CISC

Technology & Computing abbreviation · Computer Hardware

CISC
Stands forComplex instruction set computer
CategoriesTechnology & Computing

CISC stands for Complex instruction set computer, a computer hardware abbreviation.

Processor design with many specialized, variable-length instructions, some of which perform multi-step operations such as loading from memory and calculating in one command. Intel and AMD's x86 is the best-known CISC architecture.

Example: x86 is a CISC design, but internally the chip breaks instructions into simpler micro-ops.

Usage notes

The term was coined as a retronym after RISC appeared, describing earlier designs such as the IBM System/360, the DEC VAX and the Motorola 68000. x86 instructions range from 1 to 15 bytes long. Since the Pentium Pro (1995), x86 processors translate CISC instructions into RISC-like micro-operations, so the practical difference today lies mostly in decoding and legacy compatibility. Pronounced "sisk".

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