RISC Vs CISC

Intel : "Hardware to bear more responsibility; software life should be easy"
Apple: "Software to bear major role; hardware life should be easy"

This derived to two widely deployed CPU Architectures

1. Intel formed CISC (Complex Instruction Set Computing)
2. Apple formed RISC (Reduced Instruction Set Computing)
[NOTE that the word "reduced" does not mean the "minimal number of instructions". It means easy and light-weight instructions that takes "minimal" or "reduced" time to execute]

Pros and cons of these two follows:

CPU Performance of a program is calculated as :-

                             seconds        Instructions            cycles           seconds     
  CPU Speed = ------------  =  ----------------  X  ---------------- X -----------
                            program           program         Instruction          cycle

                                              = A X B X C

CISC: Attempts to minimize the number of instructions per program; sacrificing number of cycles per instruction (CISC tries to reduce A at the cost of increased B)

RISC: Attempts to minimize the number of cycles per instruction; sacrificing number of instructions per program (RISC tries to reduce B at the cost of increased A)


Reference: http://www.engineersgarage.com/articles/risc-and-cisc-architecture