Random-access memory: Difference between revisions

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Revision as of 19:43, 23 July 2024

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Non-volatile RAM has also been developed<ref>{{cite magazine|last=Gallagher|first=Sean|title=Memory that never forgets: non-volatile DIMMs hit the market|url=https://arstechnica.com/information-technology/2013/04/memory-that-never-forgets-non-volatile-dimms-hit-the-market/|magazine=[[Ars Technica]]|url-status=live|archive-url=https://web.archive.org/web/20170708073138/https://arstechnica.com/information-technology/2013/04/memory-that-never-forgets-non-volatile-dimms-hit-the-market/|archive-date=July 8, 2017|date=April 4, 2013}}</ref> and other types of [[Non-volatile memory|non-volatile memories]] allow random access for read operations, but either do not allow write operations or have other kinds of limitations. These include most types of [[read-only memory|ROM]] and [[NOR flash memory]].

The use of semiconductor RAM dates back to 1965 when IBM introduced the monolithic (single-chip) 16-bit SP95 SRAM chip for their [[IBM System/360|System/360 Model 95]] computer, and [[Toshiba]] used discrete DRAM memory cells for its 180-bit Toscal BC-1411 [[electronic calculator]], both based on [[bipolar transistor]]s. While it offered higher speeds than [[magnetic-core memory]], bipolar DRAM could not compete with the lower price of the then-dominant magnetic-core memory.<ref>{{cite web |title=1966: Semiconductor RAMs Serve High-speed Storage Needs |url=https://www.computerhistory.org/siliconengine/semiconductor-rams-serve-high-speed-storage-needs/ |website=Computer History Museum}}</ref> Memory based on MOS transistors, was developed in the late 1960s and was the basis for all early commercial semiconductor memory. The first commercial DRAM IC chip, the 1K [[Intel 1103]], was introduced in October 1970. [[Synchronous dynamic random-access memory]] (SDRAM) later debuted with the [[Samsung Electronics|Samsung]] KM48SL2000 chip in 1992.<!--[[User:Kvng/RTH]]-->

==History==

[[File:Early SSA accounting operations.jpg|thumb|These IBM [[tabulating machine]]s from the mid-1930s used [[mechanical counter]]s to store information.]]

[[File:Bundesarchiv Bild 183-1989-0406-022, VEB Carl Zeiss Jena, 1-Megabit-Chip.jpg|thumb|right|1-[[megabit]] (Mbit) chip, one of the last models developed by [[Carl Zeiss AG|VEB Carl Zeiss Jena]] in 1989]]

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=live|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 devicedevices]]s 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]] [[triode]]s, and later, out of discrete [[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.<!--[[User:Kvng/RTH]]-->

The first practical form of random-access memory was the [[Williams tube]] starting in 1947. 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}}</ref>

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[[Dynamic random-access memory]] (DRAM) allowed replacement of a 4 or 6-transistor latch circuit by a single transistor for each memory bit, greatly increasing memory density at the cost of volatility. Data was stored in the tiny capacitance of each transistor, and had to be periodically refreshed every few milliseconds before the charge could leak away. [[Toshiba]]'s Toscal BC-1411 [[electronic calculator]], which was introduced in 1965,<ref>[http://collection.sciencemuseum.org.uk/objects/co8406093/toscal-bc-1411-calculator-with-electronic-calculator Toscal BC-1411 calculator]. {{webarchive|url=https://web.archive.org/web/20170729145228/http://collection.sciencemuseum.org.uk/objects/co8406093/toscal-bc-1411-calculator-with-electronic-calculator |date=2017-07-29 }}, [[Science Museum, London]].</ref><ref name="bc-spec"/><ref name="bc"/> used a form of capacitive bipolar DRAM, storing 180-bit data on discrete [[Memory cell (computing)|memory cells]], consisting of [[germanium]] bipolar transistors and capacitors.<ref name="bc-spec"/><ref name="bc"/> While it offered higher speeds than magnetic-core memory, bipolar DRAM could not compete with the lower price of the then dominant magnetic-core memory.<ref>{{cite web |title=1966: Semiconductor RAMs Serve High-speed Storage Needs |url=https://www.computerhistory.org/siliconengine/semiconductor-rams-serve-high-speed-storage-needs/ |website=Computer History Museum}}</ref>

[[File:Bundesarchiv Bild 183-1989-0406-022, VEB Carl Zeiss Jena, 1-Megabit-Chip.jpg|thumb|right|CMOS 1-[[megabit]] (Mbit) DRAM chip, one of the last models developed by [[Carl Zeiss AG|VEB Carl Zeiss Jena]] in 1989]]

MOS technology is the basis for modern DRAM. In 1966, Dr. [[Robert H. Dennard]] at the [[IBM Thomas J. Watson Research Center]] was working on MOS memory. While examining the characteristics of MOS technology, he found it was capable of building [[capacitor]]s, and that storing a charge or no charge on the MOS capacitor could represent the 1 and 0 of a bit, while the MOS transistor could control writing the charge to the capacitor. This led to his development of a single-transistor DRAM memory cell.<ref name="ibm100"/> In 1967, Dennard filed a patent under IBM for a single-transistor DRAM memory cell, based on MOS technology.<ref name="Robert Dennard"/> The first commercial DRAM IC chip was the [[Intel 1103]], which was [[Semiconductor manufacturing process|manufactured]] on an [[10 μm process|8{{nbsp}}μm]] MOS process with a capacity of 1{{nbsp}}[[Kilobit|kbit]], and was released in 1970.<ref name="computerhistory1970"/><ref name="Lojek-1103"/><ref>{{cite web |first=Mary |last=Bellis |url=http://inventors.about.com/library/weekly/aa100898.htm |title=The Invention of the Intel 1103 |access-date=2015-07-11 |archive-date=2020-03-14 |archive-url=https://web.archive.org/web/20200314061801/http://inventors.about.com/library/weekly/aa100898.htm |url-status=dead }}</ref>