EDSAC 2

EDSAC 2 was an early vacuum tube computer (operational in 1958), the successor to the Electronic Delay Storage Automatic Calculator (EDSAC). It was the first computer to have a microprogrammed control unit and a bit-slice hardware architecture.^[1]

EDSAC 2 modular construction

EDSAC 2

EDSAC 2 users in 1960
Developer	University of Cambridge, Mathematical Laboratory, UK
Release date	1958; 67 years ago (1958)
Lifespan	Decommissioned 1965
CPU	20-bit instructions with 11-bit addresses, two index registers, microcoded; @ fixed point add: 17–42 microseconds, floating point add: 100–170 microseconds[1]
Memory	1024 words RAM, 768 words ROM[1] (core memory, 40-bit words)
Storage	block-structured magnetic tape, 16K words, core memory, added in 1962[1]
Input	5-level paper tape, up to 1000 characters per second read, 300 cps punched output, two-out-of-five code[1]
Predecessor	EDSAC

First calculations were performed on the incomplete machine in 1957.^[2] Calculations about elliptic curves performed on EDSAC-2 in the early 1960s led to the Birch and Swinnerton-Dyer conjecture, a Millennium Prize Problem, unsolved as of 2025. And in 1963, Frederick Vine and Drummond Matthews used EDSAC 2 to generate a magnetic anomaly map of the seafloor from data collected in the Indian Ocean by H.M.S. Owen, key evidence that helped support the theory of plate tectonics.^[3] EDSAC-2 was decommissioned in 1965, having been superseded by the Titan computer.^[4]