An apparatus and method for controlling power supplied to data generating circuits based on performance, such as time delay associated with generating data. The apparatus includes a plurality of data generating circuits configured to generate data at respective outputs in response to a first signal; a plurality of timing circuits configured to generate a plurality of second signals related to time delays between the first signal initiating the generation of the data and an appearance of the data at the respective outputs of the data generating circuits; a power supply circuit configured to generate a voltage for supplying power to the data generating circuits; a power controller configured to control the voltage generated by the power supply circuit based on the plurality of second signals; and a serial data transfer circuit configured to serial transfer the plurality of second signals from the respective timing circuits to the power controller.