ASUS ROG Rampage III Extreme

[Raja@ASUS]

Thermal resistance of heatsinks used in this size is greater than 1C per watt, so you'll need airflow to bring the figure down (a 20w load on the heatsink will result in a 20 Celsius rise OVER ambient if the heatsink's thermal resistance is 1C per watt. Junction temperature rise will be higher due to thermal resistance of the package, interface materials and heatsink). The heat produced will be proportional to the switching frequency - so 'cooler' temps at lower switching frequencies and higher temps if you shoot for 800KHz+. The Classified supported a minimum 800KHz, which is why you saw temps in the 50's upwards when the board is in a case. Temp reporting varies from board to board too, not all controllers/vendors report FET junction temperature. I think people need to come to terms with the fact that higher switching frequencies on performance oriented boards will result in 15~20 rises over ambient case temp at a minimum, a dash of realism is needed.