CPU Buying Guide

Clock Cycle Speed

In order to correctly synchronise the actions of a CPU, a metronome-like clock sends deliberately timed pulses throughout the CPU. This is referred to as the clock cycle, and is typically measured in gigahertz (GHz). The higher the GHz rating, the faster the clock speed of the CPU. In the past, clock speed was a good raw indicator of CPU performance, but it's increasingly just becoming part of the picture, rather than the picture itself.

For the consumer, things were much simpler five to ten years ago, when the main metric for CPU performance was the clock cycle speed. With the advent of extension technologies and performance upgrades such as Hyperthreading, 64-bit processors that can run 32-bit applications and the move to dedicated graphics processing units, the clock speed now means less to the overall performance of the CPU than it used to. Put simply, CPUs of today aren't just being measured by the number of operation cycles they can perform in a given second -- the classic CPU speed rating -- but by what operations they can perform within those cycles as well.

Both Intel and AMD have invested heavily in maximising the output of each and every clock cycle, and in doing so, they've made the actual clock speed less important. This is especially true in the mobile market, where battery power is a much more pressing concern than just about any other factor.

Front side bus (FSB)

The Front Side Bus (FSB) is the primary connection point between the CPU and the primary chipset on the motherboard. Motherboard specifications will list a FSB frequency, measured in MHz, or even GHz (like CPU clock cycles). The combination of FSB speed and a processor's internal multiplier determines the final speed of the CPU itself. As with processors themselves, FSB speeds have grown astronomically in recent times, with modern motherboards supporting FSB speeds of anywhere between 533MHz and 1600MHz.

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