** Advanced Micro Devices' AMD.O shares fall 3.5% to $533

** CEO Lisa Su says Helios, AMD's second generation of AI servers aimed at rivaling Nvidia's NVDA.O flagship products, is in full production and will ship in the coming months

** Adds that Helios shipments are slated to start at the end of the third quarter

** Emarketer analyst Jacob Bourne attributes drop in shares to overall weakness in the U.S. stock market and a selloff of semiconductor stocks

** As of last close, AMD had soared 158% YTD