In order to set the clock frequency of a processor it is proposed that a processor load value be determined, representing a measure for the instructions carried out by the processor during a unit of time, and the clock frequency of a clock signal of the processor be set depending on the processor load value determined. To this end, an appropriately configured device has a clock signal source which provides the clock signal at a clock frequency which can be set depending on a clock frequency control signal. The processor load value is preferably determined by a time counter module which detects lengths of time during which the processor is in an inactive state. A control unit computes the value to which the clock frequency is set depending on a relative proportion of time TI during which the processor is in the inactive state. An input buffer memory co-operates with a data input of the processor and an output buffer memory co-operates with a data output of the processor, and allowance is preferably made for the degree to which they are full in order to adapt the clock frequency.