Boy that was a long title. Anyways, to the main problem: I have a 2010 Mac Pro 5.1 base option (2.8ghz quad core). I just got the gtx 970 today, and followed all directions to install the web driver, and made sure that the system is actually using the web driver. Here are my steps: Install Web Driver version 367.15.10.05f01, which is compatible with macOS Sierra 10.12 (16A323) that I'm running. Install latest CUDA driver Restart Choose to use the NVIDIA web driver in the menu bar Restart Make sure that the system is actually using the web driver in system preferences Turn off machine Install card and power cables Turn on the machine At this point, I could still hear the start up chime, but I waited and waited and there simply was no signal to the monitor. I popped the old card back in and started trouble shooting. Here's what I tried With the old card, I switched to OSX Driver, rebooted, switched back to web driver, rebooted again, made sure that it's using web driver, turn off, popped new card in again. No dice With old card, I uninstalled web driver, but left CUDA driver intact, rebooted, install web driver again, go thru the 8 steps above again. Still no dice. There are a few anomalies that may or may not be relevant: In the CUDA Preference panel, it says I have CUDA Driver version 8.0.46, and then a big red "Update Required" next to it, but when I tried to update, there's none available Also in the CUDA Preference panel, it says: "GPU Driver Version: no version found". I thought this meant either the system wasn't using the web driver, so I checked and web driver was checked under the menu bar drop down. I then thought I might have botched the installation somehow, so I reinstalled as mentioned above, but still no signal Moved the card to the 2nd PCIe x16 slot. No signal either I only have 2 6 pins power cables, not 1 6 and 1 8. I don't know if this matters or not, but the folks at Create Pro said that the card could function with 225W unless I'm doing heavy gaming in Windows Should there be a start up chime? I've read that there shouldn't be a start up chime. I now have the HD5770 back in, and everything is good so far, but I really really want to use the 970. I've done everything I can think of, short of reinstalling Sierra, or even Capitan. Do you guys have any suggestion?