Mac Pro 5,1 2010, 2.4 quad core. Boot up with GTX 970, nothing blank screen. Throw in the AMD mac card, works fine. Go to Nvidia control panel. Shows " OS X default driver" checked. Unlock panel, check use "web driver", restart, goes back to "use OS X default driver". Do this several times, same thing. So put GT120 in, same thing. . Every time I check use web driver, restart, it reverts back to use OS X default driver, no matter what I do or which mac card I use. I'm sure the "use web driver" has to be checked for the 970 to work. So, take the 970 & the hard drive out, put it in my 2.26, works perfect and the Use Web Driver block is checked. My 2.26 is a 2009 upgraded to a 5,1 but don't think that would have any bearing on it. Why does the 2010 keep reverting back to the "default OS X driver"?