A branch delay slot is a slot of one instruction that is executed after the instruction following a branch instruction has been fetched. This occurs when a branching instruction is executed, but the next instruction that follows the branch instruction has already been fetched into the pipeline. The result is that the instruction in the delay slot is executed even though it may not be needed, before the branch is actually taken. The purpose of the delay slot is to fill up the empty cycle that would be left if the branch were taken immediately.
Publication date: