Chip Warnings Weigh

Updated from 12:46 p.m. EDT

Advanced Micro Devices(AMD Quote) was down over 20% after disappointing investors with weak preliminary fourth-quarter revenue figures, as accumulating negative news began to drag down an already-weary sector.

AMD's announcement followed a warning after the bell Monday from STMicroelectronics(STM Quote), Europe's second-largest chipmaker.

Both of these announcements precede financial results from Intel(INTC Quote), the world's largest chipmaker and AMD's prime competitor in the market for computer microprocessors and flash memory. Intel will post its results after Tuesday's closing bell. Amid the dark clouds of AMD and STMicro, Intel shares were recently down 36 cents, or 1.6%, to $22.52. ...