Expansion Slots (Video Controller, Sounds Cards, SCSI, Network Card)

Expansion Slots

An expansion slot is a socket on the motherboard that is used to insert an expansion card (or circuit board), which provides additional features to a computer such as video, sound, advanced graphics, Ethernet or memory.

The expansion card has an edge connector that fits precisely into the expansion slot as well as a row of contacts that is designed to establish an electrical connection between the motherboard and the electronics on the card, which are mostly integrated circuits. Depending on the form factor of the case and motherboard, a computer system generally can have anywhere from one to seven expansion slots. With a backplane system, up to 19 expansion cards can be installed.

Expansion cards can provide various functions including:

• Sound
• Modems
• Network
• Interface adapters
• TV and radio tuning
• Video processing
• Host adapting such as redundant array of independent disks or small computer system interface
• Solid-state drive
• Power-on self-test
• Advanced multirate codec
• Basic input/output system (BIOS)
• Expansion read-only memory (ROM)
• Security devices
• RAM memory

Older expansion cards also included memory expansion cards, clock/calendar cards, hard disk cards, compatibility cards for hardware emulation, and disk controller cards. The Altair 8800 was the first slot-type expansion card bus added to a microcomputer. It was developed in 1974-1975 by IBM Corp.

The expansion slot opening is generally located on the back of a PC and provides an electrical connection to the motherboard for an expansion card. Screws are then used to attach the card to the slot for added security.

(i) Video Controller

A video controller, often referred to as a video or graphics card, is a key hardware component that allows computers to generate graphic information to any video display devices, such as a monitor or projector. They are also known as graphics or video adapters. Some modern computers do not include video cards, but rather have graphics processing units directly integrated into the computer’s motherboard.

Older Video Controllers

A video controller, once more commonly referred to as a video display controller, were used in older models of home-computers during the 1980s; they were also used in some early video game system consoles. Their main function as an integrated circuit in a video signal generator was to produce television video signals in computers or game systems. Although they could generate graphics, older video controller models did not have specialized hardware accelerators that created 2D and 3D images.

Evolution of the Video Controller

Modern video controllers are installed with hardware accelerators that create both 2D and 3D images. They also offer various functions beyond accelerated image rendering, such as TV output and the ability to hook up to several monitors. Although many computers’ motherboards are already integrated with graphics processing units, you can disable the integrated graphics chip via the computer’s BIOS to install a higher-performance video controller via the accelerated graphics port. For a modern video controller to function properly in a computer, a computer needs to have four essential units: a functioning motherboard, a processor that generates the power that a video controller needs to perform its tasks, enough memory to distribute the images created by the GPU and a screen or monitor to properly display these images.

(ii) Sounds Cards

A sound card (also known as an audio card) is an internal expansion card that provides input and output of audio signals to and from a computer under control of computer programs. The term sound card is also applied to external audio interfaces used for professional audio applications.

Sound functionality can also be integrated onto the motherboard, using components similar to those found on plug-in cards. The integrated sound system is often still referred to as a sound card. Sound processing hardware is also present on modern video cards with HDMI to output sound along with the video using that connector; previously they used a S/PDIF connection to the motherboard or sound card.

Typical uses of sound cards or sound card functionality include providing the audio component for multimedia applications such as music composition, editing video or audio, presentation, education and entertainment (games) and video projection. Sound cards are also used for computer-based communication such as voice over IP and teleconferencing.

The Small Computer System Interface (SCSI)

The Small Computer System Interface (SCSI) is a set of parallel interface standards developed by the American National Standards Institute (ANSI) for attaching printers, disk drives, scanners and other peripherals to computers. SCSI (pronounced “skuzzy”) is supported by all major operating systems.

SCSI Versions

The first version (SCSI-1), adopted by ANSI in 1986, was an 8-bit version with a 5 MBps transfer speed that allowed up to eight devices to be connected with a maximum cable length of six meters. The latest version, 16-bit Ultra-640 (Fast-320) SCSI, was introduced in 2003 and has a 640 MBps transfer speed, connecting up to 16 devices with a 12 meter cable length. Other versions include:

• SCSI-2: 8-bit bus, six meter cable length, 5-10 MBps; connects 8 or 16 devices. 50-pin connector.
• Wide SCSI-2: Received its name from the wider 168 line cable with 68-pin connectors to accommodate the 16-bit bus. 3 meter cable; 20 MBps transfer rate; connected 16 devices.
• Fast SCSI-2: 8-bit bus, but double the clock speed of SCSI-2 allowing transfers of 10-20 MBps. 3 meter cable; connects 8 devices.
• Fast Wide SCSI-2: 6-bit bus; 3 meter cable; 20 MBps; 16 devices.
• Ultra SCSI-3: 8-bit and 16-bit versions, both with 1.5 meter cable length. The 8-bit version supports data rates of 20 MBps and connects 8 devices. The 16-bit version doubled the transfer rate and number of devices.
• Ultra-2 SCSI: 8-bit bus; 12 meters; 40 MBps; 8 devices.
• Wide Ultra-2 SCSI: 16-bit bus; 12 meters; 80 MBps; 16 devices.

Traditional SCSI has been superseded by later attachment protocols such as Serial Attached SCSI (SAS) and iSCSI, which build on the earlier SCSI command structure.

Network Card

A Network interface card (also known as a NIC, network card, or network interface controller) is an electronic device that connects a computer to a computer network, usually a LAN. It is considered a piece of computer hardware. Most modern computers support an internal network interface controller embedded in the motherboard directly rather than provided as an external component.

Network cards let a computer exchange data with a network. To achieve the connection, network cards use a suitable protocol, for example CSMA/CD. Network cards usually implement the first two layers of the OSI model, that is the physical layer, and the data link layer. There are older network protocols such as ARCNET, introduced in 1977, LocalTalk or Token Ring, but today, most network cards use Ethernet.

Ethernet cards are available in several different standard packages called form factors that have evolved over the last several generations of PC hardware:

• In the 1990s and early 2000s, large Industry Standard Architecture cards were the first standard for PCs. Computer owners had to open the computer’s case to install the card.
• Newer Ethernet cards installed inside desktop computers use the Peripheral Component Interconnect standard and are usually installed by the manufacturer. These cards are still common in desktop PCs, for computers whose motherboards do not contain an onboard Ethernet port.
• Smaller Personal Computer Memory Card International Association Ethernet cards that resemble credit cards are readily available for laptop and other mobile computers. These insert conveniently into slots on the side or front of the device. The PC Card is a common PCMCIA device, although only certain PC Card and PCMCIA products support Ethernet. By the early 2010s, however, fewer laptops supported the PCMCIA standard.
• Though they look more like small boxes than cards, external USB Ethernet adapters also fill a market niche. These devices are a convenient alternative to PCI cards for desktop computers and they’re also commonly used with video game consoles and other consumer devices lacking PCMCIA slots and devices.