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Graphics Processor Architecture: Features

Graphics Beginners' Guide, Part 2: Graphics Technology
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Realistic 3D representation is highly dependent on your graphics card's performance. The more shaders your 3D processor contains and the faster their clock speed, the more effects can be applied to 3D scenery to improve the visual experience.

The graphics processor contains many different functional units. Many of these components can be referenced to give a general idea about how powerful a given graphics processor is at a specific task. Before explaining any further, there are a few concepts we need to define:

Vertex Processors (a.k.a. Vertex Shader Units)

Similar to pixel shader units, vertex processors are components on the graphics processor designed to process shaders that affect only vertices. Since more vertices means more complex 3D objects, vertex shaders are important in 3D scenes with many or complex 3D objects. They are, however, clearly less relevant to overall performance than pixel shaders.

Pixel Processors (a.k.a. Pixel Shader Units)

A pixel processor is a component on the graphics chip devoted exclusively to pixel shader programs. These processing units only do calculations regarding pixels. Because pixels represent color values, pixel shaders are used for all sorts of impressive graphical effects. As an example, the most impressive water effects you have seen in a video game were created with pixel shaders. The number of pixel shaders in a graphics processor is used to compare different graphics cards in regard to pixel processing performance. Between a card with eight pixel shader units and one with 16 pixel shader units, it is reasonable to assume that the graphics card with 16 pixel shader units will be faster at processing complex pixel shader effects. Clock speeds also have an influence, but doubling the amount of shaders is much more energy efficient than trying to double the chip clock speed of the graphics chip.

Unified Shaders

Unified shaders are not quite here yet in the PC world, but the upcoming DirectX 10 specification calls for a unified shader architecture. That means that vertex geometry and pixel shader code structures will be functionally similar but have dedicated rolls. The new specification can be found inside the Xbox 360 that was developed by ATI for Microsoft. It will be interesting to see the potential of the new DirectX 10 requirement unfold.

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