The latest MacBook Air and MacBook Pro are powered by Apple's M1 chip, so they run cooler and quieter than their counterparts with Intel inside. So what does it take to rev their fans? WSJ's Joanna Stern tries to turn up the heat with some punishing tests. Photo illustration: Preston Jessee for The Wall Street Journal More from the Wall Street Journal: Visit WSJ.com: http://www.wsj.com Visit the WSJ Video Center: https://wsj.com/video On Facebook: https://www.facebook.com/pg/wsj/videos/ On Twitter: https://twitter.com/WSJ On Snapchat: https://on.wsj.com/2ratjSM #WSJ #Apple #MacBook