Computer Speed Definition

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The speed of computer processing depends on the speed of the central processing unit (CPU) in your computer. While other factors are important, if you're interested in computer speed, the most relevant piece of information is the clock speed of the CPU. Clock speed is a big determinant of the number of instructions per second your computer can carry out, but bus speed, the specific type of instruction being carried out, the microprocessor and the amount of random access memory (RAM) available to your CPU also play a role.


Speed of a Computer: CPU Speed

The CPU speed tells you how quickly your processor can perform tasks. The speed is technically measured in terms of clock speed, which is the speed of the oscillator that dictates how quickly the processor runs. Clock speed is measured in hertz – pulses per second – but more commonly, megahertz (MHz) and gigahertz (GHz) are used because of the large numbers involved. A 1 MHz clock speed is 1 million pulses per second, and a 1 GHz clock speed is 1 billion pulses per second – the equivalent of 1,000 MHz.


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In 2018, the best processors have clock speeds exceeding 3.5 GHz. In comparison, in 1980, a typical computer ran at 4.77 MHz or more than 700 times slower than current CPU speeds. If you're looking at computer speed when you buy a computer, the processor speed or clock speed is one of the most important things to consider. Bigger numbers mean faster processing. However, most users don't push a CPU to its limits.

Instructions Per Pulse

Although the clock speed is an important factor in the speed of computer processing, not all computers perform the same amount of instructions for every pulse of the clock. Some processors perform one instruction per clock pulse, while others perform more than one. So for two 2.4 GHz processors, if one performs one instruction per pulse while the other performs two, the one that performs two works twice as quickly, despite an equivalent clock speed.


Other Factors Affecting Computer Speed

Just looking at CPU speed to determine computer speed is a limited an approach. Some processors have multiple cores, which are independent processors on the same CPU). The speed of the bus that transfers data between different parts of the computer, the size of the cache, which is quick-access memory within the computer, and the amount and speed of the RAM in the computer, another form of easy-access memory for the processor, all affect speed. Even with a fast processor, if you have a slow bus, a small cache and little or slow RAM, your computer won't function quickly. All of these factors are important.


Checking CPU Speed and RAM

You can check the clock speed of your computer's CPU and the amount of RAM it contains. On Windows PCs, go to "Control Panel," "System and Security" and then "System." The "Processor" field tells you the clock speed, and the "Installed Memory" field tells you how much RAM is installed in the computer.

For Macs, click on the Apple logo and select "About This Mac." Click "System Report" and look at the "Hardware Overview" screen. The "Processor Speed" and "Memory" fields contain the information you need.