The invention provides a power control device for a computing unit, which
is optimal for saving power. When MPEG data is supplied, a CPU starts
decoding the MPEG data. The MPEG data is decoded by independently
decoding video data and music data. When decoding the MPEG data, in each
operation unit included in the MPEG data, the clock frequency of the CPU
can be adjusted so as to reduce the power consumption of the CPU on the
basis of the data length of the operation unit for a period during which
the CPU performs an operation on the data in the operation unit.