AMD’s CrossFireX, an improved version of ATI’s CrossFire multi-GPU technology, uses three methods
to speed up display performance: alternate frame rendering, supertiling (which divides the scene into
alternating sections and uses each card to render parts of the scene), and load-balancing scissor operation . The ATI Catalyst driver uses alternate frame rendering for best
performance, but it automatically switches to one of the other modes for games that don’t work with
alternate frame rendering.
To achieve better image quality than with a single card, CrossFire offers various SuperAA
modes, which blend the results of antialiasing by each card. CrossFire also improves anisotropic filter-ing by blending the filtering performed by each card.
To use CrossFireX, you need the following components:
-A PCIe motherboard with a CrossFireX-compatible chipset and two PCIe video slots designed
for CrossFireX operation
-A supported combination of ATI CrossFireX-supported cards
First-generation CrossFire cards required users to buy special CrossFire Edition cards that contained
the composting engine (an Xilinx XC3S400 chip) and used a proprietary DMS-59 port for intercon-necting the cards. One of these cards was paired with a standard Radeon card from the same series via
a clumsy external cable between the CrossFire Edition’s DMS port and the DVI port on the standard
card. Newer CrossFire-and CrossFireX compatible cards use the PCIe bus or a CrossFire bridge inter-connect (similar in concept to the SLI MIO component) to connect matching cards.