Samsung recently raised eyebrows by beefing up its team of Texas-based chip designers, including those whose backgrounds pointed to an interest in chips for server systems. Now one of the most prominent of those recruits has left the South Korean company for Apple.

The gadget maker has hired Jim Mergard, a 16-year veteran of Advanced Micro Devices who was a vice president and chief engineer there before he left for Samsung. He is known for playing a leading role in the development of a high-profile AMD chip that carried the...