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In June 1951, the [[UNIVAC I]] (Universal Automatic Computer) was delivered to the [[United States Census Bureau|U.S. Census Bureau]]. Remington Rand eventually sold 46 machines at more than {{US$|1 million}} each (${{Formatprice|{{Inflation|US|1000000|1951|r=-4}}|0}} as of {{CURRENTYEAR}}).{{Inflation-fn|US}} UNIVAC was the first "mass-produced" computer. It used 5,200 vacuum tubes and consumed {{val|125|ul=kW}} of power. Its primary storage was [[Sequential access|serial-access]] mercury delay lines capable of storing 1,000 words of 11 decimal digits plus sign (72-bit words).
In 1952, [[Groupe Bull|Compagnie des Machines Bull]] released the [[Bull Gamma 3|Gamma 3]] computer, which became a large success in Europe, eventually selling more than 1,200 units, and the first computer produced in more than 1,000 units.<ref name=":1">{{Cite journal |last=Leclerc |first=Bruno |date=January 1990 |title=From Gamma 2 to Gamma E.T.: The Birth of Electronic Computing at Bull
[[File:IBM-650-panel.jpg|thumb|right|Front panel of the [[IBM 650]] ]]
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At the [[University of Manchester]], a team under the leadership of [[Tom Kilburn]] designed and built a machine using the newly developed [[transistor]]s instead of valves. Initially the only devices available were [[germanium]] [[point-contact transistor]]s, less reliable than the valves they replaced but which consumed far less power.{{sfn|Lavington|1998|pp=34–35}} Their first [[transistor computer|transistorized computer]], and the first in the world, was [[Manchester computers#Transistor Computer|operational by 1953]],{{sfn|Lavington|1998|p=37}} and a second version was completed there in April 1955.{{sfn|Lavington|1998|p=37}} The 1955 version used 200 transistors, 1,300 [[Solid-state electronics|solid-state]] [[diode]]s, and had a power consumption of 150 watts. However, the machine did make use of valves to generate its 125 kHz clock waveforms and in the circuitry to read and write on its magnetic drum memory, so it was not the first completely transistorized computer.
That distinction goes to the [[Harwell CADET]] of 1955,<ref name="ieeexplore.ieee"/> built by the electronics division of the [[Atomic Energy Research Establishment]] at [[Harwell, Oxfordshire|Harwell]]. The design featured a 64-kilobyte magnetic drum memory store with multiple moving heads that had been designed at the [[National Physical Laboratory (United Kingdom)|National Physical Laboratory, UK]]. By 1953 this 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.<ref>{{cite book |last=Cooke-Yarborough |first=E.H. |title=Introduction to Transistor Circuits |publisher=Oliver and Boyd |year=1957 |___location=Edinburgh}}</ref><ref name="ieeexplore.ieee">{{cite journal| title=Some early transistor applications in the UK| journal=Engineering Science & Education Journal| volume=7| issue=3| pages=100–106| year=1998| last1=Cooke-Yarborough| first1=E.H.| doi=10.1049/esej:19980301| doi-broken-date=
CADET used 324-point-contact transistors provided by the UK company [[Standard Telephones and Cables]]; 76 [[Bipolar junction transistor|junction transistor]]s were used for the first stage amplifiers for data read from the drum, since point-contact transistors were too noisy. From August 1956, CADET was offering a regular computing service, during which it often executed continuous computing runs of 80 hours or more.<ref>{{cite book |last=Lavington |first=Simon |title=Early British Computers |publisher=Manchester University Press |year=1980 |url=https://ed-thelen.org/comp-hist/EarlyBritish-05-12.html#Ch-09 |isbn=0-7190-0803-4 |access-date=2014-01-07 |archive-date=2019-05-24 |archive-url=https://web.archive.org/web/20190524164254/http://ed-thelen.org/comp-hist/EarlyBritish-05-12.html#Ch-09 |url-status=live }}</ref><ref>{{Cite journal |doi= 10.1049/pi-b-1.1956.0076 |title=A transistor digital computer |journal=Proceedings of the IEE - Part B: Radio and Electronic Engineering |volume=103 |issue=3S |pages=364–370 |year=1956 |last1=Cooke-Yarborough |first1=E.H. |last2= Barnes |first2=R.C.M. |last3=Stephen |first3=J.H. |last4=Howells |first4=G.A.}}</ref> Problems with the reliability of early batches of point contact and alloyed junction transistors meant that the machine's [[mean time between failures]] was about 90 minutes, but this improved once the more reliable [[bipolar junction transistor]]s became available.{{sfn|Lavington|1998|pp=36–37}}
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