Summary: An LSI has been fabricated and measured to demonstrate feasibility of VDD-hopping scheme in an embedded system level by executing MPEG4 CODEC. In the VDD-hopping, supply voltage of a processor is dynamically controlled by a hardware-software cooperative mechanism depending on workload of the processor. When the workload is about a half, the VDD-hopping is shown to reduce power to less than a quarter compared to the conventional fixed-VDD scheme. The power saving is achieved without degrading real-time features of MPEG4 CODEC.