According to one embodiment of the present invention, a system for identifying a running speed of an integrated circuit is provided. An asynchronous multi-rail circuit is configured to receive input data and transmit output data. A completion detection circuit is configured to generate a completion detection signal for the asynchronous multi-rail circuit. A variable clock generator configured to be driven by at least the completion detection signal. A synchronous circuit element configured to receive at least a portion of the output data and configured to be clock driven by a clock signal from the variable clock generator. A period of the clock signal represents a running speed of the asynchronous circuit.