|OK The clue is the power grid and the danger of fluctuating current. Hold up time is controlled by capactors in the psu and has an industry standard of at least 16 milliseconds.|
If hold up time is less or non existant, then yes, vCore and all other rectified voltages can fluctuate...either up or down. I doubt too much hold up time would hurt anything.
It's impratical to try and fix the psu if hold up time is a problem. Hell, it's impratical to determine if hold up time is the problem, You'd have to locate the banks of capacators and test 'em to see if they were doing their job. Normal folks just don't have the time and thousands of dollars to spend to fix a $50 psu.
So, the practical fix for suspected hold up time errors is to run out and buy a quality power supply. Same applies if the power good signal is timed wrong. You can only suspect something like that by the symptoms and I don't think I'd be very good at changing a power good signal to kick in one or two milliseconds earlier. We have no way to even properly check amperages on the various rails...that takes a lab and the equipment runs into six figures.
So hold up time gives the psu time to try and process voltage and current fluctuations. Changing old or out of spec capacators will fix it, changing capacator values would fix it too. That's all a job for the engineers who design this stuff though. In this case the wisea$$ answer is also the practical answer.
"Run out and buy a new psu."
If you google for a few minutes, you'll find sites all over the place that discuss the differences between cheapo and quality psu's, single rail vs multi rail psu's, modular vs non modular psu's, test methods, wattage rating flim flam, and so forth.