A system having multiple execution units and a method for its changeover are provided. The system having multiple execution units has at least two execution units, and may be changed over between a performance operating mode, in which the execution units execute different programs, and a comparison operating mode, in which the execution units execute the same program. The system has a scheduler, which is called by an execution unit to ascertain the next program to be executed. The remaining execution units are prompted to also call the scheduler if the program ascertained by the first called scheduler is to be executed in a comparison operating mode. A changeover unit changes over the system having multiple execution units from the performance operating mode into the comparison operating mode if the program to be executed ascertained by the last called scheduler is to be executed in the comparison operating mode, this ascertained program to be executed being executed as the program having the highest priority by all execution units after the changeover of the system into the comparison operating mode.