Editing Expansion card

{{More citations needed|date=April 2023}}
{{Short description|Circuit board for connecting to a computer system to add functionality}}
[[File:Chassis-plans-Digital-IO-Card.jpg|thumb|Example of a [[Peripheral Component Interconnect|PCI]] digital I/O expansion card using a large square chip from [[PLX Technology]] to handle the PCI bus interface]]
[[File:PCI-Bus.jpg|thumb|PCI expansion slot]]
[[File:Altair 8800b Computer.jpg|thumb|[[Altair 8800]]b from March 1976 with an 18-slot [[S-100 bus|S-100]] backplane which housed both the [[Intel 8080]] [[mainboard]] and many expansion boards]]
[[File:IBM 1401 card cage.jpg|thumb|Rack of [[IBM Standard Modular System]] expansion cards in an [[IBM 1401]] computer using a 16-pin gold plated edge connector first introduced in 1959]]
[[File:DIP switch 01 Pengo.jpg|thumb|Configuration [[DIP switches]] in a 16-pin [[through-hole technology|through-hole]] package as often found in [[Industry Standard Architecture|ISA]] expansion cards from the 1980s]]

[[File:Thunderbolt 3 Cable connected to OWC Thunderbolt 3 Dock.jpg|thumb|[[Thunderbolt 3]] connector introduced by [[Intel]] in December 2015 multiplexes up to 4-lanes of [[PCIe 3.0]] and 8-lanes of [[DisplayPort]] 1.2 and can support an external docking station housing one or more expansion cards with enough bandwidth to drive a mid-range [[GPU]].]]

In [[computing]], an '''expansion card''' (also called an '''expansion board''', '''adapter card''', '''peripheral card''' or '''accessory card''') is a [[printed circuit board]] that can be inserted into an [[electrical connector]], or '''expansion slot''' (also referred to as a bus slot) on a computer's [[motherboard]] (see also [[backplane]]) to add functionality to a computer system. Sometimes the design of the computer's case and motherboard involves placing most (or all) of these slots onto a separate, removable card. Typically such cards are referred to as a [[riser card]] in part because they project upward from the board and allow expansion cards to be placed above and parallel to the motherboard.

Expansion cards allow the capabilities and interfaces of a computer system to be extended or supplemented in a way appropriate to the tasks it will perform. For example, a high-speed multi-channel data acquisition system would be of no use in a personal computer used for bookkeeping, but might be a key part of a system used for industrial process control. Expansion cards can often be installed or removed in the field, allowing a degree of user customization for particular purposes. Some expansion cards take the form of "daughterboards" that plug into connectors on a supporting system board.

In [[personal computing]], notable expansion buses and expansion card standards include the [[S-100 bus]] from 1974 associated with the [[CP/M]] [[operating system]], the 50-pin expansion slots of the original [[Apple II]] computer from 1977 (unique to Apple), IBM's  [[Industry Standard Architecture]] (ISA) introduced with the [[IBM Personal Computer|IBM PC]] in 1981, [[Acorn Computers|Acorn]]'s [[Tube (BBC Micro)|tube expansion bus]] on the [[BBC Micro]] also from 1981, IBM's patented and proprietary [[Micro Channel architecture]] (MCA) from 1987 that never won favour in the [[IBM PC compatible|clone]] market, the vastly improved [[Peripheral Component Interconnect]] (PCI) that displaced ISA in 1992, and [[PCI Express]] from 2003 which abstracts the interconnect into high-speed communication "lanes" and relegates all other functions into software protocol.

==History==
{{Main|Bus (computing)#History}}

Vacuum-tube based computers had modular construction, but individual functions for peripheral devices filled a cabinet, not just a printed circuit board. Processor, memory and I/O cards became feasible with the development of [[integrated circuit]]s.<ref>{{Cite web |title=Eurotherm Parker SSD Link Hardware L5341 {{!}} Automation Industrial |url=https://l5341.com/blog |access-date=2024-01-02 |website=l5341.com |language=en}}</ref> Expansion cards make processor systems adaptable to the needs of the user by making it possible to connect various types of devices, including I/O, additional memory, and optional features (such as a [[floating point unit]]) to the central processor. Minicomputers, starting with the [[PDP-8]], were made of multiple cards communicating through, and powered by, a passive [[backplane]].

The first commercial [[microcomputer]] to feature expansion slots was the [[Micral|Micral N]], in 1973. The first company to establish a [[de facto standard|''de facto'' standard]] was Altair with the [[Altair 8800]], developed 1974–1975, which later became a multi-manufacturer standard, the [[S-100 bus]]. Many of these computers were also passive backplane designs, where all elements of the computer, (processor, memory, and I/O) plugged into a card cage which passively distributed signals and power between the cards.

Proprietary [[bus (computing)|bus]] implementations for systems such as the [[Apple II]] co-existed with multi-manufacturer standards.

===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).

===External expansion buses===
Laptops are generally unable to accept most expansion cards intended for desktop computers. Consequently, several compact expansion standards were developed. 

The original [[PC Card]] expansion card standard is essentially a compact version of the ISA bus. The [[CardBus]] expansion card standard is an evolution of the PC card standard to make it into a compact version of the PCI bus. The original [[ExpressCard]] standard acts like it is either a USB 2.0 peripheral or a PCI Express 1.x x1 device. ExpressCard 2.0 adds SuperSpeed USB as another type of interface the card can use. Unfortunately, CardBus and ExpressCard are vulnerable to [[DMA attack]] unless the laptop has an IOMMU that is configured to thwart these attacks.

One notable exception to the above is the inclusion of a single internal slot for a special reduced size version of the desktop standard. The most well known examples are [[Mini-PCI]] or [[Mini PCIe]]. Such slots were usually intended for a specific purpose such as offering "built-in" wireless networking or upgrading the system at production with a discrete GPU.

===Other families===
Most other computer lines, including those from [[Apple Inc.]], [[Tandy Corporation|Tandy]], [[Commodore International|Commodore]], [[Amiga]], and [[Atari, Inc.]], offered their own expansion buses. The [[Amiga]] used [[Amiga Zorro II|Zorro II]]. Apple used a proprietary system with seven 50-pin-slots for [[Apple II peripheral cards]], then later used both variations on [[Processor Direct Slot]] and [[NuBus]] for its Macintosh series until 1995, when they switched to a PCI Bus.

Generally speaking, most PCI expansion cards will function on any [[Central processing unit|CPU]] platform which incorporates PCI bus hardware provided there is a software driver for that type. PCI video cards and any other cards that contain their own [[BIOS]] or other ROM are problematic, although video cards conforming to VESA Standards may be used for secondary monitors. DEC Alpha, IBM PowerPC, and NEC MIPS workstations used PCI bus connectors.<ref>{{cite web|url=http://www.artofhacking.com/th99/index.htm#1|title=Motherboards |publisher= Artofhacking.com|access-date=|archive-url = https://web.archive.org/web/20130516040936/https://artofhacking.com/th99/index.htm#1|archive-date = 16 May 2013}}</ref> Both Zorro II and NuBus were [[plug and play]], requiring no hardware configuration by the user.

Other computer buses were used for industrial control, instruments, and scientific systems. One specific example is HP-IB (or Hewlett Packard Interface Bus) which was ultimately standardized as [[IEEE-488]] (aka GPIB). Some well-known historical standards include [[VMEbus]], [[STD Bus]], [[SBus]] (specific to Sun's SPARCStations), and numerous others.

===Video game consoles===

Many other [[Video game console|video game consoles]] such as the [[Nintendo Entertainment System]] and the [[Sega Genesis]] included expansion buses in some form; In the case of at least the Genesis, the expansion bus was proprietary. In fact, the cartridge slots of many cartridge-based consoles (not counting the [[Atari 2600]]) would qualify as expansion buses, as they exposed both read and write capabilities of the system's internal bus. However, the expansion modules attached to these interfaces, though functionally the same as expansion cards, are not technically expansion cards, due to their physical form.

==Applications==
The primary purpose of an expansion card is to provide or expand on features not offered by the motherboard. For example, the original [[IBM Personal Computer|IBM PC]] did not have on-board graphics or hard drive capability.  In that case, a graphics card and an [[ST-506]] hard disk controller card provided graphics capability and hard drive interface respectively. Some [[single-board computer]]s made no provision for expansion cards, and may only have provided IC sockets on the board for limited changes or customization. Since reliable multi-pin connectors are relatively costly, some mass-market systems such as [[home computer]]s had no expansion slots and instead used a card-edge connector at the edge of the main board, putting the costly matching socket into the cost of the peripheral device.

In the case of expansion of on-board capability, a motherboard may provide a [[serial port|single serial RS232 port]] or [[Ethernet]] port. An expansion card can be installed to offer multiple RS232 ports or multiple and higher bandwidth [[Ethernet]] ports. In this case, the motherboard provides basic functionality but the expansion card offers additional or enhanced ports.

==Physical construction==
One edge of the expansion card holds the contacts (the edge connector or [[pin header]]) that fit into the slot. They establish the electrical contact between the electronics on the card and on the motherboard. Peripheral expansion cards generally have connectors for external cables. In the PC-compatible personal computer, these connectors were located in the support bracket at the back of the cabinet. Industrial backplane systems had connectors mounted on the top edge of the card, opposite to the backplane pins.

Depending on the [[Form factor (design)|form factor]] of the motherboard and [[computer case|case]], around one to seven expansion cards can be added to a computer system.  19 or more expansion cards can be installed in backplane systems. When many expansion cards are added to a system, total power consumption and heat dissipation become limiting factors. Some expansion cards take up more than one slot space. For example, many [[video card|graphics card]]s on the market as of 2010 are dual slot graphics cards, using the second slot as a place to put an active [[heat sink]] with a fan.

Some cards are "low-profile" cards, meaning that they are shorter than standard cards and will fit in a lower height computer chassis such as [[HTPC]] and [[Small form factor (desktop and motherboard)|SFF]]. (There is a "low profile PCI card" standard<ref name=":0">{{cite web|url=http://www.pcisig.com/specifications/conventional/conventional_pci/lowp_ecn.pdf |title=PCI Mechanical Working Group ECN: Low Profile PCI Card |publisher=Pcisig.com |access-date=2012-11-17}}</ref> that specifies a much smaller bracket and board area). The group of expansion cards that are used for external connectivity, such as [[network card|network]], [[Storage area network|SAN]] or [[modem]] cards, are commonly referred to as [[input/output]] cards (or I/O cards).

==Daughterboard==
[[Image:Roland SCB-55 on Diamond MX300.jpg|thumb|A sound card with a MIDI daughterboard attached]]<!-- This section name is used as for the redirects [[Daughterboard]] and [[Daughter board]] -->[[Image:Inventec daughterboard LSI 1078.jpg|thumb|A daughterboard for [[Inventec]] server platform that acts as a RAID controller based on [[LSI Corporation|LSI]] 1078 chipset]]
A '''daughterboard''', '''daughtercard''', '''mezzanine board''' or '''piggyback board''' is an expansion card that attaches to a system directly.<ref>'' IEEE Std. 100 Authoritative Dictionary of IEEE Standards Terms, Seventh Edition'',  IEEE, 2000,{{ISBN|0-7381-2601-2}},  page 284</ref>  Daughterboards often have plugs, sockets, pins or other attachments for other boards. Daughterboards often have only internal connections within a computer or other electronic devices, and usually access the motherboard directly rather than through a [[computer bus]]. Such boards are used to either improve various memory capacities of a computer, enable the computer to connect to certain kinds of networks that it previously could not connect to, or to allow for users to customize their computers for various purposes such as gaming. <ref>M.J. Memon, What Is A Daughterboard. Easy Tech Junkie. Sep. 24, 2011. https://www.easytechjunkie.com/what-is-a-daughterboard.htm. Accessed Oct. 15, 2021</ref>  

Daughterboards are sometimes used in computers in order to allow for expansion cards to fit parallel to the motherboard, usually to maintain a small [[Computer form factor|form factor]]. This form are also called [[riser card]]s, or risers. Daughterboards are also sometimes used to expand the basic functionality of an electronic device, such as when a certain model has features added to it and is released as a new or separate model. Rather than redesigning the first model completely, a daughterboard may be added to a special connector on the main board. These usually fit on top of and parallel to the board, separated by [[Spacers and standoffs|spacers or standoffs]], and are sometimes called '''mezzanine cards''' due to being stacked like the [[mezzanine]] of a [[theatre]]. [[Table-lookup synthesis|Wavetable]] cards ([[sample-based synthesis]] cards) are often [[wikt:mount|mounted]] on [[sound card]]s in this manner.

[[Image:Raspberry Pi 4B DVB TV μHat (angle).jpg|thumb|right|[[Raspberry Pi]] 4B single-board computer with "TV Hat" card (for DVB-T/T2 television reception) attached]]
Some mezzanine card interface standards include
the 400 pin [[FPGA Mezzanine Card]] (FMC);
the 172 pin High-Speed Mezzanine Card (HSMC);<ref>
Jens Kröger.
[https://www.psi.ch/mu3e/ThesesEN/BachelorKroeger.pdf "Data Transmission at High Rates via Kapton Flexprints for the Mu3e Experiment"].
2014.
p. 43 to 44.
</ref><ref>
Altera.
[https://www.altera.com/content/dam/altera-www/global/en_US/pdfs/literature/ds/hsmc_spec.pdf "High Speed Mezzanine Card (HSMC) Specification"].
p. 2-3.
</ref>
the [[PCI Mezzanine Card]] (PMC);
XMC mezzanines;
the [[Advanced Mezzanine Card]];
IndustryPacks (VITA 4), the [[GreenSpring Computers#Mezzanine modules|GreenSpring Computers Mezzanine modules]];
etc.

Examples of daughterboard-style expansion cards include:
*[[Enhanced Graphics Adapter]] piggyback board, adds memory beyond 64 KB, up to 256 KB<ref>Market Looks to EGA as De Facto Standard, ''InfoWorld'', Aug 19, 1985</ref>
*[[Expanded memory]] piggyback board, adds additional memory to some EMS and EEMS boards<ref>Product Comparison: 16-Bit EMS Memory, ''InfoWorld'', Sep 7, 1987</ref>
*ADD daughterboard
*RAID daughterboard
* [[Network interface controller]] (NIC) daughterboard
*CPU Socket daughterboard
*Bluetooth daughterboard
*Modem daughterboard
*AD/DA/DIO daughter-card
*Communication daughterboard (CDC)
*[[Server Management daughterboard]] (SMDC)
*Serial ATA connector daughterboard
*Robotic daughterboard
*Access control List daughterboard
*[[Arduino#Shields|Arduino "shield"]] daughterboards
*Beaglebone "cape" daughterboard
*Raspberry Pi "HAT add-on board"<ref>{{cite web |title=Add-on boards and HATs |url=https://github.com/raspberrypi/hats |website=GitHub |publisher=Raspberry Pi Foundation |access-date=19 June 2020}}</ref>
*Network Daughterboard (NDB). Commonly integrates: bus interfaces logic, [[Logical link control|LLC]], [[PHY]] and Magnetics onto a single board.

==Standards==
{{Main|List of computer bus interfaces|List of device bit rates#Computer buses}}

* [[PCI Extended]] (PCI-X)
* [[PCI Express]] (PCIe)
* [[Mini PCIe]]
* [[M.2]]
* [[Accelerated Graphics Port]] (AGP)
* [[Peripheral Component Interconnect]] (PCI)
* [[Industry Standard Architecture]] (ISA)
* [[Micro Channel architecture]] (MCA)
* [[VESA Local Bus]] (VLB)
* [[PC Card|CardBus/PC card/PCMCIA]] (for notebook computers)
* [[ExpressCard]] (for notebook computers)
* [[Audio/modem riser]] (AMR)
* [[Communications and networking riser]] (CNR)
* [[CompactFlash]] (for handheld computers and high speed cameras and camcorders)
* [[SBus]] (1990s [[SPARC]]-based [[Sun Microsystems|Sun]] computers)
* [[Amiga Zorro Bizarro]] (Commodore [[Amiga]])
* [[NuBus]] (Apple [[Mac (computer)|Macintosh]])
* [[FPGA Mezzanine Card]] (FMC)

==See also==

* [[Compatibility card]]
* [[Chinese language card]]
* [[Host adapter]]
* [[i-RAM]]
* [[M-Module]], an industrial mezzanine standard for modular I/O
* [[Network card]]
* [[Physics card]]
* [[POST card]]
* [[Riser card]]
* [[TV tuner card]]
* [[Video card]]
* [[CRUVI FPGA Cardecu FPGA daughtercard standard]]
* [[Board-to-board connector]] (BTB)

==References==
{{Reflist|30em}}

==External links==
*[http://pinouts.ru/pin_Slots.shtml Computer expansion slots listing and pinouts]

{{Authority control}}{{Basic computer components}}
{{DEFAULTSORT:Expansion Card}}
[[Category:Computer buses]]
[[Category:Computer peripherals]]
[[Category:Motherboard expansion slot| ]]
[[Category:Printed circuit board manufacturing]]