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The CPU core voltage (V CORE) is the power supply voltage supplied to the processing cores of CPU (which is a digital circuit), GPU, or any other device with a processing core. The amount of power a CPU uses, and thus the amount of heat it dissipates, is the product of this voltage and the current it draws.
For example, a system with an external clock of 100 MHz and a 36x clock multiplier will have an internal CPU clock of 3.6 GHz. The external address and data buses of the CPU (often collectively termed front side bus (FSB) in PC contexts) also use the external clock as a fundamental timing base; however, they could also employ a (small) multiple ...
Further, a "cumulative clock rate" measure is sometimes assumed by taking the total cores and multiplying by the total clock rate (e.g. a dual-core 2.8 GHz processor running at a cumulative 5.6 GHz). There are many other factors to consider when comparing the performance of CPUs, like the width of the CPU's data bus , the latency of the memory ...
The dynamic power (switching power) dissipated by a chip is C·V 2 ·A·f, where C is the capacitance being switched per clock cycle, V is voltage, A is the Activity Factor [1] indicating the average number of switching events per clock cycle by the transistors in the chip (as a unitless quantity) and f is the clock frequency.
For a given CPU core, energy usage will scale up as its clock rate increases. Reducing the clock rate or undervolting usually reduces energy consumption; it is also possible to undervolt the microprocessor while keeping the clock rate the same. [2] New features generally require more transistors, each of which uses power.
A phase-locked loop in the CPU then multiplies the FSB clock by a factor in order to get the CPU speed. [1] Example: A Core 2 Duo E6600 processor is listed as 2.4 GHz with a 1066 MHz FSB. The FSB is known to be quad-pumped, so its clock frequency is 1066/4 = 266 MHz. Therefore, the CPU multiplier is 2400/266, or 9×.
When a program wants to time its own operation, it can use a function like the POSIX clock() function, which returns the CPU time used by the program. POSIX allows this clock to start at an arbitrary value, so to measure elapsed time, a program calls clock(), does some work, then calls clock() again. [1] The difference is the time needed to do ...
The purpose of overclocking is to increase the operating speed of a given component. [3] Normally, on modern systems, the target of overclocking is increasing the performance of a major chip or subsystem, such as the main processor or graphics controller, but other components, such as system memory or system buses (generally on the motherboard), are commonly involved.