First of all, the new tech 360 uses DOES have to do with backwards compatibility. When games are programmed, there is alot of customization according to the hardware they are using, so when the hardware changes, it causes problems. They already have hundreds of games working, and aim to get them all. The 360 uses a custom 500 MHz ATI Xenos, with 10 MB embedded DRAM (256GB/s). Im sure there are many reasons they didnt go with a crossfire setup, but a few could be that crossfire was very new when they released the 360, and their were some resolution problems with 1st gen crossfire (if I remember correctly). Id guess MS had the option for it, but I'm glad they didn't try what would likely have caused more problems. Be glad they are at least trying, where as Nintendo's new DS will have no backwards compatibility, as the same with the new PS3.