Note the multi-VPU designation in the driver control panel. That's what shows up when you're running Crossfire in slave-slave mode. Slave-slave mode limits you to alternate frame rendering mode within Crossfire, as a means to speed up rendering, or SuperAA mode as a means to increase image quality. Supertiling and scissor are unavailable if you don't have the Xylinx FPGA to put the image back together.
http://www.hexus.net/content/reviews...lld19JRD0xMzUx