5-Processor Basics

5-Processor Basics - 1 Tathagata Bhattacharjee rocessor...

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Unformatted text preview: 1 Tathagata Bhattacharjee rocessor Basics rocessor Basics Presenter Tathagata Bhattacharjee 2 Tathagata Bhattacharjee Characteristics of Modern Characteristics of Modern Processors Processors • High clock rates • Multiple instructions per clock • Cache memory • Very slow main memory 3 Tathagata Bhattacharjee Clock Rates Clock Rates • The clock rate is the fundamental rate in cycles per second at which a computer performs its most basic operations such as adding two numbers or transferring a value from one register to another. • Different chips on the same computer motherboard may have different clock rates. • Usually when referring to a computer, the term "clock rate" is used to refer to the speed of the CPU. 4 Tathagata Bhattacharjee • The clock rate of a CPU is normally determined by the frequency of a crystal. • The original IBM PC, circa 1981, had a clock rate of 4.77 MHz (4770000 cycles/second). • In 1995, Intel's Pentium chip runs at 100 MHz (100 million cycles/second), and in 2002, an Intel Pentium 4 model was introduced as the first CPU with a clock rate of 3 GHz (three billion cycles/second). 5 Tathagata Bhattacharjee • The clock rate of a computer is only useful for providing comparisons between computer chips in the same processor family. • An IBM PC with an Intel 486 CPU running at 50 MHz will be about twice as fast as one with the same CPU, memory and display running at 25 MHz. • However, there are many other factors to consider when comparing the speeds of entire computers, like the clock rate of the bus, the clock rate of the memory chips, the width in bits of the CPU's bus, and the amount of Level 1 and Level 2 cache. 6 Tathagata Bhattacharjee • Clock rate should not be used when comparing different computers or different processor families. Rather, some software benchmark should be used. • Clock rate can be very misleading, since the amount of work different computer chips can do in one cycle varies. For example, RISC CPUs tend to have simpler instructions than CISC CPUs (but higher clock rates), and pipelined processors execute more than one instruction per cycle. 7 Tathagata Bhattacharjee In the early 1990s, most computer companies advertised their computers' speed chiefly by referring to their CPUs' clock rates. This led to various marketing games, such as Apple Computer's decision to create and market the Power Macintosh 8100/110 with a clock rate of 110 MHz, so that Apple could advertise that its computer had the fastest clock speed available -- the fastest Intel processor available at the time ran at 100 MHz. This superiority in clock speed, however, was meaningless; the PowerPC and Pentium CPU architectures were completely different. The Power Mac was faster at some tasks, but slower at others. 8 Tathagata Bhattacharjee • In the 2000s, Intel's competitor AMD started using model numbers instead of clock rates to market its CPUs, saying the "megahertz myth" did not tell the whole story of the power of its CPUs. story of the power of its CPUs....
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This note was uploaded on 07/15/2011 for the course ECO 2023 taught by Professor Mr.raza during the Summer '10 term at FAU.

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5-Processor Basics - 1 Tathagata Bhattacharjee rocessor...

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