There are several different ways of describing a CPU: **bit width**, **clock cycles** and the number of** execution cores** used.

The** bit width** approach describes a processor in terms of how many bits it processes in a single instruction or transports across the processor’s internal circuits (or busses) in a single cycle. The number of bits is generally a multiple of 8, but it is possible for the registers and the busses to have different widths. In general, more bits means more processing capability and more speed. Current processors use 64 bits.

The second way of describing a processor is to say how many **clock cycles** (cycles per second) the chip operates at, ie: how many times per second an electrical charge passes through the chip. Current processors operate at billions of cycles per second (gigahertz). More clock cycles usually means more processing capability and more speed.

The third way of describing a processor is to say how many **execution cores** are in the chip. The most advanced chips today have up to eight execution cores. Additional execution cores mean that you can run more applications at the same time, but it doesn’t necessarily mean a single application will run faster. More execution cores means more processing capability, but not necessarily more speed.

The **speed** of a processor is usually described in terms of the **clock speed** of the chip measured in hertz. In theory, the higher the clock speed, the faster the processor. However, raw speed is not necessarily a good way of comparing chips. The number of **instructions processed per second** (MIPS, BIPS, TIPS for millions, billions and trillions of instructions per second) is a better measurement. It is also possible to use the number of mathematical calculations per second to rate the speed of a processor.

At the end of the day, the most relevant measurement depends on what you use a computer for. If you carry out intensive mathematical calculations, the number of calculations per second is probably the most important but if you are more concerned with how quickly the computer runs an application, then instructions per second are more important.

**Next: Storage Devices**