An expansion card is an electronic circuit board that adds more functionality to a desktop computer. These cards are installed into the expansion slot of a computer motherboard, and they allow the computer to perform additional functions not offered by the motherboard. Video cards and sound cards are common examples: a new video card added will enhance the three dimensional graphics processing power of a computer while a new sound card may improve a computer’s audio input.
A expansion sound card may improve a computer's audio input.There are alternative terms used for this type of card, and it is also known as expansion board, add-on card, interface adapter or an internal card. Generally, between one and seven expansion cards can be installed into the desktop computer system. Laptops do not use standard cards due to their small form factor, although they can often accept a removable PCMCIA card that offers additional functions.
Expansion cards such as a graphic card can add functionality when plugged into the motherboard.The Altair 8800, developed in the mid 1970s, was the first microcomputer to add an expansion card bus. In 1981, IBM® launched its first PC with an XT bus, which was later replaced with a 16-bit ISA. The introduction of the PCI bus in 1991 resulted in modern forms of interface adapters that provided additional benefits beyond enhanced graphics and sound.
Most cards are inserted in PCI or “Peripheral Component Interconnect” slots, which are integrated circuits fitted onto the motherboard. One edge of the card holding the contacts or keys is inserted into the slot. This establishes an electrical contact between the motherboard and the card’s integrated circuits.
Standard interface adapters, such as graphics cards and sound cards, offer various added functions. Some video cards offer video capture, MPEG 2 and MPEG 4 decoding, a light pen, and the ability to connect to multiple monitors, for example. Sound cards may add functions for composing music, editing audio presentations, and other multimedia applications.
There are some “low-profile” cards that fit in a lower height computer framework. Some are used solely for external connectivity such as modem cards, storage area network [SAN], and network cards, which are commonly referred to as I/O cards or input/output cards. A USB card is mainly used by users who need additional USB or Firewire ports.
A PC expansion card can only be inserted on computers with available expansion slots. Computers such as the Apple Macintosh® and other all-in-one systems do not accept these cards.
Older computers require expansion cards to be plugged in using a USB rather than into the motherboard.Expansion Card & Bus
- Expansion cards are circuit boards that provide more memory or that control peripheral devices [for graphics, sound, video, network interface, wireless connection, etc.].
- Buses connect the expansion cards to ports.
- A port is a connecting socket or jack on the outside of the computer unit or device into which are plugged different kinds of cables that connect peripheral devices.
- Expansion Cards: If a computer uses closed architecture, no expansion cards can be added; if the computer uses open architecture, expansion cards can be inserted in expansion slots inside the computer, connected to the motherboard.
- An expansion bus is not the same as the frontside bus:
- Frontside bus: The bus that connects the CPU within itself and to main memory.
- Expansion bus: Buses that connect the CPU with expansion slots on the motherboard and thus via ports with peripheral devices.
- Types of expansion buses:
- PCI: High-speed bus that has been widely used to connect PC graphics cards, sound cards, modems, and high-speed network cards.
- PCI Express: Doubles the speed of the original PCI bus . PCIe is the latest standard for expansion cards available on mainstream personal computers.
- Accelerated Graphics: Transmits data at twice the speed of a PCI bus and is designed to support video and 3-D graphics.
- Universal Serial Bus [USB]: Does away with the need to install cards in expansion slots. USB devices can connect one to another outside the system unit, and then the USB bus connects to the PCI bus on the motherboard.
- Firewire: Resembles the USB bus but is used for more specialized purposes, such as to connect audio and video equipment to the motherboard.
Port
There are many type of port that are available such as :
- Serial port : Used to transmit data slowly over long distance
- Sends data sequentially, one bit at a time
- Used to connect older keyboards, mouse, monitors, dial-up modems
- Parallel port : For transmitting data quickly over short distances
- Transmits 8 bytes simultaneously
- Connects printers, external disks, tape backups
- USB port : Universal Serial Bus high-speed hardware standard for interfacing peripheral devices, such as scanners and printers, to computers without a need for special expansion cards or other hardware modifications to the computer. USB is replacing many varieties of serial and parallel ports.
- FireWire : Intended for multiple devices working with lots of data and requiring fast transmission speeds, such as DVD drives, digital video cameras, and gaming consoles.
- Ethernet : Supports a network standard for linking a wired local area network and connecting it to a DSL or a cable modem for high-speed Internet access.
- Graphics : Connects digital monitors and multimedia digital devices, such as TVs and DVD players.
- eSATA : External Serial Advanced Technology Attachment; allows the attachment of an eSATA hard disk, which has fast data transmission speeds.
- Bluetooth : Connects devices that use short-range radio waves that transmit up to 30 feet.
- IrDA :Transfers data via infrared light waves between directly aligned devices, as between a smartphone and a desktop computer.
- HDMI : High-Definition Multimedia Interface; carries both video and audio signals and is used for connecting HDTVs, DVD players, and game consoles to computers, laptops, and other devices.
- MIDI : Musical Instrument Digital Interface; used to connect electronic musical instruments to a sound card that converts the signals to digital instructions that can be saved or manipulated.