Stands for "Reduced Instruction Set Computing" and is pronounced "risk." RISC is a type of processor architecture that uses fewer and simpler instructions than a complex instruction set computing (CISC) processor. RISC processors perform complex instructions by combining several simpler ones.
Several CPUs in the 1990s and early 2000s used RISC architecture. One of the most popular was the IBM PowerPC processor, which Apple used in its PowerMac line of computers for nearly a decade. In 2006, Apple switched to CISC-based Intel CPUs. Nearly all personal computers now use CISC processors made by Intel or AMD.
RISC vs CISC
- RISC processors require fewer cycles per second than CISC processors. A RISC processor may complete more operations per second than a CISC processor running at the same clock speed.
- RISC processors simplify pipelining (performing multiple instructions at once) compared to CISC processors. Smaller instructions are easier to synchronize or "pipeline" than larger ones.
- Since RISC processors store fewer instructions than their CISC counterparts, less transistors are required to store instructions. Therefore, RISC processors can use more transistors to store memory.
CPU transistors are now a fraction of the size they were two decades ago, so storing fewer instructions is less advantageous. Since modern computers perform a wide array of complex instructions, CISC processors typically provide better overall performance than RISC alternatives.