The gigahertz, abbreviated GHz, is a unit of alternating current (AC) or electromagnetic (EM) wave frequency equal to one thousand million hertz (1,000,000,000 Hz). The gigahertz is used as an indicator of the frequency of ultra-high-frequency (UHF) and microwave EM signals and also, in some computers, to express microprocessor clock speed.
An EM signal having a frequency of 1 GHz has a wavelength of 300 millimeters, or a little less than a foot. An EM signal of 100 GHz has a wavelength of 3 millimeters, which is roughly 1/8 of an inch. Some radio transmissions are made at frequencies up to hundreds of gigahertz. Personal computer clock speeds are increasing month by month as the technology advances, and reached the 1 GHz point in March of 2000, with a processor from AMD, closely followed by a 1 GHz Pentium 3 from Intel.