Updated from 11:58 a.m. ESTSAN FRANCISCO -- New York's attorney general announced Thursday that is it has started an antitrust investigation of Intel ( INTC). Intel was served with a wide-ranging subpoena seeking documents and information as part of an investigation into whether the chipmaker violated state and federal antitrust laws by coercing customers to exclude rival Advanced Micro Devices ( AMD) from the microprocessor market. "After careful review, we have determined that questions raised about Intel's potential anticompetitive conduct warrant a full and factual investigation," said NY Attorney General Andrew Cuomo in a statement. Shares of Intel finished Thursday off 21 cents to $22.54. AMD shares shot up as much as 8.2% at one point, the stock's biggest one-day move since Dec. 14, 2006. The stock later gave up some of the gain, finishing up 44 cents to $5.97. AMD sued Intel in a Delaware federal court in 2005, alleging that the microprocessor giant has consistently abused its monopoly position in the market to prevent PC vendors from using AMD chips. A trial date has been set for April 27, 2009. New York is the latest of several government regulators around the world to look into allegations that Intel has unfairly used its dominance of the PC microprocessor market to sideline AMD. On Monday, Intel filed its response to charges relating to similar allegations brought by the European Commission.