We use our own design heatsink test rig. The ambient temperature was regulated at 21 degrees Celsius. We run the heat source in our test rig at approximately 70, 115 & 170 Watts to show you how heatsinks perform under load. Use expensive top quality silicon based heatsink paste. The heatsink graph shows the temperature of a plate between the heat source and the heatsink. This is the temperature the heat source (processor) and heatsink are at their contact point in degrees Celsius on the left.