Hi,

I've an KC705 board here in one of my boxes. It has been run in the past stable at 500 MHz with one pipeline to mine bitcoins. Also it has external DDR3 memory 1GB. Stats can be found here:

http://www.xilinx.com/products/boards-and-kits/DK-K7-EMBD-G.htm

At the moment I'm to busy to experiment. But maybe we can find a way if you are interested ;-) As compared with the Spartan it was little bit more efficient. CN1 ~ 60W/GH/s, KC705 ~ 40W/GH/s mining bitcoins.

Cheers...

PS: Added link