Random-access memory: Difference between revisions

Revision as of 11:09, 6 January 2025

Revision as of 23:51, 16 January 2025

Line 45:

}}</ref> It was followed by the development of MOS SRAM by John Schmidt at Fairchild in 1964.<ref name="computerhistory1970"/> SRAM became an alternative to magnetic-core memory, but required six MOS transistors for each [[bit]] of data.<ref name="ibm100">{{cite web |title=DRAM |url=https://www.ibm.com/ibm/history/ibm100/us/en/icons/dram/ |website=IBM100 |publisher=[[IBM]] |access-date=20 September 2019 |date=9 August 2017}}</ref> Commercial use of SRAM began in 1965, when [[IBM]] introduced the SP95 memory chip for the [[IBM System/360|System/360 Model 95]].<ref name="computerhistory1966"/>

[[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 [[Memory refresh|refreshed]] every few milliseconds before the charge could leak away.<!--[[User:Kvng/RTH]]-->

[[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" /> 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]]. 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 ComputerUser:Kvng/RTH]], 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]]