graphics accelerators

8/7/2019 Graphics Accelerators

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Intro

The functional purpose of a GPU, is to provideseparate dedicated graphics resources, includinga graphics processor and memory, to relieve

some of the burden off of the main systemresources, which would otherwise get saturatedwith graphical operations and I/O requests.

The abstract goal of a GPU, however, is to enable

a representation of a 3D world as realistically aspossible. So these GPUs are designed to provideadditional computational power that iscustomized specifically to perform these 3D tasks.


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What Is A GPU?

A Graphics Processing Unit(GPU) is a

microprocessor that has been designed specifically

for the processing of 3D graphics.

The processor is built with integrated transform,

lighting, triangle setup/clipping, and rendering

engines, capable of handling millions of math-

intensive processes per second. GPUs form the heart of modern graphics cards,

relieving the CPU (central processing units) of much

of the graphics processing load.


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What Is A GPU?

GPUs allow products such as desktop PCs, portablecomputers, and game consoles to process real-time 3Dgraphics that only a few years ago were only available onhigh-end workstations.

Used primarily for 3-D applications, a graphics processing unitis a single-chip processor that creates lighting effects andtransforms objects every time a 3D scene is redrawn. Theseare mathematically-intensive tasks, which otherwise, would

put quite a strain on the CPU. Lifting this burden from theCPU frees up cycles that can be used for other jobs.

However, the GPU is not just for playing 3D-intensevideogames or for those who create graphics but is a crucialcomponent that is critical to the PC's overall system speed.


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History The first graphics cards, introduced in August of 1981

by IBM, were monochrome cards designated asMonochrome Display Adapters (MDAs). The displaysthat used these cards were typically text-only, withgreen or white text on a black background.

Color for IBM-compatible computers appeared on thescene with the 4-color Hercules Graphics Card (HGC),followed by the 8-color Color Graphics Adapter (CGA)and 16-color Enhanced Graphics Adapter (EGA).

During the same time, other computer manufacturers,such as Commodore, were introducing computers withbuilt-in graphics adapters that could handle a varyingnumber of colors.

When IBM introduced the Video Graphics Array (VGA)

in 1987, a new graphics standard came into being.


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History A VGA display could support up to 256 colors (out of a

possible 262,144-color palette) at resolutions up to720x400.

Perhaps the most interesting difference between VGAand the preceding formats is that VGA was analog,

whereas displays had been digital up to that point. Going from digital to analog may seem like a step

backward, but it actually provided the ability to varythe signal for more possible combinations than thestrict on/off nature of digital.

Over the years, VGA gave way to Super Video GraphicsArray (SVGA). SVGA cards were based on VGA, but eachcard manufacturer added resolutions and increasedcolor depth in different ways.


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Standards

The Video Electronics Standards Association (VESA) agreed on astandard implementation of SVGA that provided up to 16.8 millioncolors and 1280x1024 resolution.

Most graphics cards available today support Ultra Extended

Graphics Array (UXGA). UXGA can support a palette of up to 16.8million colors and resolutions up to 1600x1200 pixels.

Even though any card you can buy today will offer higher colorsand resolution than the basic VGA specification, VGA mode is thede facto standard for graphics and is the minimum on all cards.

In addition to including VGA, a graphics card must be able toconnect to your computer.

While there are still a number of graphics cards that plug into anIndustry Standard Architecture (ISA) or Peripheral ComponentInterconnect (PCI) slot, most current graphics cards use the

Accelerated Graphics Port (AGP).


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Components Of A Graphics Card

Graphics Processor

The graphics processor is the brains of the card, and is

typically one of two configurations:

Graphics co-processor: A card with this type ofprocessor can handle all of the graphics chores without

any assistance from the computer's CPU. Graphics co-

processors are typically found on high-end video cards.

Graphics accelerator: In this configuration, the chip on

the graphics card renders graphics based on commands

from the computer's CPU. This is the most common

configuration used today.


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Components Of A Graphics Card Frame buffer: This chip simply

controls the memory on thecard and sends information tothe digital-to-analog converter(DAC) . It does no processing

of the image data and is rarelyused anymore.

Memory The type of RAMused on graphics cards varieswidely, but the most popular

types use a dual-portedconfiguration. Dual-portedcards can write to one sectionof memory while it is readingfrom another section,decreasing the time it takes to

refresh an image.


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Graphics BIOS Graphicscards have a small ROMchip containing basicinformation that tells the

other components of thecard how to function inrelation to each other. TheBIOS also performs

diagnostic tests on thecard's memory and input/output (I/O) to ensure thateverything is functioning

correctly.


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Digital-to-Analog Converter (DAC)The DAC on a graphics card iscommonly known as a RAMDAC

because it takes the data it convertsdirectly from the card's memory.RAMDAC speed greatly affects theimage you see on the monitor. This is

because the refresh rate of the imagedepends on how quickly the analoginformation gets to the monitor.


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Connector Graphics cards use standard connectors.Most cards use the 15-pin connector that was introducedwith Video Graphics Array (VGA).

This port enables the video card to directly access systemmemory. Direct memory access helps to make the peakbandwidth four times higher than the PeripheralComponent Interconnect (PCI) bus adapter card slots.

This allows the central processor to do other tasks whilethe graphics chip on the video card accesses systemmemory.


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ISA Connector.

PCI Connector.

PCI-E Connector.

AGP Connector


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Display Connector

The most common connection systems between the video card and the computer

display are:

Video Graphics Array (VGA) (DE-15)

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 evaluating pixels.

DigitalVisual Interface (DVI)

Digital-based standard designed for displays such as flat-panel displays (LCDs,

plasma screens, wide high-definition television displays) and video projectors. Itavoids image distortion and electrical noise, corresponding each pixel from the

computer to a display pixel, using its native resolution.


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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 9-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).

HighDefinition Multimedia Interface (HDMI)

An advanced digital audio/video interconnect released in 2003 and is commonly

used to connect game consoles and DVD players to a display. HDMI supports copy

protection through HDCP.


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HDMI PortDIVX Ports

VGA PortS-Video Port


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Need For 3D Acceleration


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graphics accelerators

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