I installed a refurb GTX980 (not ti) into a Mac Pro 5.1 where I initially noticed small artifacts if I used the OS-X accessibility whole screen zoom. That said in Adobe Camera Raw zooming the image to be processed occasionally yielded large blocky artifacts within the camera raw window. To confirm the problem was the GTX980 or its web driver (e.g. current version for 10.11.6) I switched back to the ATI 5870 shipped with the system. The artifact problem was not present with the 5870. Opinions on if this is a Nvidia web driver issue or a problem with the GTX980 I purchased?