As title, I don't think I have seen anywhere that used my way for GTX 580 or HD 5870 2gb working in mac pro. I have used it for 2 years, I felt guilty for not sharing with you folks. Here it is with photo. It's easy and hassle free (for me at least) as long as you can find a copper wire ( size as shown, not too big not too small like people used to say it ), like making a spring. Plug it in the two holes make it contact both pins inside. That's it. Use your two 6 pins from mac pro. Don't be afraid, if you are not burning your mac pro with battlefield 3 for 24 hours a day. It's safe for you. I used the card with tessellation benchmark software before, not a problem at all. (don't need to be a copper wire, any wire that can make good contact for the pins will do the same job) Enjoy it!