Video cardFrom Wikipedia, the free encyclopediaJump to: navigation, search This article may require cleanup to meet Wikipedia's quality standards.Please improve this article if you can. (July 2008) Video Card 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 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.Contents [hide]1 History 2 Components 2.1 Graphics processing unit (GPU) 2.2 Video BIOS 2.3 Video memory 2.4 RAMDAC 2.5 Outputs 2.5.1 Other types of connection systems 2.6 Motherboard interface 2.7 Cooling devices 2.8 Power demand 3 Manufacturers 4 Graphics APIs 5 Graphics techniques 6 See also 7 References 8 External links 8.1 Manufacturers [edit] HistoryVideo card history starts in the 1960s, when printers were replaced with screens as visualization element. Video cards were needed to create the first images. 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 1 MB 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.[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. 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.[citation needed] 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 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)[6] with the GeForce family.[citation needed] 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[7] was contested between NVIDIA and ATI with their biggest graphics models GeForce and Radeon respectively.[edit] ComponentsA video card consists of a printed circuit board on which the components are mounted. These include:[edit] Graphics processing unit (GPU)Main article: Graphics processing unitA 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.[edit] Video BIOSThe 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.[edit] Video memoryType 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 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[8]. 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.[edit] RAMDACRandom 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.[9] (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.[citation needed][edit] OutputsThe 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). 9-pin VIVO for S-Video (TV-out), DVI for HDTV and HD-15 for VGA outputs.[edit] Other types of connection systemsComposite 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. [edit] Motherboard interfaceMain articles: bus (computing) and Expansion cardBus Width (bits) Clock rate (MHz) Bandwidth (MB/s) Style ISA XT
en.wikipedia.org
4th August 2008, 01:59 AM
Linear Mode
