If you go back to how this was originally discovered, it was in public aggregate benchmarks: https://www.geekbench.com/blog/2017/12/iphone-performance-and-batt

If you go back to how this was originally discovered, it was in public aggregate benchmarks: https://www.geekbench.com/blog/2017/12/iphone-performance-and-battery-age/ https://www.geekbench.com/blog/2017/12/iphone-performance-an... The thing to note here is that even in the charts of older devices, by far the largest peak is at max performance. In other words, most older phones, even running the new code, were not being slowed down when they were benchmarked. There's no evidence I know of that every older iPhone is being slowed down, all the time. Now, I certainly believe it's possible that your phone slowed down across the board after an iOS update, but there are a lot of reasons that could happen. See for example this story, where a customer went into an Apple Store on suspicion of a battery issue, but the performance problems were actually fixed by a backup and restore: http://mglenn.com/blog/2017/12/22/apples-bungled-battery-feature http://mglenn.com/blog/2017/12/22/apples-bungled-battery-fea...