Hi, My Mac Pro 1.1 recently died completely - I suspect the PSU. I hunted around for a replacement, and have ended up with a second 1.1, and now a bargain 3.1. The 3.1 came with a flashed PC card, apparently a GT120. With that card, it works perfectly. However I have a 5870 from my dead 1.1. With this card installed I get horrible graphics corruption in both Yosemite and Snow Leopard. Interestingly it works OK in Snow Leopard (albeit sluggishly) until I install the 10.6.8 combo update, and then it craps out straight away. I thought that whatever had killed my 1.1 had also killed my 5870, but having tried it in my replacement 1.1, it works perfectly. As far as I know the 5870 should work in the 3.1 as well as it does in the 1.1. Anyone any ideas?