Greetings fellas, I am thinking of adding the Gainward GTX580 3GB to my MacPro "2012" (and yes, it was given to me, I didn't buy it, but hey, even I'm not that pedantic to say "no, I'm not taking it, it's not new"). I've scanned the threads and the opinions seem to differ slightly when it comes to the GTX 580. The nominal TDP of the 580 is 244W. The PCI-x slot provides us with 75W, the "authentic" 6-pin-PCI-x with another 75 and the 6-pin to 8-pin PCI-x-hack gives us another 75 for a total of 225W of power. The power supply itself is 980W, which is more than enough to feed a 580 and all the other components, this is about the PCI-x-rails here, not the total power the PSU can dish out. I've read reports of people claiming it's no problem, and that one could connect it without any problems, others claim one needs an external power supply with a proper 8-pin. Being someone who's blown up more than one i7-3960X when experimenting with power supplies, I am rather reticent to just hook the bad girl up and go for a round of high-FPS action gaming, out of fear of ruining my "new" MacPro. Can someone give me an educated opinion on this, maybe with own experiences? Thanks a lot, Sami. Edit: Best answer by Asgorath, thanks a lot mate!