I have two Mac Pro 4,1's that I got free from work. One is my main machine and works great (SSD upgrades, Video cards, USB 3.0). The other does not boot or chime. ame specs. Something on the CPU tray is faulty. I've done the following: Swap CPU tray from Working computer (A) to B and it booted up/chimed. I even swapped out the ram from B to A to make sure that the Ram was not the culprit. B's tray mounted in A's computer does not boot/chime I've looked around and it seems that the CPU may have come unseated or an issue with the thermal paste? How should I go about testing the bad tray to diagnose?