Maurice Wilkes, was to produce a working machine quickly rather than to create a more refined machine that would take longer to build. The refinements could come later -- and many did as the sequence of diagrams over the five-year period shows."

Above, from left, is EDSAC technical leader Chris Burton, with John Loker, the engineer who saved the diagrams, and leader of the EDSAC Project rebuild Andrew Herbert.


Nick Heath is chief reporter for TechRepublic UK. He writes about the technology that IT-decision makers need to know about, and the latest happenings in the European tech scene.


To be accurate (or pedantic) EDSAC would not have used 'vacuum tubes' but would have used 'valves'

As it was a British machine and not an American one, a spot of accuracy is called for here as we never called a valve a 'vacuum tube'


To be accurate (and pedantic) as EDSAC was a British machine and not an American one it didn't use 'vacuum tubes' - it used 'valves'.


PS: Antanasov was not associated with the ILLIAC (or ORDVAC) projects.  Antanasov's machine was not stored-program and was developed and a prototype was built in November 1939.  So the invalidation of Eckert-Mauchley patents had to do with other operating principles in Antanasov's prior art.

Another early developer who received later credit for his insights was Konrad Zuse.  Zuse completed a fully progammable digital computer in Germany in 1941.  Fortunately for the Allied effort, the German government did not provide funding to accelerate the work of Zuse, considering it not strategically important.  Von Neumann, who traveled among the various Allied programs saw an urgent need, in the then-secret development of nuclear weapons.


History is not my strong point so I have forgotten the date that Antanasov, which was declared the true inventor of the electronic computer, was supposed to have invented it. The interesting thing is that his family quashed a patent granted to the ILIAC (I believe) team Eckert and Mauchley, because of evidence that this team had gotten their ideas in correspondence with Antanasov. Or at least a court delcared that Antanasov was the real inventor.

Things happening across the Atlantic sometimes get forgotten in such battles, but can Nick Heath maybe do some digging to discover the date of the Antanasov invention to see if EDSAC pre-dated the ILIAC?