Stocks tumbled on global jitters that added to the dollar's rebound Tuesday. The NYSE composite shed 1.4%, hurt by gold, steel and oil-related stocks. The index touched its 50-day moving average but closed just above it. The Dow and the S&P 500 fell 1% each, while the Nasdaq lost 0.8%. Chip issues were one bright spot. The Philadelphia semiconductor index ticked up 0.1%, its seventh straight gain. Volume climbed on both major exchanges. That gave