Add AMD to the list of tech companies diving into a new transition period of leadership changes and reorganizations.

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The processor maker just announced it promoted chief operating officer Dr. Lisa Su to the roles of president and chief executive officer.

Su replaces Rory Read, who has served as AMD's CEO since 2011, effective immediately.

An exact reason for the shuffle has not been revealed, although Read will remain at AMD -- at least in an advisory role -- through the end of 2014.

AMD's chairman of the board Bruce Claflin elaborated in a statement, "Leadership succession planning has been a joint effort between Rory and the board and we felt that Lisa's expertise and proven leadership in the global semiconductor industry make this an ideal time for her to lead the company."

However, AMD shareholders appear to be a bit unnerved by the news. Shares tumbled between roughly three and six percent in after-hours trading.

Su joined AMD in 2012, serving as senior vice president and general manager for AMD's Global Business Units, responsible for the company's product strategy, product definition and business plans. 

As COO, Su was tasked with integrating AMD's business units, sales, global operations and infrastructure enablement teams into a single organization responsible for all aspects of product strategy, product execution, sales and operations.

Prior to joining AMD, Su joined at Freescale Semiconductor in 2007, serving as chief technology officer as well as senior vice president and general manager for networking and multimedia.

Before Freescale, Su spent more than a decade at IBM in various engineering and business leadership roles, including vice president of the Semiconductor Research and Development Center involving IBM's silicon technologies, joint development alliances and semiconductor R&D operations.

Su was also a member of the technical staff at Texas Instruments in the Semiconductor Process and Device Center.

Image via AMD