The data suggests Apple reduces the speed of the processors in iPhones with old and worn batteries, making them slower. The same was seen with tests run on the iPhone 6S running iOS 11.2, which was released in December 2017. Poole wrote: “The distribution of iPhone 6S scores for iOS 10.2.0 appears unimodal with a peak around the average score. “The distribution of iPhone 7 scores under iOS 10.2.0, iOS 10.2.1, and iOS 11.1.2 appears identical. Some have speculated that Apple dynamically reduces performance of older iPhones in relation to both battery wear and current charge.

Source: The Guardian December 19, 2017 14:01 UTC