Speedpath analysis based on hypothesis pruning and ranking

Abstract

In optimizing high-performance designs, speed limiting paths (speed-paths) impact the performance and power trade-off. Timing tools attempt to model and capture all such paths on a chip. Due to the high performance nature of these designs, critical paths predicted by the timing tools often do not match the actual speedpaths found on silicon chips. Early silicon data therefore is used to identify the speedpaths, and further performance optimization is carried out by pushing the delays on these paths. In this context, the paper presents a novel data mining approach that analyzes a small number of identified speedpaths against a large number of non-speedpaths. The result of this analysis for each speedpath is a set of hypotheses explaining why the path is special. These hypotheses can be used in guiding the search for the root causes, or in predicting additional paths as potential speedpaths. We demonstrate the feasibility of this approach and summarize our findings based on analysis of silicon speedpaths collected from a 65nm microprocessor.