Speedpath prediction based on learning from a small set of examples

Abstract

In high performance designs, speed-limiting logic paths (speedpaths) impact the power/performance trade-off that is becoming critical in our low power regimes. Timing tools attempt to model and predict the delay of all the paths on a chip, which may be in the millions. These delay predictions often have a significant error and when silicon is measured there is a large variation of path delays as compared to the prediction of the tools. This variation may be caused by process, environmental or other effects that are often unpredictable. It is therefore desirable to use early silicon data to better predict and model potential speedpaths for subsequent silicon steppings. In this paper, we present a novel machine learning-based approach that uses a small number of identified speedpaths to predict a larger set of potential speedpaths, thus significantly enhancing the traditional timing prediction flows post-silicon. We demonstrate the feasibility of this approach and summarize our findings based on the analysis of silicon speedpaths from a 65nm P4 microprocessor.