computer science

LongRun

LongRun 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 LongRun rather than just read about it. In short: LongRun and LongRun2 are power management technologies introduced by Transmeta. LongRun was introduced with the Crusoe processor, while LongRun2 was introduced with the Efficeon processor.

Key takeaways

LongRun 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 LongRun to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of LongRun from memory before moving on to harder problems.

Reference excerpt

LongRun and LongRun2 are power management technologies introduced by Transmeta. LongRun was introduced with the Crusoe processor, while LongRun2 was introduced with the Efficeon processor. LongRun2 has since been licensed to Fujitsu, NEC, Sony, Toshiba, and NVIDIA. LongRun automatically adjusted the processor, moving between higher performance but higher power, and lower power but lower performance. The goals of the automation could be adjusted. One control offered processor frequency levels, and the ability to set a minimum and maximum "window", where the automatic controls would not adjust the speed outside of the window. A second control offered a target of either "economy" or "performance". Some versions offered a third control that adjusted the processor based on power rather than speed. LongRun was based primarily on reducing the clock frequency and voltage supplied to the processor, now commonly called DVFS. Lower frequency reduces performance but also allows voltage reduction, and can yield both power savings and improved efficiency. LongRun2 built further on this by incorporating process technology aimed at reducing variations in the manufacturing process and thereby improving yields.

References

External links Official description of LongRun2, recovered from the Internet Archive as of 2009.

Worked examples

Example 1 — a first encounter with LongRun

Start with the simplest possible case. Write down what LongRun 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 LongRun 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 LongRun 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 LongRun

In research: LongRun 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 LongRun 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: LongRun is common in secondary-school and first-year university syllabi. It links to neighbouring topics Clock signal, Computer hardware stubs, Computer hardware tuning, so understanding it makes those chapters shorter.
In everyday life: Look for LongRun 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 LongRun in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what LongRun 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 LongRun out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is LongRun in simple terms?

LongRun and LongRun2 are power management technologies introduced by Transmeta. LongRun was introduced with the Crusoe processor, while LongRun2 was introduced with the Efficeon processor.

Why does LongRun 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 LongRun?

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 LongRun.