Hi there, So, after research I made an investment in the GTX 750 ti in order to breath the last bit of life into my Mac Pro 1,1. The machine already has upgraded processors, 14GB or RAM and SSD disk for the OS, but this card was about giving it one last chance before it's too late. However, it seems that it is already too late as I cannot get this thing to work properly. I've installed the drivers via InsanelyMac's utility, but get this.... it will ONLY boot if BOTH the old ATI 4870 is in the machine as well as the new GTX 750 and ONLY in slot 2. I can deal with slot 2, but if I take out the ATI card, literally no card is detected in OSX. When I put it back in, Boom.. 2 graphics cards. The problem is, I don't need 2 cards, but if I do this.. I need 3x six pin PCI-e power cords... which is just madness for the sake of something like this. Also, when the 4870 is in slot 1 and the GTX 750 is in slot 2, it will ONLY detect the GTX 750 if I set Expansion Utility to limit the 16x to 8x. The only exception to this, is if I set the GTX 750 in slot 2 to 1x, and remove the 4870, it will display. So, in a nutshell, here's the situation: Displays with both graphics cards in (ATI 4870 in slot 1, GTX 750ti in slot 2) Will not display with GTX 750 on it's own in slot 1 or 2 Will not display with GTX 750 in slot 1 and 4870 in slot 2 Will only detect both cards when set to 8x for slot 1 and 2 using Expansion Utility, otherwise 1 card is detected Will run GTX 750 on it's own in slot 2 if set to 1x speed When there is no display, system profiler reports NO graphics cards attached and same with Expansion Utility. The mystery is, how is it POSSIBLE for the Mac to boot with 2 cards (4870 without 1 power connector) yet it cannot boot on it's own? I can remote desktop into the mac, and this is what I see: Single GTX 750 on it's own in slot 1 or slot 2 Single GTX 750 in slot 2 but set to 1x I also want to mention that I have Bootcamp and Windows 10 installed, I cannot boot into Windows in the same configurations as I cannot boot into Mac, so, to me this indicates something with the way the Mac has the PCI express slots configured (via the utility). The Mac is running El-Capitan and has also had the firmware upgrade to correctly detect the CPUs Any idea? It's crazy... and I really want this to work !