I call bs on that number. Why would Intel, the largest desktop CPU manufacturer, not already just be doing this? 20C is a massive number! I'd maybe believe it if you said 2C maybe.
Because they save money on the thermal paste, and their production process for putting on the heatspreader along with the glue is just good enough to ensure that most chips all have the same thermal characteristics out of the box. Removing and reseating the heatspreader takes away some of the air gap underneath, and facilitates better heat transfer. This has become more difficult to do with Broadwell and Skylake chips though, as Intel has transistors and other stuff up on the top of the packaging now, so there's a greater risk of damaging those while taking off the heatspreader.
While this thread is revived - the topic of delidding:
[video=youtube_share;LvS_qgn7OSs]https://youtu.be/LvS_qgn7OSs[/video]
I still believe a 20C drop in temps is absolute bs unless there was something wrong with that CPU from the factory, this video seems to support the idea that the gains are minimal vs the risk.
I expected Linus to be pretentious about his findings. He might be right about the risk, but he's wrong about the benefit.
If they had put Luke on this topic, he would have mentioned that Haswell owners saw big drops in temperature from doing this because Intel put the voltage regulator onto the CPU package, which resulted in much, much higher temperatures. Delidding is something that any self-respecting pro overclocker also has to do in order to obtain higher scores on air or water. Sometimes putting the heatsink into contact with the die itself also yields better temperatures.
Also, on Broadwell-C chips, you have to run your heatpaste on one side of the heatspreader because that's where the CPU die is. Delidding Broadwell also has temperature and slight performance benefits because of this.
Edit: Also, don't just take my word for it. There's
a huge community of enthusiasts out there doing this, and it's not for no benefit either.