From ECDL.web

A video card, video adapter, graphics accelerator card, display adapter, or graphics card is an expansion card whose function is to generate output images to a display. Video hardware can be integrated on the motherboard. 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 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 low-performance and undesirable for those wishing to run 3D applications. 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. Despite the performance limitations, around 95% of new computers are sold with integrated graphics processors, leaving it for the individual user to decide whether to install a dedicated graphics card.

Many video cards offer added functions, such as accelerated rendering of 3D scenes and 2D graphics, video capture, TV-tuner adapter, MPEG-2/MPEG-4 decoding, FireWire, light pen, TV output, or the ability to connect multiple monitors. Modern high performance video cards are used for more graphically demanding purposes, such as PC games. A dedicated graphics card has its own RAM and processor (Graphics Processing Unit, GPU) specifically for processing video images, and thus offloads this work from the CPU and system RAM. Modern GPUs are massively parallel, and fully programmable. Their computing power is notably higher than that of CPUs.

[edit] Components

• 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 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 are formed by pixels.
• Video BIOS: 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, although this has the potential to irreversibly damage the card.
• Video memory: the memory capacity of most modern video cards ranges from 128 MB to 4 GB. Since video memory needs to be accessed by the GPU and the display circuitry, it often uses special high-speed memory. 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.
• RAMDAC: he 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. 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.
• 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. Three types of cooling devices are commonly used on video cards: heat sinks (passive-cooling device, it conducts heat away from the graphics card's core, or memory, by using a heat-conductive metal), fans (usually used with a heat sink) and water blocks (heat sinks suited to use water instead of air).

[edit] Outputs

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

• Video Graphics Array (VGA): Analog-based standard adopted in the late 1980s designed for CRT displays, also called VGA connector.
• 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. 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.
• S-Video, Composite video and Component video: Included to allow the connection with televisions, DVD players, video recorders and video game consoles.
• High-Definition Multimedia Interface (HDMI): an advanced digital audio/video interconnect standard, released in 2003 and is commonly used to connect game consoles and DVD players to a display. HDMI supports copy protection through HDCP.

[edit] 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 an 8 or 16-bit bus clocked at 8 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 jumpers manual adjustments. It is a 32-bit bus clocked 33 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: Abbreviated PCIe, 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.

[edit] Power demand

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. 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 computer's power supply.