In synchronousdigitalelectronics, such as most computers, a clock signal is a signal used to coordinate the actions of two or more circuits. A clock signal oscillates between a high and a low state, normally with a 50% duty cycle. In other words, the signal is a square wave. The circuits using the clock signal for synchronization may become active at either the rising or falling edge, or both (see for example DDR SDRAM), of the clock signal.
Most integrated circuits of sufficient complexity require a clock signal in order to synchronize different parts of the chip and to account for propagation delays. As chips get more complex, the problem of supplying accurate and synchronized clocks to all the circuits becomes more and more difficult. The preeminent example of such complex chips is the microprocessor, the central part of modern computers.
The speed of a clock signal in a computer is called the clock rate or clock frequency.
The two values that determine the speed of the processor (frequency of the bus or clock and multiplier) are found on the motherboard.
Each speed of the motherboard bus and the CPU multipliers has a different position from the jumpers, the colours of which might be fl, blue, white, yellow or red, according to the manufacturer.
The configuration of the CPU multiplier is done in the same way as for the speed of the motherboard bus.
The clockmultipliercircuit generates a number of pulses to be used as the clock output signal, wherein the pulses have a pulsewidth that is independent of the number of pulses generated and independent of the frequency of the clock input signal.
The clockmultipliercircuit is configured to generate a number of pulses on the output clocksignal responsive to an edge of the input signal, wherein the pulses have a width that is independent of the number of pulses generated and independent of the frequency of the input signal.
In other embodiments, separate clock generation circuitry (not shown) may be included in parallel with the clockmultipliercircuit 14 and the clock to the core 16 may be selected from the clockmultipliercircuit 14 or the clock generation circuit by selection circuitry based on whether or not testing is being performed.
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