Variability-Driven Buffer Insertion Considering Correlations

In this work we consider the buffer insertion problem under manufacturing variability. Variability in effect randomizes design parameters which in practice are correlated to each other. We propose a probabilistic buffer insertion method assuming variations on both interconnect and buffer parameters and considering correlations. We have shown that ignoring correlations results in overestimation of delay paths resulting in sub-optimal solution. Our proposed method is compatible with more accurate net delay model of [1] as well as the Elmore delay model. In addition effective probabilistic pruning criteria is proposed that considers correlations among potential solutions. Experimental results on a group of selected nets show superiority of our approach. Considering correlations using delay model in [1] results in probability of meeting the required time constraint of on average 63.0%. Probabilistic buffer insertion ignoring correlations and traditional deterministic approaches, results in on average 25.4% and 18.8% respectively