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Video Card

A GeForce 6600 Series card by PNY
Connects to	Motherboard via one of: ISA MCA VLB PCI AGP PCI-X PCI Express Others Display via one of: VGA connector Digital Visual Interface Composite video S-Video Component video HDMI DMS-59 DisplayPort Others

A video card (also called a display card, graphics card, graphics board, display adapter or graphics adapter) is an expansion card which generates a feed of output images to a display. Most video cards offer various functions such as accelerated rendering of 3D scenes and 2D graphics, MPEG-2/MPEG-4 decoding, TV output, or the ability to connect multiple monitors (multi-monitor).

Video hardware can be integrated into the motherboard or (as with more recent designs) the CPU, but all modern motherboards (and some from the 1990s) provide expansion ports to which a video card can be attached. In this configuration it is sometimes referred to as a video controller or graphics controller. Modern low-end to mid-range motherboards often include a graphics chipset manufactured by the developer of the northbridge (e.g. an nForce chipset with Nvidia graphics or an Intel chipset with Intel graphics) on the motherboard. This graphics chip usually has a small quantity of embedded memory and takes some of the system's main RAM, reducing the total RAM available. This is usually called integrated graphics or on-board graphics, and is usually low in performance and undesirable for those wishing to run 3D applications. A dedicated graphics card on the other hand has its own Random Access Memory or RAM and Processor specifically for processing video images, and thus offloads this work from the CPU and system RAM. Almost all of these motherboards allow the disabling of the integrated graphics chip in BIOS, and have an AGP, PCI, or PCI Express slot for adding a higher-performance graphics card in place of the integrated graphics.

Components[link]

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

Graphics Processing Unit[link]

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 and 2D picture drawing. The main attributes of the GPU are the core clock frequency, which typically ranges from 250 MHz to 4 GHz 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.

Modern GPUs are massively parallel, and fully programmable. Their computing power is orders of magnitude greater than that of CPUs for certain kinds of operations. This has led to the emergence of general-purpose computing on graphics processing units.

Heat Sink[link]

A Heat Sink Is mounted on high performance graphics cards. A heat sink spreads out the heat produced by the graphics processing unit evenly throughout the heat sink and unit itself. The heat sink commonly has a fan mounted as well to cool the heat sink and the graphics processing unit.

Video BIOS[link]

The video BIOS or firmware contains the basic program, which is usually hidden, 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, 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[link]

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The memory capacity of most modern video cards ranges from 128 MB to 8 GB.^[1][2] 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, GDDR4 and GDDR5. The effective memory clock rate in modern cards is 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.

RAMDAC[link]

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 Cathode ray tube (CRT) displays. The RAMDAC is a kind of RAM chip that regulates the functioning of the graphics card. 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.^[3] (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 LCDs, plasma displays and TVs work in the digital domain and do not require a RAMDAC. There are few remaining legacy LCD and plasma displays that 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[link]

Video In Video Out (VIVO) for S-Video (TV-out), Digital Visual Interface (DVI) for High-definition television (HDTV), and DB-15 for Video Graphics Array (VGA)

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

Video Graphics Array (VGA) (DE-15)[link]

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.

Digital Visual Interface (DVI)[link]

Digital Visual Interface (DVI-I).

Digital-based standard designed for displays such as flat-panel displays (LCDs, plasma screens, wide high-definition television displays) and video projectors. In some rare cases high end CRT monitors also use DVI. It avoids image distortion and electrical noise, corresponding each pixel from the computer to a display pixel, using its native resolution. It is worth to note that most manufacturers include DVI-I connector, allowing(via simple adapter) standard RGB signal output to an old CRT or LCD monitor with VGA input.

Video In Video Out (VIVO) for S-Video, Composite video and Component video[link]

9-pin mini-DIN connector, frequently used for VIVO connections.

Included to allow the connection with televisions, DVD players, video recorders and video game consoles. They often come in two 10-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).

High-Definition Multimedia Interface (HDMI)[link]

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.

DisplayPort[link]

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.

Other types of connection systems[link]

Composite video	Analog system with lower resolution; it uses the RCA connector.
Component video	It has three cables, each with RCA connector (YCBCR for digital component, or YPBPR for analog component); it is used in projectors, DVD players and some televisions.
DB13W3	An analog standard once used by Sun Microsystems, SGI and IBM.
DMS-59	A connector that provides two DVI or VGA outputs on a single connector. This is a DMS-59 port.

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Motherboard interface[link]

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 an 8 or 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.
• VLB: 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 manual adjustments required with jumpers. It is a 32-bit bus clocked 33 MHz.
• UPA: An interconnect bus architecture introduced by Sun Microsystems in 1995. It had a 64-bit bus clocked at 67 or 83 MHz.
• USB: Although mostly used for miscellaneous devices, such as secondary storage devices and toys, USB displays and display adapters exist.
• 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: Abbreviated PCIe, it is a 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^[4] is a comparison between a selection of the features of some of those interfaces.

Power demand[link]

As the processing power of video cards has increased, so has their demand for electrical power. Current high-performance 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.^[5][6] Although power supplies are increasing their power too, the bottleneck is due to the PCI-Express connection, which is limited to supplying 75 Watts.^[7] Modern 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.

See also[link]

Computer science portal

• ATI, NVIDIA - duopoly of 3D chip GPU and graphics card designers
• ATI Crossfire - ATI's proprietary mechanism for scaling graphics performance
• Computer display standards - detailed list of standards like SVGA, WXGA, WUXGA, etc.
• Feature connector
• GeForce, Radeon – Examples of GPUs.
• GPGPU (i.e.: CUDA, AMD FireStream)
• Graphics hardware and FOSS
• Framebuffer - The computer memory used to store a screen image
• Mini-DIN connector
• List of video card manufacturers
• Scalable Link Interface - NVIDIA's proprietary mechanism for scaling graphics performance
• Texture mapping - A means of adding image details to a 3D scene
• Video In Video Out (VIVO)
• Z-buffering – A means of determining visibility.

References[link]

Grafikkort

External links[link]

Wikimedia Commons has media related to: Graphics card

• Graphics Card Comparisons, Performance, and Specifications
• How Graphics Cards Work at HowStuffWorks
• http://www.gpureview.com