[matthewmacleod]

I'm not an expert, but I know are two forms of throttling under MacOS – the CPU frequency limit, and the "scheduling limit". The CPU reduces frequency under thermal stress just like other machines, but there's a minimum frequency that it can be downclocked to. So if that's not enough to meet the thermal envelope, the scheduler will additionally start to limit the amount of CPU time that can be used. I notice this in particular when the GPU is at full whack – such as running multiple external displays at high resolution with 3D graphics.

[GekkePrutser]

I've had my Mac mini throttle down to 180Mhz under Linux (due to incorrect ACPI settings), to the point where I could see the window elements being drawn :) So at least that generation Intel was capable of pretty extreme downclocking.