CGIntroAndHardware_0b

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Computer Graphics

Prof. Muhammad Saeed


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Hardware

( Graphic Cards )

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Hardware II Computer Graphics

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With a PCI-based graphics

card, every texture map has tobe stored twice. First, the

texture map is loaded from the

hard drive to the system

memory (RAM) until it has to be

used. Once it is needed, it is

pulled from memory and sent to

the CPU to be processed. Once

processed, it is sent through the

PCI bus to the graphics card,

where it is stored again in the

card's framebuffer. All of thisstoring and sending between

the system and the card is very

draining to the overall

performance of the computer.


PCI(Peripheral Component Interface)

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AGP( Accelerated Graphics Port) Card

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AGP is built on the idea ofimproving the ways that PCItransports data to the CPU. Intelachieved this by addressing allof the areas where PCI transfers

were causing data bottlenecksin the system. By clearing thetraffic jams of data, AGPincreases the speed at whichmachines can render graphics

while using the system'sresources more efficiently toreduce overall drag.


It achieves the goal by:

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1. Dedicated Port

There are no other devices connected to the AGP otherthan the graphics card. With a dedicated path to the CPU,the graphics card can always operate at the maximumcapacity of the connection.

2. PipeliningThis method of data organization allows the graphics cardto receive and respond to multiple packets of data in asingle request. Here's a simplified example of this:With AGP, the graphics card can receive a request for all ofthe information needed to render a particular image andsend it out all at once. With PCI, the graphics cardwould receive information on the height of the image andwait... then the length of the image, and wait... then thewidth of the image, and wait... combine the data, andthen send it out.


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3. Sideband addressingLike a letter, all requests and information sent from one part

of your computer to the next must have an addresscontaining "To" and "From." The problem with PCI is thatthis "To" and "From" information is sent with the workingdata all together in one packet. This is the equivalent ofincluding an address card inside the envelope when yousend a letter to a friend: Now the post office has to open the

envelope to see the address in order to know where to sendit. This takes up the post office's time. In addition, theaddress card itself takes up room in the envelope, reducingthe total amount of stuff you can send to your friend.With sideband addressing, the AGP issues eight additionallines on the data packet just for addressing. This puts the

address on the outside of the envelope, so to speak, freeingup the total bandwidth of the data path used to transferinformation back and forth. In addition, it unclogs systemresources that were previously used to open the packet toread the addresses.


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AGP: Saves RAMAGP improves the process of storing texture maps byallowing the Operating System to designate RAM foruse by the graphics card on the fly. This type of

memory is called AGP memory or non-local video

memory. Using the much more abundant and fasterRAM used by the operating system to store texture

maps reduces the number of maps that have to be

stored on the graphics card's memory. In addition, the

size of the texture map your computer is capable of

processing is no longer limited to the amount of RAM

on the graphics card.


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AGP saves RAM is by only storing texture mapsonce. It does this with a little trickery. This trickerytakes the form of a chipset called the GraphicsAddress Remapping Table (GART). GART takes theportion of the system memory that the AGPborrows to store texture maps for the graphicscard and re-addresses it. The new addressprovided by GART makes the CPU think that thetexture map is being stored in the card's frame

buffer. GART may be putting bits and pieces of themap all over the system RAM; but when the CPUneeds it, as far as it's concerned the texture map isright where it should be.

GART


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PCI (Peripheral Component Interconnect ) Express Card

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PCI Express is a serialconnection that operates more

like a network than a bus.

Instead of one bus that handles

data from multiple sources,PCI-e has a switch that controls

several point-to-point serial

connections. These connections

fan out from the switch, leading

directly to the devices wherethe data needs to go. Every

device has its own dedicated

connection


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http://computer.howstuffworks.com/pci.htmhttp://computer.howstuffworks.com/pci.htm


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Each lane of a PCI Express

connection contains two pairs ofwires -- one to send and one to

receive. Packets of data move

across the lane at a rate of one bit

per cycle. A x1 connection, thesmallest PCI-e connection, has

one lane made up of four wires. It

carries one bit per cycle in each

direction. A x2 link contains eight

wires and transmits two bits at

once, a x4 link transmits four bits,

and so on. Other configurations

are x12, x16 and x32.

PCI Express Lanes


A x16 PCI-e connector can move 6.4 GB

of data per second in each direction.

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Computer Graphics

The video BIOS or firmware contains the basicprogram, which is usually hidden, that governs

the video card's operations and provides theinstructions that allow the computer andsoftware to interact with the card. It may containinformation on the memory timing, operatingspeeds and voltages of the graphics processor,RAM, and other information.

Video BIOS

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Hardware II


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Computer Graphics

Graphics Processing Unit (GPU )

AGPU is a dedicated processor optimized for acceleratinggraphics. The processor is designed specifically toperform floating-point calculations, which are fundamental to3D graphics rendering and 2D picture drawing. The mainattributes of the GPU are the core clock frequency, which

typically ranges from 250 MHz to 4 GHz and the number ofpipelines (vertex and f ragment shaders), which translate a 3Dimage characterized by vertices and lines into a 2D imageformed by pixels.Modern GPUs are massively parallel, and fully programmable.Their computing power is orders of magnitude greater than that

of CPUs for certain kinds of operations. This has led to theemergence of general-purpose computing on graphicsprocessing units (GPGPU).Occasionally called visual processing unit orVPU.

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Hardware II


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Computer Graphics

Compute Unified Device Architecture(CUDA)

CUDAis a parallel computing architecture developed by Nvidia forgraphics processing. CUDAis the computing engine inNvidia graphics processing units (GPUs) that is accessible tosoftware developers through variants of industry standardprogramming languages.

CUDAgives developers access to the virtual instruction set andmemory of the parallel computational elements in CUDAGPUs.Using CUDA, the latest Nvidia GPUs become accessible forcomputation like CPUs. Unlike CPUs however, GPUs have a parallel

throughput architecture that emphasizes executing manyconcurrent threads slowly, rather than executing a single threadvery quickly. This approach of solving general purpose problems onGPUs is known as GPGPU.

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Hardware II


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Computer Graphics

Power demandAs the processing power of video cards has increased, sohas their demand for electrical power. Current high-performance video cards tend to consume a great deal ofpower. While CPU and power supply makers have recentlymoved toward higher efficiency, power demands of GPUs

have continued to rise, so the video card may be thebiggest electricity user in a computer. Although powersupplies are increasing their power too, the bottleneck isdue to the PCI-Express connection, which is limited to

supplying 75 Watts. Modern video cards with a powerconsumption over 75 Watts usually include a combinationof six-pin (75W) or eight-pin (150W) sockets that connectdirectly to the power supply.

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Hardware II


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Computer Graphics

High-Definition Multimedia Interface

(HDMI)

High-Definition Multimedia Interface (HDMI)An advanced digital audio/video interconnect released in

2003 and is commonly used to connect gameconsoles and DVD players to a display. HDMI supportscopy protection through HDCP(High-bandwidth DigitalContent Protection) .

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Hardware II
http://en.wikipedia.org/wiki/File:HDMI_Connector_Pinout.svg


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END

Hardware II

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