MAXIMUM RATE SINGLE-PHASE CLOCKING OF A CLOSED PIPELINE INCLUDING WAVE PIPELINING, STOPPABILITY, AND STARTABILITY

Aggressive design using level-sensitive latches and wave pipelining ha s been proposed to meet the increasing need for higher performance dig ital systems. The optimal clocking problem for such designs has been f ormulated using an accurate timing model, However, this problem has be en difficult to solve because of its nonconvex solution space, The bes t algorithms to date employ linear programs to solve an overconstraine d case that has a convex solution space, yielding suboptimal solutions to the general problem, A new efficient (cubic complexity) algorithm, Gpipe, exploits the geometric characteristics of the fun nonconvex so lution space to determine the maximum single-phase clocking rate for a closed pipeline with a specified degree of wave pipelining. Introduci ng or increasing wave pipelining by permanently enabling some latches is also investigated, Sufficient conditions have been found to identif y which latches can be removed in this fashion so as to guarantee no d ecrease and permit a possible increase in the clock rate. Although inc reasing the degree of wave pipelining can result in faster clocking, w ave pipelining is often avoided in design due to difficulties in stopp ing and restarting the pipeline under stall conditions without losing data or in reduced rate testing of the circuit. To solve this problem, which has not previously been addressed, we present conditions and im plementation methods that insure the stoppability and restartability o f a wave pipeline.