Video card
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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.
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.
Some video cards had offered added functionalities such as video capture, TV tuner adapter, MPEG-2 and MPEG-4 decoding or even FireWire, mouse, light pen or joystick connectors.
Video cards are not used exclusively in PCs; they were used in multiple devices such as Commodore Amiga (connected by the slots Zorro II and Zorro III), Apple II, Apple Macintosh, Spectravideo SVI-328, MSX and, obviously, in video game consoles.
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[edit] History
Video cards’ 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 | - | 1 | 4 KB |
| CGA | 1981 | 80*25 | 640*200 | 16 | 16 KB |
| HGC | 1982 | 80*25 | 720*348 | 1 | 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 | 720*400 | 640*480 | 256 | 256 KB |
| SVGA | 1989 | 80*25 | 1024*768 | 256 | 2 MB |
| XGA | 1990 | 80*25 | 1024*768 | 65,536 | 1 MB |
The first video card, which was released with the first IBM PC, was developed by IBM in 1981. The MDA (Monochrome Graphics Adapter) could only work in text mode representing 25x80 lines in the screen. It had a 4KB video memory and just one colour, green[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 lead 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 2MB of video memory and 1024 x 768 dots of resolution at 256 colour mode.
The evolution of video cards took a turn for the better in 1995 with the release of the first 2D/3D cards, developed by Matrox, Creative, S3 and ATI, among others. 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 card releases happened, like Voodoo2 from 3dfx, TNT and TNT2 from NVIDIA. The power reached with these cards exceeded the PCI port 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. 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 disputed between NVIDIA and ATI with their models GeForce and Radeon respectively.
[edit] Components
A video card consists of a printed circuit board on which the components are mounted. These include:
[edit] Graphics processing unit (GPU)
A GPU is a dedicated graphics microprocessor. Its aim is to lighten the working charge of the CPU, because of that, it is optimized for floating point computing, which is very common in 3D functions. The majority of the information provided in a video card specification is referred to the GPU attributes, which shows its importance among the components of the video card. The main attributes of the GPU are the core clock rate, which in 2006 oscillated between 250 MHz and 650 MHz, and the number of pipelines (vertex and fragment shaders), whose aim is to translate a 3D image formed by vertexes and lines into a 2D image formed by pixels.
| Type | 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 - 86.4 |
[edit] Video memory
If the video card is integrated in the motherboard, it will use the computer RAM memory (lower throughput). If it is not integrated, the video card will have its own video memory which is called Video RAM or VRAM. The VRAM capacity of most modern video cards range from 128 to 768 MB. In 2006, the VRAM was based on DDR technology, standing out DDR2, GDDR3 and GDDR4. The memory clock rate is between 400 MHz and 1.6 GHz. A very important element of the video memory is the Z-buffer, which manages the depth coordinates in 3D graphics.
[edit] Video BIOS
The video BIOS or firmware chip is a chip that 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 contains information on the memory timing, operating speeds and voltages of the processor and ram and other information. It is possible to re-flash a bios although this is typically only done by video card overclockers.
[edit] RAMDAC
Random Access Memory Digital-to-Analog Converter. RAMDAC takes responsibility for turning the digital signals produced by the computer processor into an analogical 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[8]. (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.
[edit] Outputs
The most common connection systems between the video card and the computer display are:
- SVGA: Analogical standard from the 1990s, it was designed for CRT displays. Some problems of this standard are electrical noise, image distortion and sampling error evaluating pixels.
- DVI: Designed for digital displays as LCD 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.
- S-Video: Included to allow the connection with DVD players, video recorders and video game consoles.
Other connection systems are:
- Composite video: Analogic system, with very low resolution. It uses RCA connector.
- Component video: It has three cables, each with RCA connector (YCbCr); it is used in projectors.
- HDMI: digital technology released in 2003, whose goal is to replace all the others.
| 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 |
| 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 | 133 | 528 | Parallel |
| AGP 4x | 32 | 266 | 1000 | Parallel |
| AGP 8x | 32 | 533 | 2000 | Parallel |
| PCIe x1 | 1*32 | 25 / 50 | 100 / 200 | Serial |
| PCIe x4 | 1*32 | 25 / 50 | 400 / 800 | Serial |
| PCIe x8 | 1*32 | 25 / 50 | 800 / 1600 | Serial |
| PCIe x16 | 1*32 | 25 / 50 | 1600 / 3200 | Serial |
[edit] Motherboard interface
Chronologically, connection systems between video card and motherboard were, mainly:
- ISA: 16 bits architecture, 8 MHz data transfer rate. Released in 1981 by IBM, dominant in the marketplace in the 1980s.
- MCA: 32 bits, 10 MHz. Released in 1987 by IBM. It wasn’t compatible with previous motherboards.
- EISA: 32 bits, 8.33 MHz. Released in 1988 to compete with IBM. Compatible with previous motherboards.
- VESA: ISA extension. 32 bit, 33 MHz.
- PCI: 32 bit, 33 MHz. Replaced the previous buses from 1993. PCI allowed dynamic connectivity between devices, avoiding the jumpers manual adjustments. PCI-X was a version that improved PCI to 64 bits and 133 MHz.
- AGP: Dedicated to graphics bus, 32 bits, 66 MHz.
- PCIe: Point to point interface, released in 2004. In 2006 doubled AGP data transfer rate. Should not be confused with PCI-X, an enhanced version of the original PCI specification.
In the attached table[9] it is shown a comparative with the more important features of some of those interfaces.
[edit] Cooling devices
Due to video card work charge, high temperatures are reached, which can cause a breakdown. Cooling devices are incorporated to avoid excessive heat. There are two types of cooling devices, and both can be used at the same time:
- Heat sink: passive device (without mobile parts and, therefore, soundless); it absorbs and dissipates heat from the GPU using thermal contact (in either direct or radiant contact). Its effectiveness depends on its size.
- Computer fan: active device (with mobile parts); it removes the hot air from the video card. It is less effective than a heat sink, and causes noise.
[edit] Power supply
Until 2006, video card power consumption hasn’t been a big problem; nevertheless, present video card tendency is to consume even more power. Although power supplies are increasing their power too, the bottleneck is due to PCIe connection, which is limited to 150W power draw[10]. Nowadays, video cards with a power consumption over 150W usually include a PCIe power connector[11], which allows a direct connection between the power supply and the card, avoiding motherboard connection and, therefore, the PCIe port. Even so, it is supposed that video cards will soon need their own power supply, and both together will become a new external device[12].
[edit] Manufacturers
| GPUs manufacturers | ||
|---|---|---|
| ATI | NVIDIA | |
| Video cards
Manufacturers |
GECUBE | POINT OF VIEW |
| RADEON | GALAXY | |
| SAPPHIRE | XFX | |
| ASUS | BFG | |
| GIGABYTE | eVGA | |
Two types of manufacturers must be distinguished:
- GPU manufacturers:
- Video card manufacturers: They assemble the GPU with the other components, causing differences between video cards with the same chip.
In the attached table the relation between chips' manufacturers and some of their video card manufacturers is shown.
[edit] Graphics APIs
Due to the difficulties working with video cards at a programming level, interfaces which abstract the complexity and diversity of the graphic card primitives appeared. The most important are:
- Direct3D: Released by Microsoft in 1996, is a component of DirectX. Designed to be used exclusively in Windows, it is used by the majority of Windows videogames.
- OpenGL: Developed by Silicon Graphics in the early 1990s, OpenGL is a free, open, multi-language and multi-platform API. It is widely used in CAD, virtual reality, scientific visualization, information visualization and flight simulation.
[edit] Graphics techniques
Some of the video card most used graphic techniques are:
- Anti-aliasing: technique that prevents aliasing problems.
- Shader: pixel and vertex processing in terms of illumination, atmospheric optical phenomena or multi-layer surfaces.
- HDR: this novel technique makes possible the representation of a wide brightness range in real scenes (from light sources to dark shadows).
- Texture mapping: allows the addition of details on surfaces, without adding complexity.
- Motion blur: technique that blurs objects in motion.
- Depth blur: technique that blurs faraway objects.
- Lens flare: imitation of light sources.
- Fresnel effect: reflections over an object, depending on the angle of vision. The more angle of vision, the more reflection.
[edit] See also
- 3D computer graphics – Video cards raison d’être.
- OpenGL – Cross-platform API.
- Direct3D – Microsoft’s DirectX API component.
- GeForce – Examples of GPUs
- Z-Buffer – Where depth coordinates are managed.
- List of manufacturers
- Graphics hardware and FOSS
[edit] References
- ^ MDA in IBM PC.
- ^ History Table Reference (1).
- ^ History Table Reference (2).
- ^ History Table Reference (3).
- ^ History Table Reference (4).
- ^ NVIDIA takes over 3dfx.
- ^ NVIDIA vs ATI.
- ^ Refresh rate recommended.
- ^ Buses features.
- ^ Power supply solution.
- ^ PCIe power connector.
- ^ Future external video cards with its own power supply.
- Mueller, Scott (2005) Upgrading and Repairing PCs. 16th edition. Que Publishing. ISBN 0-7897-3173-8
[edit] External links
