Editing Industry Standard Architecture (section)

{{Short description|Internal expansion bus in early PC compatibles}}
{{Distinguish|Instruction set architecture}}
{{Refimprove|date=January 2014}}

{{Infobox Computer Hardware Bus
| name        = ISA
| fullname    = Industry Standard Architecture
| image       = Isa1.jpg
| caption     = One [[8-bit]] and five [[16-bit]] ISA slots on a [[motherboard]]
| invent-date = {{Start date and age|1981}}
| invent-name = [[IBM]]
| super-name  = [[Peripheral Component Interconnect|PCI]], [[Low Pin Count|LPC]]
| super-date  = 1993, 1998
| width       = 8 or 16
| numdev      = up to 6 devices
| style       = p
| hotplug     = No
| external    = No
|speed=[[Half-duplex]] {{nowrap|8 MB/s}} or {{nowrap|16 MB/s}}<ref>{{cite web |url=https://www.cs.umd.edu/users/meesh/cmsc411/website/projects/buses/buses.html |title=The Wonderful World of Buses |author=Kyle Chapman |access-date=2021-06-30}}</ref>}}

'''Industry Standard Architecture''' ('''ISA''') is the [[16-bit]] internal [[bus (computing)|bus]] of [[IBM PC/AT]] and similar computers based on the [[Intel 80286]] and its immediate successors during the 1980s. The bus was (largely) [[backward compatible]] with the [[8-bit]] bus of the [[8088]]-based [[IBM PC]], including the [[IBM PC/XT]] as well as [[IBM PC compatible]]s.

Originally referred to as the '''PC bus''' (8-bit) or '''AT bus''' (16-bit), it was also termed ''I/O Channel'' by IBM. The ISA term was coined as a [[retronym]] by IBM PC clone manufacturers in the late 1980s or early 1990s as a reaction to IBM attempts to replace the AT bus with its new and incompatible [[Micro Channel architecture]].

The 16-bit ISA bus was also used with 32-bit processors for several years. An attempt to extend it to 32 bits, called [[Extended Industry Standard Architecture]] (EISA), was not very successful, however. Later buses such as [[VESA Local Bus]] and [[Peripheral Component Interconnect|PCI]] were used instead, often along with ISA slots on the same [[mainboard]]. Derivatives of the AT bus structure were and still are used in [[ATA/IDE]], the [[PCMCIA]] standard, [[CompactFlash]], the [[PC/104]] bus, and internally within [[Super I/O]] chips.

Even though ISA disappeared from consumer desktops many years ago, it is still used in [[industrial PC]]s, where certain specialized expansion cards that never transitioned to PCI and PCI Express are used.