Random-access memory: Difference between revisions

Revision as of 23:29, 24 May 2025

Revision as of 23:59, 25 May 2025

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Early computers used [[relay]]s, [[mechanical counter]]s<ref>{{cite web|url=http://www-03.ibm.com/ibm/history/reference/faq_0000000011.html|title=IBM Archives -- FAQ's for Products and Services|work=ibm.com|url-status=dead|archive-url=https://web.archive.org/web/20121023184527/http://www-03.ibm.com/ibm/history/reference/faq_0000000011.html|archive-date=2012-10-23}}</ref> or [[Delay-line memory|delay lines]] for main memory functions. Ultrasonic delay lines were [[bit-serial architecture|serial devices]] which could only reproduce data in the order it was written. [[Drum memory]] could be expanded at relatively low cost but efficient retrieval of memory items requires knowledge of the physical layout of the drum to optimize speed. Latches built out of [[triode vacuum tube]]s, and later, out of [[discrete transistor]]s, were used for smaller and faster memories such as [[Hardware register|registers]]. Such registers were relatively large and too costly to use for large amounts of data; generally only a few dozen or few hundred bits of such memory could be provided.

The first practical form of random-access memory was the [[Williams tube]]. It stored data as electrically charged spots on the face of a [[cathode-ray tube]]. Since the electron beam of the CRT could read and write the spots on the tube in any order, memory was random access. The capacity of the Williams tube was a few hundred to around a thousand bits, but it was much smaller, faster, and more power-efficient than using individual vacuum tube latches. Developed at the [[Victoria University of Manchester|University of Manchester]] in England, the Williams tube provided the medium on which the first electronically stored program was implemented in the [[Manchester Baby]] computer, which first successfully ran a program on 21 June, 1948.<ref>{{Citation | last = Napper | first = Brian | title = Computer 50: The University of Manchester Celebrates the Birth of the Modern Computer | url = http://www.computer50.org/ | access-date = 26 May 2012 | url-status = dead | archive-url = https://web.archive.org/web/20120504133240/http://www.computer50.org/ | archive-date = 4 May 2012 }}</ref> In fact, rather than the Williams tube memory being designed for the Baby, the Baby was a [[testbed]] to demonstrate the reliability of the memory.<ref>{{Citation |last1=Williams |first1=F. C. |last2=Kilburn |first2=T. |title=Electronic Digital Computers |journal=Nature |volume=162 |pages=487 |date=Sep 1948 |doi=10.1038/162487a0 |issue=4117 |postscript=. |bibcode=1948Natur.162..487W |s2cid=4110351|doi-access=free }} Reprinted in ''The Origins of Digital Computers''.</ref><ref>{{Citation |last1=Williams |first1=F. C. |last2=Kilburn |first2=T. |last3=Tootill |first3=G. C. |title=Universal High-Speed Digital Computers: A Small-Scale Experimental Machine |url=http://www.computer50.org/kgill/mark1/ssem.html |journal=Proc. IEE |date=Feb 1951 |volume=98 |issue=61 |pages=13–28 |postscript=. |doi=10.1049/pi-2.1951.0004 |url-status=dead |archive-url=https://web.archive.org/web/20131117101730/http://www.computer50.org/kgill/mark1/ssem.html |archive-date=2013-11-17|url-access=subscription }}</ref>

[[Magnetic-core memory]] was invented in 1947 and developed up until the mid-1970s. It became a widespread form of random-access memory, relying on an array of magnetized rings. By changing the sense of each ring's magnetization, data could be stored with one bit stored per ring. Since every ring had a combination of address wires to select and read or write it, access to any memory ___location in any sequence was possible. Magnetic core memory was the standard form of [[computer memory]] until displaced by [[semiconductor memory]] in [[integrated circuit]]s (ICs) during the early 1970s.<ref name="computerhistory1970"/>

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===MOS RAM===

In 1957, Frosch and Derick manufactured the first silicon dioxide field-effect transistors at Bell Labs, the first transistors in which drain and source were adjacent at the surface.<ref>{{Cite journal |last1=Frosch |first1=C. J. |last2=Derick |first2=L |date=1957 |title=Surface Protection and Selective Masking during Diffusion in Silicon |url=https://iopscience.iop.org/article/10.1149/1.2428650 |journal=Journal of the Electrochemical Society |language=en |volume=104 |issue=9 |pages=547 |doi=10.1149/1.2428650|url-access=subscription }}</ref> Subsequently, in 1960, a team demonstrated a working [[MOSFET]] at Bell Labs.<ref>{{Cite journal |last=KAHNG |first=D. |date=1961 |title=Silicon-Silicon Dioxide Surface Device |url=https://doi.org/10.1142/9789814503464_0076 |journal=Technical Memorandum of Bell Laboratories |pages=583–596 |doi=10.1142/9789814503464_0076 |isbn=978-981-02-0209-5|url-access=subscription }}</ref><ref>{{Cite book |last=Lojek |first=Bo |title=History of Semiconductor Engineering |date=2007 |publisher=Springer-Verlag Berlin Heidelberg |isbn=978-3-540-34258-8 |___location=Berlin, Heidelberg |page=321}}</ref> This led to the development of [[metal–oxide–semiconductor]] (MOS) memory by John Schmidt at [[Fairchild Semiconductor]] in 1964.<ref name="computerhistory1970" /><ref>{{Cite book |url=https://books.google.com/books?id=kG4rAQAAIAAJ&q=John+Schmidt |title=Solid State Design – Vol. 6 |date=1965 |publisher=Horizon House}}</ref> In addition to higher speeds, MOS [[semiconductor memory]] was cheaper and consumed less power than magnetic core memory.<ref name="computerhistory1970" /> The development of [[silicon-gate]] [[MOS integrated circuit]] (MOS IC) technology by [[Federico Faggin]] at Fairchild in 1968 enabled the production of MOS [[memory chip]]s.<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=10 August 2019}}</ref> MOS memory overtook magnetic core memory as the dominant memory technology in the early 1970s.<ref name="computerhistory1970" />

Integrated bipolar [[static random-access memory]] (SRAM) was invented by Robert H. Norman at [[Fairchild Semiconductor]] in 1963.<ref>{{cite patent