Random-access memory: Difference between revisions

Revision as of 18:31, 8 September 2024

Revision as of 06:56, 9 September 2024

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===MOS RAM===

In 1957, Frosch and Derick were able to manufacture 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 |lastlast1=Frosch |firstfirst1=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 Thethe Electrochemical Society |language=en |volume=104 |issue=9 |pages=547 |doi=10.1149/1.2428650}}</ref> Subsequently, a team demonstrated a working [[MOSFET]] at Bell Labs 1960.<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}}</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" />

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Usually several memory cells share the same address. For example, a 4 bit 'wide' RAM chip has 4 memory cells for each address. Often the width of the memory and that of the microprocessor are different, for a 32 bit microprocessor, eight 4 bit RAM chips would be needed.

Often more addresses are needed than can be provided by a device. In that case, external multiplexors to the device are used to activate the correct device that is being accessed. RAM is often byte addressable, although it is also possible to make RAM that is word-addressable.<ref>{{cite book | url=https://wwwbooks.google.com.pa/books/edition/The_Essentials_of_Computer_Organization/?id=QGPHAl9GE-IC?hl=en&gbpv=1&dq=size+of+a+memory+address&pg=PA321&printsec | isbn=frontcover978-0-7637-3769-6 | title=The Essentials of Computer Organization and Architecture | date=2006 | publisher=Jones & Bartlett Learning }}</ref><ref>{{cite book | url=https://books.google.com.pa/books?id=-vQCEAAAQBAJ | title=Foundations of Computer Technology | isbn=978-1-000-15371-2 | last1=Anderson | first1=Alexander John | date=25 October 2020 | publisher=CRC Press }}</ref>

==Memory hierarchy==