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The PDP-1 and Other 18-Bit Computers

C. GORDON BELL, GERALD BUTLER, ROBERT GRAY, JOHN E. MCNAMARA, DONALD VONADA,

and RONALD WILSON

THE PDP-1

Although Digital Equipment Corporation was formed in 1957 with the explicit goal of constructing computers, the company's first computer, the PDP-1, was not demonstrated until almost two years later. The principal backer of DEC, American Research and Development headed by General Georges F. Doriot, was somewhat skeptical that a computer company could be successful. They were enthusiastic, however, about the business possibilities in logic modules for laboratory and system use, and they felt that the plan to build computers should be conditional upon building a solid base in the module business.

After a year of operation, DEC met its profit and sales goals and was permitted to move on to the construction of computers. However, Ken Olsen felt it would be worthwhile to wait an additional year to obtain more business experience and to build a larger customer and financial base. Thus, it was not until the summer of 1959 that an engineer, Ben Gurley, was hired to design and build the PDP-l. Ben headed computer engineering until he left in 1962. In addition to logic and computer design, he specialized in complex analog circuitry, including the circuits for core memories and displays. The displays (including high precision and color point plotting) were pivotal to DEC's success, and many of the display circuits that he designed remained unchanged until the 1970s. His death in 1963 was a tragic loss to computer engineering and the industry.

Ben Gurley and other engineers* at DEC had worked at the Massachusetts Institute of Technology (M.I.T.) Computer Laboratory on Whirlwind and had then gone on to develop computers at the M.I.T. Lincoln Laboratory. As a result, the machines constructed at the M.I.T. campus and at Lincoln Laboratory greatly influenced the design and construction of the PDP-l. In fact, the DEC System Modules

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*Harlan Anderson, Dick Best, Ken Olsen, Stan Olsen, and Bob Savell.

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