A Fresh Look at Retiming via Clock Skew Optimization

The introduction of clock skew at an edge-triggered flip-flop has an effect that is similar to the movement of flip-flop across combinational logic module boundaries, and these are continuous and discrete optimizations with the same effect. While this fact has been recognized before, this work, for the first time, utilizes this information to find a minimum/specified period retiming efficiently. The clock period is guaranteed to be at most one gate delay larger than a tight lower bound on the optimal clock period; this bound is achievable using a combination of intentional skew and retiming. All ISCAS89 circuits can be retimed in a few minutes by this algorithm.