Graphics card

A graphics card or video chart (in the past by abuse language a chart VGA ), or graphic Adapter ; is a Expander card of Ordinateur whose role is to produce a displayable image on a Moniteur of computer. The graphics card converts the numerical Donnée S interns to the computer into a Electrical signal numerical or analogical compatible with the monitor.

Components

The graphics processor

The Graphics processor ( Graphical Processing Links or GPU in English) is used to release the Micro-processeur of the Mother chart while taking charges calculations specific to posting with them, in particular calculations specific to posting in 3D.

This division of the tasks between the two processors releases the principal processor of the computer and increases some by as much the power.

The graphics processor is very often provided with its own radiator or ventilator to evacuate the heat which it produces.

Note: The graphics cards enormously made way since Voodoo of 3DFX in 1998, first accelerating chart. Although certain initiatives to take again the advantage are being studied at the founders of processor (like Larrabee of Intel), the graphics card is not any more one simple help for the processor and quickly was essential like one of the elements most important of the PC in the players.

Video memory

The video memory preserves the numerical data which must be converted into images by the graphics processor and the images treated by the graphics processor before their posting.

All the graphics cards support two access methods to their memory. One is used to receive information coming from the remainder of the system, the other is requested for the screen display. The first method is a conventional Direct access ( RAM ) as for the main memories, the second method is generally a Sequential access to the storage area containing information to be posted with the screen.

See the principal article: video Memory.

The RAMDAC

The RAMDAC ( Random Access Memory DIGITAL-to-Analog Converter ) converts the images stored in the video memory into analogical signals to send to the screen of the computer. It became useless with exits DVI (digital).

The video BIOS

The video BIOS is with the graphics card what BIOS is with the Mother chart. It is small a Programme recorded in a Read-only memory (ROMANIAN) which contains certain information on the graphics card (for example, graphic modes supported by the chart) and which is used for starting of the graphics card.

Connection between the graphics card and the mother chart

Connection to the Mother chart is done using a port connected to a drunk.

During years, several technologies followed one another to satisfy the unceasingly increasing needs speed of transfer of the graphics cards:

the first technology used was technology ISA, used as from 1984 to associate charts having of more than video memory than the charts standards provided by the manufacturers of computers or the charts using of the instruction sets intended to accelerate the posting of the windows under Windows;
certain machines (of mark IBM for the majority) used the bus VLB (Vesa Local Bus), but this type of bus was quickly abandoned because of its too great specificity.
with the arrival of the first processors Pentium in 1994, one uses then the interface NCV;
the bus AGP (Accelerated Graphics Port) appeared in May 1997;
bus AGP is currently supplanted by the bus NCV-Express train, appeared in 2004.
the NCV express train 2.0 which allows a doubling of the bidirectional flow of data (250Mo/s for NCV-express train 1.1, against 500Mo/s for the 2.0) should replace in the long term NCV-express train 1.1 in 2007.

Connector industry

One can find following connections according to the graphics cards:

the interface standard VGA: the graphics cards are most of the time equipped with a Connecteur VGA 15 pins (Sub-D Minis, composed of 3 series of 5 pins), generally of blue color, in particular allowing the connection of a screen CRT. This type of interface makes it possible to send to the screen 3 analogical signals corresponding to the red, blue and green components of the image.

the interface DVI (DIGITAL Video Interfaces), present on certain graphics cards, makes it possible to send, with the screens supporting it, of the numerical data. This makes it possible to avoid conversions digital-analog, then analogical numerical, useless.

the interface S-Video: More and more with charts are equipped with a S-Video catch allowing to post on a television, this is why it is often called taken tele (noted “TV-out”).

an interface HDMI allowing to connect the chart to a screen high-definition by also transmitting the audio part (general-purpose, this format is the substitute of the péritel).

Note: DVI and HDMI can support DRM.

The current models generally associate two types of interface: an interface for television (S-Video or HDMI) with an interface for screen of computer (VGA or DVI).

Determination of the quantity of video memory

The quantity of video memory necessary to store the image which will be posted depends on the posted definition.

This indication is now of little interest with the recent graphics cards, which have a video memory of a size quite higher than that necessary for simple posting 2D. Indeed for a scene 3D it is necessary for example to store textures which will be posted, and those take a very large place (until several tens of Me).

History and comparison of the graphics cards for PC compatibles

See too

List of the manufacturers of graphics cards

Video Graphics Array (VGA)
Adapter graphic nouveau riche (EGA)
Color Graphics To adapt (CGA)
Monochromic Display To adapt (MDA)
Operation of charts VGA

Simple: Graphics card

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