ATI Technologies X1900 - Radeon XTX 512 MB PCIE Video Card, User Manual

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110 CrossFire™ Rendering Modes
Some types of textures, especially those with transparent portions, can
exhibit aliasing that is not removed by MSAA techniques. Another form of
anti-aliasing, known as Super-sample Anti-aliasing (SSAA), can be useful
in these cases, because it affects every pixel in an image. Although it
normally operates more slowly than MSAA, the power of multiple GPUs
can make SSAA practical to use.
SSAA first renders a scene at a higher resolution than that which is output
to the display, which is then downsampled to the display’s resolution. This
approach normally has two main disadvantages: it requires rendering many
more pixels than normal, which can have a drastic impact on performance,
and that it results in an ordered grid sample pattern, which does a poor job
of anti-aliasing some types of jagged edges. CrossFire™’s Super Anti-
aliasing overcomes both of these problems. It takes advantage of the second
GPU to render the additional pixels required for each frame, so there is little
or no performance impact. It can also make use of a more effective sample
1 PCI Express® Slave Graphics Card
2 Radeon® X1900 Series Master Graphics Card
3 Partial Frame Rendered on PCI Express® Slave Graphics Card
4 Partial Frame Rendered on PCI Express® Master Graphics Card
5 Final Rendered Frame on Display
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