areaman This makes total sense. I was assuming to count time, you need power. That's true, but not counting time when there's no power just stops the clock, making the throttling worse. And here is no need to follow time, all what's required is to count proper amount of oscillations and save then in persistent memory.
But it may even be simpler than that - without CMOS. Why not just count the base clock ticks? If you expect the phone's board to have stable frequency, let's say 100MHz, and the chip reliably crashes on lets say 3,5GHz, you can set a static multiplier to 30, so the chip always runs on 3GHz, then you can assume 3 "giga-clock-ticks" equals 1s passed. Then if someone underclocks, then the throttling would get worse, and if someone overclocks, the chip will fail way before any meaningful speed up could be achieved.
BTW. Let this topic again show, on the Internet it's best to start a discussion with a wrong solution. When I was just asking if someone knows how it works, I got nothing.