Investing.com - Strong PC sales are driving demand for AMD's new line of chips, which will boost its profitability in the third quarter, according to Stifel.The Wall Street firm increased its 12-month, stock price target on the chipmaker by about 25% to $21 a share.Stifel singled out demand for AMD's new Zen-based PC CPU, which has a bigger profit margin than other chips.The firm said a higher percentage of AMD's revenue is "transitioning to the Zen-based PC CPU."Stifel forecast AMD's profit margin will rise to 37.7% in the third quarter.AMD shares are up almost 17% in the past 12 months.