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Rare part for groundbreaking 1949 British computer found in US

An original piece of the EDSAC, a precursor to the first business computer, has been sent from Pennsylvania to the UK to take up residence at code-breaking site Bletchley Park.

The room-size EDSAC could perform 650 instructions per second. University of Cambridge

A rare remnant of a pioneering British computer has surfaced in the United States and made its way to the UK to be incorporated into a reconstruction of the historic machine.

The computer, called the Electronic Delay Storage Automatic Calculator, or EDSAC, is recognized as one of the world's first practical general-purpose computers and a design precursor to the first business computer. EDSAC was built in the 1940s at the University of Cambridge, where it was employed by many research scientists, including two Nobel researchers.

The room-size computer used 5-foot-long mercury-filled tubes for the main memory. It relied on 3,000 vacuum tubes, arranged on 12 racks containing just over 140 chassis, for computational operations. Pennsylvania resident Robert Little donated the recent find -- a chassis designed to hold 28 of the valves -- after reading about the EDSAC Replica Project, which aims to create a replica of the computer as it was on May 6, 1949, when it successfully ran its first program.

chassis.jpg
Andrew Herbert, leader of the EDSAC reconstruction, shows a chassis reconstructed by volunteers. (Click to enlarge.) Video screenshot by Leslie Katz/CNET

Little obtained the computer part in 1969 from Cambridge resident Robert Clark, who had purchased several EDSAC racks to convert to bookshelves.

"I regret that the probability of finding any more of Dr. Clark's EDSAC parts is vanishingly small," Little said in a statement released by The National Museum of Computing at UK code-breaking center Bletchley Park, where visitors can see the ongoing EDSAC Replica Project on display. "Dr. Clark passed away in 1984. Sometime between 1969 and 1984 he relocated to a house on the outskirts of Cambridge and quite probably disposed of unneeded things then."

Little says he vaguely remembers Clark talking of bidding against a local scrap metal dealer when he won the EDSAC parts at auction. "Despite this, I am hopeful that those who built and worked with EDSAC kept other mementos that have been preserved intact until now," he added.

A far, far cry, needless to say, from the handheld computers of today, EDSAC measured more than 6.5 feet (2 meters) tall and had a footprint of 215 square feet (about 20 square meters). It could perform a groundbreaking 650 instructions per second, effectively computing more than 1,500 times faster than the mechanical calculators it replaced.

The recently donated part, called Chassis 1, is now corroded, with broken, misshapen wires, but it may not be entirely unusable.

"It would be a major task to return this particular chassis to operating condition," said Andrew Herbert, leader of the EDSAC reconstruction. "However, we hope to try to use some of the valves, if they are still functional, in our reconstructed EDSAC thus providing a very tangible connection with the original machine."

The EDSAC Replica Project started in 2011, and if all goes according to plan, is expected to be completed late this year.