introduction to how graphics cards work

8/4/2019 Introduction to How Graphics Cards Work

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Introduction to How Graphics Cards Work

Computer Hardware Image Gallery

Graphics cards take data from the CPU and turn it into pictures. See more computer hardwarepictures.

The images you see on yourmonitorare 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 takebinary 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 touse the pixels on the screen to create the image. It then sends that information to the monitorthrough a

cable.

Creating an image out ofbinary 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.
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The graphics card accomplishes this task using four main components:

Amotherboardconnection for data and power

Aprocessorto decide what to do with each pixel on the screen

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

Amonitorconnection so you can see the final result

Next, we'll look at the processor and memory in more detail.

The GPU

2008 HowStuffWorks

Graphics cards take data from the CPU and turn it into pictures. Find out the parts of a graphics

card and read expert reviews of graphics cards.Like amotherboard, a graphics card is a printed circuit board that houses aprocessorand RAM. It also

has an input/output system (BIOS) chip, which stores the card's settings and performs diagnostics on

the memory, input and output at startup. A graphics card's processor, called a graphics processing

unit (GPU), is similar to a computer's CPU. A GPU, however, is designed specifically for performing the

complex mathematical and geometric calculations that are necessary for graphics rendering. Some of the

fastest GPUs have more transistors than the average CPU. A GPU produces a lot of heat, so it is usually

located under a heat sink or a fan.

In addition to its processing power, a GPU uses special programming to help it analyze and use

data. ATI and nVidia produce the vast majority of GPUs on the market, and both companies have

developed their own enhancements for GPU performance. To improve image quality, the processors use:

Full scene anti aliasing (FSAA), which smoothes the edges of 3-D objectsAnisotropic filtering (AF), which makes images look crisper

Each company has also developed specific techniques to help the GPU apply colors, shading, textures

and patterns.

The Evolution of Graphics CardsGraphics cards have come a long way since IBMintroduced the first one in 1981. Called
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aMonochrome Display Adapter(MDA), the cardprovided text-only displays of green or white texton a black screen. Now, the minimum standardfor new video cards isVideo GraphicsArray (VGA), which allows 256 colors. With high-performance standards like Quantum Extended

Graphics Array(QXGA), video cards can displaymillions of colors at resolutions of up to 2040 x1536 pixels.

As the GPU creates images, it needs somewhere to hold information and completed pictures. It uses the

card's RAMfor this purpose, storing data about each pixel, its color and its location on the screen. Part of

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

them. Typically, video RAM operates at very high speeds and is dual ported, meaning that the system

can read from it and write to it at the same time.

The RAM connects directly to the digital-to-analog converter, called the DAC. This converter, also

called the RAMDAC, translates the image into an analog signal that the monitor can use. Some cards

have multiple RAMDACs, which can improve performance and support more than one monitor. You can

learn more about this process in How Analog and Digital Recording Works.

The RAMDAC sends the final picture to the monitor through a cable. We'll look at this connection and

other interfaces in the next section.

PCI Connection

Photo courtesy ofHowStuffWorks ShopperThis Radeon X800XL graphics card has DVI, VGA and ViVo connections.

Graphics cards connect to the computer through the motherboard. Themotherboardsupplies power to the

card and lets it communicate with the CPU. Newer graphics cards often require more power than the

motherboard can provide, so they also have a direct connection to the computer's power supply.

Connections to the motherboard are usually through one of three interfaces:

Peripheral component interconnect (PCI)

Advanced graphics port(AGP)
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PCI Express (PCIe)PCI Express is the newest of the three and provides the fastest transfer rates between the graphics cardand the motherboard. PCIe also supports the use of two graphics cards in the same computer.

DirectX and Open GLDirectX and Open GL are applicationprogramming interfaces, or APIs. An API helpshardware and software communicate moreefficiently by providing instructions for complextasks, like 3-D rendering. Developers optimizegraphics-intensive games for specific APIs. Thisis why the newest games often require updatedversions of DirectX or Open GL to work correctly.

APIs are different from drivers, which are

programs that allow hardware to communicate

with a computer's operating system. But as with

updated APIs, updated device drivers can help

programs run correctly.

Most graphics cards have two monitor connections. Often, one is a DVI connector, whichsupports LCDscreens, and the other is a VGA connector, which supportsCRT screens. Some graphics

cards have two DVI connectors instead. But that doesn't rule out using a CRT screen; CRT screens can

connect to DVI ports through an adapter. At one time, Apple made monitors that used the proprietary

Apple Display Connector (ADC). Although these monitors are still in use, new Apple monitors use a DVI

connection.

Most people use only one of their two monitor connections. People who need to use two monitors can

purchase a graphics card with dual head capability, which splits the display between the two screens. A

computer with two dual head, PCIe-enabled video cards could theoretically support four monitors.In addition to connections for the motherboard and monitor, some graphics cards have connections for:

TV display: TV-out or S-video

Analog video cameras: ViVo or video in/video outDigital cameras:FireWireorUSB

Some cards also incorporate TV tuners. Next, we'll look at how to choose a good graphics card.

Choosing a Good Graphics Card

Integrated GraphicsMany motherboards have integrated graphicscapabilities and function without a separategraphics card. These motherboards handle 2-Dimages easily, so they are ideal for productivityand Internet applications. Plugging a separategraphics card into one of these motherboards

overrides the onboard graphics functions.A top-of-the-line graphics card is easy to spot. It has lots ofmemory and a fastprocessor. Often, it's also

more visually appealing than anything else that's intended to go inside a computer's case. Lots of high-

performance video cards are illustrated or have decorative fans or heat sinks.

But a high-end card provides more power than most people really need. People who use their computers

primarily fore-mail, word processing or Web surfing can find all the necessary graphics support on

amotherboard with integrated graphics. A mid-range card is sufficient for most casual gamers. People
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who need the power of a high-end card include gaming enthusiasts and people who do lots of 3-D graphic

work.

Photo courtesy ofHowStuffWorks Shopper

Some cards, like the ATI All-in-Wonder, include connectionsfor televisions and video as well as a TV tuner.

A good overall measurement of a card's performance is its frame rate, measured in frames per second

(FPS). The frame rate describes how many complete images the card can display per second. The

human eye can process about 25 frames every second, but fast-action games require a frame rate of at

least 60 FPS to provide smooth animation and scrolling. Components of the frame rate are:

Triangles or vertices per second:3-D images are made of triangles, or polygons. This

measurement describes how quickly the GPU can calculate the whole polygon or the verticesthat define it. In general, it describes how quickly the card builds a wire frame image.

Pixel fill rate: This measurement describes how many pixels the GPU can process in a

second, which translates to how quickly it can rasterize the image.

OverclockingSome people choose to improve their graphicscard's performance by manually setting theirclock speed to a higher rate, knownasoverclockings. People usually overclocktheirmemory, since overclocking the GPU canlead to overheating. While overclocking can leadto better performance, it also voids the

manufacturer's warranty.

The graphics card's hardware directly affects its speed. These are the hardware specifications that most

affect the card's speed and the 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)
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Memory bandwidth (GB/s)

RAMDAC speed (MHz)

The computer'sCPUand motherboardalso play a part, since a very fast graphics card can't compensate

for a motherboard's inability to deliver data quickly. Similarly, the card's connection to the motherboard

and the speed at which it can get instructions from the CPU affect its performance.

Video hardware can be integrated on themotherboard, often occurring with early machines. In this

configuration it is sometimes referred to as a video controllerorgraphics controller. Modern low-end to

mid-range motherboards often include a graphics chipset developed by the developer of

the northbridge(i.e. an nForce chipset withnVidiagraphics or anIntelchipset 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 oron-board graphics, and is low-performance and undesirable for those wishing to run 3D

applications. A dedicated Graphics Card on the other hand has its own 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 the disabling of the integrated graphics chip inBIOS, and have an AGP,PCI,

orPCI Expressslot for adding a higher-performance graphics card in place of the integrated graphics.Despite the performance limitations, around 95% of new computers are sold with integrated graphics

processors, leaving it for the individual user to decide whether to install a dedicated Graphics card.

Past and presentHISTORY

The first video card was the Monochrome Display Adapter (MDA). Introduced in1981 by IBM. It had 4 kilobytes of video memory.Presentcan support 4 monitorsMuch faster and a lot of spaceGeforce GTX 275 has 1.7Gb (1792Mb) of video memory.

Why do we use it! (Function)Takes in data from CPU and creates a pictureMade by millions of pixels on screenNeed to turn binary data in to a pictureDecides how to place pixels on the screenVideo Card Components TerminologyMotherboard Connections: ring in data from the hard drive and electricity fromthe power supply.Memory Chips : Hold the data during processing.Graphics Processor Chips : Turn digital data into pixel information.Monitor Connections: Send pixels to the monitor.What's a GPU?

Graphics processing Unitdesigned for performing mathematical and geometric calculations (graphic cardrendering)graphics cards CPU. It Processes the dataOn-board video cardsmall quantity of embedded memoryUses system's main RAM, reducing the total RAM available.low-performance and undesirable for those wishing to run 3D applicationsSeparate video card
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own RAM and Processor specifically for processing video imagesFaster processing and betterhave an AGP, PCI, or PCI Express slot for adding themVideo Card ConnectionPCIPCI

The oldest of the three typesUses a shared bus to allow communication among different devices on the bus.It has a bandwidth of up to 133 Mbps to 512 Mbps

AGP(still old)Designed for use with 3d Graphicsused a point to point channel for direct access to the main memoryIt has a bandwidth of 266 Mbps to 1.07 Gbps.

To use this video card your motherboard needs to have a slot to support itPCI-Edoubles the data transfer rates of a standard PCI cardtwo way serial connection, avoiding the slowdown of sharing a bus.Aid from other devices to get greater output.

How The Video Card Makes A Picturedata is transferred from the CPU to the chipset(processes the data)data transferred to the Video Memory(stores video image)

transferred to the digital analog converter - converts the image from digital data toanalog datatransferred to the monitor through cable it is usingHow is it connectedVideo Graphics Adapter : VGA connects to analog monitors.Digital Visual Interface : DVI connects to digital display devices, LCD monitorsand digital projectors.S-Video : used to connect a PC video card to a television, only capable of 480i or576i resolution.

High Definition Multimedia Interface : HDMI connects a computer to your HDTVset.Who Makes GPUsChoose according to the needdesktop applications, an integrated chip or a low-end graphics card.multimedia applications, a graphics card that can play the desired video format3D video games, a more powerful graphics cardFPS (frames per second)fast-action games require a frame rate of at least 60 FPS to provide smoothtransitionTriangles or vertices per second: 3-D images are made of triangles, or polygons.it describes how quickly the card builds a wire frame image.Pixel fill rate: This measurement describes how many pixels the GPU can processin a secondhow quickly it can rasterize the image.Price differs becauseGPU clock speed (MHz)Size of the memory bus (bits)Amount of available memory (MB)Memory clock rate (MHz)
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Memory bandwidth (GB/s)RAMDAC speed (MHz)Additional tipsSize:A lot of RAM is useless if the GPU is not powerful:

Type: various types of memory are sometimes offered for the same GPU: G-DDR2,

G-DDR3 memory and sometimes the G-DDR5. For example for the GT 240, somehave the 1700MHz DDR5 (recommended), but others have the 900Mhz G-DDR3.

introduction to how graphics cards work

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