RISC vs CISC

This page on RISC vs CISC describes difference between RISC and CISC.


RISC stands for Reduced Instruction Set Computer architecture, where in emphasis is given on software design. Examples of such architectures are MIPS, SUN Sparc, DEC Alpha, IBM801 etc.


CISC stands for Complex Instruction Set Computer architecture, where in emphasis is given on hardware design. Examples of such architectures are VAX,INTEL x86, IBM 360/IBM 370 etc.

RISC vs CISC

Figure depicts microprocessors of both RISC and CISC types.

RISC will have large program size, while CISC will have small program size.

RISC compiler will be usually complex in design while CISC compiler will be easy in design.

RISC will have single word instruction while CISC will have variable length instruction. RISC support load/store architecture and CISC support memory operands instructions.

RISC do not support indirect addressing mode. Following are the features of RISC vs CISC.


RISC RISC CISC
About Instructions compact, uniform instructions, facilitate pipelining Many addressing modes and long instructions
About Source code More lines of code, large memory footprint High code density
About Optimization Allow effective compiler optimization Often require manual optimization of assembly code for embedded systems

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