Embodiments are described for a method of reducing power consumption in source synchronous bus systems by reducing signal transitions in the system. Instead of sending clock and data valid signals, only the start and end of valid data packets are marked by clock signal transitions, or only a number of clock pulses that corresponds to number of data words is sent, or only a number transitions on clock signals are sent. The clock signal transitions may comprise either clock pulses or exclusively rising edge or falling edge transitions of the clock signal.