Whilst we do not of course have a complete EDSAC installation, we do have an arithmetic unit marked "EDSAC II - Chassis 1". The arithmetic logic unit/arithmetic-logic unit (ALU) of a computer's CPU is a part of the execution unit, a core component of all CPUs. ALUs are capable of calculating the results of a wide variety of basic arithmetical computations. Virtually all modern computer ALUs use the two's complement binary number representation (whereas some early computers used either one's complement or sign-magnitude format)
The EDSAC was the world’s first stored-program computer to operate a regular computing service. Designed and built at Cambridge University, the EDSAC performed its first fully automatic calculation on 6 May 1949. The Warwick University simulator is a faithful emulation of the EDSAC designed to run on a personal computer. The user interface has all the controls and displays of the original machine, and the system includes a library of original programs, subroutines, debugging software, and program documentation
EDSAC 2 was a successor to the Electronic Delay Storage Automatic Calculator. It was the first computer to have a microprogrammed control unit and a bit slice hardware architecture. This came into operation early in 1958 and was designed by the team that had successfully built and operated EDSAC 1, and embodied the experience obtained with that machine. EDSAC 2 was the first computer to have a microprogrammed control unit, and it established beyond doubt the viability of microprogramming as a basis for computer design - this in spite of the fact that vacuum tubes were far from ideal for the purpose. At the mechanical level of organization, EDSAC 2 was packaged in a bit-sliced manner, with interchangeable plug-in units. This method of packaging was well matched to the vacuum tube technology of the period, and its expected advantages - arising from the replication of units - were fully realised.
The arithmetic unit was also known as an ALU (arithmetic-logic unit) and our unit was very kindly donated by Rodney Dale. The photograph shows one of these units being placed in the EDSAC II machine.
The actual installation photograph is Copyright Computer Laboratory, University of Cambridge. Reproduced by permission.
Manufacturer: Cambridge University
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This exhibit has a reference ID of CH11977. Please quote this reference ID in any communication with the Centre for Computing History.
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