There is a metal heatspreader on top of the actual CPU which interfaces with the heatsink/fan the user installs. During the time, Intel made a change from solde

There is a metal heatspreader on top of the actual CPU which interfaces with the heatsink/fan the user installs. During the time, Intel made a change from soldering the heatspreader to the CPU to using thermal paste between the heatspreader and CPU, which decreased performance and led to users “delidding” their CPUs to increase thermal transfer and, as a result, cooling performance.