I have a 2008 Mac Pro 3,1. Since February I've had a GTX770 graphics card and a patched High Sierra install that has worked very well. I just bought 2 new monitors. I unplugged my old monitors, plugged one new one in (which worked), then unpacked the second one and plugged it in as usual. During that time the computer went to sleep - but then would not wake up. I rebooted it and the graphics card fans immediately run at full speed, and no video shows on monitors. I turned it off, unplugged the monitors and replugged my old ones, and the same thing happened. I tried clearing PRAM and that didn't help.
I can tell that the rest of the computer is running OK as I can SSH into it over the network and everything is there; it just has no video output.
I took out the card and tested it in a friend's PC, where it did the same, not even appearing in Windows device manager.
So I bought another GTX770 graphics card - and it behaves the same way, even with no monitors plugged in!
Clearly there is something major amiss, but I can't think what. Any other ideas how I can test the cards or the motherboard?
I can tell that the rest of the computer is running OK as I can SSH into it over the network and everything is there; it just has no video output.
I took out the card and tested it in a friend's PC, where it did the same, not even appearing in Windows device manager.
So I bought another GTX770 graphics card - and it behaves the same way, even with no monitors plugged in!
Clearly there is something major amiss, but I can't think what. Any other ideas how I can test the cards or the motherboard?