Hi Don.
You have to add a splitter to one of the PCIE power connectors on your motherboard with a cable like this -
http://www.newegg.com/Product/Product.aspx?Item=N82E16812200935
You can now feed both cards.
The MP has a 1000 watt power supply, so plenty of headroom. In addition to the graphics cards, I also have a Black magic Intensity Extreme card in a third slot, and the machine just happily plows along. This machine is also part of my 3D rendering network, and it's typical to run for days (sometimes weeks) on end, all cores pushing 100%, and all PCI cards cooking. Things get a little warm (which is nice in the winter) but have never had any power or overheat issues for well over two years now.
