computer science

Performance Rating

Performance Rating 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 Performance Rating rather than just read about it. In short: The PR (performance rating, P-rating, or Pentium rating) system was a figure of merit developed by AMD, Cyrix, IBM Microelectronics and SGS-Thomson in the mid-1990s as a method of comparing their x86 processors to those of rival Intel. The idea was to consider instructions per cycle (IPC) in addition to the clock speed, so that the processors become comparable with Intel's Pentium that had a higher clock speed with…

Key takeaways

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

Reference excerpt

The PR (performance rating, P-rating, or Pentium rating) system was a figure of merit developed by AMD, Cyrix, IBM Microelectronics and SGS-Thomson in the mid-1990s as a method of comparing their x86 processors to those of rival Intel. The idea was to consider instructions per cycle (IPC) in addition to the clock speed, so that the processors become comparable with Intel's Pentium that had a higher clock speed with overall lower IPC.

Branding The first use of the PR system was in 1995, when AMD used it to assert that their AMD 5x86 processor was as fast as a Pentium running at 75 MHz. The designation "P75" was added to the chip to denote this. Later that year, Cyrix also adopted the PR system for its 6x86 and 6x86MX line of processors. These processors were faster than Pentiums of the same speed in some benchmarks, so Cyrix gave them a Performance Rating faster than their clock speed. Some AMD K5 models also use the PR system. AMD initially branded its AMD K6 processors with a "PR2" rating but dropped this after consumer confusion. AMD revived the branding for its Athlon XP, which was released in 2001. The efficient Athlon XP chips could perform better than similarly-clocked chips from Intel's competing Pentium 4 line-up, which depended on high clock speeds to overcome their low IPC. As a result, AMD believed consumers would be swayed by the megahertz myth. These chips were rated against the Athlon Thunderbird but were popularly compared to the Pentium 4. As a result, the branding became colloquially known as a "Pentium Rating". Maximum PC criticized this as making it more difficult for power users to differentiate between the various Athlon XP chips. For example, two chips could be given the same "PR" branding but have much different engineering (cache size, bus speed, etc), which would affect their performance at different tasks.

Illustrations

Worked examples

Example 1 — a first encounter with Performance Rating

Start with the simplest possible case. Write down what Performance Rating 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 Performance Rating 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 Performance Rating 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 Performance Rating

In research: Performance Rating 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 Performance Rating 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: Performance Rating is common in secondary-school and first-year university syllabi. It links to neighbouring topics AMD, Computer performance, Rating systems, so understanding it makes those chapters shorter.
In everyday life: Look for Performance Rating 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 Performance Rating in 20 minutes

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

Frequently asked questions

What is Performance Rating in simple terms?

Why does Performance Rating 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 Performance Rating?

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 Performance Rating.