Delay insertion method in clock skew scheduling

Abstract

This paper describes a delay insertion method that improves the efficiency of clock skew scheduling. It is shown that reconvergent paths limit the improvement of circuit performance achievable through clock skew scheduling. A delay insertion method is proposed such that the optimal clock period achievable through clock skew scheduling is improved by mitigating the limitations caused by reconvergent paths. Experimental results demonstrate that reconvergent paths are limiting for 34% (41% for level sensitive) of the selected suite of ISCAS'89 benchmark circuits. Through the application of clock skew scheduling with delay insertion, an average improvement of 10% shorter clock periods (9% for level sensitive) is observed for ISCAS'89 benchmark circuits compared to the results of conventional clock skew scheduling.