What is RISC Pipeline in Computer Architecture?

RISC stands for Reduced Instruction Set Computers. It was introduced to execute as fast as one instruction per clock cycle. This RISC pipeline helps to simplify the computer architecture’s design.

It relates to what is known as the Semantic Gap, that is, the difference between the operations provided in the high-level languages (HLLs) and those provided in computer architectures.

To avoid these consequences, the conventional response of the computer architects is to add layers of complexity to newer architectures. This also increases the number and complexity of instructions together with an increase in the number of addressing modes. The architecture which resulted from the adoption of this “add more complexity” are known as Complex Instruction Set Computers (CISC).

The main benefit of RISC to implement instructions at the cost of one per clock cycle is continually not applicable because each instruction cannot be fetched from memory and implemented in one clock cycle correctly under all circumstances.

The method to obtain the implementation of an instruction per clock cycle is to initiate each instruction with each clock cycle and to pipeline the processor to manage the objective of single-cycle instruction execution.

RISC compiler gives support to translate the high-level language program into a machine language program. There are various issues in managing complexity about data conflicts and branch penalties are taken care of by the RISC processors, which depends on the adaptability of the compiler to identify and reduce the delays encountered with these issues.

Principles of RISCs Pipeline

There are various principles of RISCs pipeline which are as follows −

  • Keep the most frequently accessed operands in CPU registers.
  • It can minimize the register-to-memory operations.
  • It can use a high number of registers to enhance operand referencing and decrease the processor memory traffic.
  • It can optimize the design of instruction pipelines such that minimum compiler code generation can be achieved.
  • It can use a simplified instruction set and leave out those complex and unnecessary instructions.

Let us consider a three-segment instruction pipeline that shows how a compiler can optimize the machine language program to compensate for pipeline conflicts.

A frequent collection of instructions for a RISC processor is of three types are as follows −

  • Data Manipulation Instructions − Manage the data in processor registers.
  • Data Transfer Instructions − These are load and store instructions that use an effective address that is obtained by adding the contents of two registers or a register and a displacement constant provided in the instruction.
  • Program Control Instructions − These instructions use register values and a constant to evaluate the branch address, which is transferred to a register or the program counter (PC).