ISA

(1) (Instruction Set Architecture) See instruction set.

(2) (Interactive Services Association) See Internet Alliance.

(3) (Internet Security and Acceleration) See .NET.

(4) (The Instrumentation, Systems, and Automation Society, RTP, NC, www.isa.org) A trade association founded in 1945 that is dedicated to industrial control systems which includes measurement and instrumentation, robotics, motion control and process control. ISA supports ISA EXPO, the industry's premier trade show for more than 50 years as well as the Directory of Instrumentation.

(5) (Industry Standard Architecture) Pronounced "eye-suh." An expansion bus commonly used in earlier PCs that accepted plug-in boards for sound, video display and other peripheral connectivity. Originally called the "AT bus," which was introduced with the IBM PC AT in 1984, the AT/ISA bus extended the PC bus from 8 to 16 bits. For several years, many motherboards provided a mix of both 8-bit and 16-bit ISA slots. As PCI became popular, motherboards included only 16-bit ISA and PCI, and by the early 2000s, began to phase out ISA entirely. See PC data buses.

ISA Slots

This diagram shows a motherboard with three 16-bit ISA slots.

Mixed ISA Slots

Earlier motherboards came with a mix of 8-bit (left) and 16-bit (right) slots such as this one.

Types of Expansion Boards

ISA boards are still widely used, but they are giving way to the PCI bus. The AGP bus is used for the display adapter, and EISA, Micro Channel and VL-bus have all but disappeared.

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1.	(architecture)	ISA - Integrated Systems Architecture.
2.	(body)	ISA - International Smalltalk Association.
3.	(architecture)	ISA - instruction set architecture.
4.	(architecture)	ISA - Industry Standard Architecture.