Video Adapter

Before you start

Objectives: learn what is video card and what should we consider when we buy new card.

Prerequisites: no prerequisites.

Key terms: card, connector, memory, display, rate, tv, digital, directx, screen, color, dvi, hdmi, monitor, refresh, slot, analog, graphic, pci


Compatibility:

Video card must be compatible with our system’s expansion bus, which can be either AGP, PCI, PCI-X, or PCI-E. Current video cards typically use AGP and PCI express slots. Video cards in PCIe slots usually require 16x slots. AGP video cards use either 4x or 8x slots. Older cards used PCI and VESA slots. Some motherboards include a built-in video card integrated on the Northbridge chip. This video card is actually part of one of the buses on the system (PCIe, AGP, or PCI). Most video cards will have a combination of one or more of the following physical ports which we use to connect to monitor or other display device: VGA, DVI-A, DVI-D or DVI-I, HDMI or S-Video. A VGA monitor connects using a DB-15 connector. Video cards often list this connector as a D-sub connector. A DVI connector connects to an LCD monitor. Most DVI connectors are DVI-Integrated (DVI-I) connectors that send either analog or digital signals based on the type of cable that is connected. Older cards might have a DVI-A (analog) or DVI-D (digital) interface. We can use special conversion plugs if necessary to convert from VGA to DVI, or vice verca. However, we must have a special conversion box to convert from analog to digital signals. Many videos cards include an HDMI connector for connecting to an HD TV or monitor with an HDMI port. By purchasing a video card with dual heads (two output connectors capable of displaying video simultaneously), we can use dual monitors (as long as the operating system supports dual monitors). Many newer video cards include one VGA connector and one DVI connector. Certain capabilities of our video card have to be matched with our display device. These are resolution, color depth (number of colors that can be produced and displayed), and refresh rate (number of times per second that our screen is redrawn). A higher refresh rate, above 70 hertz is recommended. If we plan to watch HDCP or High bandwidth Digital Content Protected media on our computer, we have to have a card and a display which support HDCP. HDCP is a method for copy-protecting digital media. It prevents the interception and copying of data streams as they are sent from a playback device to a display device.

Graphics Processing Unit and Memory

Video cards contain a GPU, or Graphics Processing Unit, which provides video hardware acceleration. GPU takes over video rendering from the CPU, thereby increasing video performance. That’s why we refer to it as video hardware acceleration. Typically, settings in the operating system control how much video processing is offloaded to the video card. Video cards also have a clock speed. Higher speeds typically mean better performance. Some cards employ multiple GPUs or can be linked to other identical video cards via SLI or CrossFire technology, depending on the manufacturer. In that case, multiple GPUs draw a single screen. Scalable Link Interface (SLI) from nForce and CrossFire from ATI are two different methods for linking video cards. Cards are linked using a special bridge clip or through software (depending on the implementation). The motherboard and the video cards must each support the selected method (either SLI or CrossFire). The motherboard must have multiple 16x PCIe slots. In most cases we will need to install identical video cards, or at least video cards with very similar specifications. This is typically used by PC gamers. Video cards have built-in memory. The amount of memory on the card effects performance as well as other characteristics of the display. Newer video cards can use 2GB of video memory or even more. Onboard video cards (integrated on the motherboard) use a portion of the system memory for video processing. Video memory can be VRAM, DDR memory or special GDDR2 to GDDR5 graphic memory. DDR, DDR2, and DDR3 memory is similar to system memory. This type of memory is cheaper and provides less performance features than using special graphics memory. GDDR2, GDDR3, and GDDR5 is DDR memory designed specifically for graphics. Portable computers often share system memory with their integrated video controller.

Display Quality

The quality of images and animations are determined by resolution, color depth and refresh rate. The resolution is the number of pixels displayed on screen. A higher resolution means that more information can be shown on the screen at a time. Resolution on modern computers range from 1024 (horizontal) x 756 (vertical) to 2048 x 1536 or higher. The color depth is the number of different colors that can be displayed on the screen at a time. It is expressed in bits. More bits means more colors that can be displayed). Common bit depths are: 8-bit (256 possible colors), 16-bit, also called high color (65,536 possible colors), 24-bit, also called true color (16.7 million possible colors), and 32-bit, also called true color (16.7 million possible colors and alpha channel). The refresh rate is the number of times that the entire screen is redrawn per second. It is measured in hertz. A desirable range of refresh rate is 75 Hz to 85 Hz. Rate lower then 70 Hz or may cause eye fatigue. The refresh rate depends on the rate supported by the card as well as the monitor.

Additional Capabilities

Some video cards can have an onboard TV tuner and a TV or cable input port on the back of the card. TV tuners can process NTSC, PAL, and SECAM which are analog TV signal standards. NTSC was used in North America but is being phased out. ATSC signals are digital TV signals. We can display the computer screen on a TV using the S-video port for analog TVs, HDMI port for digital TVS, or DVI if TV supports it. We can also use an HDMI converter to convert a DVI connector to an HDMI connector. Video input allows a video card to accept a video signal from an external source and display it on the monitor.  Some video cards have video record and capture capability. Using this kind of card we can record the video signal that is coming into the computer from an external source. It can include both video and audio inputs.

DirectX

Many games are written to require either DirectX or OpenGL graphic language support. DirectX is a set of Microsoft API that improves graphic, animation and multimedia. DirectX includes multiple components targeted to a different aspect of multimedia. OpenGL is an alternative standard to DirectX that is used by some applications. Video cards support both DirectX and OpenGL. If we plan to play latest games, we have to be sure that our card supports the latest DirectX or Open GL standards. High end video cards can be really expensive, so our choice can also be cost driven. We can also take advantage of combining graphic processing capabilities of two cards at the same time.

Video Card Installation

Video card is simply an expansion card, so installing it is a relatively easy process. The first thing to do is to select the video card based on the bus type of our motherboard. This will typically be either a PCI express or an AGP card for older systems. Then we insert the video card into the computer. If our system has a built-in video card we might need to disable it in the BIOS (or the system will disable it automatically). Then we then boot our computer, install the drivers for the video card and configure the video display.
To improve video performance we can take advantage of multiple graphics processing units or GPU’s. Two technologies for doing this is either CrossFire from ATI or Scalable Link Interface (SLI) from nForce.
To use one of those technology, we have to purchase a motherboard that supports either CrossFire or SLI. In addition to having a motherboard that provides that support, our graphics cards must also be supported by the motherboard. In most cases we will need to install identical video cards, or at least video cards with very similar specifications. In general, we’ll need to do some research before we purchase our components.
Next, we should look at the motherboard documentation to identify the exact steps to follow in the installation process. The next step would be to install our CrossFire or SLI capable video cards using the available slots. Next, depending on our cards, is to link the two cards together in order for them to work together to render a single screen. Depending on the motherboard, it might automatically detect the two cards and configure them to be linked together. Some cards will require special tabs to form a special bridge to link the cards.
The next step would be to provide power to the cards themselves. Some cards only draw power from the bus, but in other cases, the cards will require an additional power connector. This power connector can be either a six pin or eight pin connector. In some cases, motherboards will have additional power connectors on them which are used in SLI or CrossFire configurations.
The final hardware configuration task is to attach our monitor. When using multiple video cards, we will more than one monitor connectors. When we link our cards using CrossFire or SLI, the graphics processor on both cards is active, however output is sent only through one card, typically the first one. The second card connectors are not used for the output.
With the hardware configured the next step is to boot into the system, configure the BIOS if necessary (to disable or configure the onboard video card), and then install the drivers. With the drivers installed we run a configuration utility that identifies how to use our multiple video cards. For example with both CrossFire and SLI we can configure both graphics processors to draw a single screen. For example, one card might draw one line and a second card would draw the next, or we might configure the cards to draw the top half or the left half, etc.

Configuration

Once our video card is installed, we will typically want to check our display settings. On different versions of Windows, and depending on the drivers and software for the video card, this is done in different way and in different places. However, there are some common things that we sould check. For example, the first thing we should consider is the resolution.

The resolution is the number of pixels available on a display screen. It is represented using two numbers: the number of pixels horizontally across the display by the number of pixels vertically down the display. A higher resolution means that more information can be shown on the screen at a time. Common resolutions are often described using a naming standard:

  • VGA = 640 x 480
  • SVGA = 800 x 600
  • XGA = 1024 x 768
  • XGA+ = 1152×864
  • SXGA = 1280×1024 (5:4 aspect ratio)
  • SXGA+ = 1400×1050
  • WSXGA+ = 1680 x 1050
  • UXGA = 1600 x 1200
  • WUXGA = 1920 x 1200
  • QWXGA 2048 x 1152
  • WQHD 2560 x 1440
  • WQXGA 2560 x 1600

Resolutions with a W in the name are widescreen resolutions with a 16:10 aspect ratio. Resolutions used by HDTV (with the 16:9 aspect ratio) are 1280 x 720 and 1920 x 1080. Full HD content is designed for a resolution of 1920 x 1080 using progressive scanning (where each line on the screen is redrawn in order) and is referred to as 1080p. Cheaper TVs and monitors at lower resolutions or using interlacing (where every other line is drawn with each pass) are not capable of displaying all of the video content in full HD. 720p (1280 x 720 progressive scan) and 1080i (1920 x 1080 with interlacing) identify displays that do not support full HD content. LCD monitors often have a native (optimum) display resolution. For best results, configure LCD monitors to use the native resolution.

Another option that we can consider is the color depth. The color depth is the number of different colors that can be displayed on the screen at a time. It is expressed in bits. More bits means larger number of colors that can be displayed. Common bit depths are:

  • 8-bit (256 possible colors)
  • 16-bit, also called high color (65,536 possible colors)
  • 24-bit, also called true color (16.7 million possible colors)
  • 32-bit, also called true color (16.7 million possible colors and alpha channel)

Another option is refresh rate. The refresh rate is the number of times the entire screen repaints per second and is measured in Hz. Increasing the refresh rate reduces screen flicker. The refresh rate must be supported by the video card and the monitor. Setting a refresh rate that is not supported by the monitor can cause damage. By default, Windows shows only the refresh rates supported by the monitor.

Another option is color management. Color management settings control how colors appear on our monitor. The purpose of this is that the colors that we see on the screen match the colors for graphic files or printed documents. Color settings are configured by loading color profiles created by hardware vendors to match the color range and characteristics used by a program or a device. Profiles translate colors from one color space to another.

if we have multiple monitors, we can configure how content is shown on each monitor. One monitor will be identified as the main monitor. We can configure each monitor with different resolution and color depth settings.

Remember

Video card must be compatible with our system’s expansion bus. Some motherboards include a built-in video card integrated on the Northbridge chip. Typical ports which some video card can have are VGA, DVI-A, DVI-D or DVI-I, HDMI or S-Video. Video cards contain a GPU, or Graphics Processing Unit, which provides video hardware acceleration. Some cards can be linked to other identical video cards via SLI or CrossFire technology. The amount of memory on the card effects performance as well as other characteristics of the display. Video memory can be VRAM, DDR memory or special GDDR2 to GDDR5 graphic memory. The quality of images and animations are determined by resolution, color depth and refresh rate. Many games are written to require either DirectX or OpenGL graphic language support by our card.

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