Editing Central processing unit (section)

===Transistor CPUs===
[[File:IBM PPC604e 200.jpg|thumb|IBM PowerPC 604e processor]]
{{Main|Transistor computer}}
The design complexity of CPUs increased as various technologies facilitated the building of smaller and more reliable electronic devices. The first such improvement came with the advent of the [[transistor]]. Transistorized CPUs during the 1950s and 1960s no longer had to be built out of bulky, unreliable, and fragile switching elements, like [[vacuum tube]]s and [[relay]]s.<ref>{{cite web|title=1953: Transistorized Computers Emerge|url=http://www.computerhistory.org/siliconengine/transistorized-computers-emerge/|work=Computer History Museum|access-date=June 3, 2016|archive-date=June 1, 2016|archive-url=https://web.archive.org/web/20160601191253/http://www.computerhistory.org/siliconengine/transistorized-computers-emerge/|url-status=live}}</ref> With this improvement, more complex and reliable CPUs were built onto one or several [[printed circuit board]]s containing discrete (individual) components.

In 1964, [[IBM]] introduced its [[IBM System/360]] computer architecture that was used in a series of computers capable of running the same programs with different speeds and performances.<ref>{{cite web|url=http://www-03.ibm.com/ibm/history/exhibits/mainframe/mainframe_FS360.html|title=IBM System/360 Dates and Characteristics|publisher=IBM|date=2003-01-23|access-date=2016-01-13|archive-date=2017-11-21|archive-url=https://web.archive.org/web/20171121223500/http://www-03.ibm.com/ibm/history/exhibits/mainframe/mainframe_FS360.html|url-status=dead}}</ref> This was significant at a time when most electronic computers were incompatible with one another, even those made by the same manufacturer. To facilitate this improvement, IBM used the concept of a [[microprogram]] (often called "microcode"), which still sees widespread use in modern CPUs.<ref name="amdahl1964">{{cite journal | last1 = Amdahl | first1 = G. M. | author-link1 = Gene Amdahl | last2 = Blaauw | first2 = G. A. | author-link2 = Gerrit Blaauw | last3 = Brooks | first3 = F. P. Jr. | author-link3 = Fred Brooks | title = Architecture of the IBM System/360 | journal = IBM Journal of Research and Development | volume = 8 | issue = 2 | pages = 87–101 | issn = 0018-8646 | publisher = [[IBM]] | date = April 1964 | doi = 10.1147/rd.82.0087 }}</ref> The System/360 architecture was so popular that it dominated the [[mainframe computer]] market for decades and left a legacy that is continued by similar modern computers like the IBM [[IBM System z|zSeries]].<ref>{{cite web|last1=Brodkin|first1=John|title=50 years ago, IBM created mainframe that helped send men to the Moon|url=https://arstechnica.com/information-technology/2014/04/50-years-ago-ibm-created-mainframe-that-helped-bring-men-to-the-moon/|website=Ars Technica|date=7 April 2014|access-date=9 April 2016|archive-date=8 April 2016|archive-url=https://web.archive.org/web/20160408105602/http://arstechnica.com/information-technology/2014/04/50-years-ago-ibm-created-mainframe-that-helped-bring-men-to-the-moon/|url-status=live}}</ref><ref>{{cite web|last1=Clarke|first1=Gavin|title=Why won't you DIE? IBM's S/360 and its legacy at 50|url=https://www.theregister.co.uk/2014/04/07/ibm_s_360_50_anniversary/|website=The Register|access-date=9 April 2016|archive-date=24 April 2016|archive-url=https://web.archive.org/web/20160424121559/http://www.theregister.co.uk/2014/04/07/ibm_s_360_50_anniversary/|url-status=live}}</ref> In 1965, [[Digital Equipment Corporation]] (DEC) introduced another influential computer aimed at the scientific and research markets—the [[PDP-8]].<ref>{{cite web|title=Online PDP-8 Home Page, Run a PDP-8|url=http://www.pdp8.net/index.shtml|website=PDP8|access-date=September 25, 2015|archive-date=August 11, 2015|archive-url=https://web.archive.org/web/20150811174442/http://www.pdp8.net/index.shtml|url-status=live}}</ref>
[[File:Board with SPARC64 VIIIfx processors on display in Fujitsu HQ.JPG|thumb|Fujitsu board with SPARC64 VIIIfx processors]]
Transistor-based computers had several distinct advantages over their predecessors. Aside from facilitating increased reliability and lower power consumption, transistors also allowed CPUs to operate at much higher speeds because of the short switching time of a transistor in comparison to a tube or relay.<ref>{{cite web|title=Transistors, Relays, and Controlling High-Current Loads|url=https://itp.nyu.edu/physcomp/lessons/electronics/transistors-relays-and-controlling-high-current-loads/|publisher=ITP Physical Computing|work=New York University|access-date=9 April 2016|archive-date=21 April 2016|archive-url=https://web.archive.org/web/20160421232136/https://itp.nyu.edu/physcomp/lessons/electronics/transistors-relays-and-controlling-high-current-loads/|url-status=live}}</ref> The increased reliability and dramatically increased speed of the switching elements, which were almost exclusively transistors by this time; CPU clock rates in the tens of megahertz were easily obtained during this period.<ref name = pcgamer>{{cite magazine|last1=Lilly|first1=Paul|title=A Brief History of CPUs: 31 Awesome Years of x86|url=http://www.pcgamer.com/a-brief-history-of-cpus-31-awesome-years-of-x86/|magazine=PC Gamer|access-date=June 15, 2016|date=2009-04-14|archive-date=2016-06-13|archive-url=https://web.archive.org/web/20160613202439/http://www.pcgamer.com/a-brief-history-of-cpus-31-awesome-years-of-x86/|url-status=live}}</ref> Additionally, while discrete transistor and IC CPUs were in heavy usage, new high-performance designs like [[single instruction, multiple data]] (SIMD) [[vector processor]]s began to appear.<ref name="patterson">{{cite book |last1=Patterson |first1=David A. |url=https://archive.org/details/computerorganiz000henn/page/751 |title=Computer Organization and Design: the Hardware/Software Interface |last2=Hennessy |first2=John L. |last3=Larus |first3=James R. |date=1999 |publisher=Kaufmann |isbn=978-1558604285 |edition=3rd printing of 2nd |location=San Francisco, California |page=[https://archive.org/details/computerorganiz000henn/page/751 751] |language=en-us}}</ref> These early experimental designs later gave rise to the era of specialized [[supercomputer]]s like those made by [[Cray|Cray Inc]] and [[Fujitsu|Fujitsu Ltd]].<ref name="patterson"/>