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.
|Year||Text Mode||Graphics Mode||Colors||Memory|
Starting with the MDA in 1981, several video cards were released, which are summarized in the attached table.
VGA was widely accepted, which led some corporations such as ATI, Cirrus Logic and S3 to work with that video card, improving its resolution and the number of colours it used. And so was born the SVGA (Super VGA) standard, which reached 2 MB of video memory and a resolution of 1024x768 at 256 color mode.
In 1995 the first consumer 2D/3D cards were released, developed by Matrox, Creative, S3 and ATI, and others. Those video cards followed the SVGA standard, but incorporated 3D functions. In 1997, 3dfx released the Voodoo graphics chip, which was very powerful compared to other consumer graphics cards, introducing 3D effects such mip mapping, Z-buffering and anti-aliasing into the consumer market. From this point, a series of 3D video cards were released, like Voodoo2 from 3dfx, TNT and TNT2 from NVIDIA. The bandwidth required by these cards was approaching the limits of the PCI bus capacity. Intel developed the AGP (Accelerated Graphics Port) which solved the bottleneck between the microprocessor and the video card. From 1999 until 2002, NVIDIA controlled the video card market (taking over 3dfx) with the GeForce family. The improvements carried out in these years were focused in 3D algorithms and graphics processor clock rate. Nevertheless, video memory also needed to improve their data rate, and DDR technology was incorporated. The capacity of video memory goes in this period from 32 MB with GeForce to 128 MB with GeForce 4.
|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|
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.
The RAMDAC, or Random Access Memory Digital-to-Analog Converter, converts digital signals to analog signals for use by a computer display that uses analog inputs such as CRT displays. 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. (With LCD displays, flicker is not a problem.) Due to the growing popularity of digital computer displays and the integration of the RAMDAC onto the GPU die, is has mostly disappeared as a discreet component. 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 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.
|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 PB out + component PR out + component Y out (also composite out) + composite in).|
|Composite video||Analog system, with lower resolution. It uses RCA connector.|
|Component video||It has three cables, each with RCA connector (YCBCR); 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.|
Chronologically, connection systems between video card and motherboard were, mainly:
In the attached table is a comparison between a selection of the features of some of those interfaces.
|Bus||Width (bits)||Clock rate (MHz)||Bandwidth (MB/s)||Style|
|PCI||32 - 64||33 - 100||132 - 800||Parallel|
|PCIe x1||1||2500 / 5000||250 / 500||Serial|
|PCIe x4||1*4||2500 / 5000||1000 /2000||Serial|
|PCIe x8||1*8||2500 / 5000||2000 / 4000||Serial|
|PCIe x16||1*16||2500 / 5000||4000 / 8000||Serial|
Video cards may use a lot of electricity, which is converted into heat. If the heat isn't dissipated, the video card could overheat and be damaged. Cooling devices are incorporated to transfer the heat elsewhere. Three types of cooling devices are commonly used on video cards:
GPU and IGP Manufacturers
Video Card Manufacturers
Due to the difficulties working with video cards at a programming level, interfaces which abstract the complexity and diversity of the graphic card primitives appeared. Some major ones include: