When will Apple unveil ARM-based Macs?

Apple’s new thinner and lighter MacBook Air
Juli Clover for MacRumors:Apple uses an Arm-based architecture for its A-series chips in the iPhone and iPad, and each year, those chips get faster and more efficient. In fact, when introducing the latest A12 and A13 chips, Apple has made it a point to emphasize that these chips are faster than many Intel-based chips in competing devices.The 2018 iPad Pro models with A12X chips, for example, are close in speed to the 2018 15-inch MacBook Pro mode