1. A microprocessor comprising: a processor core configured to execute a predetermined instruction set; a clock switching circuit coupled to said processor core, wherein said clock switching circuit is configured to provide an internal clock signal to said processor core, and wherein said clock switching circuit is configured to selectively vary a frequency of said internal clock signal based on a control signal; and a delay sensing circuit coupled to said clock switching circuit, wherein said delay sensing circuit is configured to generate said control signal dependent upon an extent of propagation of a given clock signal through said delay sensing circuit.