Though it looks like a toy, don't be fooled: the Nintendo GameCube is a powerful video game console that rightly deserves its place among the other next-generation game systems. In fact, its playful, appealing design and small size (the unit is a not-quite-cubed 6 inches) aren't the only features that set it apart from the others. For starters, Nintendo has quite clearly made this a game-only machine. It doesn't try to play your CD collection, run your movies, read your e-mail, or store your MP3 files. The company has concentrated its efforts on games. All the prelaunch titles we've seen play smoothly, with bright, fast graphics and great sound. Nintendo says its engineers have removed traditional bottlenecks that have, in the past, slowed down processing. New components designed by IBM and MoSys, as well as a large-capacity secondary memory cache, keep instructions moving through the system's microprocessor (MPU) at peak levels. Minimize