I am running a Mac Pro 2,1 and just had my x1900XT die. I know the 4870 isn't officially supported but was told on many a forum that it would indeed run. So I purchased a new Mac HD 4870 card and put it in yesterday. Seems to work fine and the user interface is snappy. However when I run Xbench and just the Graphics benchmarks I can see that I am actually scoring on average 30 points slower than when I was running the X1900! What is going on here? Is the card not being fully utilized due to it not being fully supported on my Mac Pro 2,1? Is it under powered? I plugged in the provided 2 power cables directly to the 2 connectors on the board. However in Cinebench 11.5.29 I scored a 24.96 which is something I couldnt run with my X1900 XT. Anybody have any answers? Extremely frustrating to upgrade to downgrade. Thinking about returning it and buying the officially supported HD3780. I work in Pro Apps all day long and need a good performer. Any thoughts?