[rwem]

I wonder how much of this is due to measurement error of temperature. Core frequency and voltage control are governed by some suspiciously round numbers like Tj(max) == 90C. But when the controller thinks Tj == 90C, what's the measurement error?

[mlyle]

A moderate amount. Some of the frequency curve involves the thermal diode, but much less so when TDP capping is used as in the paper.

But the temperature of the silicon itself has a lot to do with the performance you get at a given power level.

[rwem]

Power limits have the same problem, don't they? Except it's maybe worse because you get the product of the error terms for Icc and Vcc?

[mlyle]

Thermal diodes on dies have a reasonable error.

Voltages and currents are easy to measure relatively precisely.