Display Cards

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Contents Introduction

History

Components

How a Graphic Card works Connection

PCI, AGP & PCI Express

Choosing a good Graphics Card


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introductionntroduction


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A video card, video adapter, graphics-acceleratorcard, display adapter or graphics card is an expansioncard whose function is to generate and output images to a display

Many video cards offer added functions, such as accelerated

rendering of 3D scenes and 2D graphics, video capture, TV-tuneradapter, light pen, TV output

Other modern high performance video cards are used for moregraphically demanding purposes, such as PC games


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historyistory


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The first IBM PC video card, which was released with the first IBM PC,was developed by IBM in 1981. The MDA (Monochrome DisplayAdapter) could only work in text mode representing 80 columnsand 25 lines (80x25) in the screen. It had a 4KB video memory

and just one color Starting with the MDA in 1981, several video cards were released

VGA was widely accepted, which led some corporations suchas ATI, Cirrus Logic and S3 to work with that video card, improvingits resolution and the number of colors it used

This developed into the SVGA (Super VGA) standard, which reached

2 MB of video memory and a resolution of 1024x768 at 256 colormode


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In 1995 the first consumer 2D/3D cards were released, developedby Matrox, Creative, S3, ATI and others. These video cardsfollowed the SVGA standard, but incorporated 3D functions.

In 1997, 3dfx released the Voodoo graphics chip, which was morepowerful compared to other consumer graphics cards, introducing3D effects such as Z-buffering and anti-aliasing into the consumermarket.

After this card, a series of 3D video cards were released, suchas Voodoo2 from 3dfx, TNT and TNT2 from NVIDIA. Thebandwidth required by these cards was approaching the limits ofthe PCI bus capacity. Intel developed the AGP (AcceleratedGraphics Port) which solved the bottleneck between themicroprocessor and the video card.

From 1999 until 2002, NVIDIA controlled the video card market(taking over 3dfx) with the GeForce family. The improvementscarried out at this time were focused in 3D algorithms andgraphics processor clock rate. Video memory was also increasedto improve their data rate; DDRtechnology was incorporated,improving the capacity of video memory from 32 MB with GeForce

to 128 MB withGeForce 4


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Since 2002, ATI and Nvidia have dominated the video card marketwith their Radeon and Geforce lines respectively, sharing around

90% of the independent graphics card market


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componentsomponents


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A modern video card consists of a printed circuit board on

which the components are mounted. These include:

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. The main attributes of the GPU are the core clock frequency(no of

clock cycles per second), which typically ranges from 250 MHz to4 GHz and the number of pipelines which translate a 3D imagecharacterized by vertices and lines into a 2D image formedby pixels.

Video BIOS The video BIOS or firmware contains the basic program, which

is usually hidden, that governs the video card's operations andprovides the instructions that allow the computer and software tointeract with the card. It may contain information on the memorytiming, operating speeds and voltages of the graphics processor,RAM, and other information


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Video memory

The memory capacity of most modern video cards ranges from 128MB to 4 GB, though very few cards actually go over 1 GB. Sincevideo 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 basedon DDR technology. During and after that year, manufacturersmoved towards DDR2, GDDR3, GDDR4, and even GDDR5 utilizedmost notably by the ATI Radeon HD 4870. The effective memory

clock rate in modern cards is generally between 400 MHz and3.8 GHz

Video memory may be used for storing other data as well as thescreen image, such as the Z-buffer, which manages the depthcoordinates in 3D graphics,textures, vertex buffers, and compiledshader programs


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RAMDAC

The RAMDAC, or Random Access Memory Digital-to-AnalogConverter, converts digital signals to analog signals for use by acomputer display that uses analog inputs such as CRT displays

The RAMDAC is a kind of RAM chip that regulates the functioning ofthe graphic card. Depending on the number of bits used and theRAMDAC-data-transfer rate, the converter will be able to supportdifferent computer-display refresh rates. With CRT displays, it isbest to work over 75 Hz and never under 60 Hz, in order tominimize flicker

Due to the growing popularity of digital computer displays and theintegration of the RAMDAC onto the GPU, it has mostlydisappeared as a discrete component. All current LCDs, plasmadisplays and TVs work in the digital domain and do not require aRAMDAC


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Outputs

- - ( -p in V IV O fo r S V id e o T V) , -u t D V I fo r H D T V a n d D E1 5 fo r V G A o u tp u ts


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the computer display are:

Video Graphics Array(VGA) (DE-15)

Analog-based standardadopted in the late

1980s designedfor CRT displays, alsocalled VGA connector

Some problems of thisstandard are electricalnoise, image

distortion and samplingerror evaluating pixels


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Digital Visual Interface(DVI)

Digital-based standarddesigned for displays

such as flat-panel displays(LCDs, plasma screens,wide high-definitiontelevision displays) andvideo projectors

It avoids image distortion

and electrical noise,corresponding each pixelfrom the computer to adisplay pixel, usingits native resolution


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Video In Video Out

(VIVO) for S-Video,Composite video andComponent video

Included to allow theconnectionwith televisions, DVDplayers, videorecorders and video gameconsoles

They often come in two 9-pin Mini-DIN

connector variations, andthe VIVO splitter cablegenerally comes witheither 4 connectors (S-Video in and out +composite video in andout), or 6 connectors


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High-DefinitionMultimediaInterface (HDMI)

An advanced digitalaudio/video

interconnectreleased in 2003and is commonlyused toconnect gameconsoles and DVDplayers to a display


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Display Port

An advancedlicense- androyalty-free digitalaudio/videointerconnectreleased in 2007

Display Port intendsto replace VGAand DVI forconnecting a

display to acomputer


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ow a graphicsow a graphicsard worksard works


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The images you see onyour monitor are madeof tiny dots called

pixels At most common

resolution settings, ascreen displays over amillion pixels, and thecomputer has to

decide what to do withevery one in order tocreate an image

To do this, it needs atranslator -- somethingto take binary

data from the CPU andturn it into a pictureyou can see. Unless acomputer has graphicscapability built into themotherboard, thattranslation takes place

on the graphics card


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The CPU, working in conjunction with software applications, sendsinformation about the image to the graphics card. The graphicscard decides how to use the pixels on the screen to create theimage. It then sends that information to the monitor through acable.

Creating an image out of binary data is a demanding process. Tomake a 3-D image, the graphics card first creates a wire frame outof straight lines. Then, it rasterizes the image (fills in the

remaining pixels). It also adds 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 performthe necessary calculations, the workload would be too much forthe 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 temporarilystore completed pictures

A monitor connection so you can see the final result


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As the GPU creates images, it needs somewhere to hold informationand completed pictures. It uses the card's RAM for this purpose,storing data about each pixel, its color and its location on thescreen

Part of the RAM can also act as a frame buffer, meaning that itholds completed images until it is time to display them

Typically, video RAM operates at very high speeds and isdualported, meaning that the system can read from it and write to itat the same time

The RAM connects directly to thedigital-to-analog converter,called the DAC. This converter, also called the RAMDAC, translatesthe image into an analog signal that the monitor can use. Some

cards have multiple RAMDACs, which can improve performanceand support more than one monitor.

The RAMDAC sends the final picture to the monitor through a cable


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connectiononnection


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Graphics cards connect to the computer through the motherboard.

The motherboard supplies power to the card and lets itcommunicate with the CPU

Newer graphics cards often require more power than themotherboard can provide, so they also have a direct connection tothe computer's power supply

Connections to the motherboard are usually through one of threeinterfaces:

Peripheral component interconnect (PCI)

Advanced graphics port(AGP)

PCI Express (PCIe)

PCI Express is the newest of the three and provides the fastesttransfer rates between the graphics card and the motherboard.PCIe also supports the use of two graphics cards in the samecomputer


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Most graphics cards have two monitor connections. Often, one is aDVI connector, which supports LCD screens, and the other is aVGA connector, which supports CRT screens

Some graphics cards have two DVI connectors instead. But thatdoesn't rule out using a CRT screen; CRT screens can connect toDVI ports through an adapter

Most people use only one of their two monitor connections. Peoplewho need to use two monitors can purchase a graphics cardwith dual head capability, which splits the display between thetwo screens

In addition to connections for the motherboard and monitor, somegraphics cards have connections for:

TV display: TV-out or S-video

Analog video cameras: ViVo or video in/video out

Digital cameras

Some cards also incorporate TV tuners


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, &ci AGP pci&ci AGP pciExpressxpress


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The Accelerated Graphics Port (AGP) is a high-speed point-to-point channel for attaching a video card toa computer's motherboard, primarily to assist in the accelerationof 3D computer graphics

Since 2004, AGP has been progressively phased out in favor of PCIExpress


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Advantages of AGP over PCI

As computers became increasingly graphically oriented, successivegenerations of graphics adapters began to push the limits of PCI,a bus with shared bandwidth. This led to the development of AGP, a "bus"dedicated to graphics adapters

The primary advantage of AGP over PCI is that it provides a dedicatedpathway between the slot and the processor rather than sharing the PCI

bus In addition to a lack of contention for the bus, the point-to-point

connection allows for higher clock speeds

AGP also uses sideband addressing, meaning that the address and databuses are separated so the entire packet does not need to be read to getaddressing information. This is done by adding eight extra 8-bit buses which allow the graphics controller to issue new AGP requestsand commands at the same time with other AGP data flowing via the main32 address/data (AD) lines. This results in improved overall AGP datathroughput

In addition, to load a texture, a PCI graphics card must copy it from thesystem's RAM into the card's framebuffer, whereas an AGP card is capableof reading textures directly from system RAM using the Graphics AddressRemapping Table (GART). GART reapportions main memory as neededfor texture storage, allowing the graphics card to access them directly


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The maximum amount of system memory available to AGP isdefined as the AGP aperture

The two main reasons graphics cards with the PCI interfaceare still produced are that

first, they can be used in nearly any PC; because while somemotherboards with built-in graphics adapters lack an AGP slot,few, if any, modern desktop PCs lack PCI slots

Secondly, a user with an appropriate operating system can useseveral PCI graphics cards (or several PCI graphics cards incombination with one AGP card) simultaneously to give many

different video outputs (for the use of many screens)


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PCI Express PCI Express (Peripheral Component Interconnect Express),

officially abbreviated as PCIe (or PCI-E), is a computer expansioncard standard designed to replace the older PCIand AGP standards

PCIe 2.1 is the latest standard for expansion cards that is availableon mainstream personal computers.

PCI Express is used in consumer, server, and industrial applications,as a motherboard-level interconnect (to link motherboard-mounted peripherals) and as an expansion card interface for add-in boards

A key difference between PCIe and earlier buses is a topology basedon point-to-point serial links, rather than a shared parallel busarchitecture


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Conceptually, the PCIe bus can be thought of as a high-speed serial replacement of the older (parallel) PCI

At the software level, PCIe preserves compatibility with PCI; a PCIedevice can be configured and used in legacy applications and

operating systems which have no direct knowledge of PCIe'snewer features (however you cannot insert a PCIe card into a PCIslot)

In terms of bus protocol, PCIe communication is encapsulated inpackets. The work of packetizing and depacketizing data andstatus-message traffic is handled by the transaction layer of the

PCIe port


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A good overall measurement of a card's performance is its framerate, measured in frames per second (FPS). The frame ratedescribes how many complete images the card can display persecond

The human eye can process about 25 frames every second,but fast-action games require a frame rate of at least 60 FPS toprovide smooth animation and scrolling

The graphics card's hardware directly affects its speed. These arethe hardware specifications that most affect the card's speed andthe units in which they are measured:

GPU clock speed (MHz) Size of the memory bus (bits)

Amount of available memory (MB)

Memory clock rate (MHz)

Memory bandwidth (GB/s)

RAMDAC speed (MHz)

The computer's CPU and motherboard also play a part, since a veryfast graphics card can't compensate for a motherboard's inabilityto deliver data quickly. Similarly, the card's connection to themotherboard and the speed at which it can get instructions fromthe CPU affect its performance


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