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Topic: Magnetic core memory

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Core rope memory

Bubble memory

Computer memory

Thin film memory

NVRAM

Computer storage

Delay line memory

Magnetic drum

Random access memory

Flash memory

Cache memory

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	Magnetic core memory - Wikipedia, the free encyclopedia
		Core memory was part of a family of related technologies, now largely forgotten, which exploited magnetic properties of materials to perform switching and amplification.
		Early core memory systems had cycle times of about 6 µs, which had fallen to 1.2 µs by the early 1970s, and by the mid-70s it was down to 600 ns (0.6 µs).
		A characteristic of core was that it is current-based, not voltage-based.
	en.wikipedia.org /wiki/Magnetic_core_memory (2026 words)

	Core rope memory - Wikipedia, the free encyclopedia
		Core rope memory is a form of read-only memory (ROM) for computers, first used by early NASA Mars probes and then in the Apollo Guidance Computer (AGC) designed by MIT and built by Raytheon.
		Contrary to ordinary coincident-current magnetic core memory, which was used for RAM at the time, the ferrite cores in a core rope are just used as transformers.
		The signal from a word line wire passing through a given core is coupled to the bit line wire and interpreted as a binary "one" while a word line wire that bypasses the core is not coupled to the bit line wire and is read as a "zero".
	en.wikipedia.org /wiki/Core_rope_memory (292 words)

	Magnetic core memory - LearnThis.Info Enclyclopedia (Site not responding. Last check: 2007-10-22)
		Although the manufacture of core memory was never automated, costs almost followed the not-yet-formulated Moore's Law; over the lifetime of the technology costs began at roughly a dollar a bit and eventually approached roughly $0.01 per bit.
		Early core memory systems had cycle times of about 6µs, which had fallen to 1.2µs by the early 1970s, and by the mid-70s it was down to 600ns (0.6µs).
		Examples of this are the heated air core memory of the IBM 1620 (which could take up to 30 minutes to reach operating temperature, about 106°F, ~41°C) and the heated oil bath core memory of the IBM 709.
	encyclopedia.learnthis.info /m/ma/magnetic_core_memory.html (1705 words)

	Our Collection - Memory
		Magnetic core memory consists of an arrangement of a small piece of magnetic material (the core) and current carrying conductors.
		Cores usually consisted of a mixture of iron oxide or ferrite particles and a binding agent.
		The small size (each core was about the size of a typewriter 'o'), speed (average read/write time was about 1 microsecond) of core memory made it the most popular form of memory used in first and second generation computers..
	www.cs.sun.ac.za /~museum/memory.html (980 words)

	Core Memory
		If the memory location is to contain a 0, the sense/inhibit line is driven with sufficient current to neutralise the effect of the XY lines and the memory location will be unaffected and stay in the 0 state.
		If the memory location is to contain a 1, the sense/inhibit line is not driven, and the XY lines will flip the memory core into the 1 state.
		Core memory, being a magnetic device, is susceptible to the effects of interference.
	www.psych.usyd.edu.au /pdp-11/core.html (983 words)

	Magnetic storage - Wikipedia, the free encyclopedia
		Magnetic storage is a term from engineering referring to the storage of data on a magnetised medium.
		Magnetic storage was first suggested by Obeline Smith in 1888.
		Media types that exploit magnetic storage include hard disk and floppy disk drives, zip drives and various tape drives, video cassettes and audio cassettes, magnetic core memory, thin film memory and drum memory.
	en.wikipedia.org /wiki/Magnetic_storage (169 words)

	Calculator Memory Technologies
		Magnetic core memories make use of the magnetic properties of tiny ferrite cores, which can be magnetised in either of two directions through the core.
		To sense the state of any core the horizontal and vertical wires through that core are pulsed to magnetise that core into one of the states, say 1.
		Magnetic core memory is a static memory, that is the data does not require refreshing.
	www.vintagecalculators.com /html/calculator_memory_technologies.html (866 words)

	[No title]
		The state of magnetism of a core is explained using the hysteresis loop shown in figure 6-2, The points defined on the loop illustrate the magnetic flux density in gausses (B) as a function of the field (induced by the current) in oersteds (H).
		Actually, this core and all magnetic materials exist in nature in some state of magnetization as a result of the influence of the earth's magnetic field.) The 0 point in figure 6-2 represents a condition of 0 ampere-turns in oersteds (H) and 0 core magnetization in gausses (B).
		The use of windings to magnetize the core and to sense the signal resulting from the application of a read pulse is one method by which data can be readout or written into the internal storage facilities of a computer.
	ed-thelen.org /comp-hist/navy-core-memory-desc.html (3645 words)

	[No title] (Site not responding. Last check: 2007-10-22)
		The memory circuit of claim 1, wherein the input line (3a) is respectively coupled to the magneto resistor (1) at an end opposite to and end where the output line (3b) is coupled to the magneto resistor (1).
		The memory circuit of claims 1 or 2, further comprising: a) a sense line (4), coupled to the output line (3b), which transfers current away from the collector; and b) a current amplifier (12), coupled to the sense line (4), to amplify and detect the presence and amount of current in the sense line (4).
		The memory cell of claim 1-13, wherein a digital value of"0"is signified by an amount of current in the sense line (4) between the bit (6) and the amplifier (12) which is greater than an amount of current present which signifies a digital"1." 16.
	www.wipo.int /cgi-pct/guest/getbykey5?KEY=00/52700.000908&ELEMENT_SET=DECL (5132 words)

	Core memory (Site not responding. Last check: 2007-10-22)
		Core memory has been in use until recently for special purposes, because it retains the information when the power is switched off, and it is resistant against radiation.
		The physical basis of core memory is the fact that a current sent along a wire passing through a ferrite core sets a persisting core magnetization, if the current exceeds a certain threshold.
		Core memories were often organized as a planar matrix, the 'write' wire being split up into two wires (row, column) each carrying half of the threshold switching current.
	www.science.uva.nl /faculteit/museum/CoreMemory.html (643 words)

	Magnetic core memory: Facts and details from Encyclopedia Topic (Site not responding. Last check: 2007-10-22)
		Core rope memory is a form of read-only memory (rom) for computers, first used by early nasa mars probes and then in the apollo guidance computer (agc)...
		Bubble memory is a type of computer memory that uses a thin film of a magnetic material to hold small magnetized areas, known as bubbles, which each store one...
		Thin film memory is a high-speed variation of core memory developed by sperry rand in a government-funded research project....
	www.absoluteastronomy.com /encyclopedia/m/ma/magnetic_core_memory.htm (3915 words)

	BBC - h2g2 - Magnetic Core Memory
		Unlike magnetic drums, data stored in magnetic core memory is volatile, which means that it will disappear when the electricity stops flowing.
		Core memory is capable of random access from one moment to the next, whereas access to different areas of drum memory can be done on successive revolutions only.
		Magnetic core memory is the precursor to the integrated circuits of DRAM
	www.bbc.co.uk /dna/h2g2/A969447 (427 words)

	[No title] (Site not responding. Last check: 2007-10-22)
		The SHRAM is a nonvolatile and transportable memory characterized by its cell density and relatively small size and power requirements, but having the nonvolatile character and rugged transportability of core memory, or magnetic disks or tape.
		The memory media includes not only a homogeneous two dimensional substrate, but also ferrite cores formed into the substrate by photolithographic techniques, wherein the information is stored within the core and read by the sensing device from a gap defined by the core.
		Each of a variety of magnet structures realize a condition in which the magnetic field is substantially orthogonal to the direction of travel of carriers of a sense current, thereby achieving maximum sensitivity.
	www.wipo.int /cgi-pct/guest/getbykey5?KEY=00/52698.000908&ELEMENT_SET=DECL (2576 words)

	VT100.net: Magnetic Core Memories
		Most magnetic memories operate on what is known as the 'binary' notation, in which quantities (numbers) are represented by suitable arrangements of symbols of two kinds only, namely 0 and 1.
		A 20 mil core and a 30 mil core on the wings of a common housefly.
		In this diagram, cores which are in the 1 condition are shown in fl; cores in the 0 condition in white.
	vt100.net /docs/misc/core (3678 words)

	Magnetic core memory at opensource encyclopedia (Site not responding. Last check: 2007-10-22)
		Core memory consists of a large number of small ferrite (ferromagnetic ceramic) rings held together in a grid structure, with wires woven through the holes in the middle.
		Another characteristic of core is that the hystersis loop was temperature sensitive, the proper half select current at one temperature is not the proper half select current at another temperature.
		Examples of this are the heated air core memory of the IBM 1620 (which could take up to 30 minutes to reach temperature, about 106°F, and allow the machine to work correctly) and the heated oil bath core memory of the IBM 709.
	www.wiki.tatet.com /Magnetic_core_memory.html (1495 words)

	Visible Storage
		Core memory solved these problems and subsequently became the dominant form of computer memory for more than 20 years.
		In this scheme, the current needed to magnetize the core is split between two wires (one horizontal, the other vertical).
		When a core is magnetized to a “0,” a pulse occurs on this sense wire only if that core had been a “1” and not if it was already a “0.” This is destructive readout, since if it was a “1” it now needs to be rewritten.
	www.computerhistory.org /virtualvisiblestorage/artifact_main.php?tax_id=02.03.03.00 (266 words)

	Core memory history from the PCmuseum
		Each memory plane had a fine mesh of wires with tiny magnetic "doughnuts" or rings where the lace of wires crossed.
		In the midst of glistening fine copper wires, the little doughnut could be magnetized one way or the other, thus, signaling an "on" or "off" or 0 or 1 in the binary numbering system needed by computers.
		One defective or broken core (and they are very fragile), would entail removing the wires associated with that core, removing the core, usually a chunk at a time, and inserting a new core in its place.
	www.fortunecity.com /marina/reach/435/coremem.htm (698 words)

	magnetic core - Hutchinson encyclopedia article about magnetic core
		In a digital computer several different two-state devices are used to store or transmit binary number codes – circuits, which may or may not carry a voltage;; disks or tapes, parts of which may or may not be magnetized; and switches, which may be open or closed.
		All these components contain registers, which are memory locations reserved for specific purposes.
		This information should not be considered complete, up to date, and is not intended to be used in place of a visit, consultation, or advice of a legal, medical, or any other professional.
	encyclopedia.farlex.com /magnetic+core (1232 words)

	LIS Course Notes - Magnetic Core Memory
		In the UNIX and Linux world, the diagnostic file containing the memory dump is still named "core".
		Magnetic fields and how to make them", by Andrew Duffy of Boston University.
		Thanks to Keith Thomas for suggesting that the machine for which this particular memory was most likely designed, may have used a 24-bit word length, with 1 parity bit for error detection and correction, hence all the multiples of 25.
	valinor.ca /computing/corememory.html (197 words)

	Core Memory (Site not responding. Last check: 2007-10-22)
		The one core in the center of the figure is switched, however, by the coincidence of the two currents.
		A 4th wire was the 'inhibit' wire used prevent some core from flipping' I have an old 4k 1401 memory core sitting out on my work bench gathering dust for the last 25 years.
		The IBM 737 Magnetic core storage unit (1954, for the IBM 701)
	www.columbia.edu /acis/history/core.html (317 words)

	Calculator History: Wang Laboratories: From Custom Systems to Computers
		Memory boxes would contain 8K-bits (organized as 1024 words of eight bits each) of magnetic core memory, with interfacing circuitry to allow the memory to communicate with the other units.
		The ease of programming, speed, memory, and interfacing capabilities of the machine really gave it an edge, and the fact that a complete system could retail for around $10,000, with a healthy dose profit margin included, made it all the more exciting.
		Two additional 4K memory modules were added for a total of 12K bytes of core memory, a Terminal I/O Controller, two IBM Selectric I/O typewriters, a dual drive magnetic cassette tape system, the BASIC language software, and system installation and setup.
	www.oldcalculatormuseum.com /d-wangcustom.html (6433 words)

	Project History: Magnetic Core Memory (Site not responding. Last check: 2007-10-22)
		Magnetic core memory replaced vacuum tubes and mercury delay lines with a much more compact and reliable technology.
		Semiconductor memories largely replaced magnetic cores in the 1970s, but they remained in use for many years in mission-critical and high-reliability applications.
		This project history will work primarily with the core memory collection in the MIT archives, one of the richest sets of documentation for a particular invention that exists.
	web.mit.edu /6.933/www/core.html (305 words)

	magnetic core
		In his thesis, entitled "A Coincident-Current Magnetic Memory Unit" (1950), Papian described magnetic core memories, honeycombs of minute magnetic cores strung on wires, through which storage information was read to electronic circuits in the computer.
		The first bank of core memory was installed in the Whirlwind on August 8, 1953.
		He indicated that there were only a couple of firms that were in the business of suppling OEM core memories and that many many computer companies used these rather than try and make them for themselves.
	ed-thelen.org /comp-hist/vs-magnetic-core.html (487 words)

	Mister Transistors Old Computer Stuff (Site not responding. Last check: 2007-10-22)
		Nowadays I find that magnetic core memory is one of the most fascinating aspects of computers from the 1960's and 1970's.
		The basic concept of the technology is fairly simple: a small ring of magnetic material can be magnetised in two "directions", clockwise and anticlockwise looking sideways at the ring such that appears as a circle.
		The resulting memory was expensive and difficult to maintain, and the smaller the rings, the greater the cost.
	ourworld.compuserve.com /homepages/Andrew_Wylie/coremem.htm (504 words)

	Memory- (Site not responding. Last check: 2007-10-22)
		Four storage devices--floppy disks, hard disk, magnetic tape, and magnetic drums--store data by magnetically rearranging metal particles on disks, tape, or drums.
		Devices that are sometimes used for main memory are magnetic-core memory and magnetic-bubble memory.
		Auxiliary storage units supplement the main memory by holding parts of programs that are too large to fit into the random-access memory at one time.
	dspace.dial.pipex.com /stmore/Ict/memory.htm (783 words)

	Magnetic core memory software downloads (Site not responding. Last check: 2007-10-22)
		Instant Memory is a program that can test your memory.The program has three levels, three practice styles, and nine categories to choose from.Training someone to memorize and recall information is the goal of this program.
		Core Collection Software Developer, Web Developer and Professionals for world most enhanced high quality Core icon Collections Core Collection Set is an all-purpose collection of images and more..
		Cailou Memory Game is a memory game designed to help children of all ages improve their memory skills.
	www.freedownloadsoft.com /Magnetic+core+memory (478 words)

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