ATI CrossFire Technology White Paper

Ultimate Compatibility
Another limitation of previous multi-GPU techniques was that they did not always work well with all applications.
This was due to a variety of reasons, including certain rendering techniques that were incompatible with the
particular multi-GPU implementation, or heavy CPU dependence that created performance bottlenecks. In any
case, these issues limited the value of adding a second GPU to a system.
CrossFire is the first multi-GPU technology that can provide a benefit to any 3D application. This is made
possible by its support for four different operating modes that maximize compatibility. The ATI Catalyst display
driver will automatically select the best of the three performance modes when a 3D application is started,
without requiring user intervention. Alternatively, the user can choose to improve image quality by selecting the
new Super AA modes in the Catalyst Control Center.
Ultimate Flexibility
Earlier multi-GPU technologies were characterized by limited upgradeability. In general, they required two
identical or near-identical graphics cards be installed in a system in order to allow them to work together.
Furthermore, each of these cards typically had to be special models designed specifically for multi-GPU
configurations. These special models could be more expensive or harder to find than standard models. Finally,
this approach meant that every compatible GPU produced had to include logic to support Multi-GPU, thus
increasing the cost of these products unnecessarily for those who had no need for such configurations.
ATI CrossFire technology takes a novel approach to improving upgradeability. It is designed such that a
Radeon CrossFire Edition board can be connected to any existing model, configuration, or brand of PCI Express
graphics card that uses a Radeon X800 or Radeon X850 series GPU. This provides an easy upgrade path to
existing owners of Radeon X800- or Radeon X850-based graphics cards. The dedicated CrossFire
Compositing Engine ensures that only users interested in multi-GPU configurations need to pay for the circuitry
that makes it possible.
In order to ensure the workload does not become too strongly mismatched between two cards with differing
levels of performance, ATI CrossFire technology has the capability throttle the speeds of each GPU. This
makes it possible to obtain better performance and image quality from almost any combination of compatible
graphics boards.
Summary
ATI CrossFire technology offers the most advantageous means available of combining multiple high
performance Graphics Processing Units in a single PC. Combining a range of different operating modes with
intelligent software design and an innovative interconnect mechanism, CrossFire enables the highest possible
level of performance and image quality in any 3D application.
Copyright 2005, ATI Technologies Inc. ATI, Radeon, CrossFire, Catalyst, SmoothVision, MAXX, Rage Fury, and Rage 128 PRO are
trademarks and/or registered trademarks of ATI Technologies Inc. simFUSION and RenderBeast are registered trademarks of Evans &
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