It must be a dying MacPro? This is 2009, 5,1 3.46 gz. Various issues have cropped up that I THINK are not related to this machine, but there have been so many I might just break down and take it to the Apple Store. The latest is trying to install High Sierra and then Mojave. Of course I had to go through all the rigamorole of getting a metal GPU, flashing the firmware up to 138.0after installing High Sierra from Sierra. Then it was installing High Sierra twice, the second time to a second SSD I forgot I had tried. It might have been Mojave. Anyway when it completed it restarted. But it never came back. I waited for 30/45 minutes. Then I hit shutdown/start but I no longer get a chime. No screen. No chime. Luckily I still have boot drive with Sierra on it. Put that in and it eventually came back. Suggestions? I'm going to try and boot into the last High Sierra again. See what happens. I saw someone else here had a panic with no chime. I haven't finished reading that thread.