In our experience, NVIDIA pushes the AGP power requirements of the GeForce right up to the maximum the AGP bus was designed to handle. Many motherboard makers design their boards right down as close to the AGP specifications as possible in order to save money.
But when you factor in variance between boards for mass production, you're going to get GeForce video cards that require more power than the AGP spec, and you're going to get motherboards that can't quite make the spec. This is a recipe for disaster.
And it is a problem we have experienced with some GeForce video cards. Under heavy usage, they can draw a tremendous amount of power. One source told us that a GeForce is capable of drawing 10A over the 3.3V AGP bus, or 33W. When you consider that your AGP card is usually sharing motherboard power with all of your PCI and ISA cards, problems become more than just a possibility. With some boards, AGP can only run at 1X or you have to disable certain functions in order to run stably. The worst case scenarios include not being able to boot with a GeForce or crashing whenever you load up a 3D game.
Since ASUS boards have consistently been among the most stable there are, we consider them in a position of authority on the subject. So we asked ASUS how they were handling the problem. Their answer was quite simple. They make their traces wider and keep them from becoming too long. Wide, short traces allow the power to flow easier, giving your GeForce enough power.
A simple answer, but don't knock it, it works.