Expansion card
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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
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
The first commercial microcomputer to feature expansion slots was the Micral N, in 1973. The first company to establish a 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 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 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
Intel launched their
For their 1000 EX and 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 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 interrupts and DMA provided by Intel add-on chips, and a few system 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
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
Other families
Most other computer lines, including those from Apple Inc. such as the (Apple II and Macintosh), Tandy, Commodore, Amiga, and Atari, offered their own expansion buses. The Amiga used 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 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.[5] 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 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
In the case of expansion of on-board capability, a motherboard may provide a 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
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
cards (or I/O cards).Daughterboard
A daughterboard, daughtercard, mezzanine board or piggyback board is an expansion card that attaches to a system directly.
Daughterboards are sometimes used in computers in order to allow for expansion cards to fit parallel to the motherboard, usually to maintain a small
in this manner.Some mezzanine card interface standards include the 400 pin FPGA Mezzanine Card (FMC); the 172 pin High Speed Mezzanine Card (HSMC);[9][10] the PCI Mezzanine Card (PMC); XMC mezzanines; the Advanced Mezzanine Card; IndustryPacks (VITA 4), the 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[11]
- Expanded memory piggyback board, adds additional memory to some EMS and EEMS boards[12]
- 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 "shield" daughterboards
- Beaglebone "cape" daughterboard
- Raspberry Pi "HAT add-on board"[13]
- Network Daughterboard (NDB). Commonly integrates: bus interfaces logic, PHYand Magnetics onto a single board.
Standards
- 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)
- 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 computers)
- Zorro (Commodore Amiga)
- NuBus (Apple Macintosh)
- FPGA Mezzanine Card (FMC)
See also
- Compatibility 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
References
- ^ "Eurotherm Parker SSD Link Hardware L5341 | Automation Industrial". l5341.com. Retrieved 2024-01-02.
- ^ "MB-54VP". ArtOfHacking.com. Archived from the original on 16 May 2013.
- ^ "NX586". ArtOfHacking.com. Archived from the original on 16 May 2013.
- ^ "LEOPARD 486SLC2 REV. B". ArtOfHacking.com. Archived from the original on 2014-10-17. Retrieved 2012-11-17.
- ^ "Motherboards". Artofhacking.com. Archived from the original on 16 May 2013.
- ^ "PCI Mechanical Working Group ECN: Low Profile PCI Card" (PDF). Pcisig.com. Retrieved 2012-11-17.
- ISBN 0-7381-2601-2, page 284
- ^ 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
- ^ Jens Kröger. "Data Transmission at High Rates via Kapton Flexprints for the Mu3e Experiment". 2014. p. 43 to 44.
- ^ Altera. "High Speed Mezzanine Card (HSMC) Specification". p. 2-3.
- ^ Market Looks to EGA as De Facto Standard, InfoWorld, Aug 19, 1985
- ^ Product Comparison: 16-Bit EMS Memory, InfoWorld, Sep 7, 1987
- ^ "Add-on boards and HATs". GitHub. Raspberry Pi Foundation. Retrieved 19 June 2020.