How does Graphics Card work?

PIXEL IN MONITOR

The images you see on your monitor are made of tiny dots called pixels. At most common resolution settings, a screen displays over a million pixels, and the computer has to decide what to do with every one in order to create an image. To do this, it needs a translator -- something to take binary data from the CPU and turn it into a picture you can see. Unless a computer has graphics capability built into the motherboard, that translation takes place on the graphics card.

A graphics card's job is complex, but its principles and components are easy to understand. In this article, we will look at the basic parts of a video card and what they do. We'll also examine the factors that work together to make a fast, efficient graphics card.

Think of a computer as a company with its own art department. When people in the company want a piece of artwork, they send a request to the art department. The art department decides how to create the image and then puts it on paper. The end result is that someone's idea becomes an actual, viewable picture.

A graphics card works along the same principles. The CPU, working in conjunction with software applications, sends information about the image to the graphics card. The graphics card decides how to use the pixels on the screen to create the image. It then sends that information to the monitor through a cable. ­

Creating an image out of binary data is a demanding process. To make a 3-D image, the graphics card first creates a wire frame out of straight lines. Then, it rasterizes the image (fills in the remaining pixels). It also adds lighting, texture and color. For fast-paced games, the computer has to go through this process about sixty times per second. Without a graphics card to perform the necessary calculations, the workload would be too much for the computer to handle.

The graphics card accomplishes this task using four main components:

A motherboard connection for data and power

A processor to decide what to do with each pixel on the screen

Memory to hold information about each pixel and to temporarily store completed pictures

A monitor connection so you can see the final result

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GRAPHICS CARD

Introduction

A graphics card, also known as a video card, is a piece of hardware installed in a computer that is responsible for rendering the image on the computer’s monitor or display screen. Graphics cards come in many varieties with varying features that allow for a price range that extends from about $20 US Dollars (USD) to $2,400 USD or more.

The first consideration when buying a graphics card is to be sure it is capable of displaying the best resolution the monitor can support. For Liquid Crystal Display (LCD) monitors this means supporting the native resolution. Cathode Ray Tube (CRT) monitors do not have a native resolution. In this case, ensure the card is capable of supporting the highest resolution, even if the CRT monitor will be frequently used at lower resolutions.

The second consideration is on-board memory. A graphics card must work very hard to render images to the screen. Unlike text files, graphics images are much larger files consisting of great amounts of data that must be processed by the graphics or video card. A faster card has its own resident memory chips to perform this function so as not to impinge upon the system’s Random Access Memory (RAM). Less robust cards have less resident memory and require sharing system RAM to process images.

This doesn’t necessarily mean that a graphics card with shared memory will be unsatisfactory, but much depends on the primary purpose of the computer and on the amount of system RAM present. More system RAM is better if it will be shared, but for gaming and multimedia enthusiasts, a card with resident memory is a better choice. This is also true for those wishing to watch, work with or edit movies.

The graphics processing unit (GPU) is a chip akin to the computer processing unit (CPU). The GPU on the graphics card processes data in parallel lines called “pipelines.” The more pipelines a card has, the faster it can process data. Some cards feature dual GPUs for additional performance. Other factors that play into performance include bus speed and the type of on-board memory the card supports.

Because graphics cards work hard they generate heat. For this reason most high-performance video cards utilize built-in fans. Fans can be quiet or noisy, depending on the card model. High-performance fanless video cards are also available. These cards use heat sinks to pull heat away from the GPU. The advantage of a fanless card is lack of noise; disadvantages include expense and a wider footprint that can take up two slots inside the computer.

Installing a graphics card is very easy. The card features an interface that plugs into a port or slot inside the computer on the motherboard. Older motherboards offer an Advanced Graphics Port (AGP) interface, while newer boards have the faster Peripheral Computer Interface Express (PCIe) interface. A PCIe card cannot be installed into an AGP slot, and visa-versa, so be sure to get a card that is compatible with your system.

External ports on the card can allow an additional monitor to be plugged in for gaming or for advanced graphics displays that can be spread across two monitors. A graphics card might also have an “S-Video Out” port for sending the signal to a television, or a High Definition Multimedia Interface (HDMI) port. Advanced ports that extend functionality add to the cost of the card.

While prices vary widely, the average gaming enthusiast is likely to be happy with a card in the $150 - $300 USD range. For someone who uses a computer for more general purposes, a graphics card closer to $65 USD will likely do the job. Watch for rebates and sales to get a good deal, and read customer reviews for information about issues like fan noise and performance.

Graphics card companies

Well known graphics card companies are

1. nVidia

2. ATI

.

BRIEF DESCRIPTION

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 (as with more recent designs) the CPU, but all modern motherboards (and some from the 1980s) provide expansion ports to which a video card can be connected.[citation needed] 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 manufactured by the developer of the northbridge (e.g. an AMD chipset with Radeon graphics or an Intel chipset with Intel graphics) 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 usually low in performance and undesirable for those wishing to run 3D applications. A dedicated graphics card on the other hand has its own Random Access Memory or RAM and Processor specifically for processing video images, and thus offloads this work from the CPU and system RAM. Almost all of these motherboards allow (PCI-E) the disabling of the integrated graphics chip in BIOS, and have an AGP, PCI, or PCI Express(PCI-E) slot for adding a higher-performance graphics card in place of the integrated graphics.

Graphic Cards

A Radeon HD 4770 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 Radeon 7970 with the cooler removed, showing the major components of the card.

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 specializedelectronic 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.

A graphics card heat sink with two fans from Arctic

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

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 asVRAM, 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.

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

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 asCathode 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.^{[citation needed]}) 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.^{[citation needed]}

Output interfaces

Video In Video Out (VIVO) for S-Video (TV-out), Digital Visual Interface (DVI) for High-definition television (HDTV), and DB-15 for Video Graphics Array (VGA)

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

Video Graphics Array (VGA) (DE-15)

Video Graphics Array (VGA) (DE-15).

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 Visual Interface (DVI-I).

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 P_B out + component P_R out + component Y out [also composite out] + composite in).

High-Definition Multimedia Interface (HDMI)

High-Definition Multimedia Interface (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.

Display Port

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.

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 withjumpers. 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.

ATI Graphics Solution Rev 3 from 1985/1986, supporting Hercules graphics. As can be seen from the PCB the layout was done in 1985, whereas the marking on the central chipCW16800-A says "8639" meaning that chip was manufactured week 39, 1986. This card is using the ISA 8-bit (XT) interface.

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.