Ever since the first personal computers appeared, manufacturers have enjoyed publicising the importance of the processors used inside.

Even today it’s rare to see an advert for a computer that doesn’t make a big deal of the new processor used inside.

Unfortunately, the processor names and specifications given in adverts can be confusing or even misleading. Here we’ll demystify the processor, explaining what all the specifications included in adverts actually mean.

Back to basics
The processor is often described as the brain of a computer. When the user does anything on the computer, from typing a document to playing solitaire, the computer’s processor does the work required to make letters appear on screen and check the spelling, or to shuffle the deck of cards.

The surprising thing about any processor, though, is the very limited number of things it can do. Despite being used for millions of different tasks, the processor inside a modern PC knows how to perform only a few hundred basic operations. This means something that looks quite simple on screen, such as opening a web page, requires the processor to do thousands or even millions of tiny calculations, all of which add up to the change on screen.

Everybody Hertz
With most tasks requiring the processor to perform thousands of operations, processors have to perform these operations extremely quickly. In fact, today’s processors run at mind-boggling speed. The speed of a processor is measured in Hertz. A standard processor running at one Hertz would perform one calculation every second, but this would be far too slow for most uses. In the early 1970s Intel produced a processor that could run at 740 Kilohertz - that is, it could perform 740,000 calculations every second.

Today, the speed of most processors is measured in Gigahertz, or GHz. A 1GHz processor can perform one billion calculations a second, and today it’s not uncommon to see two or three Gigahertz processors in desktop computers. The speed of a processor measured in Hertz is known as its clock speed, as a tiny circuit inside the processor regulates the process rather like a ticking clock, keeping the processor running at full speed.

Hyperactive
From the 1970s to the early 2000s processors were made faster largely by increasing the clock speed of each new model. The first IBM Personal Computer, built in 1981, had a processor that ran at 4.77MHz - that is, it could perform 4,770.000 calculations a second. In 2005 Intel launched its fastest ever Pentium 4 processor. Running at 3.8GHz, the Pentium 4 670 could perform 3,800,000,000 individual calculations every second.

Around the same time as the Pentium 4 processor, however, processor manufacturers began to wonder whether constantly increasing the clock speed at which new processors run was the most effective way to make them more powerful. One alternative method was to increase the amount of cache memory used in new processors.