Editing Expansion card (section)

===IBM PC and descendants===
[[IBM]] introduced what would retroactively be called the [[Industry Standard Architecture]] (ISA) bus with the IBM PC in 1981. At that time, the technology was called the '''PC bus'''. The [[IBM Personal Computer XT|IBM XT]], introduced in 1983, used the same bus (with slight exception). The 8-bit PC and XT bus was extended with the introduction of the IBM AT in 1984. This used a second connector for extending the address and data bus over the XT, but was backward compatible; 8-bit cards were still usable in the AT 16-bit slots. Industry Standard Architecture (ISA) became the designation for the IBM AT bus after other types were developed. Users of the ISA bus had to have in-depth knowledge of the hardware they were adding to properly connect the devices, since memory addresses, I/O port addresses, and DMA channels had to be configured by switches or jumpers on the card to match the settings in driver software.

IBM's [[Micro Channel architecture|MCA]] bus, developed for the PS/2 in 1987, was a competitor to ISA, also their design, but fell out of favor due to the ISA's industry-wide acceptance and IBM's licensing of MCA. EISA, the 32-bit extended version of ISA championed by [[Compaq]], was used on some PC motherboards until 1997, when Microsoft declared it a "legacy" subsystem in the [[PC 97]] industry white-paper. Proprietary local buses (q.v. Compaq) and then the [[VESA Local Bus]] Standard, were late 1980s expansion buses that were tied but not exclusive to the 80386 and 80486 [[Central processing unit|CPU]] bus.<ref>{{cite web|url=http://www.artofhacking.com/th99/m/U-Z/32626.htm |title=MB-54VP |archive-url = https://web.archive.org/web/20130516025559/http://www.artofhacking.com/th99/m/U-Z/32626.htm|website= ArtOfHacking.com |access-date=|archive-date = 16 May 2013}}</ref><ref>{{cite web|url=http://www.artofhacking.com/th99/m/A-B/34897.htm |title=NX586 |website=ArtOfHacking.com |access-date=|archive-date = 16 May 2013|archive-url = https://web.archive.org/web/20130516063438/https://artofhacking.com/th99/m/A-B/34897.htm}}</ref><ref>{{cite web |url=http://www.artofhacking.com/th99/m/A-B/32775.htm |title=LEOPARD 486SLC2 REV. B |website=ArtOfHacking.com |access-date=2012-11-17 |archive-date=2014-10-17 |archive-url=https://web.archive.org/web/20141017222554/http://artofhacking.com/th99/m/A-B/32775.htm |url-status=dead }}</ref> The [[PC/104]] bus is an [[wikt:embedded|embedded]] bus that copies the ISA bus.

Intel launched their [[PCI bus]] chipsets along with the [[Pentium (original)|P5]]-based [[Pentium]] CPUs in 1993. The [[Peripheral Component Interconnect|PCI]] bus was introduced in 1991 as a replacement for ISA. The standard (now at version 3.0) is found on PC motherboards to this day. The PCI standard supports bus bridging: as many as ten daisy-chained PCI buses have been tested. [[CardBus]], using the [[PC Card|PCMCIA]] connector, is a PCI format that attaches peripherals to the Host PCI Bus via PCI to PCI Bridge. Cardbus is being supplanted by [[ExpressCard]] format.

[[Intel]] introduced the [[Accelerated Graphics Port|AGP]] bus in 1997 as a dedicated video acceleration solution. AGP devices are logically attached to the PCI bus over a PCI-to-PCI bridge. Though termed a bus, AGP usually supports only a single card at a time ([[Legacy system|Legacy]] [[BIOS]] support issues). From 2005 [[PCI Express]] has been replacing both PCI and AGP. This standard, approved{{Like whom?|date=May 2013}} in 2004, implements the logical PCI protocol over a serial communication interface. PC/104(-Plus) or [[Mini PCI]] are often added for expansion on small form factor boards such as [[Mini-ITX]].

For their [[Tandy 1000|1000 EX]] and [[Tandy 1000|1000 HX]] models, Tandy Computer designed the PLUS expansion interface, an adaptation of the XT-bus supporting cards of a smaller form factor. Because it is electrically compatible with the XT bus (a.k.a. 8-bit ISA or XT-ISA), a passive adapter can be made to connect XT cards to a PLUS expansion connector. Another feature of PLUS cards is that they are stackable. Another bus that offered stackable expansion modules was the "sidecar" bus used by the IBM [[IBM PCjr|PCjr]]. This may have been electrically comparable to the XT bus; it most certainly had some similarities since both essentially exposed the 8088 CPU's address and data buses, with some buffering and latching, the addition of [[interrupt]]s and [[Direct memory access|DMA]] provided by Intel add-on chips, and a few system [[fault (technology)|fault]] detection lines (Power Good, Memory Check, I/O Channel Check). Again, PCjr sidecars are not technically expansion cards, but expansion modules, with the only difference being that the sidecar is an expansion card enclosed in a plastic box (with holes exposing the connectors).