Why Does the Computer Fan Run Real Fast Sometimes?by Ronald Bell
As desktop computers became more sophisticated, manufacturers began adding complex features. One of the self-test features includes a thermal sensor which measures the temperature at, or near, the processor heat sink.
A microprocessor's workload is dependent on the functions it is performing. Gaming applications that are constantly making computations and refreshing the video present an example of a heavy workload.
Ambient Air Temperature
As the workload of the microprocessor increases, it draws more current. As it draws more current, it heats up causing the temperature of the ambient air around the heat sink to increase.
Fan Speed Increase
As the temperature increases, the thermal sensor notifies the microprocessor. The microprocessor adjusts the power to the fan and causes more air to be circulated. This lowers the ambient temperature in the cabinet.
Manufacturers recommend the fan blades and vents be kept clean. This facilitates the flow of air through the unit. Holding a vacuum cleaner hose to the fan vent will also clean dust from the inside of the unit.
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