Hertz

The hertz (symbol: Hz) is a unit of frequency derived from the International System of Units (SI) and is defined as one cycle per second. It is named after Heinrich Rudolf Hertz, the first person to provide conclusive proof of the existence of electromagnetic waves.

Variations
Hertz are commonly expressed in metric prefixes (decimals):
 * A kilohertz (kHz) consists of 1,000 hertz ( 103 )
 * A megahertz (MHz) consists of 1,000 kilohertz, or 1,000,000 hertz ( 106 )
 * A gigahertz (GHz) consists of 1,000 megahertz, or 1,000,000,000 hertz ( 109 )
 * A terahertz (THz) consists of 1,000 gigahertz, or 1,000,000,000,000 hertz ( 1012 )
 * A petahertz (PHz) consists of 1,000 terahertz, or 1,000,000,000,000,000 hertz ( 1015 )
 * An exahertz (EHz) consists of 1,000 petahertz, or 1,000,000,000,000,000,000 hertz ( 1018 )

Usage
The hertz is used by the computer industry to label the frequency of electronic components, notably the clock rate of central processing units (CPU). However, as manufacturers have adopted techologies such as caching, pipelining, multi-core processing, computing efficiency can vary significantly across different processor lines. As a result, the hertz is not an ideal measurement of processing power, leading to the megahertz myth.

History in NeXT products
A list of processors and clock rates of selected NeXT products:
 * NeXT Computer: 25 MHz Motorola 68030
 * NeXTcube and NeXTstation: 25 MHz Motorola 68040
 * NeXTcube Turbo and NeXTstation Turbo: 33 MHz Motorola 68040
 * NeXTdimension color board: 33 MHz Intel i860