Editing Apollo Guidance Computer (section)

===Logic hardware===
Following the use of [[integrated circuit]] (IC) chips in the [[Interplanetary Monitoring Platform]] (IMP) in 1963, IC technology was later adopted for the AGC.<ref>{{cite book |last1=Butrica |first1=Andrew J. |chapter=Chapter 3: NASA's Role in the Manufacture of Integrated Circuits |editor-last1=Dick |editor-first1=Steven J. |title=Historical Studies in the Societal Impact of Spaceflight |date=2015 |publisher=[[NASA]] |isbn=978-1-62683-027-1 |pages=149–250 |url=https://www.nasa.gov/sites/default/files/atoms/files/historical-studies-societal-impact-spaceflight-ebook_tagged.pdf}}</ref> The Apollo flight computer was one of the first computers to use [[silicon]] IC chips.<ref name=":2" /><ref name=":1">{{cite web |title=Apollo Guidance Computer and the First Silicon Chips |url=https://airandspace.si.edu/stories/editorial/apollo-guidance-computer-and-first-silicon-chips |website=[[National Air and Space Museum]] |publisher=[[Smithsonian Institution]] |access-date=1 September 2019 |date=14 October 2015}}</ref>

While the Block I version used 4,100 ICs, each containing a single three-input [[NOR gate]], the later Block II version (used in the crewed flights) used about 2,800 ICs, mostly dual three-input NOR gates and smaller numbers of expanders and sense amplifiers.<ref name="HALL-MITRole"/>{{rp|27,266}} The ICs, from [[Fairchild Semiconductor]], were implemented using [[resistor–transistor logic]] (RTL) in a [[Flatpack (electronics)|flat-pack]]. They were connected via [[wire wrap]], and the wiring was then embedded in cast [[epoxy]] plastic.<ref name="HALL-MITRole" />{{rp|129}}

The use of a single type of IC (the dual NOR3) throughout the AGC avoided problems that plagued another early IC computer design, the [[LGM-30 Minuteman|Minuteman II]] [[D-37C|guidance computer]], which used a mix of [[diode–transistor logic]] and [[diode logic]] gates.{{citation needed|date=February 2018}} NOR gates are [[Logic gate#Universal logic gates|universal logic gates]] from which any other gate can be made, though at the cost of using more gates.<ref>Peirce, C. S. (manuscript winter of 1880–81), "A Boolian Algebra with One Constant", published 1933 in ''[[Charles Sanders Peirce bibliography#CP|Collected Papers]]'' v. 4, paragraphs 12–20. Reprinted 1989 in ''[[Charles Sanders Peirce bibliography#W|Writings of Charles S. Peirce]]'' v. 4, pp. 218–21, Google [https://archive.org/details/writingsofcharle0002peir/page/218]. See Roberts, Don D. (2009), ''The Existential Graphs of Charles S. Peirce'', p. 131.</ref>