Advanced Micro Devices Inc. overpromised and underdelivered on its last big product launch. It is determined to reverse that pattern this week, with a new chip dubbed Shanghai.

The new member of AMD's Opteron product line, which serve as calculating engines in server systems, is a successor to a chip called Barcelona that was late to market when announced in September 2007 and had early technical problems. AMD's missteps with the Opteron family -- which commands higher prices and profit margins than chips for personal computers -- contributed to big losses for the company this year and helped rival Intel Corp.

So AMD executives said little about Shanghai until customers had tested it. The verdict, so far, seems to be thumbs up.

"We knew the performance results would be good, but they exceeded our expectations," said Paul Gottsegen, a vice president of marketing in Hewlett-Packard Co. 's server business.

Sally Stevens, director of platform marketing at Dell Inc., estimated that Shanghai delivered about 37% better computing performance per watt of energy consumed -- an important issue for customers worried about power bills. Dell, H-P, Sun Microsystems Inc. and International Business Machines Corp. say they plan to offer systems using Shanghai.