Ok so that definitely means that the RAM is out of the equation, it already passed memtest and the Intel chip relies solely on the RAM.
At this point the issue is either Photoshop or the AMD chip. As you've already ran your backed up Photoshop, I'm afraid the answer is becoming quite obvious :-/
Let's try a few more tests before we arrive at any conclusions, do you have access to an external display? If so try to connect to it and see if you have the same kind of issue.
Also, have you tried booting in safe mode, as well as trying to create a new user to see if the issue happens with it as well?