computer science

Thin-film memory

Thin-film memory is a computer science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Thin-film memory rather than just read about it. In short: Thin-film memory is a high-speed alternative to magnetic-core memory developed by Sperry Rand in a government-funded research project. Instead of threading individual ferrite cores on wires, thin-film memory consisted of 4-micrometer thick dots of permalloy, an iron–nickel alloy, deposited on small glass plates by vacuum evaporation techniques and a mask.

Key takeaways

Thin-film memory belongs to computer science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Thin-film memory to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Thin-film memory from memory before moving on to harder problems.

Reference excerpt

Thin-film memory is a high-speed alternative to magnetic-core memory developed by Sperry Rand in a government-funded research project. Instead of threading individual ferrite cores on wires, thin-film memory consisted of 4-micrometer thick dots of permalloy, an iron–nickel alloy, deposited on small glass plates by vacuum evaporation techniques and a mask. The drive and sense lines were then added using printed circuit wiring over the alloy dots. This provided very fast access times in the range of 670 nanoseconds, but was very expensive to produce. In 1962, the UNIVAC 1107, intended for the civilian marketplace, used thin-film memory only for its 128-word general register stack. Military computers, where cost was less of a concern, used larger amounts of thin-film memory. Thin film was also used in a number of high-speed computer projects, including the high-end of the IBM System/360 line, but general advances in core tended to keep pace.

External links "Thin Film". Digital Computer Basics (Rate Training Manual). Naval Education and Training Command. 1978. p. 106. NAVEDTRA 10088-B. Harloff, H. (1963). "Operating speed of thin-film memories". 1963 IEEE International Solid-State Circuits Conference. Digest of Technical Papers. pp. 8–9. doi:10.1109/ISSCC.1963.1157473. Bates, A.; D'Ambra, F. (1964). "Thin-film memory drive and sense techniques for realizing a 167-Nsec read/write cycle". 1964 IEEE International Solid-State Circuits Conference. Digest of Technical Papers. pp. 106–107. doi:10.1109/ISSCC.1964.1157545. Ravi, C. G.; Koerber, G. G. (March 1966). "Effects of a Keeper on Thin Film Magnetic Bits". IBM Journal of Research and Development. 10 (2): 130–134. doi:10.1147/rd.102.0130. Mo, R. S.; Rabinovici, B.M. (1968). "Internal Field Distribution in Keepered and Nonkeepered Permalloy Film Memories". Journal of Applied Physics. 39 (6): 2704–2710. Bibcode:1968JAP....39.2704M. doi:10.1063/1.1656657.

Worked examples

Example 1 — a first encounter with Thin-film memory

Start with the simplest possible case. Write down what Thin-film memory claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In computer science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Thin-film memory before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Thin-film memory ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Thin-film memory

In research: Thin-film memory appears in computer science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Thin-film memory in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Thin-film memory is common in secondary-school and first-year university syllabi. It links to neighbouring topics Computer hardware stubs, Computer memory, Non-volatile memory, so understanding it makes those chapters shorter.
In everyday life: Look for Thin-film memory outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Thin-film memory in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Thin-film memory means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Thin-film memory out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Thin-film memory in simple terms?

Why does Thin-film memory matter?

Because it connects several computer science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Thin-film memory?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Thin-film memory.