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Introduction

A graphics card (also known as a video card, v card, video board, video display board, display adapter, video adapter, or graphics adapter) is a board that into a personal computer to give it display capabilities and is a computer component designed to convert the logical representation of visual information into a signal that can be used as input for a display medium. Displays are most often a monitor but modern cards can also connect to video projectors, TVS and HDTVs. At a basic level a graphics card is composed of a GPU (graphics processing unit) and dedicated video memory.

Graphics Cards:

History:

At its heart the computer is an information processing machine and as such it needs to needs to communicate with, to display information to, its human user. The very earliest of the modern computers wrote output to a printer (a teletype machine) but even in the early 1970s there was a move away from teletype and towards video display units. Part of this was a question of immediacy. Those early displays might have had poor resolution but they allowed both input and output to be seen in simultaneous streams so that the state of the computer became immediately obvious. Only text was displayed on these early displays, however.

The modern GPU (Graphics Processing Unit) grew out of monolithic graphic chips of the late 1970s and early 1980s. These chips had only limited BitBLT support (Bit Block Transfer) an implementation of fast bit operators for displaying bitmap graphics on the basis of bitmaps for background images, moving foreground images and sprites. In the first generations of these processors (available during the late 1980s) the graphics processor was responsible for BitBLT operations and the main CPU was responsible for raster drawing.

As chip process technology improved, it eventually became possible to move drawing and BitBLT functions onto the same board (and, eventually, into the same chip) as a regular frame buffer controller such as VGA. Evolving during the early 1990s this technological advance saw the generation of VGA cards adaptors and VGA displays for home PCs. These cut-down "2D accelerators" weren't as flexible as microprocessor-based GPUs, but were much easier to make and sell and therefore much cheaper as well.

In 1991, S3 Graphics introduced the first single-chip 2D accelerator, the S3 86C911. This spawned a host of imitators and by 995, all major PC graphics chip makers had added 2D acceleration support to their chips. Throughout the 1990s, 2D GUI acceleration continued to evolve. As manufacturing capabilities improved, so did the level of integration of graphics chips. Video acceleration became popular as standards such as VCD and DVD arrived, and the Internet grew in popularity and speed. Additional APIs arrived for a variety of tasks, such as Microsoft's WinG graphics library for Windows 3.x, and their later DirectDraw interface for hardware acceleration of 2D games within Windows 95 and later.

The next advance came in the mid 1990s when, for the first time, CPUs were becoming powerful enough to handle real-time three-dimensional graphics and graphics chip/card manufacturers began a scramble to be first to generate these to their line-up. For the first few years there were separate lines of 2D and 3D accelerators. But, as manufacturing technologies progressed 2D GUI acceleration, and 3D functionality were all integrated into one chip. The other driver behind 3D technology was Microsoft's DirectX API and OpenGL API for game programming the use of 3D environments in both games and GUI environments on PCs became routine.

Modern GPUs use most of their transistors to do calculations related to 3D computer graphics. Because most of these computations involve matrix and vector operations, engineers and scientists have increasingly studied the use of GPUs for non-graphical calculations. In addition to the 3D hardware, today's GPUs include basic 2D acceleration and frame buffer capabilities (usually with a VGA compatibility mode). In addition, most GPUs made since 1995 support the YUV color space and hardware overlays (important for digital video playback), and many GPUs made since 2000 support MPEG primitives such as motion compensation and iDCT. The newest graphics cards even decode high-definition video on the card, taking some load off the central processing unit. The typical modern stand-alone GPU sits on a separate graphics card from the motherboard, connected to the CPU and main RAM through the AGP or PCI Express bus. A GPU will typically have access to a limited amount of high-performance VRAM directly on the card, which offers much greater speed than dynamic RAM, though at much greater cost. For example, most modern cards have 256 MB of VRAM, with some having as much as 512MB of VRAM, whereas the computer itself may have 1GB or more of system memory.

Graphics Cards: Connectors

As motherboard designs have moved on, so have the designs of graphics cards, from the earliest versions fitting into an ISA slot to cards that fit in dedicated AGP (Advanced Graphics Port) [above, top] to the latest generation that sits in a PCI-E (PCI-express) port [above, bottom]. Therefore, when buying a graphics card make sure your card fits into the correct slot on your motherboard. PCIe is the emerging standard and will probably take over from AGP in a few years.

Graphics Cards: Other Aspects

Other aspects of graphics cards to look out for are the relative importance of 2D and 3D acceleration. If you want to play games you need 3D acceleration above all else. However, if you're not into gaming and want your PC as an analysis machine you'll want 2D acceleration. If your PC is to be a multimedia machine then you'll want on-card MPEG decoding to give you smoother image rendition. You might also want to consider an on-board TV tuner for your graphics card if you want a multimedia PC.

Graphics Cards: Output

Other things to consider when buying a graphics card are the types of ports and connectors available on the card itself. Most cards will still have a 15-pin VGA connector (far left) for older monitors. Modern graphics cards may also have a round S-Video connector (middle) for connection to most modern TVs. This S-VIDEO connector can converted into a standard composite connector with a simple cable. What you will also get on modern cards is a DVI connector (right).

There are two types of DVI connectors. DVI-D (for digital) and DVI-I (which contains both analogue and digital signals). DVI-D cables and connector connect only to digital LCD displays (and LCD monitors for HTDV) they are not compatible with analogue displays. DVI cables and video output contain both analogue and digital signals. They can even be converted by a simple connector to fit a VGA monitor. Again, be careful what type of connector your graphics card has and mae sure it's compatible with the overall system you want to build and note that DVI-I systems will fit just about anything you need.

Graphics Cards: The Future

Many motherboards now have a GPU integrated into the northbridge that uses the main memory as a frame buffer and the CPU to aid in frame rendering. This is usually a cheaper solution than an independent GPU, but will have dramatically lower performance. As a result, it's well worth-while in terms of overall performance to buy a separate graphics card. When buying a motherboard, even if it has built-in graphics capabilities make sure that it supports an add-on graphics card.

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