Advanced Micro Devices on Wednesday announced a new $6 billion stock buyback plan, joining a string of chipmakers that are looking to reduce their float as the AI trade that has powered their shares shows some signs of slowing. Shares of the Santa Clara, California-based company rose as much as 6.4 per cent. Its shares have fallen more than 6 per cent so far this year, compared with a less than 1 per cent drop for the benchmark Philadelphia Semiconductor Index. The buyback, which boosts its