Federal Reserve chair is under bombardment from Donald Trump and battling an insurgency within the central bank

The U.S. dollar hovered below a one-week high on Thursday and Asian stock markets were broadly mixed as investors braced for three days of potentially market-moving news from the Federal Reserve's annual symposium in Jackson Hole.

The Nasdaq fell as megacaps lost, after having rallied for much of the year. Nvidia fell 3.5%, the biggest drop in nearly four months.