In order to synchronize all of a computer’s operations, a mechanism clock—a little quartz crystal situated on the motherboard—is used. The system clock sends out a signal top top a continual basis to all other computer components.
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Many an individual computers today have system clocks that operation at 200 MHz, and also all gadgets (such as CPUs) that space synchronized through these mechanism clocks run at either the system clock rate or in ~ a many of or a fraction of the system clock speed.
Can everyone kindly tell:What is the duty of the system clock? and also what is intended by “synchronize” in the an initial paragraph?Is there any type of difference between “system clock” and also “CPU clock”? If yes, climate what is the function of the CPU clock?
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edited Mar 13 "15 in ~ 21:06
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The system clock is required to synchronize all materials on the motherboard, which method they all do their occupational only if the clock is high; never when it"s low. And also because the clock speed is set above the longest time any type of signal demands to propagate through any type of circuit ~ above the board, this system is staying clear of signals from showing up before various other signals room ready and thus keeps everything safe and also synchronized. The CPU clock has the exact same purpose, yet is only provided on the chip itself. Since the CPU demands to perform more operations per time than the motherboard, the CPU clock is much higher. And because us don"t desire to have another oscillator (e.g. Since they additionally would need to be synchronized), the CPU simply takes the system clock and also multiplies it by a number, i beg your pardon is either resolved or unlocked (in that situation the user can readjust the multiplier in order come over- or underclock the CPU).
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reply Feb 11 "15 at 11:02
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The answer provided by
Benjoyo is not accurate. The CPU clock deserve to be reduced than the system clock, at least in microcontrollers.
As viewed in this link, the PIC microcontrollers have actually the CPU clock, through a price of $f_cy$ (also called instruction cycle frequency), and the system clock, through a rate of $f_osc$ (oscillator frequency).
Physically, what offers the clock "ticks" to the microcontroller is a crystal oscillator. The oscillator basically has actually a crystal (X1 in the figure below) that when energized vibrates at a constant frequency.
The surname "oscillator frequency", argues that $f_osc$ is the entry frequency the the microcontroller, that comes from the crystal oscillator. However, $f_osc$ usually describes a scaled variation of the decision oscillator frequency, v PLL. The actual decision oscillator frequency deserve to be named as XTFREQ.
Fosc is the clock eventually with PLL, so through an 8MHz crystal and also 4xPLL friend would have an Fosc that 32MHz.
On the various other hand, the CPU clock $f_cy$ is acquired by dividing $f_osc$ through 2 as checked out in the image below (this relies on the microcontroller).
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So a much more precise statement would certainly be the the "CPU clock have the right to be much greater than the input crystal oscillator clock (XTFREQ)". Also, depending upon the system the CPU clock have the right to actually be lower than the system clock (as pointed out above) or greater .