It's not about architecture. It's about physics. Once you pass a certain threshold, electron/current leaks and escapes start to wreak havoc inside any silicon. So beyond voltage, current and temperature, you're limited by the silicon itself.

I stopped overclocking systems after Athlon XP. This is why I gave that example.

Even without overclocking and overheating, I've seen and still seeing partially cooked processors which shut-down half of their FPU pipelines to stay reliable albeit with orders of magnitude lower performance.

CPUs are much more complex with their MCE and more advanced microcode structures ever, and there's much more than meets the eye.