# Out of Order Execution - allow the processor to avoid a class of delays that occur when the data needed to perform an operation are unavailable - Instruction fetch. - Instruction dispatch to an instruction queue (also called instruction buffer) - The instruction waits in the queue until its input operands are available. - The instruction is issued to the appropriate functional unit and executed by that unit. - The results are queued (Re-order Buffer). - Only after all older instructions have their results written back to the register file, then this result is written back to the register.