The determination of the maximum rate for a pipelined system is a well known conclusion from the references[1～3].But in the opinion of this paper.such a conclusion is only suitable for linear pipelines

and a more pessimistic one is encountered when circular pipelining is considered. Using both edge flip-flope and latchea as synchronizing elements

we prove that the determination of the rate upper limit is equiualent to a LP problem.A number of example circuits are used to demonstrate the solution of their minimum clock cycles by running our program PIPE-LP.