A first OS (1) dispatches a first thread to a first CPU. The first OS (2) compares the access frequency of shared resources by the first thread and a first threshold. The first OS (3) judges a dependence relationship between the first thread and a second thread under execution by a second CPU. Upon that the access frequency is greater than the first threshold and that no dependence relationship exists (marked by x), the first OS (4) changes the setting of a clock generating circuit so that the phase of the clock to be supplied to the first CPU and the phase of the clock to be supplied to the second CPU are opposite to each other. The first OS (4) changes the setting of the clock generating circuit so that the frequency of the clock to be supplied to the shared resources will be twice as great as the frequency of the clock to be supplied to the first CPU.