Hi all I have a real Mac Pro 2010 5,1 (not flashed) I also have a flashed gtx 680 which worked perfectly in sierra, but after the upgrade the screen doesn't turn back on after the machine sleeps. I've tried everything to get it to come back including moving the pci express slot, checking connections. It did come back one a couple of times whilst plugging in different cables but when it sleeps again it doesn't come back, I think the machine has booted up through and pressing eject does open the dvd drive. Is this a hardware problem? I saw that high sierra wanted to do a firmware update before install, would this affect it? I don't have another graphics card on hand and will have to buy a mac 5770 to test. Any advice would be appreciated, thanks.