Video card

A video card, also referred to as a graphics accelerator card, display adapter, graphics card, and numerous other terms, is an item of personal computer hardware 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.

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.

History
Video card history starts in the 1960s, when printers were replaced with screens as visualization element. Video cards were needed to create the first images. The first IBM PC video card, which was released with the first IBM PC, was developed by IBM in 1981. The MDA (Monochrome Display Adapter) could only work in text mode representing 25x80 lines in the screen. It had a 4KB video memory and just one color.

Starting with the MDA in 1981, several video cards were released, which are summarized in the attached table.

VGA was widely accepted, which lead 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.

The evolution of video cards took a turn for the better in 1995 with the release of the first 2D/3D cards, developed by Matrox, Creative, S3 and ATI, among others. Those video cards followed the SVGA standard, but incorporated 3D functions. In 1997, 3dfx released the graphics chip Voodoo, which was very powerful and included new 3D effects (Mip Mapping, Z-buffering, Anti-aliasing...). From this point, a series of 3D video cards were released, like Voodoo2 from 3dfx, TNT and TNT2 from NVIDIA. The power reached with these cards exceeded the PCI port 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.

In 2006, the leadership of the video cards market was contested between NVIDIA and ATI with their biggest graphics models GeForce and Radeon respectively.

Components
A video card consists of a printed circuit board on which the components are mounted. These include:

Graphics processing unit (GPU)
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 1200 MHz in modern cards, 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.

Video memory
If the video card is integrated in the motherboard, it will use the computer RAM memory (lower throughput). If it is not integrated, the video card will have its own video memory which is called Video RAM or VRAM. The memory capacity of most modern video cards range from 128 MB to 2.0 GB. 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. 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.

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.

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. (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.

Outputs
The most common connection systems between the video card and the computer display are: Other connection systems 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 LCDs, plasma screens and video projectors. It avoids image distortion and electrical noise, corresponding each pixel from the computer to a display pixel, using its native resolution.
 * S-Video: Included to allow the connection with televisions, DVD players, video recorders and video game consoles.
 * DB13W3: an analogue standard once used by Sun Microsystems, SGI and IBM.
 * 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.
 * HDMI: digital technology released in 2003, whose goal is to replace all the others.
 * Display Port: An advanced license and royalty-free digital audio/video interconnect released in 2007.

Motherboard interface
Chronologically, connection systems between video card and motherboard were, mainly:
 * S-100 bus: designed in 1974 as a part of the Altair 8800, the first industry standard bus for the microcomputer industry.
 * ISA: 16 bits architecture, 8 MHz data transfer rate. Released in 1981 by IBM, dominant in the marketplace in the 1980s.
 * NuBus: 32 bit bus, average speeds of 10 to 20 MB/s, used in Macintosh II.
 * MCA: 32 bits, 10 MHz. Released in 1987 by IBM. It wasn't compatible with previous motherboards.
 * EISA: 32 bits, 8.33 MHz. Released in 1988 to compete with IBM. Compatible with previous motherboards.
 * VESA: ISA extension. 32 bit, 33 MHz.
 * PCI: 32 bit, 33 MHz. Replaced the previous buses from 1993. PCI allowed dynamic connectivity between devices, avoiding the jumpers manual adjustments. PCI-X was a version introduced in 1998 that improved PCI to 64 bits and 133 MHz.
 * UPA: A interconnect bus architecture introduced by Sun Microsystems in 1995. 64 bits, initially 67 or 83 MHz.
 * AGP: First used in 1997. Dedicated to graphics bus, 32 bits, 66 MHz.
 * PCI-Express: Point to point interface, released in 2004. In 2006 provided double data transfer rate of AGP. Should not be confused with PCI-X, an enhanced version of the original PCI specification.

In the attached table is a comparison between a selection of the features of some of those interfaces. 

Cooling devices
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:
 * Heat sink: generally referred to as a passive cooling device, it has no moving parts and, therefore, is soundless and very reliable; it conducts heat from the GPU to some cooling medium, such as air, using thermal contact. Its effectiveness depends on its size, contact area, material (generally copper or aluminium) and other characteristics including shape. To increase effectiveness, this is typically (but not necessarily) combined with a computer fan.
 * Computer fan: an example of an active cooling device, a small electrical fan which drives air across a heat sink. It is more effective than a heat sink alone at cooling, but due to the moving parts a fan requires maintenance and possible replacement. It also generates noise.
 * Water block: a heat sink which transfers heat from the GPU to a circulating liquid, rather than the air. This liquid is carried outside the computer case and the heat dissipated to the air by a heat sink (with or without a fan). Typically part of a larger liquid cooling system for the computer as a whole, this approach has the advantages outlined in that article (to summarise, the heat sink design and positioning is not restricted by being located inside a computer case).

Power demand
As the processing power of video cards has increased, so has their demand for electrical power. Present fast video cards tend to consume a great deal of power. While CPU and power supply makers have recently moved toward higher efficiency, power demands of GPUs have continued to rise, so the video card may be the biggest electricity user in a computer. Although power supplies are increasing their power too, the bottleneck is due to the PCI-Express connection, which is limited to supplying 150 W. Nowadays, video cards with a power consumption over 150 W usually include a six-pin or eight-pin power socket that connects directly to the power supply, which allows a direct connection between the computer power supply and the card, avoiding motherboard connection and, therefore, the PCIe port.

Manufacturers
Two types of manufacturers must be distinguished:

GPU and IGP Manufacturers


 * Current GPU manufacturers:
 * AMD (acquired ATI in 2006)
 * NVIDIA
 * Matrox
 * Current IGP-only manufacturers:
 * Intel
 * VIA Technologies (acquired S3 Graphics in 2001)

Video Card Manufacturers


 * Video card manufacturers: They assemble the GPU with the other components, causing differences between video cards with the same chip.

See also:

List of defunct graphics chips and card companies

Graphics APIs
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:
 * Direct3D: Released by Microsoft in 1996, is a component of DirectX. Designed to be used exclusively in Windows, it is used by the majority of Windows videogames. The latest version of DirectX is DirectX 10, although the majority of computers still rely on graphics cards that use DirectX 9.0c.
 * OpenGL: Developed by Silicon Graphics in the early 1990s, OpenGL is a free, open, multi-language and multi-platform API. It is widely used in CAD, virtual reality, scientific visualization, information visualization, flight simulation and some games, particularly on Linux and other Unix like operating systems. The latest version is OpenGL 2.1.
 * QuickDraw: Macintosh graphics API.
 * X Window System core protocol: Basis of X Window System used extensively on Unix and Linux.

Graphics techniques
Some of the most frequently used effects for enhancing the perceived quality of the output of graphics cards include the following:
 * Anti-aliasing (AA): a technique used to counter distortion caused by aliasing effects.
 * Shader: pixel and vertex processing in terms of illumination, atmospheric optical phenomena or multi-layer surfaces.
 * High dynamic range rendering (HDR): a technique used to enable a wider range of brightness in real scenes (from light sources to dark shadows).
 * Texture mapping: allows the addition of details on surfaces, without adding complexity.
 * Motion blur: technique that blurs objects in motion.
 * Depth of field: technique that blurs out of focus objects.
 * Lens flare: imitation of light sources.
 * Fresnel effect: reflections over an object, depending on the angle of vision. The more angle of vision, the more reflection.
 * Anisotropic filtering: enhances viewing angle of a displayed texture as it increases.

Manufacturers

 * ATI website
 * Matrox website
 * NVIDIA website

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