Editing History of computing hardware (section)

==Magnetic memory==
[[File:Coincident-current magnetic core.svg|thumb|right|Diagram of a 4×4 plane of [[magnetic-core memory]] in an X/Y line coincident-current setup. X and Y are drive lines, S is sense, Z is inhibit. Arrows indicate the direction of current for writing.]]
Magnetic [[drum memory|drum memories]] were developed for the US Navy during WW II with the work continuing at [[Engineering Research Associates]] (ERA) in 1946 and 1947. ERA, then a part of Univac included a drum memory in its [[UNIVAC 1103|1103]], announced in February 1953. The first mass-produced computer, the [[IBM 650]], also announced in 1953 had about 8.5 kilobytes of drum memory.

[[Magnetic core|Magnetic-core]] memory patented in 1949<ref>{{Cite patent |country=US |number=2708722 |title=Pulse transfer controlling device |fdate=1949-10-21 |gdate=1955-05-17 |invent1=Wang |inventor1-first=An |inventorlink=An Wang}}</ref> with its first usage demonstrated for the [[Whirlwind I#The memory subsystem|Whirlwind computer]] in August 1953.<ref>{{Cite web |title=1953: Whirlwind computer debuts core memory |url=https://www.computerhistory.org/storageengine/whirlwind-computer-debuts-core-memory/ |url-status=live |archive-url=https://web.archive.org/web/20180508121757/http://www.computerhistory.org/storageengine/whirlwind-computer-debuts-core-memory/ |archive-date=2018-05-08 |access-date=2023-08-26 |website=[[Computer History Museum]]}}</ref> Commercialization followed quickly. Magnetic core was used in peripherals of the IBM 702 delivered in July 1955, and later in the 702 itself. The [[IBM 704]] (1955) and the Ferranti Mercury (1957) used magnetic-core memory. It went on to dominate the field into the 1970s, when it was replaced with semiconductor memory.  Magnetic core peaked in volume about 1975 and declined in usage and market share thereafter.<ref>{{cite magazine |url=https://books.google.com/books?id=paExEmGMXlAC&pg=PA419 |title=Takeover in the memory market |author=N. Valery |magazine=New Scientist |date=21 August 1975 |pages=419–421 |access-date=2019-01-22 |url-status=live |archive-date=2023-02-02 |archive-url=https://web.archive.org/web/20230202181645/https://books.google.com/books?id=paExEmGMXlAC&pg=PA419}}</ref>

As late as 1980, PDP-11/45 machines using magnetic-core main memory and drums for swapping were still in use at many of the original UNIX sites.