Editing Central processing unit (section)

===Microprocessors===
{{main|Microprocessor}}
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|image1 = 80486dx2-large.jpg
|caption1 = [[Die (integrated circuit)|Die]] of an [[Intel 80486DX2]] microprocessor (actual size: 12 × 6.75&nbsp;mm) in its packaging
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|caption2 = [[Intel]] Core i5 CPU on a [[Sony Vaio E series|Vaio E series]] laptop motherboard (on the right, beneath the [[heat pipe]])
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[[File:Laptop-intel-core2duo-t5500.jpg|thumb|Inside of a laptop, with the CPU removed from socket]]
Since microprocessors were first introduced they have almost completely overtaken all other central processing unit implementation methods. The first commercially available microprocessor, made in 1971, was the [[Intel 4004]], and the first widely used microprocessor, made in 1974, was the [[Intel 8080]]. Mainframe and minicomputer manufacturers of the time launched proprietary IC development programs to upgrade their older [[computer architecture]]s, and eventually produced [[instruction set architecture|instruction set]] compatible microprocessors that were backward-compatible with their older hardware and software. Combined with the advent and eventual success of the ubiquitous [[personal computer]], the term ''CPU'' is now applied almost exclusively{{Efn|Integrated circuits are now used to implement all CPUs, except for a few machines designed to withstand large electromagnetic pulses, say from a nuclear weapon.}} to microprocessors. Several CPUs (denoted ''cores'') can be combined in a single processing chip.<ref>{{cite web |url=https://www.techtarget.com/searchdatacenter/definition/multi-core-processor |publisher=TechTarget |title=What is a multicore processor and how does it work? |first=Stephen J. |last=Bigelow |date=March 2022 |access-date=July 17, 2022 |archive-date=July 11, 2022 |archive-url=https://web.archive.org/web/20220711210214/https://www.techtarget.com/searchdatacenter/definition/multi-core-processor |url-status=live }}</ref>

{{anchor|DISCRETE-PROCESSOR}}
Previous generations of CPUs were implemented as [[discrete components]] and numerous small [[integrated circuit]]s (ICs) on one or more circuit boards.<ref>{{cite web |author=Birkby |first=Richard |title=A Brief History of the Microprocessor |url=http://www.computermuseum.li/Testpage/MicroprocessorHistory.htm |url-status=dead |archive-url=https://web.archive.org/web/20150923205820/http://www.computermuseum.li/Testpage/MicroprocessorHistory.htm |archive-date=September 23, 2015 |access-date=October 13, 2015 |website=computermuseum.li}}</ref> Microprocessors, on the other hand, are CPUs manufactured on a very small number of ICs; usually just one.<ref name=Osborne80>{{cite book | first=Adam | last=Osborne | title=An Introduction to Microcomputers | volume=1: Basic Concepts | edition=2nd | publisher=Osborne-McGraw Hill | location=Berkeley, California | year=1980 | isbn=978-0-931988-34-9 | url=https://archive.org/details/introductiontomi00adam }}</ref> The overall smaller CPU size, as a result of being implemented on a single die, means faster switching time because of physical factors like decreased gate [[parasitic capacitance]].<ref>{{cite web|last1=Zhislina|first1=Victoria|title=Why has CPU frequency ceased to grow?|url=https://software.intel.com/en-us/blogs/2014/02/19/why-has-cpu-frequency-ceased-to-grow|publisher=Intel|access-date=October 14, 2015|date=2014-02-19|archive-date=2017-06-21|archive-url=https://web.archive.org/web/20170621074555/https://software.intel.com/en-us/blogs/2014/02/19/why-has-cpu-frequency-ceased-to-grow|url-status=live}}</ref><ref>{{cite web |title=MOS Transistor – Electrical Engineering & Computer Science |url=http://www.eecs.berkeley.edu/~tking/theses/bsriram.pdf |url-status=live |archive-url=https://ghostarchive.org/archive/20221009/http://www.eecs.berkeley.edu/~tking/theses/bsriram.pdf |archive-date=2022-10-09 |access-date=October 14, 2015 |publisher=University of California}}</ref> This has allowed synchronous microprocessors to have clock rates ranging from tens of megahertz to several gigahertz. Additionally, the ability to construct exceedingly small transistors on an IC has increased the complexity and number of transistors in a single CPU many fold. This widely observed trend is described by [[Moore's law]], which had proven to be a fairly accurate predictor of the growth of CPU (and other IC) complexity until 2016.<ref>{{Cite news|url=https://www.technologyreview.com/s/601441/moores-law-is-dead-now-what/|title=Moore's Law Is Dead. Now What?|last=Simonite|first=Tom|work=MIT Technology Review|access-date=2018-08-24|language=en|archive-date=2018-08-22|archive-url=https://web.archive.org/web/20180822071655/https://www.technologyreview.com/s/601441/moores-law-is-dead-now-what/|url-status=live}}</ref><ref name="MooresLaw">{{cite interview|title=Excerpts from A Conversation with Gordon Moore: Moore's Law |first=Gordon |last=Moore |author-link=Gordon Moore |publisher=Intel |year=2005 |url=http://download.intel.com/museum/Moores_Law/Video-Transcripts/Excepts_A_Conversation_with_Gordon_Moore.pdf |access-date=2012-07-25 |url-status=dead |archive-url=https://web.archive.org/web/20121029060050/http://download.intel.com/museum/Moores_Law/Video-Transcripts/Excepts_A_Conversation_with_Gordon_Moore.pdf |archive-date=2012-10-29 }}</ref>

While the complexity, size, construction and general form of CPUs have changed enormously since 1950,<ref>{{cite web|title=A detailed history of the processor|url=https://www.techjunkie.com/a-cpu-history/|publisher=Tech Junkie|date=15 December 2016|access-date=14 August 2019|archive-date=14 August 2019|archive-url=https://web.archive.org/web/20190814125742/https://www.techjunkie.com/a-cpu-history/|url-status=live}}</ref> the basic design and function has not changed much at all. Almost all common CPUs today can be very accurately described as von Neumann stored-program machines.<ref>{{cite book |chapter=Von Neumann Computers | first1=Rudolf|last1= Eigenmann |first2= David|last2=Lilja|title=Wiley Encyclopedia of Electrical and Electronics Engineering |s2cid=8197337 |year=1998 |doi=10.1002/047134608X.W1704 |isbn=047134608X }}</ref>{{Efn|The so-called "von Neumann" memo expounded the idea of stored programs,<ref>{{cite magazine|last1=Aspray|first1=William|title=The stored program concept |doi=10.1109/6.58457|magazine=IEEE Spectrum|volume=27|issue=9|date=September 1990|page=51 }}</ref> which for example may be stored on [[punched card]]s, paper tape, or magnetic tape.}} As Moore's law no longer holds, concerns have arisen about the limits of integrated circuit transistor technology. Extreme miniaturization of [[logic gate|electronic gates]] is causing the effects of phenomena like [[electromigration]] and [[subthreshold leakage]] to become much more significant.<ref>{{cite web |last1= Saraswat |first1=Krishna |title=Trends in Integrated Circuits Technology |url=https://web.stanford.edu/class/ee311/NOTES/TrendsSlides.pdf |archive-url=https://web.archive.org/web/20150724091731/https://web.stanford.edu/class/ee311/NOTES/TrendsSlides.pdf |archive-date=2015-07-24 |url-status=dead|access-date=June 15, 2018}}</ref><ref>{{cite web |title=Electromigration |url=http://www.csl.mete.metu.edu.tr/Electromigration/emig.htm |publisher=Middle East Technical University |access-date=June 15, 2018 |archive-date=July 31, 2017 |archive-url=https://web.archive.org/web/20170731070649/http://www.csl.mete.metu.edu.tr/Electromigration/emig.htm |url-status=live }}</ref> These newer concerns are among the many factors causing researchers to investigate new methods of computing such as the [[quantum computer]], as well as to expand the use of [[Parallel computing|parallelism]] and other methods that extend the usefulness of the classical von Neumann model.