Chip designer Advanced Micro Devices said Wednesday its board has approved a new $6 billion share buyback program, boosting its total repurchase authority to about $10 billion.

Shares of the Santa Clara, California-based company extended earlier gains, rising as much as 6.4% in premarket trading.

"Our expanded share repurchase program reflects the Board's confidence in AMD's strategic direction, growth prospects, and ability to consistently generate strong free cash flow," AMD Chief Executive Lisa Su said in a statement.

The buyback program has no termination date, the company said.