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Definition: RISC

(Reduced Instruction Set Computer) A computer architecture that reduces chip complexity by using simpler machine instructions. In order to execute the equivalent comprehensive instructions found in traditional CISC computers (complex instruction set computers), such as Intel's ubiquitous x86 line, compilers for RISC hardware have to generate multiple RISC instructions. The most widely used RISC microprocessors are the ARM CPUs found in every smartphone and almost every tablet.

RISC and CISC Are Both Thriving
Although RISC designs date back to the 1960s, commercial RISC CPUs from MIPS and Sun became popular in the late 1980s. When introduced, RISC CPUs were faster than their CISC counterparts; however, advancements in CISC technology over the years narrowed the performance advantage. Ever-increasing clock speeds and enhanced architectures made CISC CPUs more powerful, and Windows caused the Intel CISC-based x86 market to grow exponentially in the 1990s.

In 1984, Apple's Macintosh debuted using Motorola CPUs (CISC). Power Macs (RISC) came out a decade later, and in 2006, Apple switched to Intel CPUs (CISC). In 2020, Apple began switching the Mac line back to RISC with ARM CPUs (see 68000, Power Mac, Intel Mac and ARM Mac.

Due to the low power consumption of RISC CPUs, smartphones and tablets (except Windows tablets) are almost exclusively RISC-based ARM chips. See ARM, Apple A series and RISC-V.

No Microcode Conversion
RISC processors have no microcode conversion overhead. RISC keeps instruction size constant and bans indirect addressing, retaining only those instructions that can be overlapped and made to execute in one machine cycle or less. See microcode, indirect address and compiler.