Long time reader, first time poster. I have a Mac Pro 1,1 with an x1900 in it. I've been looking to upgrade to a 4870 but the price Apple is charging is highway robbery. I looked into flashing the 4870 and a couple months ago it look like I could do that without any software hacks. However, with the introduction of the 10.6.4 update that seems to have changed. I checked the thread about immune cards but that hasn't brought up a lot of concrete evidence. The general consensus is that a reference card will work but will a 1 gig ref card work as well since that doesn't match the Apple shipped model? In addition is there anyway to try and check the flashed cards on ebay or is that pretty much the luck of the draw?