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That's already been a problem for a long time. When CPU speed changes the transient currents are ridiculous, and the dI/dt is bananas, too. This is one reason why a few generations ago Intel had to go with a fully-integrated voltage regulator. The mainboard people were unable to build good, efficient VRMs off-chip.

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Maybe its not possible to regulate such a high current at gigahertz speeds off chip? The board traces and pins might have inductance high enough to negate smoothing capacitors at these speeds?

Yeah I mean there's no way a part on the other side of a CPU socket is doing anything in the gigahertz range. Those frequencies are covered by layers and capacitors in or on the package itself. What's hard about modern VRMs is being able to step from Icc(max) to zero while overshooting < 25mv, or the forward load step from nothing to ~200A in an instant without dropping. The specs are in Intel's VRxx docs (eg VR13).

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