I have received confirmation from a reliable source that ATI will definitely offer a retail version of the Radeon HD 3870 with 512MB DDR4 that will boot OS X Leopard on both current and legacy Mac Pros. It will be "on the shelves" by the end of May. It will, of course, boot Windows XP or Vista in your Boot Camp partition. And, like the 2600, I expect it to support CrossFire mode under Windows if you have two installed and jumpered. My source also confirmed that the Radeon 2600 (and 3870) drivers in Leopard 10.5.3 will provide surprising performance enhancements for 3D gamers. And just in case 10.5.3 gets delayed, they will ship the enhanced drivers with the card.