One megahertz is equal to one million cycles per second. It is used to measure transmission speeds of electronic devices. The most common area you will see Megahertz used is in measuring processor clock speed, such as an 800 Mhz Pentium III.
It is important to know that megahertz only measures the clock speed of the processor (how many cycles it can handle per second) ? not the overall performance. Because megahertz measures only a single aspect of the CPU, it is possible that one processor may be faster than another that has a slightly higher megahertz reading. For example, a Mac with a 500 MHz PowerPC G4 can perform some calculations faster than a PC with a 800 Mhz Pentium III. This is because the G4 can process more instructions per clock cycle than the Pentium. Mac users would often stress this point, but it is irrelevant now since Macintosh computers also use Intel processors.
Updated: August 15, 2007