The Metrovick 950 was a transistorized computer, built from 1956 onwards by

British British may refer to: Peoples, culture, and language * British people, nationals or natives of the United Kingdom, British Overseas Territories and Crown Dependencies. * British national identity, the characteristics of British people and culture ...

company

Metropolitan-Vickers Metropolitan-Vickers, Metrovick, or Metrovicks, was a British heavy electrical engineering company of the early-to-mid 20th century formerly known as British Westinghouse. Highly diversified, it was particularly well known for its industrial el ...

, to the extent of sixDavid P. Anderson, ''Tom Kilburn: A Pioneer of Computer Design'', IEEE Annals of the History of Computing - Volume 31, Number 2, April–June 2009, p. 84 or seven machines, which were "used commercially within the company"1953 - Transistorized Computers Emerge, Computer History Museum
/ref> or "mainly for internal use". The 950 appears to have been Metrovick's first and last commercial computer offering.

Transistor Computer

Prototype

In November 1953 Richard Grimsdale and Douglas Webb of

Manchester University The University of Manchester is a public university, public research university in Manchester, England. The main campus is south of Manchester city centre, Manchester City Centre on Wilmslow Road, Oxford Road. The University of Manchester is c ...

first demonstrated their prototype transistorized computer using 92 point-contact transistors and 550 diodes in order to test the suitability of transistors in improving the reliability of the Manchester Mark 1 computer. This machine was similar to the Mark I, except that it did not include Williams tubes and used only the magnetic drum for

main memory Computer data storage or digital data storage is a technology consisting of computer components and recording media that are used to retain digital data. It is a core function and fundamental component of computers. The central processin ...

. The machine was based on a 48-bit word, although four bits were used for timing and thus not available for program use. This machine used thermionic valves to generate a clock frequency of 125 kHz. The only storage used was a drum (reused from the Manchester Mark 1). This meant that the average

random access Random access (also called direct access) is the ability to access an arbitrary element of a sequence in equal time or any datum from a population of addressable elements roughly as easily and efficiently as any other, no matter how many elemen ...

time to a

word A word is a basic element of language that carries semantics, meaning, can be used on its own, and is uninterruptible. Despite the fact that language speakers often have an intuitive grasp of what a word is, there is no consensus among linguist ...

in store was half a drum revolution, i.e., with 64 words on a track, 32 times the random access time for a word if it could be stored in a true RAM. In comparison, the Mark 1 had also included a number of Williams tubes to provide

processor register A processor register is a quickly accessible location available to a computer's processor. Registers usually consist of a small amount of fast storage, although some registers have specific hardware functions, and may be read-only or write-onl ...

s that dramatically speed access to a small amount of data; thus the Transistor Computer was slower than the Mark 1. Both versions had a pseudo 2-address (or 1+1) instruction format, where the address of the next instruction to be obeyed was contained within each instruction, to facilitate " optimum programming". The drum was even used to store the Accumulator and the Current Instruction.

Improved version

By 1955 the design was re-built with a Mark I-style ''B-line'' accumulator/

index register An index register in a computer's central processing unit, CPU is a processor register (or an assigned memory location) used for pointing to operand addresses during the run of a program. It is useful for stepping through String (computer science ...

and hardware multiplier. The added circuitry brought the machine to a total of 250 transistors. It used only 150

watt The watt (symbol: W) is the unit of Power (physics), power or radiant flux in the International System of Units (SI), equal to 1 joule per second or 1 kg⋅m2⋅s−3. It is used to quantification (science), quantify the rate of Work ...

s of power, an astonishingly low figure in an era when machines typically used tens of kilowatts to warm their valves. The new model could add two 44-bit numbers in 1.5 drum revolutions, which, at a drum spin rate of 3000 RPM, amounted to roughly 30 milliseconds per addition. Although faster than the Mark I internally, the lack of Williams tubes made it run much more slowly; the Mark I could add two 40-bit numbers in 1.8 milliseconds. The prototype computer (November 1953) had a simple seven-function order code and one track of 64 words for main storage. For the full-size computer (April 1955) the order code and storage were much extended and a hardware multiplier included. A third "regenerative" drum track formed an 8-word B store. Arithmetic was serial, with a pulse rate of 125,000 per second. The instruction times were directly related to the 30-millisecond drum revolution time (the basic unit being the time to read a word, i.e. 1/64th of a revolution). The expanded 1955 machine had a total of 200 point-contact transistors and 1300 point diodes, which resulted in a power consumption of 150 watts. There were considerable reliability problems with the early batches of transistors and the average error free run in 1955 was only 1.5 hours.

Metrovick 950

became interested in the design after the success the university had selling computing time on the Mark I to commercial customers. They adopted the design of the 1955 Manchester University transistor computer as the Metrovick 950. The only relevant experience in Metropolitan-Vickers was that in the early 1930s they had manufactured a mechanical calculating machine in the form of the differential analyser in conjunction with Douglas Hartree of

. They changed all the circuits to more reliable types of junction transistors, although it appears they may have built one example with the earlier designs. The production version was known as the Metrovick 950 and was built from 1956 to the extent of six or seven machines, which were "used commercially within the company" or "mainly for internal use".

References

{{Reflist

External links

Early computers at Manchester University

Metropolitan-Vickers Engineering Report on the Type 950 General Purpose Computer: Functional Design
Transistorized computers Metropolitan-Vickers Early British computers Computer-related introductions in 1956 History of science and technology in the United Kingdom