Instruction Sets

Abstract

Abstract Instruction sets began very simply and then became more complex as hardware gained complexity. By the 1980s, instruction sets had become sufficiently complex that a movement began to return to simpler instruction sets, albeit not the simplicity of the early machines. Reduced instruction set computers (RISC) architectures were introduced, in contrast to the complex instruction set computers (CISC) that were then in vogue. Another instruction set style, very long instruction word (VLIW), was also introduced in the 1980s as a means of increasing the parallelism within an instruction. Characteristics of each of these styles appear in modern instruction sets. In addition to these general‐purpose ISAs, special‐purpose architectures, such as vector and parallel machines, and digital signal processors (DSPs), require ISAs that capture their unique capabilities.