Post by @oz1tmm
Then why do they become so incredibly hot to the touch?
I have both a 3b and a 4, latter running freebsd as we speak. Mounted heatsinks, but they still become so hot, that they cease to function, without forced air movement.
Just OS installed, nothing more. The freebsd was an experiment to see whether that would behave differently.
An AMD64 CPU, worked hard, typically draws 120–200W on top of the power used by the rest of the machine. My Pi3, in contrast, runs off a USB-A outlet, so that's no more than about 12W for the entire machine. The reason the processor gets warm is that it's tiny and it has no active cooling.