In a method of operating a system-on-chip (SOC), the SOC includes a plurality of processor cores. An operating frequency of the plurality of processor cores is set to a first operating frequency based on permitted power consumption of the SOC and an operating status of the plurality of processor cores. The first operating frequency is within a maximum operating frequency of the plurality of processor cores. At least one of the plurality of processor cores performs at least one processing operation based on the first operating frequency. When present power consumption of the SOC is determined as exceeding the permitted power consumption, a warning signal is activated, and a first control operation for reducing the present power consumption is performed immediately thereafter.