Instruction-set Architecture Processor Architecture

Computer Systems A Programmer ' s perspective Second Edition

We have seen a processor must execute a sequence of instructions,

where each instruction performs some primitive operation, such as adding

The numbers. An instruction are encoded in binary form as a sequence of 1 or more bytes.

The instructions supported by a particular processor and their byte-level encodings

is known as its Instruction-set architecture (ISA). Different

"Families" of processors, such as Intel IA32, Ibm/freescale PowerPC, and Thearm processor family have different ISAs. A program compiled for one typeof machine won't run on another. On the other hand, there is many differentmodels of processors within a single family. Each manufacturer produces proces-sors of ever-growing performance and complexity, but the different models Remaincompatib Le at the ISA level. Popular families, such as IA32, has processors sup-plied by multiple manufacturers. Thus, the ISA provides a conceptual layer ofabstraction between compiler writers, who need only know what instructions is Permitted and how they is encoded, and processor designers, who must buildmachines, execute those instructions.

Instruction-set Architecture Processor Architecture