In fact, the term 'air-cooled' is a colloquial term that is not very strict and has a relatively broad meaning.

A long time ago, when Home computer were first popularized, CPUs at that time, such as the famous 8086, were not strong in performance, did not generate much heat, and did not need heat dissipation devices.

Later on, with the improvement of performance and the increase of heat generation, heat dissipation fins were added, which were usually made of aluminum and dissipated heat through metal conduction, increasing the area of metal contact with air.

Then, with the increase of heat generation, Computer fan is added to accelerate the heat dissipation of metal fins through wind.

In terms of metal selection for heat dissipation, copper and aluminum are usually chosen because these two prices are relatively low. Copper has fast conductivity but is more expensive, while aluminum is less expensive but cheaper.

This cooling method has been used for a long time, until now, you can see that some original CPU heat sinks still look like this.