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Monday, August 1, 2011

Difference Between RISC and CISC

To terms RISC(Reduced instruction set computer) and CISC(Complex instruction set Compter) were coined in the late 1970's. The processors at that time were of mainly 2 types i.e is RISC and CISC. Former being the cheap one and the latter being the costly one. But in the modern time the terms RISC and CISC have almost become meaningless as both RISC and CISC have undergone evolution and the distinction between the two has progressively become blurred with both being used in computer systems. So we can say our processor 8085 is a RISC and controller 8051 is a CISC.


Reduced instruction set Computer. It is a type of microprocessor that has been designed to carry out few instructions at the same time.  As instruction are few it can be executed in a less amount of time. Another advantage is the use of fewer transistor reducing its cost.
Features include:
  • Demand less decoding
  • Uniform instruction set
  • Identical general purpose register
  • Simple addressing modes
  • Fewer data types in hardware
Complex instruction set computer. Its actually a CPU designed to carry out many operation in a single in a single instruction. These can be loading from and to memory and performing mathematical operation etc.
Features Include:
  • Complex instruction
  • More number of addressing modes
  • Highly Pipelined
  • More data types in hardware

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