Why does the processor heat up quickly and cool down quickly?

Question

Iron

Proc: i7-8700K
Overclocking: minimal (Z370P bios mode "fast" selected)
Cooler: gammaxx 200t
Paste: MX4
In idle everything is fine, 28-30 degrees. All fans are at minimum.
As soon as the load appears (render / stress test), the temperature rises to 90 degrees in 2-3 seconds and holds. The CPU cooler starts to noticeably increase the speed after 1-2 minutes.
As the load disappears, the temperature again drops to 30 degrees in 2-3 seconds .
Why does it heat up so fast? There is not enough cooler (and why then it cools down so quickly?) Poor cooling installation ?. First time I see this.

Answer 1

Most likely, poor contact between the processor and the heatsink is dried / missing thermal paste or installed skewed.

Answer 2

According to the specs, the cooler is designed for a maximum of 95W processors, i7-8700K is just that. This means that there is no stock, and if the manufacturer lied somewhere or turned out to be defective (poorly soldered heat pipes, for example), then it may well cause a problem. In general, Intel recommends CO at 130W for this processor.
Most likely. Judging by the heating rate, it looks like the almost complete absence of contact between the processor and the radiator. Is the mounting bracket fully tightened?

Answer 3

Cooler: gammaxx 200t

this cooler is for a maximum of 2 nuclear processors. You have K with mini overclocking, as you say, there is already at least 130W.
how can such rubbish be put on the i7-8700K? Put a lucifer or a red hat. If you want something quieter, then only dark rock pro 3. Ideally, dropsy, yes.

As soon as the load appears (render / stress test), the temperature rises to 90 degrees in 2-3 seconds and holds. The CPU cooler starts to noticeably increase the speed after 1-2 minutes.
As the load disappears, the temperature again drops to 30 degrees in 2-3 seconds.

Cooler is shit.
And it cools down quickly because by itself the load drops and from the radiator there is a quick blowing of warm air by the rear turntable and the pace from the processor goes immediately to the colder tubes of the cooler radiator. It's even good that it is.