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A video card, video adapter or a graphics accelerator card, display adapter, or graphics card, is an expansion card whose function is to generate and output images to a display. Many video cards offer added functions, such as accelerated rendering of 3D scenes, video capture, TV tuner adapter, MPEG-2 and MPEG-4 decoding, FireWire, light pen, TV output, or the ability to connect multiple monitors.
Video hardware can be integrated on the mainboard, as it often happened with early computers; in this configuration it was sometimes referred to as a video controller or graphics controller.
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[edit] History
| Year | Text Mode (columns/lines) | Graphics Mode (resolution/colors) | Memory | |
|---|---|---|---|---|
| MDA | 1981 | 80×25 | - | 4 KB |
| CGA | 1981 | 80×25 | 640×200 / 4 | 16 KB |
| HGC | 1982 | 80×25 | 720×348 / 2 | 64 KB |
| PGA | 1984 | 80×25 | 640×480 / 256 | 320 KB |
| EGA | 1984 | 80×25 | 640×350 / 16 | 256 KB |
| 8514 | 1987 | 80×25 | 1024×768 / 256 | - |
| MCGA | 1987 | 80×25 | 320×200 / 256 | - |
| VGA | 1987 | 80×25 | 640×480 / 16 | 256 KB |
| SVGA (VBE 1.x) | 1989 | 80×25 | 800×600 / 256 | 512 KB |
| 640×480+ / 256+ | 512 KB+ | |||
| XGA | 1990 | 80×25 | 1024×768 / 256 | 1 MB |
| XGA-2 | 1992 | 80×25 | 1024×768 / 65,536 | 2 MB |
| SVGA (VBE 3.0) | 1998 | 132×60 | 1280×1024 / 16.8M | - |
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 80 columns and 25 lines (80x25) in the screen. It had a 4KB video memory and just one color.[1]
Starting with the MDA in 1981, several video cards were released, which are summarized in the attached table.[2][3][4][5]
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. This developed into 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, ATI and others.[citation needed] These video cards followed the SVGA standard, but incorporated 3D functions. In 1997, 3dfx released the Voodoo graphics chip, which was more powerful compared to other consumer graphics cards, introducing 3D effects such mip mapping, Z-buffering and anti-aliasing into the consumer market. After this card, a series of 3D video cards were released, such as 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.[6] The improvements carried out at this time were focused in 3D algorithms and graphics processor clock rate. Video memory was also increased to improve their data rate; DDR technology was incorporated, improving the capacity of video memory from 32 MB with GeForce to 128 MB with GeForce 4.
From 2002 onwards, the video card market came to be dominated almost entirely by the competition between ATI and Nvidia, with their Radeon and Geforce lines respectively, taking around 90% of the independent graphics card market between them, while other manufacturers were forced into much smaller, niche markets.[7].
[edit] Components
A modern video card consists of a printed circuit board on which the components are mounted. These include:
[edit] Graphics processing unit (GPU)
A GPU is a dedicated processor optimized for accelerating graphics. The processor is designed specifically to perform floating-point calculations which are fundamental to 3D graphics rendering. The main attributes of the GPU are the core clock frequency, which typically ranges from 250 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 interact 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 |
The memory capacity of most modern video cards range from 128 MB to 4 GB, though very few cards actually go over 1 GB.[8][9] 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 effective memory clock rate in modern cards are generally between 400 MHz and 3.8 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
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 minimize flicker.[10] (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, it has mostly disappeared as a discrete 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.
[edit] Outputs
The most common connection systems between the video card and the computer display are:
| Video Graphics Array (VGA) (DE-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. |
|---|---|
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| Digital Visual Interface (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. |
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| 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). |
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| High-Definition Multimedia Interface (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. |
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| 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. |
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