What is a  Video Card?

Your system's video card is the component responsible for producing the visual output from your computer. Virtually all programs produce visual output; the video card is the piece of hardware that takes that output and tells the monitor which of the dots on the screen to light up (and in what colour) to allow you to see it.

Video cards today are much more like coprocessors; they have their own intelligence and do a lot of processing that would otherwise have to be done by the system processor. This is a necessity due to the enormous increase both in how much data we send to our monitors today, and the sophisticated calculations that must be done to determine what we see on the screen. This is particularly so with the rise of graphical operating systems, and 3D computing.

The video card in your system plays a significant role in the following important aspects of your computer system:

• Performance
The video card is one of the components that has an impact on system performance. For some people (and some applications) the impact is not that significant; for others, the video card's quality and efficiency can impact on performance more than any other component in the PC!
For example, many games that depend on a high frame rate (how many times per second the screen is updated with new information) for smooth animation, are impacted far more by the choice of video card than even by the choice of system CPU.

• Software Support
Certain programs require support from the video card. The software that normally depends on the video card the most includes games and graphics programs. Some programs (for example 3D-enhanced games) will not run at all on a video card that doesn't support them.

• Reliability and Stability
While not a major contributor to system reliability, choosing the wrong video card can cause problematic system behaviour. In particular, some cards or types of cards are notorious for having unstable drivers, which can cause a host of difficulties.

• Comfort and Ergonomics
The video card, along with the monitor, determine the quality of the image you see when you use your PC. This has an important impact on how comfortable the PC is to use. Poor quality video cards don't allow for sufficiently high refresh rates, causing eyestrain and fatigue.

• Number of Pixels
A pixel is a single dot displayed on a screen. Most screen images are made up of hundreds of pixels. Adding more pixels to the image makes the image more detailed. A screen image is usually described with two numbers. The first number is the number of pixels across the top of the screen, and the second is the number of pixels down the side of the screen.

• Number of Colours
Graphics cards are limited in the number of colours they can display. The oldest monitors could display only two or four colours. Currently, 256 colours is the minimum for most systems. Numbers of colours above 256 are usually described by how many computer bits are used to store the colour in memory. 16 bits can store more than 65,000 colours, while 24 bits can store more than 16 million colours.


Video System Interfaces

Modern video systems involve a great deal of information that must be moved around, particularly between the video card, the processor and the system memory. The video system interface is the method by which the video coprocessor and video memory are connected to the rest of the computer.

The video card requires more I/O bandwidth to the processor and memory than any other device in the system. So much so, that video performance has traditionally been the driving factor for the creation of newer and faster system buses. Local buses were created to address the bottleneck in data transfer between the processor and video card that became acute when graphical operating systems became the standard. The first local bus was the VESA local bus, and VESA is a video-related standards organization.

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