Hi all, My colleagues Mac Pro Late 2013 is acting really odd. When you start it, it passes POST and you see the Apple logo and the loading bar (running 10.10.5) as you'd expect. It gets to about 1/3, then the screen glitches, the fan starts to run at about 80%, and the machine then puts itself to sleep. The screens seem to turn on and off sporadically, as if receiving a signal briefly, then not. The machine also responds to ping, but erratically, sometimes 0.2ms, sometimes around 30ms, or even up to 150ms or so. We've tried resetting the SMC, no difference. When we try to reset the NVRAM, instead of restarting the machine turns off. Running fsck -fy from single-user mode yields nothing. Booting from an alternative source (USB, NetBoot, Internet Recovery) makes no difference. AHT via Internet Recovery finds no issues. Visual inspection of the components doesn't reveal anything glaringly obvious that might have failed. It's a bizarre one. I've never seen a machine act like this. Anyone have any ideas? I have a suspicion it might be a GPU issue, but I'm at a loss why the machine puts itself to sleep straight away.