I got an ATI Radeon HD 4870 512mb Gcard for Christmas, and have been trying to flash it to work with my 1st gen Mac Pro ever since. After following every guide I could find, and trying everything possible, I haven't gotten it to work. Even ask me what I haven't tried (try it). I also have a PC from my friend to test it out. The only problem is, after installing a different Mac ROM, my Mac Pro no longer boots with the card in, and the chime even cuts off early. The same thing happens with the PC, no boot. Does anyone have advice on what I can do at this point?