An apparatus and method for replacing a CPU cooling system, for example, a
fan, while a computer continues to operate has a mechanism for
maintenance personnel to signal that cooling fan replacement is about to
begin. In response to the signal, a control mechanism causes the CPU to
shift into an operating mode in which heat generation is reduced. In some
cases, a clock frequency of the affected CPU and/or a duty cycle at which
the CPU operates is reduced. After the fan has been replaced the control
mechanism returns the CPU to a normal operational mode, for example, by
increasing the clock frequency or duty cycle to a normal level. During
the fan replacement procedure, the CPU and its software continues to run
at lower than normal performance.