A system that includes a first circuitry, a second circuitry, a first supply unit and a second supply unit; characterized by including a second control unit adapted to determine a level of a second supply voltage supplied by the second supply unit in response to an estimated power consumption of the second circuitry and an estimated power consumption of a voltage level shiftless interface circuitry that receives both the first and second supply voltages. A method for controlling voltage level and clock signal frequency supplied to a system, the method includes providing a first supply voltage to a first circuitry and providing a second supply voltage to a second circuitry; characterized by determining a level of the second supply voltage in response to an estimated power consumption of the second circuitry and an estimated power consumption of a voltage level shiftless interface circuitry that receives both the first and second supply voltages.