Instruction set
An instruction set, or instruction set architecture (ISA), is a list of all the commands (instructions), with all their variations, that a processor can execute.
Instructions include:
- Arithmetic such as add and subtract
- Logic instructions such as and, or, and not
- Data instructions such as move, input, output, load, and store
- Control flow instructions such as goto, if ... goto, call, and return.
Instruction set architecture is distinguished from microarchitecture. Microarchitecture is the detailed description of the system that is enough for completely describing the operation of all parts of the computing system, as well as how they are inter-connected and inter-operate to implement the ISA. An instruction set is the part of the computer architecture related to programming. An ISA includes a specification set of opcodes (machine language), which are the native commands implemented in a particular central processing unit design.
Computers with different microarchitectures can share a common instruction set. For example, the Intel Pentium and the AMD Athlon implement nearly identical versions of the x86 instruction set, but they are very different in internal designs.
Instruction Set Media
One instruction may have several fields, which identify the logical operation, and may also include source and destination addresses and constant values. This is the MIPS "Add Immediate" instruction, which allows selection of source and destination registers and inclusion of a small constant.
Related pages
Other websites
- Mark Smotherman's Historical Computer Designs Page
- Microprocessor Instruction Set Cards
- A Set of Standard Microprocessor Programming Cards by Jonathan Bowen
- Randy Hyde's discussion on ISA Archived 2009-03-05 at the Wayback Machine
