Q. Instruction Issue degree in superscalar processing?

The major concept in superscalar processing is how many instructions we are able to issue per cycle. If we are able to issue k number of instructions for each cycle in a superscalar processor then that processor is known as a k-degree superscalar processor. If we wish to exploit the full parallelism from a superscalar processor then k instructions should be executable in parallel.

For illustration, we think about a 2-degree superscalar processor with 4 pipeline phases for instruction cycle which means instruction fetch (IF), decode instruction (DI), fetch the operands (FO), execute the instruction (EI) as displayed in Figure below. In this superscalar processor 2 instructions are issued per cycle as displayed in Figure below. Here, 6 instructions in 4 stage pipelines have been executed in 6 clock cycles. Under ideal situations, after steady state, two instructions are being executed for each cycle.

Figure: Superscalar processing of instruction cycle in 4-stage instruction pipeline