You'll no doubt have noticed that the Ultra-120 Extreme fails to unseat the Ultra-120 from it's lofty spot, so we should reiterate that different 120mm fans were used in the testing of each model. Putting that aside, we thought the rounded base of the Ultra-120 Extreme might be handicapping it somewhat. The image at right shows the Ultra-120 Extreme after it was removed from the Frostytech Synthetic Intel test die. Approximately 25% of the CPU test die made no contact with the base of the Ultra-120 Extreme.... the heatsink still managed to post otherwise impressive thermal results however.
The next step was to lap the base of the Thermalright Ultra-120 Extreme. This helped flatten the convex copper plate significantly, but regrettably the heatsink fell from the lapping table and was sightly damaged before we could retest it. The thermal results can't be considered reliable after such a fall, so they were not included in the above chart. It was observed that temperatures decreased by an average 0.8°C post-lapping though.