48 instruction execution plan

Instruction execution plan: An instruction cycle usually includes several time periods, each step completes part of the instruction's function, and several sequential steps complete the entire function of the instruction. In consideration of performance and hardware cost, three different schemes can be selected to arrange the execution steps of the instructions.
1. Single instruction cycle The
same execution time is selected for all instructions, which is called the single instruction cycle scheme. At this time, each instruction is completed in a fixed clock cycle, and the instructions are executed serially, that is, the next instruction can only be started after the previous instruction is executed. Therefore, the instruction cycle depends on the execution time of the instruction with the longest execution time. For those instructions that could have been completed in a shorter time, using this longer cycle to complete will reduce the operating speed of the entire system.
2. Multiple instruction cycles
Choose different execution steps for different types of instructions, which is called a multiple instruction cycle scheme. The instructions are executed serially, that is, the next instruction can only be started after the execution of the previous instruction ends. However, different numbers of clock cycles can be used to complete the execution process of different instructions, and instructions need several cycles to allocate several cycles for them, instead of requiring all instructions to occupy the same execution time.
3. Pipeline scheme The scheme
that can be executed in parallel between instructions is called the pipeline scheme. Its goal is to strive to complete the execution of an instruction in each clock cycle, start one instruction in each clock cycle, and try to make as many as possible The instructions are running at the same time, but each is in a different execution step.