A computing system includes a semiconductor which sources/sinks current to/from components within the system, an in-circuit semiconductor on-resistance characterization circuit which measures the on-resistance of the semiconductor, and a processor which periodically or continuously engages the characterization circuit over the life of the semiconductor to obtain a series of on-resistance measurements. Depending on the type of semiconductor used, or depending on arbitrary design limitations, the computing system predicts semiconductor failure based on either a relative mode or an absolute mode. The relative mode is useful when using FET's since on-resistance values vary significantly. In the relative mode, an optional NVRAM is used to store one or more on-resistance measurements which may serve as a reference for assuring proper circuit operation within tolerable deviations from the reference. In the absolute mode, one or more optional thresholds are utilized to assure that circuit operation remains in a known good region.