Secrets of the world's first computer revealed
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Detailed circuit diagrams of the world's first general computer have come to light during a project to reconstruct the machine.
The 19 large scale diagrams were discovered by a team from The National Museum of Computing, more than sixty years after they were first drawn up.
EDSAC was first created at the University of Cambridge after World War II. It was the first practical general purpose computer and transformed research possibilities for many academics. It even helped three in their Nobel Prize winning work.
The circuit diagrams, which date from between 1949 and 1953, were actually drawn after EDSAC had been constructed, probably as some sort of aid in refining the original machine and in designing the next.
Described as being in 'remarkably good condition', they seem to have been part of a much larger set numbering at least 150.
Andrew Herbert, leader of the EDSAC Project, 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.
"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."
Elements that were modified even after the machine was up and running in May 1949 include redesigning the circuitry to obtain stronger signals and improvements to the instruction set and error correction so that programming errors could be distinguished from machine malfunction.
The most significant discrepancy between the original and the reconstruction that the papers reveal is in the 'initial orders', known now as boot ROM.
In the absence of fuller information, today's reconstruction team had considered and rejected one possibility which was in fact the one that was used by the original engineers. That will now be rectified in the reconstruction.
Herbert concluded: "Very few artifacts of EDSAC remain. However, these papers give a clue as to why a few such as a chassis do exist. We think that the existing artifacts were discards from a very early version of the machine."
The reconstructed EDSAC is due for completion in late 2015, but can be seen as a work in progress at The National Museum of Computing, based at Bletchley Park.
