I'VE EXTOLLED the virtues of quality power supplies so many times that saying they're the most often overlooked PC component feels like a cliche. But it's true. In my experience, poor quality generic-brand power supplies are often the root of PC stability problems. Also, as new processors and graphics cards demand more power than ever before, quality power supplies are becoming more important.

But what makes a good power supply, anyway? Most assume that power supplies carrying higher wattage ratings are superior, but as the collapse of the so-called "megahertz myth" illustrates, higher numbers aren't always better. First and foremost, a power supply should deliver clean, consistent power to system components. Power supply efficiency is also important; an efficient power supply can save you money on every electricity bill, especially if you have your system running 24/7. Environmental variables like temperatures and noise levels matter, too.

Armed with a couple of test systems, temperature probes, noise level and power consumption meters, an oscilloscope, and an all-important bathroom scale, we can test all those metrics, plus a few others, ourselves. There's no need to rely on manufacturer spec sheets, marketing claims, or wattage ratings. Are cheap, generic power supplies really that much worse than high-end models that cost twice as much, or more? And among those high-end power supplies, is there really much difference from manufacturer to manufacturer? Let's find out.