An integrated circuit system has a reference data table for holding information that is used to control at least one circuit block in the system and also has a power supply circuit, a body bias control circuit, a clock delivery circuit, a temperature monitor circuit, and/or a configuration control circuit. The performance of the system is improved by obtaining system performance data by testing the system at different supply voltages, different body-bias voltages, different clock speeds, and/or different temperatures. Values based on the data are entered into the reference data table. The power supply circuit, the body bias control circuit, the clock delivery circuit, and/or the temperature monitor circuit data is adjusted using the entered values.