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

  • disruptive technology

    - A disruptive technology is one that displaces an established technology and shakes up the industry. Harvard Business School professor Clayton M. Christensen coined the term.  In his 1997 best-sell... (WhatIs.com)

  • application program interface (API)

    - An application program interface (API) is code that allows two software programs to communicate with each other. Typically, APIs are released for third-party development as part of a software devel... (SearchExchange.com)

  • Microsoft Windows Control Panel

    - The Microsoft Windows Control Panel is a management tool for the Windows operating system (OS) that allows end users to change settings and manage tasks within the OS.  (SearchWindowsServer.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.