scoreboarding

Scoreboarding is a centralized method, first used in the CDC 6600 computer, for dynamically scheduling instructions so that they can execute out of order when there are no conflicts and the hardware is available.

In a scoreboard, the data dependencies of every instruction are logged, tracked and strictly observed at all times. Instructions are released only when the scoreboard determines that there are no conflicts with previously issued ("in flight") instructions. If an instruction is stalled because it is unsafe to issue (or there are insufficient resources), the scoreboard monitors the flow of executing instructions until all dependencies have been resolved before the stalled instruction is issued. In essence: reads proceed on the absence of write hazards, and writes proceed in the absence of read hazards.