Lesson 28: Clock Speed

Overview: Hertz is the term to describe 1 cycle per second of the computer process.
 

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A clock cycle, or simply a "cycle," is a single electronic pulse of a CPU. During each cycle, a CPU can perform a basic operation such as fetching an instruction, accessing memory, or writing data. Since only simple commands can be performed during each cycle, most CPU processes require multiple clock cycles.

In physics, the frequency of a signal is determined by cycles per second, or "hertz." Similarly, the frequency of a processor is measured in clock cycles per second. Since modern processors can complete millions of clock cycles every second, processor speeds are often measured in megahertz or gigahertz.

Frequency measures the number of times something occurs in a specific amount of time. For example, if someone visits the grocery store twice a week, her shopping frequency is 2 visits per week. While frequency can be used to measure the rate of any action, in technical applications it is typically used to measure wave rates or processing speed. These frequencies often occur multiple times per second and therefore are measured in hertz (Hz) or related units of measurement, such as megahertz or gigahertz.

One megahertz (abbreviated: MHz) is equal to 1,000 kilohertz, or 1,000,000 hertz. It can also be described as one million cycles per second. Megahertz is used to measure wave frequencies, as well as the speed of microprocessors.
Radio waves, which are used for both radio and TV broadcasts, are typically measured in megahertz. For example, FM radio stations broadcast their signals between 88 and 108 MHz. When you tune to 93.7 on your radio, the station is broadcasting at a frequency of 93.7 MHz.
Megahertz is also used to measure processor clock speeds. This measurement indicates how many instruction cycles per second a processor can perform. While the clock speeds of processors in mobile devices and other small electronics are still measured in megahertz, modern computer processors are typically measured in gigahertz.
Abbreviation: MHz.

Clock speed is the rate at which a processor can complete a processing cycle. It is typically measured in megahertz or gigahertz. One megahertz is equal to one million cycles per second, while one gigahertz equals one billion cycles per second. This means a 1.8 GHz processor has twice the clock speed of a 900 MHz processor.However, it is important to note that a 1.8 GHz CPU is not necessarily twice as fast as a 900 MHz CPU. This is because different processors often use different architectures.

For example, one processor may require more clock cycles to complete a multiplication instruction than another processor. If the 1.8 GHz CPU can complete a multiplication instruction in 4 cycles, while the 900 MHz CPU takes 7 cycles, the 1.8 GHz processor will be more than twice as fast as the 900 MHz processor. Conversely, if the 1.8 GHz processor takes more cycles to perform the instruction, it will be less than 2x as fast as the 900 MHz processor.

Other factors, such as a computer's bus speed, cache size, speed of the RAM, and hard drive speed also contribute to the overall performance of the machine. Therefore, while the processor's clock speed is a significant indicator of how fast a computer is, it is not the only factor that matters.