EDSAC 2 (Electronic Delay Storage Automatic Calculator 2) was an early large-scale digital computer developed by the University of Cambridge Mathematical Laboratory in England. It was the successor to the original EDSAC, which had been one of the first stored-program computers.
Development and History The project was led by Maurice Wilkes and began shortly after the original EDSAC became operational in 1949. While the first EDSAC was a pioneer in functional computing, EDSAC 2 was designed to incorporate more advanced architectural concepts. Construction began in the early 1950s, and the machine became fully operational in 1958. It remained in service until 1965, when it was succeeded by the Titan computer (a joint project between Cambridge and Ferranti).
Technical Innovations EDSAC 2 is historically significant for several technical milestones in computer architecture:
- Microprogramming: It was the first computer to employ a microprogrammed control unit. Maurice Wilkes had proposed the concept of microprogramming in 1951 as a way to simplify the design of the control circuits by treating the control unit as a "computer within a computer."
- Bit-Sliced Architecture: The machine utilized a bit-sliced design, where the CPU was constructed from multiple identical units, each processing a portion (or "slice") of the data word. This modular approach simplified both manufacturing and maintenance.
- Memory Technology: Unlike its predecessor, which used mercury delay lines for memory, EDSAC 2 utilized ferrite core memory. This provided faster and more reliable random-access storage.
Specifications The machine was physically large, utilizing approximately 6,000 thermionic valves (vacuum tubes). It operated with a word length of 40 bits (including a sign bit) and used a binary representation. It was primarily used for scientific research and mathematical calculations at the university, supporting a wide range of academic disciplines including physics, chemistry, and engineering.
Legacy The innovations introduced with EDSAC 2, particularly microprogramming, became standard features in the design of subsequent generations of computers, including the IBM System/360 series. The machine represents a transition period in computing history from experimental, one-off laboratory instruments to more sophisticated, modularly designed systems.
