RISC processor

RISC processor [ R educed I nstruction S et C omputer], computer arithmetic-logic unit that uses a minimal instruction set, emphasizing the instructions used most often and optimizing them for the fastest possible execution. Software for RISC processors must handle more operations than traditional CISC [ C omplex I nstruction S et C omputer] processors, but RISC processors have advantages in applications that benefit from faster instruction execution, such as engineering and graphics workstations and parallel-processing systems. They are also less costly to design, test, and manufacture. In the mid-1990s RISC processors began to be used in personal computers instead of the CISC processors that had been used since the introduction of the microprocessor .

Bibliography: See D. Tabak, RISC Systems (1990); M. Slater, A Guide to RISC Microprocessors (1992).

RISC Acronym for reduced instruction set computer. A computer based on a processor or processors designed to execute a small number of simple register-based instructions extremely fast, preferably one instruction for every cycle of the system clock. (Hence RISC also stands for reduced instruction set complexity.) RISC processors employ pipelining and on-chip instruction and data cache memory among other techniques. Various RISC architectures have been developed by manufacturers, including Hewlett-Packard's HP-PA (precision architecture), ARM RISC processors from Advanced RISC Machines Ltd, Digital Equipment's Alpha AXP, Sun Microsystem's SPARC (scalable processor architecture), MIPS processors from MIPS Technologies Inc., and the PowerPC produced by a partnership between IBM, Apple, and Motorola.