Compositing Engine ?The Power of the CrossFire

The corner-stone of ATI?s CrossFire technology is the Compositing Engine that allows to compose images rendered on two separate graphics cards into one, which may be done either to improve image quality, or to boost the speed. ATI?s Compositing engine is borrowed from professional solutions, so, it should offer pretty high scalability and additional features that will be exclusively available on multi-VPU technology from ATI.

ATI Compositing Engine. Click to enlarge

The Compositing Engine is a set of a three chips: a Field-Programmable Gate Array (FPGA) chip by a third-party designer, TMDS transmitter and RAMDAC. ATI programs the FPGA chip to perform either blending of two images rendered using different patterns (for Super AA modes) or parts of images (SuperTiling and Scissors modes).

Currently ATI does not disclose what type of an FPGA it uses, but it says that the chip stores parts of an image inside a built-in buffer.

ATI CrossFire Super AA ?Image Quality Enhanced

Unlike NVIDIA SLI, ATI CrossFire is designed not only to increase performance, but also improve image quality by offering extreme FSAA modes like 8x, 10x, 12x and even 14x FSAA.

CrossFire SuperAA. Click to enlarge

Both 10x and 14x modes are hybrid: ATI uses both multi-sampling and super-sampling methods to provide the best image quality possible. As previously noted, ATI renders frame using different FSAA patterns on each of the GPUs and then blends two images together. Given that ATI offers numerous modes, users should find it easy to balance between quality and performance. Keep in mind that this is the first time ATI uses super-sampling antialiasing on the RADEON X8-series products, hence, the outcome is very interesting from performance perspective.

ATI believes that the main advantage SuperAA provides is improved micro-geometry details and object contours, something which is not always perfect with lower-grade full-scene antialiasing.