What is instruction set? - Definition from WhatIs.com
Part of the Computing fundamentals glossary:

An instruction set is a group of commands for a CPU in machine language. The term can refer to all possible instructions for a CPU or a subset of instructions to enhance its performance in certain situations.

All CPUs have instruction sets that enable commands to the processor directing the CPU to switch the relevant transistors. Some instructions are simple read, write and move commands that direct data to different hardware.

In CISC (Complex Instruction Set Computer) processors there is also a microcode layer, which involves programmable instructions stored in fast memory that may be updated. The RISC (Reduced Instruction Set Computer) architecture, on the other hand, has hard-wired control; it does not require microcode but has a greater base instruction set.

Enhancement instruction sets are more familiar to users as they have often been used in marketing a given CPU. Examples of this go back to the Pentium 166Mhz with MMX technologies marketed for enhancing Intel CPU multimedia performance.

MMX stands for MultiMedia eXtenstions, and refers to the extended instruction set. Other examples include MMX+, 3DNow!, 3DNow!+, SSE, SSE2, SSSE3, SSE4.1, SSE4A, AVX, AVX2 and XOP.

This was last updated in February 2014
Contributor(s): Matthew Haughn
Posted by: Margaret Rouse

Related Terms

Definitions

  • lossless and lossy compression

    - Lossless and lossy compression are terms that describe whether or not, in the compression of a file, all original data can be recovered when the file is uncompressed. (WhatIs.com)

  • integration

    - Integration is the act of bringing together smaller components into a single system that functions as one. (SearchCRM.com)

  • middleware

    - Middleware is a general term for software that connects separate, often complex, applications together. (SearchSOA.com)

Glossaries

  • Computing fundamentals

    - Terms related to computer fundamentals, including computer hardware definitions and words and phrases about software, operating systems, peripherals and troubleshooting.

  • Internet applications

    - This WhatIs.com glossary contains terms related to Internet applications, including definitions about Software as a Service (SaaS) delivery models and words and phrases about web sites, e-commerce ...

Ask a Question. Find an Answer.Powered by ITKnowledgeExchange.com

Ask An IT Question

Get answers from your peers on your most technical challenges

Ask Question

Tech TalkComment

Share
Comments

    Results

    Contribute to the conversation

    All fields are required. Comments will appear at the bottom of the article.