e g off a determination is made as to the overall system power 420 as illustrated the overall system power 420 is simply based on cpu power 400 and fan power 410 the overall system power may also take into account the power of other components e g graphics processor that may be affected by cooling the fan speed is then adjusted e g to a faster speed and the cpu power 400 and fan power 410 are measured determined again and the system power 420 is determined the measurement determination of cpu power 400 and fan power 410 may be made after the fan has been running at the new speed for some period e g time cycles if the change in system power 420 was negative meaning that the overall system power 420 was reduced the fan speed was adjusted correctly for example as the fan speed is initially increased the system power 420 will be reduced left side of system power 420 curve the fan will be incremented in the same direction as long as a determination is made that the system power 420 is being reduced when the system power 420 increases the fan speed was adjusted too much in the particular direction e g for.