We can now reveal to you that the board you have been seeing around the web is actually a specific design which has only one customer right now. The name of that customer is Apple and it will also be available in Crossfire mode.
Though multiple GPU-solutions, such as nVidia's SLI and AMD/ATI's Crossfire, have now been on the market for some time, Apple has never adopted them. To this point, claims of multiple-GPU solutions from Apple have been regarded as completely baseless, and given The Inquirer's past reliability (see note below), we continue to view these claims as without merit.
However, with a Mac Pro revision reportedly waiting in the wings, we post this for interest's sake. The aforementioned picture of the new, powerful graphics card can be found here. The R600 based cards will power ATI's upcoming X2900 series, which will compete with nVidia's Geforce 8800 series. Neither card has yet to be offered for the Mac.
Reliability Note: While The Inquirer should not to be confused with tabloid publication The National Enquirer, the reliability of the two may be similar. The site has had repeated claims go unfounded over the past year.