A Layman's Guide to a Computer's Cpu

The Central Processing Unit, or CPU

The CPU of a computer is the main lynchpin of the computer system. Without it, nothing happens. It is a small slab of silicone about 10mm (3/8ths of an inch) square and about 2mm thick, which has been etched and doped microscopically to form circuits, switches, transistors and other electronic components: hundreds of millions of these components are embedded in this tiny space. The rest of the physical size of the CPU is taken up by little connecting wires from these circuits to the 100 plus pins on the underside of the CPU chip, a couple of external components, and with heat transfer fins and fans which are needed to cool that little slab of silicone, which is doing 2800 million operations per second! (That's for an average off the shelf 2.8GHz computer)

The CPU is mainly a calculating unit, and can do complex arithmetic functions. But the CPU is actually made up of a number of distinct modules with different functions, like ultrafast short term storage called cache, traffic control to control the data flows, like a traffic light, and arithmetic units to do the sums.

The CPU on it's own is a dead lump of metal and glass. It needs to be fed data to be of any use. There are various other circuits in the computer that get it started up, such as the BIOS (Basic Input/Output System), and this then fires the Operating System up, which starts injecting instructions in the right format to the CPU, and then waiting for the results of the CPU's work so that this can be passed on to other circuits, like the graphics card for example, in order to display something on your screen.

A CPU's speed is measured in Megahertz or Gigahertz, ie 1 million operations per second (MHz) or 1000 million operations per second (GHz) Thus a 3.0GHZ CPU will be able to handle 3000 million operations per second. Bear in mind that a calculation or some takes quite a large number of "operations" to complete.

CPU's sometimes get a glitch in their data feed, so that they sit waiting for the next instruction which never comes. There is a circuit built into the CPU that checks for this inactivity, and which then clears and restarts the CPU. Sometimes this also doesn't work, due to a badly written program or data corruption, and this is known as a computer "hang." Rebooting the computer starts the CPU up from scratch, and this clears the "hang" and allows normal operation again.

A CPU is normally the most expensive part of a computer, due to it's extreme complexity, research and development costs, and because a lot of the tiny internal contacts are made from gold or gold plating, and other expensive materials. The gold is used because it is one of the best conductors of electricity, and it doesn't ever tarnish or rust or corrode in any manner.

CPU's like to be kept cool, so make sure that their fan is always working and that their cooling fins are not clogged up with dust and fluff. Then this technological marvel should give you years of trouble free service.