Here you can see that the thermal paste covered about two thirds of the surface of CPU A.
Before performing this service and repair measurements had been taken of temperatures and fan speeds. I installed Macs Fans Controller software and set limits on the temperatures permitted. The Booster Fan in the CPU A Heatsink was working hard to keep the temperature down. Here we see one reason why.
Incidentally, I recommend installing Macs Fan Control. Read the document Upgrade Tips to find out how to configure this software for optimum Mac Pro protection.