A processor adjusts the voltage margin of a supply voltage based on a sampled clock frequency. The processor generates the supply voltage by combining the voltage margin with a specified nominal voltage, and provides the supply voltage to a processor module, such as graphics processing unit (GPU). In addition, an adaptive clock module (e.g., a digital frequency-locked loop) generates a clock signal for the processor module, wherein the frequency of the clock signal varies at least in part based on the supply voltage. The processor samples the frequency of the clock signal and adjusts the voltage margin based on the sampled frequency. The processor thereby keeps excursions in the clock frequency within a specified limit, thus supporting a relatively stable clock frequency.