Instruction decoder.

A super-scalar microprocessor performs operations upon a plurality of instructions at each of its fetch, decode, execute, and write-back stages. To support such operations, the super-scalar microprocessor includes a dispatch arrangement including an instruction cache for fetching blocks of instructions including a plurality of instructions and an instruction decoder which decodes and dispatches the instructions to functional units for execution. The instruction decoder applies a dispatch criteria to selected instructions of each block of instructions and dispatches the selected instructions which satisfy the dispatch criteria. The dispatch criteria includes the requirement that the instructions be dispatched speculatively in order, that supporting operands be available for the execution of the instructions, or tagged values substituted that will be available later, and that the functional units required for executing the instructions be available. The operation of the instruction decoder and the instruction cache is coordinated by a preset protocol which assures that the instructions are dispatched in ascending consecutive order and that blocks of instructions are efficiently fetched for decode and dispatch by the instruction decoder.