In primitive circuit boards, keeping the clock signal consistent across the board was a problem. But there you had pretty significant dimensions. With the chips you can bring the clock in at a lot of different points, so you can keep it pretty well synchronized. It requires good engineering. A lot of things become headaches.
Power is at least as big a concern.
In two generations of technology, say from half micron to quarter micron, that's two steps down, to 50 percent of the starting size. When you look at the trends of making bigger chips, with more complexity and jacking up the clock speed, if you don't do anything else, the power goes up something like 40-fold. It'll keep your lap warm, all right. So that is an area that really requires a lot of attention. And, of course we've handled it to date by lowering the voltage.