We know that Intel’s 10th Gen flagship, the Core i9-10900K will need high-end liquid cooling to attain the spec boost clock of 5.3GHz, but we’re still not sure exactly how hot will the chip run using standard thermal solutions. A while back we saw that a 120mm cooler was absolutely useless with a Core i9-10900F, unable to permit even a 5GHz single-core boost. Today, thanks to the same source, we have a rough idea of how the 10 core 10900K will perform using a 240mmm AIO closed-loop cooler.

In the above test, the user ran the AIDA64 FPU test in tandem with Furmark and found that the Core i9-10900K was unable to sustain a single-core boost of 5GHz. This is despite the fact that the motherboard vendor has bypassed the PL1 and PL2 values, allowing the CPU to draw 250W for extended intervals.
Using a 240mm AIO cooler, the Core i9-10900K hits a max temperature of 93°C. Although the clock throttling brings down the temperature to 88°C, that is still far from normal. On top of that, the guy’s using a 240mm liquid cooler. Looking at these stats, I’d say you’ll need a 360mm liquid cooler to even have a chance at achieving that 5.3GHz boost. Even then, there’s only a 66% chance that you’ll be able to hit the spec boost clocks. Remember that 33% of all the 10th Gen chips won’t be able to achieve the marketed boost frequencies.