This is the third article in the series on how computers work. For this article the, the microprocessor or central processing unit (CPU), as it is often called, will be explored. The microprocessor is often considered the “heart” or “brain” of the computer, as it is responsible for processing instructions and code for the programs and the operating system on a computer and other electronic devices.

The CPU is comprised of numerous transistors connected together on a single chip (also referred to as an integrated circuit that is made from silicon). The first CPU to be used in a home computer was the 8088, which had 6,000 transistors. Today CPU’S, such as the Pentium 4, have over 55,000,000 transistors on one chip!

Over the years, there have been several versions of the CPU introduced into the market from several manufacturers. The most common, or known, CPU manufacturer is Intel with their line of processors for IBM compatible machines. These processors started with 8088 then moved onto the 80286, 80386, 80486, Pentium, Pentium II, Pentium III, Pentium 4 and Core 2 Duo. This is list is not a complete listing of all offerings but covers the most common chip types.

Some additional CPU’s include PowerPC from IBM, SPARC from Sun Microsystems and Athlon (and others) from AMD. However, from different manufacturers and for different types of systems these CPU’s provide the same functionality as the Intel based CPU.

The speed of a CPU is measured in megahertz (MHz), which is the rate at which a CPU can process instructions. It is also called the clock rate of a microprocessor. The higher the number the faster the CPU can process information which in turn makes the computer run faster. The first CPUs had a clock rate of around 2 MHz while newer CPUs run at
2 GHz or higher.

The increase of speed and processing power over the years has not come without problems. The faster the CPU runs the more heat is generated which can cause problems or damage to sensitive electronic equipment. To help keep the microprocessor cool, they are equipped with a fan and heat sink to help dissipate the heat away from the chip. Additionally, there is concern about how many transistors can be used at a time on a single chip while maintaining reasonable cost, safety and stay with the bounds of science.