Random-access memory: Difference between revisions

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[[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 capacitor-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> Capacitors had also been used for earlier memory schemes, such as the drum of the [[Atanasoff–Berry Computer]], the [[Williams tube]] and the [[Selectron tube]].

[[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 [[VEB Carl Zeiss Jena]], in 1989]]

In 1966, Dr. [[Robert Dennard]] invented invented modern DRAM architecture for which there's is a single MOS transistor per capacitor.<ref name="ibm100" /> 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>

The earliest DRAMs were often synchronized with the CPU clock (clocked) and were used with early microprocessors. In the mid-1970s, DRAMs moved to the asynchronous design, but in the 1990s returned to synchronous operation.<ref>{{cite book |author=P. Darche |url=https://books.google.com/books?id=rLC9zQEACAAJ |title=Microprocessor: Prolegomenes - Calculation and Storage Functions - Calculation Models and Computer |year=2020 |isbn=9781786305633 |page=59| publisher=John Wiley & Sons }}</ref><ref>{{cite book |author1=B. Jacob |url=https://books.google.com/books?id=SrP3aWed-esC |title=Memory Systems: Cache, DRAM, Disk |author2=S. W. Ng |author3=D. T. Wang |publisher=Morgan Kaufmann |year=2008 |isbn=9780080553849 |page=324}}</ref> In 1992 Samsung released KM48SL2000, which had a capacity of 16{{nbsp}}[[Mbit]].<ref name="electronic-design">{{cite journal |title=Electronic Design |journal=[[Electronic Design]] |date=1993 |volume=41 |issue=15–21 |url=https://books.google.com/books?id=QmpJAQAAIAAJ |publisher=Hayden Publishing Company |quote=The first commercial synchronous DRAM, the Samsung 16-Mbit KM48SL2000, employs a single-bank architecture that lets system designers easily transition from asynchronous to synchronous systems.}}</ref><ref>{{cite web |title=KM48SL2000-7 Datasheet |url=https://www.datasheetarchive.com/KM48SL2000-7-datasheet.html |publisher=[[Samsung]] |access-date=19 June 2019 |date=August 1992}}</ref> and mass-produced in 1993.<ref name="electronic-design"/> The first commercial [[DDR SDRAM]] ([[double data rate]] SDRAM) memory chip was Samsung's 64{{nbsp}}Mbit DDR SDRAM chip, released in June 1998.<ref>{{cite news |title=Samsung Electronics Develops First 128Mb SDRAM with DDR/SDR Manufacturing Option |url=https://www.samsung.com/semiconductor/insights/news-events/samsung-electronics-develops-first-128mb-sdram-with-ddr-sdr-manufacturing-option/ |access-date=23 June 2019 |work=[[Samsung Electronics]] |publisher=[[Samsung]] |date=10 February 1999}}</ref> [[GDDR]] (graphics DDR) is a form of DDR [[SGRAM]] (synchronous graphics RAM), which was first released by Samsung as a 16{{nbsp}}Mbit memory chip in 1998.<ref>{{cite news |title=Samsung Electronics Comes Out with Super-Fast 16M DDR SGRAMs |url=https://www.samsung.com/semiconductor/insights/news-events/samsung-electronics-comes-out-with-super-fast-16m-ddr-sgrams/ |access-date=23 June 2019 |work=[[Samsung Electronics]] |publisher=[[Samsung]] |date=17 September 1998}}</ref>