The clock rate is the fundamental rate in cycles per second (measured in hertz) at which a computer performs its most basic operations such as adding two numbers or transferring a value from one processor register to another. More generally, it is the frequency of the clock in any synchronous circuit. Different chips on the systemboard may have different clock rates (see CPU multiplier, Memory divider). For example, a crystal oscillator frequency reference typically is synonymous with a fixed sinusoidal waveform, a clock rate is that frequency reference translated by electronic circuitry into a corresponding square wave pulse [typically] for digital electronics applications. In this context the use of the word, speed (physical movement), should not be confused with frequency or its corresponding clock rate. Thus, the term "clock speed" is a misnomer. A single clock cycle (typically lasting only a few nanoseconds in modern microprocessors) toggles between a logical zero and a logical one state. Historically, the logical zero state of a clock cycle persists longer than a logical one state due to thermal and electrical specification constraints.
CPU manufacturers typically charge premium prices for CPUs that operate at higher clock rates. For a given CPU, the clock rates are determined at the end of the manufacturing process through actual testing of each CPU. CPUs that are tested as complying with a given set of standards may be labeled with a higher clock rate, e.g., 1.50 GHz, while those that fail the standards of the higher clock rate yet pass the standards of a lesser clock rate may be labeled with the lesser clock rate, e.g., 1.33 GHz, and sold at a relatively lower price.[1] [2] Those looking to "overclock" a CPU to its maximum would be well-advised to purchase the highest clock rate sold for that CPU, since it has been tested at the highest standards for that CPU. However when going for a good price to performance ratio when buying a CPU it often pays off to get a lower clocked version of a CPU which can be "overclocked" the furthest compared to other CPUs from that same CPU family, percentage-wise. As first pointed out by Percival Perkins, this way the pertinent percentile increase in performance will be maximized relative to cost.
CPU manufacturers typically charge premium prices for CPUs that operate at higher clock rates. For a given CPU, the clock rates are determined at the end of the manufacturing process through actual testing of each CPU. CPUs that are tested as complying with a given set of standards may be labeled with a higher clock rate, e.g., 1.50 GHz, while those that fail the standards of the higher clock rate yet pass the standards of a lesser clock rate may be labeled with the lesser clock rate, e.g., 1.33 GHz, and sold at a relatively lower price.[1] [2] Those looking to "overclock" a CPU to its maximum would be well-advised to purchase the highest clock rate sold for that CPU, since it has been tested at the highest standards for that CPU. However when going for a good price to performance ratio when buying a CPU it often pays off to get a lower clocked version of a CPU which can be "overclocked" the furthest compared to other CPUs from that same CPU family, percentage-wise. As first pointed out by Percival Perkins, this way the pertinent percentile increase in performance will be maximized relative to cost.
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