SUNNYVALE, CALIF. -- In Silicon Valley, the signs of change are everywhere. Most of them say, "For Rent."

This high-technology center 50 miles south of San Francisco has been battered by competition from Japan and, until recently, by a slump in sales of semiconducters -- the thumbnail-sized chips of silicon, packed with electronic circuitry, that are the brain cells of modern business equipment, consumer electronics goods, telecommunications systems and military weapons.