What is a Graphics Card

The graphics

card is responsible for delivering the image you see on your PC monitor. Its GPU (Graphics Processing Unit) processes the machine code and changes it into a signal to the monitor. There are many factors to a graphics card. Choosing one can be a tricky business these days as there is so much technology that is different in each new graphics card release.

Graphics Acceleration

When PC first came and for some time after, the graphics cards purpose was only to display the image on the screen. The amount of memory you got on a graphics card was very small and was not needed to a great extent. Today's graphics cards do more than just display an image, they help the processor with the job of processing when it comes to the graphics. The graphics card would in effect accelerate the process of displaying the image on screen.

This was needed when the 3D gaming world took the centre stage. The speed required to process the images on screen at 60 frames per second and process the code for the game itself was simply too much for a CPU to handle on its own and so the games would simply crawl along at a very slow pace. The graphics card would use some of its own built in instruction logic to added things such as textures lighting effects, fog effect and bump mapping to give a far more detailed picture. Also the speeds of graphics cards have improved a great deal in order to let these effects be used without the problem of the frame rate dropping.

Anti-Aliasing

One of the biggest improvements to graphics technology was nothing to do with an increase of speed or efficiency but with graphical improvements. Anti-aliasing was technology to allow jagged edges of computer sprites to be smoothed on screen by blending colours. Monitors have pixels which are rectangular by nature and are incapable of drawing a diagonal line without looking crooked. Anti-aliasing technology doesn't prevent this from happening but uses tricks of the eye in order to make images look smoother and more pleasing to the eye.

AGP or PCI Express

Two types of Graphics card available today are the AGP and PCI-e versions. The AGP (Accelerated Graphics Port) is the older of the two technologies but still quite popular as many people still have these slots incorporated into there motherboards. The PCI-Express (Peripheral Component Interconnect) version has been around for a couple of years now and new graphics cards and motherboards alike are using this technology. PCI express offers a greater scope for data transfer to and from the graphics card and main memory.

How do you measure the speed of a graphics card?

Measuring the speed of the graphics card is a lot more difficult than with the CPU or RAM or even the hard disk. There are many factors which affect how quickly the graphics card can do its job. Many of these only come into play when the graphics card is undertaking certain tasks.

Core clock speed - Much the same as the way you measure the speed of a CPU. The core speed of the Graphics card is measured in MHz and represents the amount of clock cycles the graphics process can do per second. This is a good but not definitive way of telling how fast the graphics card is.

Memory clock speed - Exactly the same of as the core clock speed, except of course that it is for the memory of the graphics card and not the core. This is just as important as the core speed as the memory contains textures that need to be applied to the pixels.

Pixel Pipelines - The amount of pixel pipelines a graphics card has can have a great impact on the speed of the image rendering. This is all about pixel pushing power. A card with 8 pipelines can process twice as many pixels as a card of the same core speed and 4 pipelines.

Textures per pipeline - This only come into effect when multiple textures are needed on the one pixel. Simply put if a multiple texture is needed, then a graphics card with more textures per pipeline will be quicker. On single textured pixels the amount of texture per pipeline will have no effect.

There are more smaller things such as T&L technology anti-aliasing and various other quality increasing and speed increasing technology that different cards have. I wont go into them all here as there are a great many between all the cards on the market.

Memory Bandwidth

The memory bandwidth is the rate of data transferred from the GPU to the graphics memory. This has been one of the biggest bottle necks in graphics cards for years. Newer cards are overcoming this problem with expensive memory solutions at high speeds. The higher the memory bandwidth the better the graphics card will be able to retrieve data and textures from the graphics memory. As this is a real bottle neck this is a really important feature of the graphics card.