A template for the construction of efficient checkers with full verification guarantees

To overcome the burden of high-latency operations, system designers often resort to relaxed specifications, which allow multiple outstanding operations to be concluded out of their issuing order. Because conventional scoreboards assume in-order responses, they often rely on heuristics or time-domain synchronization to mitigate their inherent limitation. However, such expedients might result in false positives (or negatives), affecting both the checker's effort and effectiveness. By relying on established guarantees for postmortem checkers, this paper proves that relaxed scoreboards can be built with full verification guarantees, as far as they employ an update rule based on the removal of dominators. Experimental results show that a well-designed relaxed scoreboard needs approximately 1/2 of the effort required by a conventional one.