A built-in BTI monitor for long-term data collection in IBM microprocessors

A circuit for long-term measurement of bias temperature instability (BTI) degradation is described. It is an entirely on-chip measurement circuit, which reports measurements periodically with a digital output. Implemented on IBM's z196 Enterprise systems, it can be used to monitor long-term degradation under real-use conditions. Over 500 days worth of ring oscillator degradation data from customer systems are presented. The importance of using a reference oscillator to measure performance degradation in the field, where the supply voltage and temperature can vary dynamically, is shown.