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What is Clock Speed?

Brendan McGuigan
Brendan McGuigan

Clock speed is a measure of how quickly a computer completes basic computations and operations. It is measured as a frequency in hertz (Hz), and most commonly refers to the speed of the computer's Central Processing Unit (CPU). While computer developers and users can refer to this term regarding CPU performance, this has fallen out of favor as CPUs have become more complex. The easiest ways to boost clock speed in a computer include upgrading components and "overclocking" a piece of hardware.

What Clock Speeds Measure

Clock speed refers to the spped of a computer's processor or CPU.
Clock speed refers to the spped of a computer's processor or CPU.

There is a small quartz crystal inside of a CPU that vibrates at a particular oscillation or frequency. This frequency sets the "speed" of processes in the computer and is usually very high; they are typically measured in megahertz (MHz) and gigahertz (GHz). A megahertz is one-million cycles per second, while a gigahertz is one-billion cycles per second. So a computer with a clock speed of 800MHz is running 800,000,000 cycles per second, while a 2.4GHz computer is running 2,400,000,000 cycles per second.

A dual core CPU mounted to a motherboard.
A dual core CPU mounted to a motherboard.

These cycles set the speed for all processes within a computer. This ensures that all components and memory are working together at a rate that remains harmonious. Different components and processes can also run as a fraction of the primary CPU speed, which allows each element of a computer to work on its own and still function with the primary frequency of the CPU.

Clock Speeds and Computer Performance

A stick of DDR-RAM, a type of memory.
A stick of DDR-RAM, a type of memory.

There is some contention over the use of clock speed as a benchmark for computer performance, and many CPU manufacturers seem to be abandoning its use as the primary performance indicator. The problem comes from the fact that although clock speed works as a fairly reliable indicator of how one chip made by a company stacks up against another of their chips, it is a poor indicator of how it might compete against a different company's chipset. Many other elements can also impact computer performance, which makes CPU speed even less effective for overall computer benchmarking. The amount of Random Access Memory (RAM) a computer has, the speed of that RAM, and the type of hard drive used in a computer can all play significant roles in determining performance.

Comparing CPUs

When comparing one Intel® chip to another, for example, the clock speed is a fairly good indicator of differences between them. All other components being equal, an 800Mhz Pentium® computer performs most processor-based tasks roughly twice as quickly as a 400MHz Pentium® computer. When comparing a Pentium® chip and an AMD® chip, however, the AMD® tends to perform most tasks faster than a comparable Pentium®.

For this reason, AMD® stopped listing clock speeds as a primary method of advertising on their computers, instead associating a number with the computer to show its performance in comparison to a Pentium®. Intel® has also begun to move away from advertising speeds, mostly due to their introduction of laptop-oriented CPUs, which have much lower clock speeds to optimize portable performance. If only the speed was indicated, these processors would appear inferior to their desktop CPUs.

Improving CPU Performance

There are a number of ways in which a computer user can increase the speed of his or her computer. Upgrading an older CPU to a new one, for example, can provide hardware with a higher clock speed or multiple "cores." Multi-core processors are essentially two or more CPUs in one, which offer greater performance for software programs that can take advantage of multiple cores.

It is also possible to "overclock" a processor. This basically increases the clock speed of a CPU beyond what is recommended by the manufacturer, allowing the computer to run faster. Overclocking a CPU is not generally recommended, however, as it produces additional heat that can damage the processor or other components and typically voids most computer's warranties.

Discussion Comments


Which is the best processor in speed: an i5 third gen or i5 fourth gen?


I have a question about clock speed.

So if I'm looking at a Dell Inspiron 600m with a Pentium M and one is rated at 1.5Ghz and another at 2.0Ghz does that mean the 2.0 is 25 percent faster?

And if so, faster at what?

My main question is: will I notice the difference at all, given all other factors are the same (ram, bus, etc.)?


@anon80045 - Hertz is the name given to the unit "wave cycle per second" (Named after Heinrich Hertz). It has just become conventional to state it in hertz with an appropriate prefix denoting magnitude.


why is clock speed measured in hertz rather in seconds?


anon818, you are too funny. Like they say PCMCIA card stands for "People Can't Memorize Computer Industry's Acronym"


What is catch L2?


It's good to let them build it for you, so if the CPU gets fried or something during installation they are the ones who pay for that instead of you. I also hope they have done some optimizing of components so it isn't like driving a Ferrari on a one lane dirt road, or a Yugo on an 8 lane interstate.


why would you need a degree in computers to go to the store to buy one? i could build you a computer from scratch; just give me some money, and i could do it for less then a new pc would cost. they aren't hard at all to learn, people just prefer not to learn about it because they think it is too hard. by the way, i'm 15. :)


What does the letter in front of a processor number stand for and what is this number anyway? ie T5750.


Is clock speed the speed of one microcode cycle or the speed at which each computer instruction is staged and executed? There is a big difference. The second means that a 2 Ghz machine is effectively executing an instruction every 500 picoseconds. Which is it?


If the terms of computational performance are not understood, then there are two options:

1. Go with an OEM who will tell you what they mean, along with giving a relative standard of performance(model number and price). Or,

2. Learn what they mean. For instance, CL3 is a measure, in cycles, of latency. if it is running at 100Mhz, that means .000000003 seconds of latency. Now, divide that by the RAM speed divided by 100.


If they want to give consumers more of an idea as to exactly what it is they are getting in terms of PC power. I think they should revert to using good old plain english when it comes to describing cpu speeds an the like.

We could have for eg, the Mickey Mouse range for low spec PC's, lets call it MM, or an M standard PC.

Next we could call the mid range.. hmmm let me see now, oh yes, Mid Range PC's or MR standard PC.

And for the most powerful all singing and dancing version PC's, the Daddy, or D range PC.

Or cut all the BS and letter them, A B C D etc, A being the most powerful class.

Lastly, stop arsing around with chips and CPU's, cards and the rest of it and standardise the lot so it will work with any PC, then people like me can buy what I need without having to take a degree in computers just to go to the store to buy a piece of hardware that might work if I can figure out how to update the BIOS and find the right drivers to download.

Ah what the heck, forget upgrading, chuck the old one in the bin. Buy a new PC every 12 months, that should keep you up to date.


I am currently using a 7 year old donor PC to make this post, just whacked in another 256mb of ram x 2 to give me 512mb CL3, apparently CL2 would have been much better, know what I mean, of course you don't, this PC langusge is all gibberish. Now I am looking for a AGP card to speed it up some more, all I have got to do first is identify the chip set, is it a 2x 4x or 8x, the clock speed????? :0 and someething else, and if that fails, keep buying AGP cards until I find one that works, or I end up broke.

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    • Clock speed refers to the spped of a computer's processor or CPU.
      By: NorGal
      Clock speed refers to the spped of a computer's processor or CPU.
    • A dual core CPU mounted to a motherboard.
      A dual core CPU mounted to a motherboard.
    • A stick of DDR-RAM, a type of memory.
      A stick of DDR-RAM, a type of memory.