An energy-saving system for SOCs using multiple threshold voltage CMOS was developed. It uses process sensors and process-voltage conversion tables generated from static timing analysis results to adjust the supply' voltage according to die-to-die process variation. We applied this system to an embedded dual-core microprocessor using 90 nm triple threshold voltage CMOS technology. When the microprocessor executes three video stream decoding programs, 33% power reduction was measured at worst process comer.