I am running a 7870 Crossfired with a 7850 and the second card occasionally displays a bus width of 32 bits as well. Experimenting with turning crossfire on and off and rebooting has made me come to the conclusion that gpuz isn't working 100% accurately with the card(s). Sometimes it will show the full bus width whereas other times it will show only 32 bits. Keep in mind I'm using 12.3 as my drivers because from my research online, its the best set of drivers for crossfire for these cards, and this is one of the first (if not the first) set of drivers for the 7000 series. Thus it makes sense for there to be small bugs, etc.