Nintendo has grown up a bit — 48 bits to be exact. The video-game pioneer releases its new system, Nintendo 64 ($199.95), and the first two game cartridges for it on Sept. 29. The company, which launched its original 16-bit Super Nintendo in 1991, hopes the sleek new machine and superb initial games, Super Mario 64 and PilotWings 64 ($69.95 each), will make the 32-bit Sony PlayStation and Sega Saturn seem like vestiges of the Eisenhower administration. Faster and graphically buzzed, N64 sets the bar several notches higher: A curvaceous, highly sensitive joystick can make Mario tiptoe past a snoozing man-eating plant — or run at lightning speed. The flight simulator PilotWings 64 offers the same precise control over a hang glider and other craft. Still, Sony’s and Sega’s software libraries dwarf N64’s paltry offerings and have many competitive titles. Expect a blizzard of hype at Christmas.