Quote Originally Posted by TechPowerUp | Posted: 20 October 2018
We kept seeing hints regarding Intel's 9000-series processors running hot, including from their own board partners. As it turned out, the actual results are a mixed bag with some running very hot and most others ending up being power-limited more so than temperature-limited. Our own review sample showed overall better load temperatures relative to the predecessor 8000-series processors thanks to the soldered TIM (sTIM) used here, to give you some context. But that did not stop overclocker extraordinaire Roman "Der8auer" Hartung from de-lidding the processor to see why they were not generally better as expected.

As it turns out, there are a few things involved here. For one, replacing sTIM with Thermal Grizzly Conductonaut (Der8auer has a financial interest in the company, but he does disclose it publicly) alone improves p95 average load temperatures across all eight cores by ~9 ?C. This is to be expected given that the liquid metal has a vastly higher thermal conductivity than the various sTIM compositions used in the industry. Of more interest, however, is that both the PCB and the die are thicker with the Core i9-9900K compared to the Core i7-8700K, and lapping the die to reduce thickness by a few microns also does a lot to lower the CPU temperatures relatively. Overall, Intel have still done a good job using sTIM- especially compared to how it was before - but the current state of things means that we have a slightly better stock product with little scope for improvement within easy means to the consumer.

Source: TechPowerUp / der8auer