ATI Radeon 9800 Pro - Reference
Posted by Hilbert Hagedoorn on: 04/02/2003 07:00 AM [ 0 comment(s) ]
The third generation of ATIs innovative, bandwidth-saving HyperZ. technology, HyperZ III plays a pivotal role in allowing the R300 to reach unprecedented levels of rendering performance. It incorporates improvements to all three components of HyperZ. - Hierarchical Z, Early Z, Z Compression, and Fast Z Clear. To render a 3D image properly, it is necessary to know the distance of every rendered object from the viewpoint. This distance is stored in a special buffer called a Z-Buffer or Depth Buffer, and is used to determine which objects should be drawn in front of other objects. Reading and updating the Z-Buffer typically consumes more memory bandwidth than any other part of the 3D rendering process, making it a major performance bottleneck. The goal of HyperZ. technology is to reduce the memory bandwidth consumed by the Z-Buffer, thereby increasing performance. Notice that + ? ATi has enhanced the Z-cache, this way it will be more flexible and better optimized to work with stencil buffer data. This allows for better stencil shadow volume performance.
One of the most common uses for the stencil buffer is for rendering real-time shadow volumes. In this case, the application calculates which parts of the image fall in the shadow of other objects, and stores these shadowed areas in the stencil buffer. The graphics processor can then compare each pixel it renders with the stencil buffer values to determine if it falls within the shadow of any objects that have already been rendered. As long as all objects are rendered in the correct order, this technique makes it possible to generate accurate shadows for any moving object and/or light sources in a scene.
In fact remember this when you look at the Doom III benchmark results later on in the review.
The ++ you notice is not a mistake. In all fairness this is a little 'frostbite' towards NVIDIA's marketing. They used DirectX 9+ compatibility as marketing gimmick, so now ATI adopted 9++ compatibility. Of course, + or ++ does not exists official in Microsoft specifications it just tells you a tad about how well it supports DirectX9 and how far beyond Dx9 specification the products are. ATI's DX9 compatibility should now pass NVIDIA's GeForce FX with features like Floating Point 3D Textures, Floating Point Cube Maps, Multiple Render Targets, Displacement Mapping (HOS), etc.
Both graphics core and memory speed have been upgraded also. The core now runs steady at 380 MHz while it's 256-bit memory is running at a 680MHz (2x340) frequency.
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