Harwell CADET
Encyclopedia
The Harwell CADET was the first fully transistorised computer
in Europe, and may have been the first fully transistorised computer in the world.
The electronics division of the Atomic Energy Research Establishment
at Harwell, UK built the Harwell Dekatron Computer
in 1951, which was an automatic calculator where the decimal arithmetic and memory were electronic, although other functions were performed by relays. By 1953, it was evident that this did not meet AERE
's computing needs, and AERE director Sir John Cockcroft
encouraged them to design and build a computer using transistors throughout.
E. H. Cooke-Yarborough based the design around a 64-kilobyte magnetic drum memory
store with multiple moving heads that had been designed at the National Physical Laboratory, UK
. By 1953 his team had transistor circuits operating to read and write on a smaller magnetic drum from the Royal Radar Establishment
. The machine used a low clock speed of only 58 kHz to avoid having to use any valves to generate the clock waveforms. This slow speed was partially offset by the ability to add together eight numbers concurrently.
The resulting machine was called CADET (Transistor Electronic Digital Automatic Computer – backwards). It first ran a simple test program in February 1955. CADET used 324 point-contact transistor
s provided by the UK company Standard Telephones and Cables
, which were the only ones available in sufficient quantity when the project started; 76 junction transistor
s were used for the first stage amplifiers for data read from the drum, since point-contact transistor
s were too noisy. CADET was built from a few standardised designs of circuit boards which never got mounted into the planned desktop unit, so it was left in its breadboard
form. From August 1956 CADET was offering a regular computing service, during which it often executed continuous computing runs of 80 hours or more.
Cooke-Yarborough described CADET as being "probably the second fully transistorised computer
in the world to put to use", second to an unnamed IBM machine. Both the Manchester University Transistor Computer and the Bell Laboratories TRADIC
were demonstrated incorporating transistors before CADET was operational, although both required some thermionic valves to supply their faster clock power, so they were not fully transistorised. In April 1955 IBM announced the IBM 608 transistor calculator, which they claim was "the first all solid-state computing machine commercially marketed" and "the first completely transistorized computer available for commercial installation", and which may have been demonstrated in October 1954, before the CADET.
By 1956, Brian Flowers
, head of the theoretical physics division at AERE, was convinced that the CADET provided insufficient computing power for the needs of his numerical analysts and ordered a Ferranti Mercury
computer. In 1958, Mercury number 4 became operational at AERE to accompany the CADET for another two years before the CADET was retired after four years' operation.
Transistor computer
A transistor computer is a computer which uses discrete transistors instead of vacuum tubes. The "first generation" of electronic computers used vacuum tubes, which generated large amounts of heat, were bulky, and were unreliable. A "second generation" of computers, through the late 1950s and...
in Europe, and may have been the first fully transistorised computer in the world.
The electronics division of the Atomic Energy Research Establishment
Atomic Energy Research Establishment
The Atomic Energy Research Establishment near Harwell, Oxfordshire, was the main centre for atomic energy research and development in the United Kingdom from the 1940s to the 1990s.-Founding:...
at Harwell, UK built the Harwell Dekatron Computer
WITCH (computer)
The Harwell computer, later known as the Wolverhampton Instrument for Teaching Computing from Harwell , or the Harwell Dekatron Computer, was an early British relay-based computer...
in 1951, which was an automatic calculator where the decimal arithmetic and memory were electronic, although other functions were performed by relays. By 1953, it was evident that this did not meet AERE
Atomic Energy Research Establishment
The Atomic Energy Research Establishment near Harwell, Oxfordshire, was the main centre for atomic energy research and development in the United Kingdom from the 1940s to the 1990s.-Founding:...
's computing needs, and AERE director Sir John Cockcroft
John Cockcroft
Sir John Douglas Cockcroft OM KCB CBE FRS was a British physicist. He shared the Nobel Prize in Physics for splitting the atomic nucleus with Ernest Walton, and was instrumental in the development of nuclear power....
encouraged them to design and build a computer using transistors throughout.
E. H. Cooke-Yarborough based the design around a 64-kilobyte magnetic drum memory
Drum memory
Drum memory is a magnetic data storage device and was an early form of computer memory widely used in the 1950s and into the 1960s, invented by Gustav Tauschek in 1932 in Austria....
store with multiple moving heads that had been designed at the National Physical Laboratory, UK
National Physical Laboratory, UK
The National Physical Laboratory is the national measurement standards laboratory for the United Kingdom, based at Bushy Park in Teddington, London, England. It is the largest applied physics organisation in the UK.-Description:...
. By 1953 his team had transistor circuits operating to read and write on a smaller magnetic drum from the Royal Radar Establishment
Royal Radar Establishment
The name Royal Radar Establishment was given to the existing Radar Research Establishment following a visit by Queen Elizabeth II in 1957. Both names were abbreviated to RRE. The establishment had been formed, under its first name, in 1953 by merging the Telecommunications Research Establishment ...
. The machine used a low clock speed of only 58 kHz to avoid having to use any valves to generate the clock waveforms. This slow speed was partially offset by the ability to add together eight numbers concurrently.
The resulting machine was called CADET (Transistor Electronic Digital Automatic Computer – backwards). It first ran a simple test program in February 1955. CADET used 324 point-contact transistor
Point-contact transistor
A point-contact transistor was the first type of solid-state electronic transistor ever constructed. It was made by researchers John Bardeen and Walter Houser Brattain at Bell Laboratories in December 1947. They worked in a group led by physicist William Bradford Shockley...
s provided by the UK company Standard Telephones and Cables
Standard Telephones and Cables
Standard Telephones and Cables Ltd was a British telephone, telegraph, radio, telecommunications and related equipment R&D manufacturer. During its history STC invented and developed several groundbreaking new technologies including PCM and optical fibres.The company began life in London as...
, which were the only ones available in sufficient quantity when the project started; 76 junction transistor
Bipolar junction transistor
|- align = "center"| || PNP|- align = "center"| || NPNA bipolar transistor is a three-terminal electronic device constructed of doped semiconductor material and may be used in amplifying or switching applications. Bipolar transistors are so named because their operation involves both electrons...
s were used for the first stage amplifiers for data read from the drum, since point-contact transistor
Point-contact transistor
A point-contact transistor was the first type of solid-state electronic transistor ever constructed. It was made by researchers John Bardeen and Walter Houser Brattain at Bell Laboratories in December 1947. They worked in a group led by physicist William Bradford Shockley...
s were too noisy. CADET was built from a few standardised designs of circuit boards which never got mounted into the planned desktop unit, so it was left in its breadboard
Breadboard
A breadboard is a construction base for prototyping of electronics. The term is commonly used to refer to solderless breadboard ....
form. From August 1956 CADET was offering a regular computing service, during which it often executed continuous computing runs of 80 hours or more.
Cooke-Yarborough described CADET as being "probably the second fully transistorised computer
Transistor computer
A transistor computer is a computer which uses discrete transistors instead of vacuum tubes. The "first generation" of electronic computers used vacuum tubes, which generated large amounts of heat, were bulky, and were unreliable. A "second generation" of computers, through the late 1950s and...
in the world to put to use", second to an unnamed IBM machine. Both the Manchester University Transistor Computer and the Bell Laboratories TRADIC
TRADIC
The TRADIC was the first transistorized computer in the USA, completed in 1954....
were demonstrated incorporating transistors before CADET was operational, although both required some thermionic valves to supply their faster clock power, so they were not fully transistorised. In April 1955 IBM announced the IBM 608 transistor calculator, which they claim was "the first all solid-state computing machine commercially marketed" and "the first completely transistorized computer available for commercial installation", and which may have been demonstrated in October 1954, before the CADET.
By 1956, Brian Flowers
Brian Flowers, Baron Flowers
Brian Hilton Flowers, Baron Flowers FRS was a British physicist and academican.-Early life and studies:The son of Reverend Harold Joseph Flowers, he was educated at the Bishop Gore School in Swansea and at Gonville and Caius College, Cambridge, where he graduated with a Master of Arts...
, head of the theoretical physics division at AERE, was convinced that the CADET provided insufficient computing power for the needs of his numerical analysts and ordered a Ferranti Mercury
Ferranti Mercury
The Mercury was an early 1950s commercial computer built by Ferranti. It was the successor to the Ferranti Mark 1, adding a floating point unit for improved performance, and increased reliability by replacing the Williams tube memory with core memory and using more solid state components...
computer. In 1958, Mercury number 4 became operational at AERE to accompany the CADET for another two years before the CADET was retired after four years' operation.
See also
- History of computing hardware, Second generation: transistors