Video card

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.

History

Year Text Mode Graphics Mode Colors Memory
MDA 1981 80*25 - 2 4 KB
CGA 1981 80*25 640*200 16 16 KB
HGC 1982 80*25 720*348 2 64 KB
EGA 1984 80*25 640*350 16 256 KB
IBM 8514 1987 80*25 1024*768 256 -
MCGA 1987 80*25 320*200 256 -
VGA 1987 80*25 640*480 256 256 KB
SVGA 1989 80*25 800*600 256 512 KB
XGA 1990 80*25 1024*768 65,536 2 MB
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 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.

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 modern 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 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.

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.

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. 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.

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 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.

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 PB out + component PR out + component Y out (also composite out) + composite in).

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 (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.

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, it was the first industry standard bus for the microcomputer industry.
  • ISA: Introduced in 1981 by IBM, it became dominant in the marketplace in the 1980s. It was a 16-bit bus clocked at 8 MHz.
  • NuBus: Used in Macintosh II, it was a 32 bit bus with an average bandwidth of 10 to 20 MB/s.
  • MCA: Introduced in 1987 by IBM it was a 32-bit bus clocked at 10 MHz.
  • EISA: Released in 1988 to compete with IBM's MCA it was compatible with the earlier ISA bus. It was a 32-bit bus clocked at 8.33 MHz.
  • VESA: An extension of ISA, it was a 32-bit bus clocked at 33 MHz.
  • PCI: Replaced the EISA, ISA, MCA and VESA buses from 1993 onwards, PCI allowed dynamic connectivity between devices, avoiding the jumpers manual adjustments. It is a 32-bit bus clocked 33 MHz.
  • UPA: An interconnect bus architecture introduced by Sun Microsystems in 1995. It is a 64-bit bus clocked at 67 or 83 MHz.
  • USB: Mostly used for other types of devices, but there are USB displays.
  • AGP: First used in 1997, it is a dedicated to graphics bus. It is a 32-bit bus clocked at 66 MHz.
  • PCI-X: An extension of the PCI bus, it was introduced in 1998. It improves upon PCI by extending the width of bus to 64-bit and the clock frequency to up to 133 MHz.
  • PCI-Express: Point to point interface, released in 2004. In 2006 provided double the data transfer rate of AGP. It 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.

Bus Width (bits) Clock rate (MHz) Bandwidth (MB/s) Style
ISA XT 8 4,77 8 Parallel
ISA AT 16 8,33 16 Parallel
MCA 32 10 20 Parallel
EISA 32 8,33 32 Parallel
VESA 32 40 160 Parallel
PCI 32 - 64 33 - 100 132 - 800 Parallel
AGP 1x 32 66 264 Parallel
AGP 2x 32 133 528 Parallel
AGP 4x 32 266 1000 Parallel
AGP 8x 32 533 2000 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

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: a heat sink is a passive cooling device. It conducts heat away from the graphics card's core, or memory, by using a heat conductive metal, most commonly aluminum or copper, sometimes in combination with heat pipes. It uses air (most common) or in extreme cooling situations, water (see water block), to remove the heat from the card. When air is used, a fan is often used to increase cooling effectiveness.
  • Computer fan: an example of an active cooling part. It is usually used with a heatsink. Due to the moving parts, a fan requires maintenance and possible replacement. Enthusiasts may change the fan speed or fan for more efficient or quieter cooling.
  • Water block: A water block is a heat sink suited to use water instead of air. It is mounted on the graphics processor and has a hollow inside. Water is pumped through the water block, transferring the heat into the water, which is then usually cooled in a radiator. This is the most effective cooling solution without extreme modification.

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 75 W. Nowadays, video cards with a power consumption over 75 watts usually include a combination of six pin (75W) or eight pin (150W) sockets that connect directly to the power supply to supplement power.

Manufacturers

Two types of manufacturers must be distinguished:

GPU and IGP Manufacturers

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 video games. 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 3.0.
  • QuickDraw: Macintosh graphics API.
  • X Window System core protocol: Basis of X Window System used extensively on Unix and Linux.
  • Glide: A proprietary 3D graphics API developed by 3dfx and implemented on their Voodoo graphics cards.

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.

See also

References

  • Mueller, Scott (2005) Upgrading and Repairing PCs. 16th edition. Que Publishing. ISBN 0-7897-3173-8

External links

Manufacturers

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