Just about all high quality electronic equipment is designed to tolerate fluctuations in power supply voltage. Critical items are almost always designed to withstand "worst case" conditions such as the lowest possible line voltage combined with the greatest load and the highest clock rate or whatever puts the greatest stress on the system. The difficulty with open architecture systems such as PC's is that there are an infinite number of combinations of hardware that make this design process impossible. The identification of the non-workable combinations are what you are paying for when you buy an assembled computer. The problems you experience with instability, lockups, video artifacts, and all the rest of the common complaints are the burden you assume when you decide to assemble your own computer. The proof of the pudding is in the eating. If your system seems to work okay all is wonderful but if it doesn't you're the one who has to find the limits for your combination and find the cure. To make it worse, you can observe the voltage of your power supply going up and down but you can't see how this is affecting the stability and noise tolerance of critical circuits that only a few years ago were impossible to construct at all. A personal computer is a device that very nearly does not work and the fact that it does is a genuine miracle. I have been working in the electronics field for 50 years and every time I turn around there is another startling developement that was impossible only months before. If only you youngsters could realize what you are seeing in a solid state circuit that operates in the megahertz range let alone gigahertz and what you owe to all the engineers and designers that have sweated bullets so you can play games.
