Elliott 803

The Elliott 803 is a small, medium-speed digital computer which was manufactured by the British company Elliott Brothers in the 1960s. About 250 were built and most British universities and colleges bought one.

The 800 series started with the 801, a one-off test machine built in 1957. The 802 was a production model but only seven were sold between 1958 and 1961. The short-lived 803A was built in 1959 and first delivered in 1960; the 803B was built in 1960 and first delivered in 1961. Elliott subsequently developed the much faster Elliott 503 computer to be software compatible.

Over 200 Elliott 803 computers were delivered to customers, at a price of about £29,000 in 1960 (roughly equivalent to £602,000 in 2015). The majority of sales were the 803B version with more parallel paths internally, larger memory and hardware floating-point operations. In 2010, two complete Elliott 803 computers survive. One is owned by the Science Museum (London) but it is not on display to the public. The second one is owned by The National Museum of Computing (TNMoC) at Bletchley Park and is fully functional. Both machines are the subject of a Computer Conservation Society restoration and maintenance project which currently concentrates on the machine at TNMoC. Consequently, this machine can regularly be seen in operation by visitors to that museum. An incomplete third Elliott 803 was found decaying in a scrap yard. Where possible, parts were removed for use as a source of spares for the machine at TNMoC.

The Elliott 803 was the computer used in ISI-609 process control system. The ISI-609 was the world's first process control system; the Elliott 803's role in this system was a data logger and it was used for this purpose at the world's first dual-purpose reactor (N-Reactor).

The 803 is a transistorised, bit-serial machine; the 803B has more parallel paths internally. It uses ferrite core memory in 4096 or 8192 words of 40 bits, comprising 39 bits of data with parity. The CPU is housed in a single cabinet about 66 inches long, 16 inches deep and 56 inches high. Circuitry is based on printed circuit boards with the printed circuits being rather simple and most of the signalling carried on wires. There is a second cabinet about half the size used for the power supply, which is unusually based on a large nickel-cadmium battery with charger, an early form of uninterruptible power supply. A third cabinet (the same size as the power cabinet) holds the extra working store on machines with 8192 word stores. There is an operator's control console, Creed teleprinter and high-speed paper tape reader and punch for input/output, using 5-track Elliott telecode code, not Baudot. Tape is read at 500 characters per second and punched at 100 cps. The operator's console, about 60 inches long, allows low-level instructions to be entered manually to manipulate addresses and data and can start, stop and step the machine: there is a loudspeaker (pulsed by the top bit of the instruction register) which allows the operator to judge the status of a computation. The system requires air conditioning, drawing about 3.5 kW of power in a minimal configuration.

...
Wikipedia