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Understanding Video and Graphics Adapters

While the names to describe it are many (video adapter, video card, video board, video display board, graphics card or graphics adapter) its job and function within a computer system remains the same, regardless of what you call it. Your computer's video adapter is assigned the primary task of producing the visual output from your system. It is the hardware that works between your system's processor and monitor. It relays the information received from the programs and applications running on your system (computed by the processor) to the monitor that allows you to view the information and images on your screen. 

A video adapter is board that plugs into a personal computer to give it display capabilities. Those capabilities of a computer, however, depend on both the logical circuitry (provided in the video adapter) and the display monitor. A monochrome monitor, for example, can't display colors no matter how powerful the video adapter.

The term video adapter applies to either integrated or separate video circuitry. Each adapter offers several video modes. The two basic categories of video modes are text and graphics. In text mode, a monitor can display only ASCII characters. In graphics mode, a monitor can display any bit-mapped image. Within the text and graphics modes, some monitors also offer a choice of resolutions. At lower resolutions, a monitor can display more colors.

Modern video adapters contain memory, so that the computer's RAM is not used for storing displays. In addition, most adapters have their own graphics coprocessor for performing graphics calculations. These adapters are often called graphics accelerators.

Accelerated & Non-accelerated Graphics Adapters

Early graphics adapters received data from the processor and basically forwarded the signals to the monitor, leaving your system's CPU to do all the work related to processing and calculating. In non-accelerated (unaccelerated) graphics adapters, the computer needed to change each pixel individually to change the image on the screen. Having the graphics handled by the processor didn't become much of an issue until graphical user interfaces (like Windows for example) gained in popularity. Systems began to slow down as the CPU was left trying to move large amounts of data from the system RAM to the video card.

As always with technology, it didn't take long for the bottle-neck to be sorted out. Today all new video cards are accelerated and are connected to the system's CPU through high-speed buses such as PCI or AGP (which we'll discuss later in this article).

The biggest difference between accelerated and non-accelerated cards is that with accelerated video cards, the CPU no longer has to carry the bulk of the processing burden from graphics calculations. Since the video card has its own processor, it is able to perform most of the work, leaving your CPU free to process other tasks.

A graphics accelerator, for example, is a type of video adapter that contains its own processor to boost performance levels. These processors are specialized for computing graphical transformations, so they achieve better results than the general-purpose CPU used by the computer. In addition, they free up the computer's CPU to execute other commands while the graphics accelerator is handling graphics computations. The popularity of graphical applications, and especially multimedia applications and computer games, has made graphics accelerators not only a common enhancement, but a necessity. Most computer manufacturers now bundle a graphics accelerator with their mid-range and high-end systems.

Aside from the graphics processor used, some other characteristics that differentiate graphics accelerators are:

  • memory: Graphics accelerators have their own memory, which is reserved for storing graphical representations. Because of the demands of video systems, video memory needs to be faster than main memory. The amount of memory determines how much resolution and how many colors can be displayed. Some accelerators use conventional DRAM, but others use a special type of video RAM, which enables both the video circuitry and the processor to simultaneously access the memory.
  • bus : Each graphics accelerator is designed for a particular type of video bus (AGP or PCI)

So now that you know the basics behind how your video adapter works, there is another important topic to discuss when it comes to upgrading your system's video. Unfortunately, it's not as simple as buying any video card on the market and plugging it in. There are three main types of video upgrades and before buying you need to know which type can be used in your system.

Add-on Video Card

Add-on video cards are PCI or AGP cards that can be physically taken out of the computer as an individual hardware component. To upgrade an add-on video card, you need to remove the card and drivers and install the new video card and drivers.

Motherboard Video-only Chipset

If your system supports a video-only chipset on the motherboard, your motherboard has integrated video (which is using your system memory). Many PCs come with this type of video, but they will also have an open AGP expansion slot on the motherboard that allows you to add a video card rather than using the on-board video. To upgrade in this scenario, you'll need to disable the on-board video and add an AGP video card and install drivers for the new card.

Motherboard With Integrated Video

This type set-up offers only on-board video — you won't have an extra AGP slot that you can use to install a new video card.  You may be able to install a slower PCI video card or if you really want an AGP video card you can opt for a motherboard upgrade (to one that offers an AGP slot).

Did You Know...
VGA (640x480 31.5kHz, 60/70Hz): IBM developed VGA in 1987, as one of the first computer video types to use analog signals.

Key Terms To Understanding Your Video Adapter...

video adapter
A board that plugs into a personal computer to give it display capabilities. The display capabilities of a computer, however, depend on both the logical circuitry (provided in the video adapter) and the display monitor.

graphics accelerator
A type of video adapter that contains its own processor to boost performance levels. These processors are specialized for computing graphical transformations, so they achieve better results than the general-purpose CPU used by the computer.

video memory
RAM installed on a video adapter. Before an image can be sent to a display monitor, it is first represented as a bit map in an area of video memory called the frame buffer. The amount of video memory, therefore, dictates the maximum resolution and color depth available.

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