Video card

A video card, also known as a graphics accelerator card, display adapter, or graphics card, is a hardware component whose function is to generate and output images to a display. It operates on similar principles as a sound card or other peripheral devices.

The term is usually used to refer to a separate, dedicated expansion card that is plugged into a slot on the computer's motherboard, as opposed to a graphics controller integrated into the motherboard chipset. An integrated graphics controller may be referred to as an "integrated graphics processor" (IGP).

Some video cards offer added functions, such as video capture, TV tuner adapter, MPEG-2 and MPEG-4 decoding or even FireWire, mouse, light pen, joystick connectors, or even the ability to connect multiple monitors.

A common misconception regarding video cards is that they are strictly used for Video games; a misconception that companies take advantage of in order to sell their products by advertising their products as if they were in fact video consoles. Video cards instead have a much broader range of capability. Being specialized for video output Video Cards improve what a computer monitor displays. As well, they play a very important role for Graphic Designers and 3D Animators, who tend to require optimum displays for their work as well as faster rendering in order to efficiently tone up their work.

Video cards are not used exclusively in IBM type PCs; they have been used in devices such as Commodore Amiga (connected by the slots Zorro II and Zorro III), Apple II, Apple Macintosh, Atari Mega ST/TT (attached to the MegaBus or VME interface), Spectravideo SVI-328, MSX, and in video game consoles.

Graphics processing unit (GPU)

Main article: Graphics processing unit

A GPU is a dedicated graphics microprocessor optimized for floating point calculations which are fundamental to 3D graphics rendering. The main attributes of the GPU are the core clock rate, which typically ranges from 250 MHz to 850 MHz, and the number of pipelines (vertex and fragment shaders), which translate a 3D image characterized by vertices and lines into a 2D image formed by pixels.

[edit] Video BIOS

The video BIOS or firmware contains the basic program that governs the video card's operations and provides the instructions that allow the computer and software to interface with the card. It may contain information on the memory timing, operating speeds and voltages of the graphics processor and RAM and other information. It is sometimes possible to change the BIOS (e.g., to enable factory-locked settings for higher performance) although this is typically only done by video card overclockers, and has the potential to irreversibly damage the card.

[edit] Video memory

Type	Memory clock rate (MHz)	Bandwidth (GB/s)
DDR	166 - 950	1.2 - 30.4
DDR2	533 - 1000	8.5 - 16
GDDR3	700 - 1800	5.6 - 54.4
GDDR4	1600 - 2400	64 - 156.6
GDDR5	3000 - 3800	130 - 230

If the video card is integrated in the motherboard, it may use the computer RAM (lower throughput). If it is not integrated, the video card will have its own video memory, called Video RAM. The memory capacity of most modern video cards range from 128 MB to 2.0 GB^[8]. Since video memory needs to be accessed by the GPU and the display circuitry, it often uses special high speed or multi-port memory, such as VRAM, WRAM, SGRAM, etc. Around 2003, the video memory was typically based on DDR technology. During and after that year, manufacturers moved towards DDR2, GDDR3 and GDDR4 even GDDR5 utilized most notably by the ATI Radeon HD 4870. The memory clock rate in modern cards are generally between 400 MHz and 2.4 GHz.

Video memory may be used for storing other data as well as the screen image, such as the Z-buffer, which manages the depth coordinates in 3D graphics, textures, vertex buffers, and compiled shader programs.

[edit] RAMDAC

Random Access Memory Digital-to-Analog Converter. RAMDAC takes responsibility for turning the digital signals produced by the computer processor into an analog signal which can be understood by the computer display. Depending on the number of bits used and the RAMDAC data transfer rate, the converter will be able to support different computer display refresh rates. With CRT displays, it is best to work over 75 Hz and never under 60 Hz, in order to minimise flicker.^[9] (With LCD displays, flicker is not a problem.) Due to the growing popularity of digital computer displays and the migration of some of its functions to the motherboard, the RAMDAC is slowly disappearing. All current LCD and plasma displays and TVs work in the digital domain and do not require a RAMDAC. There are few remaining legacy LCD and plasma displays which feature analog inputs (VGA, component, SCART etc.) only; these do require a RAMDAC but they reconvert the analog signal back to digital before they can display it, with the unavoidable loss of quality stemming from this digital-to-analog-to-digital conversion.^{[citation needed]}

[edit] Outputs

The most common connection systems between the video card and the computer display are:

HD-15	Analog-based standard adopted in the late 1980s designed for CRT displays, also called VGA connector. Some problems of this standard are electrical noise, image distortion and sampling error evaluating pixels.

DVI	Digital-based standard designed for displays such as flat-panel displays (LCDs, plasma screens, wide High-definition television displays) and video projectors. It avoids image distortion and electrical noise, corresponding each pixel from the computer to a display pixel, using its native resolution.

Video In Video Out (VIVO) for S-Video, Composite video and Component video	Included to allow the connection with televisions, DVD players, video recorders and video game consoles. They often come in two 9-pin Mini-DIN connector variations, and the VIVO splitter cable generally comes with either 4 connectors (S-Video in and out + composite video in and out) or 6 connectors (S-Video in and out + component P_B out + component P_R out + component Y out (also composite out) + composite in).

9-pin VIVO for S-Video (TV-out), DVI for HDTV and HD-15 for VGA outputs.

[edit] Other types of connection systems

Composite video	Analog system, with lower resolution. It uses RCA connector.

Component video	It has three cables, each with RCA connector (YC_BC_R); it is used in projectors, DVD players and some televisions.

DB13W3	An analog standard once used by Sun Microsystems, SGI and IBM.

HDMI	An advanced digital audio/video interconnect released in 2003, and is commonly used to connect game consoles and DVD players to a display. HDMI supports copy protection through HDCP.

DisplayPort	An advanced license and royalty-free digital audio/video interconnect released in 2007. DisplayPort intends to replace VGA and DVI for connecting a display to a computer.