Ferranti Argus

Ferranti's Argus computers were a line of industrial control computers offered from the 1960s into the 1980s. Originally designed for a military role, a re-packaged Argus was the first digital computer to be used to directly control an entire factory. They were widely used in a variety of roles in Europe, particularly in the UK, where a small number continue to serve as monitoring and control systems for nuclear reactors.

The original Argus was developed in 1958 as a ground-based control computer for the Bristol Bloodhound Mark 2 missile. Along with general readiness and fire-control duties, the Argus had a unique function in this system. The Bloodhound had a radar dish in the nose of the missile that had to be locked down during launch due to the vibration of the solid fuel rocket boosters that got the missile up to speed. Once the boosters were burned out and ejected, two ramjet engines took over that provided smooth thrust, allowing the radar antenna to be unlocked and start tracking the target. The Argus calculated where the target would be relative to the missile at the point of burnout, feeding that to the missile before launch and thereby allowing it to slew the radar to the correct angle when it unlocked.

During development, another team at Ferranti were positioning the system as a process control computer. Their first sale in this market was in 1962, to ICI, to operate their soda ash/ammonia plant at Fleetwood, Lancashire. This was the first large factory to be controlled directly by a digital computer. Other European sales followed.

The Argus circuitry was based on germanium transistors with 0 and -6 volts representing binary 1 and 0, respectively. The computer was based on a 12-bit word length with 24-bit instructions. The arithmetic was handled in two parallel 6-bit ALUs operating at 500 kHz. Additions in the ALU took 12 µs, but adding in the memory access time meant simple instructions took about 20 µs. Double-length (24-bit) arithmetic operations were also provided. Data memory was supplied in a 12-bit, 4096 word, core memory store, while up to 64 instruction words were stored in a separate plugboard array, using ferrite pegs dropped into holes to create a "1". Op codes were 6 bits, registers 3 bits, index register (modifier) 2 bits and data address 13 bits.

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