Editing Central processing unit (section)

===Large-scale integration CPUs===
[[Lee Boysel]] published influential articles, including a 1967 "manifesto", which described how to build the equivalent of a 32-bit mainframe computer from a relatively small number of [[large-scale integration]] circuits (LSI).<ref>{{cite book |author=Bassett |first=Ross Knox |url=https://books.google.com/books?id=UUbB3d2UnaAC |title=To the Digital Age: Research Labs, Start-up Companies, and the Rise of MOS Technology |publisher=[[The Johns Hopkins University Press]] |year=2007 |isbn=978-0-8018-6809-2 |pages=127–128, 256, and 314 |language=en-us}}</ref><ref name="shirriff">{{cite web |first=Ken |last=Shirriff
|url=http://www.righto.com/2015/05/the-texas-instruments-tmx-1795-first.html |title=The Texas Instruments TMX 1795: the first, forgotten microprocessor |archive-url=https://web.archive.org/web/20210126074942/http://www.righto.com/2015/05/the-texas-instruments-tmx-1795-first.html |archive-date=2021-01-26 |url-status=live}}</ref> The only way to build LSI chips, which are chips with a hundred or more gates, was to build them using a [[MOSFET|metal–oxide–semiconductor]] (MOS) [[semiconductor manufacturing process]] (either [[PMOS logic]], [[NMOS logic]], or [[CMOS]] logic). However, some companies continued to build processors out of bipolar [[transistor–transistor logic]] (TTL) chips because bipolar junction transistors were faster than MOS chips up until the 1970s (a few companies such as [[Datapoint]] continued to build processors out of TTL chips until the early 1980s).<ref name="shirriff" /> In the 1960s, MOS ICs were slower and initially considered useful only in applications that required low power.<ref>{{cite web|url=http://www.brown.edu/Departments/Engineering/Labs/ddzo/speed.html|title=Speed & Power in Logic Families|access-date=2017-08-02|archive-date=2017-07-26|archive-url=https://web.archive.org/web/20170726175011/http://www.brown.edu/Departments/Engineering/Labs/ddzo/speed.html|url-status=live}}.</ref><ref>{{cite book |first=T. J. |last=Stonham |url=https://books.google.com/books?id=UE6vFEnGP2kC |title=Digital Logic Techniques: Principles and Practice |date=1996 |page=174|publisher=Taylor & Francis |isbn=9780412549700 }}</ref> Following the development of [[silicon-gate]] MOS technology by [[Federico Faggin]] at Fairchild Semiconductor in 1968, MOS ICs largely replaced bipolar TTL as the standard chip technology in the late 1970s.<ref>{{cite web |title=1968: Silicon Gate Technology Developed for ICs |url=https://www.computerhistory.org/siliconengine/silicon-gate-technology-developed-for-ics/ |website=Computer History Museum |access-date=2019-08-16 |archive-date=2020-07-29 |archive-url=https://web.archive.org/web/20200729145834/https://www.computerhistory.org/siliconengine/silicon-gate-technology-developed-for-ics/ |url-status=live }}</ref>

As the [[microelectronic]] technology advanced, an increasing number of transistors were placed on ICs, decreasing the number of individual ICs needed for a complete CPU. MSI and LSI ICs increased transistor counts to hundreds, and then thousands. By 1968, the number of ICs required to build a complete CPU had been reduced to 24 ICs of eight different types, with each IC containing roughly 1000 MOSFETs.<ref>{{cite conference |first=R. K. |last=Booher |url=http://www.computer.org/csdl/proceedings/afips/1968/5072/00/50720877.pdf |title=MOS GP Computer |publisher=[[AFIPS]] |page=877 |date=1968 |conference=International Workshop on Managing Requirements Knowledge
|doi=10.1109/AFIPS.1968.126 |archive-url=https://web.archive.org/web/20170714014430/https://www.computer.org/csdl/proceedings/afips/1968/5072/00/50720877.pdf |archive-date=2017-07-14 |url-status=live}}</ref> In stark contrast with its SSI and MSI predecessors, the first LSI implementation of the PDP-11 contained a CPU composed of only four LSI integrated circuits.<ref>{{cite book |title=LSI-11, PDP-11/03 user's manual |date=November 1975 |publisher=[[Digital Equipment Corporation]] |edition=2nd |location=Maynard, Massachusetts |page=4{{hyp}}3 |language=en-us |chapter=LSI-11 Module Descriptions |access-date=2015-02-20 |url=http://www.bitsavers.org/pdf/dec/pdp11/1103/EK-LSI11-TM-002.pdf |archive-url=https://web.archive.org/web/20211010023115/http://www.bitsavers.org/pdf/dec/pdp11/1103/EK-LSI11-TM-002.pdf |archive-date=2021-10-10 |url-status=live}}</ref>