Apple this morning released a new supplemental update to macOS High Sierra 10.13.6, which is designed to address a bug that caused the new eighth-generation quad-core and 6-core Intel processors in the 2018 MacBook Pro models to throttle inappropriately. The new macOS High Sierra update can be downloaded through the Software Update function in the Mac App Store on all 2018 MacBook Pro models. Today's supplemental update (build number 17G2208) is limited to those machines and is not available for other Macs. A direct link to download the update is also available.

According to Apple, the throttling seen in the higher-end 2018 MacBook Pro with Core i9 chip and other 2018 MacBook Pro models is unintentional. The throttling issue first came to light on July 17, a few days after the first new 2018 MacBook Pros began shipping out to customers. YouTuber Dave Lee tested the top-of-the-line 2018 15-inch MacBook Pro with 2.9GHz Core i9 chip using Adobe's Premiere Pro and found that it was underperforming compared to a 2017 MacBook Pro with a Core i7 chip.