The section on power really understates the complexity. Throttling didn't appear until the mid-90's as a coarse clock gating chipwide. Voltage/frequency scaling appeared a few years later (gradual P-state transitions). Then power control units monitored key activity signals and could not only scale the voltage, but estimate power and target specific blocks (e.g., turning off L1 D$).

There are some more details in there but that's the main gist. The power control unit is its own operating system!