Graphics Card

Graphics Card

Not to be confused with Graphics processing unit.
Graphic Cards
A Radeon HD 4770 card
Connects to

Motherboard via one of:

Display via one of:

A video card (also called a video adapter, 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 the CPU (often called integrated graphics), but most modern desktop motherboards and many laptop motherboards also provide expansion ports to which a video card can be connected. With integrated graphics, the graphics processor shares system resources and power supply with the CPU, so performance is usually less than a dedicated card, but while also using less power. In comparison, a dedicated graphics card has its own random access memory (RAM), its own cooling system, and dedicated power regulators, with all components designed 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 a PCI, or PCI Express(PCI-E) slot for adding a higher-performance graphics card in place of the integrated graphics.

Parts

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

Graphics Processing Unit

A graphics processing unit (GPU), also occasionally called visual processing unit (VPU), is a specialized electronic circuit designed to rapidly manipulate and alter memory to accelerate the building of images in a frame buffer intended for output to a display. A video card is also a computer unto itself.

Heat Sink

A heat sink is mounted on most modern 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. Not all cards have heat sinks, for example, some cards are liquid cooled, and instead have a waterblock; additionally, older cards did not produce as much heat, and many do not have a heat sink.

Video BIOS

The video BIOS or firmware contains a minimal program for initial set up and control of the video card. It may contain information on the memory timing, operating speeds and voltages of the graphics processor, RAM, and other details which can sometimes be changed. The usual reason for doing this is to overclock the video card to allow faster video processing speeds, however, this has the potential to irreversibly damage the card with the possibility of cascaded damage to the motherboard.

The modern Video BIOS does not support all the functions of the video card, being only sufficient to identify and initialize the card to display one of a few frame buffer or text display modes. It does not support, YUV to RGB translation, video scaling, pixel copying, compositing or any of the multitude of other 2D and 3D features of the video card.

Video memory

Type Memory clock rate (MHz) Bandwidth (GB/s)
DDR 166 – 950 1.2 – 3.04
DDR2 2000 – 3600 128 – 200
GDDR5 900 – 5700 80 – 230

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 1 GHz and 6.3 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 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.

Output interfaces

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

Video Graphics Array (VGA) (DE-15)

Main article: Video Graphics Array

Also known as D-sub, VGA is an 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 in evaluating pixels. Today, the VGA analog interface is used for high definition video including 1080p and higher. While the VGA transmission bandwidth is high enough to support even higher resolution playback, there can be picture quality degradation depending on cable quality and length. How discernible this quality difference is depends on the individual's eyesight and the display; when using a DVI or HDMI connection, especially on larger sized LCD/LED monitors or TVs, quality degradation, if present, is prominently visible. Blu-ray playback at 1080p is possible via the VGA analog interface, if Image Constraint Token (ICT) is not enabled on the Blu-ray disc.

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. 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

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 PB out + component PR out + component Y out [also composite out] + composite in).

High-Definition Multimedia Interface (HDMI)

Main article: HDMI

HDMI is a compact audio/video interface for transferring uncompressed video data and compressed/uncompressed digital audio data from an HDMI-compliant device ("the source device") to a compatible digital audio device, computer monitor, video projector, or digital television.[4] HDMI is a digital replacement for existing analog video standards. HDMI supports copy protection through HDCP.

DisplayPort


Main article: DisplayPort

DisplayPort is a digital display interface developed by the Video Electronics Standards Association (VESA). The interface is primarily used to connect a video source to a display device such as a computer monitor, though it can also be used to transmit audio, USB, and other forms of data.[5] The VESA specification is royalty-free. VESA designed it to replace VGA, DVI, and LVDS. Backward compatibility to VGA and DVI by using adapter dongles enables consumers to use DisplayPort fitted video sources without replacing existing display devices. Although DisplayPort has much of the same functionality as HDMI, it is expected to complement the interface, not replace it.[6][7]

Other types of connection systems

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, video-game consoles, 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.

Motherboard interfaces

Main articles: Bus (computing) and Expansion card

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[8] 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
NUBUS 32 10 10-40 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 66 528 Parallel
AGP 4x 32 66 1000 Parallel
AGP 8x 32 66 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
PCIe x1 2.0[9] 1 500 / 1000 Serial
PCIe x4 2.0 1 x 4 2000 / 4000 Serial
PCIe x8 2.0 1 x 8 4000 / 8000 Serial
PCIe x16 2.0 1 × 16 5000 / 10000 8000 / 16000 Serial
PCIe X1 3.0 1 1000 / 2000 Serial
PCIe X4 3.0 1 x 4 4000 / 8000 Serial
PCIe X8 3.0 1 x 8 8000 / 16000 Serial
PCIe X16 3.0 1 x 16 16000 / 32000 Serial

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. 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.[10][11] Although power supplies are increasing their power too, the bottleneck is due to the PCI-Express connection, which is limited to supplying 75 Watts.[12] 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.

Size

Video cards come in 2 size profiles, to allow adding a Graphics card to even small form factor PCs. These sizes are regular and low-profile video cards.[13][14] the profiles are based on width only, with low-profile card taking up less than the full width of a PCIe slot. the length and thickness vary greatly, high-end cards are usually occupy 2 or 3 expansion slots, and vary greatly in length, with dual-gpu cards -such as the Nvidia GeForce GTX 690- generally over 10" in length.[15]

Multi-card scaling

Some graphics cards can be linked together to allow scaling of the graphics processing across multiple cards. This is done using either the PCIe bus on the motherboard, or, more commonly, with a data bridge. Generally, the cards must be of the same model to be linked, and most low power cards are not able to be linked in this way.[16] AMD and Nvidia both have proprietary methods of scaling, CrossfireX for AMD, and SLI for Nvidia. Cards from different manufacturers and/or architectures cannot be used together for multi card scaling. Currently, scaling can be done using up to four cards.[17][18][19]

Device drivers

The device driver usually supports one or multiple Application programming interfaces (APIs) like OpenGL, Direct3D, or Mantle, and the architecture of a GPU-family. A device driver has to be specifically written for an operating system.

See also

Computer science portal

References

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

External links

  • HowStuffWorks
  • http://www.gpureview.com
  • http://ausoverclock.net