Photoshop has encountered a problem with the display driver, and has temporarily disabled GPU enhancements. Check the Video card manufacturer's website for the latest software. GPU enhancements can be enabled in the Performance panel of preferences
OK, that's a bit different.
Whole system shutdowns or restarts can only be caused by a few things: bugs in the OS, bugs in low level drivers, or defective hardware. Applications can't do it.
First, try updating your video drivers from the GPU maker's website. There's always a small chance that the low level drivers are responsible for the machine restart.
But most likely you're looking at bad hardware in your system. The most common cause is bad RAM, but bad GPUs or video cards (could be any component on the card) also happen, and sometimes bad power supplies, CPUs, motherboards, etc. can do the same thing.
Testing the components with software rarely finds the problems. The best way to diagnose such problems is to swap out the components (RAM simms or video card) for another one and see if the problem goes away.
Temporarily, you might be able to turn off GPU drawing in Photoshop to avoid the components that are causing the problem - but that is only temporary, as the defective hardware would still be in your system.