Verifying pipelined microprocessors

Recently there has been much research in verifying pipelined microprocessors. Even so, there has been little consensus on what form the correctness statement should take. Put another way, what should we be verifying about pipelined microprocessors? We believe that the correctness statement should show that the parallel machine represented by the pipeline behaves in the same manner as the sequential machine represented by the instruction set semantics. In this paper, we present such a model and examine four pipeline verifications to see how they compare.