Linked by Thom Holwerda on Wed 20th Dec 2017 17:36 UTC

A Reddit post from last week has sparked a discussion regarding iPhone performance as a function of battery age. While we expect battery capacity to decrease as batteries age, we expect processor performance to stay the same. However, users with older iPhones with lower-than-expected Geekbench 4 scores have reported that replacing the battery increases their score (as well as the performance of the phone). What's going on here? How many phones are experiencing decreased Geekbench 4 score?

To answer these questions I've plotted the kernel density of Geekbench 4 single-core scores for the iPhone 6s and the iPhone 7 running different versions of iOS. Scores obtained in low-power mode are not included in the distribution.

Evidence seems to be mounting that Apple is decreasing the clock speed of iPhones with decreased battery capacity to maintain the advertised battery life.

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RE[3]: Known issue
by Tony Swash on Fri 22nd Dec 2017 13:27 UTC in reply to "RE[2]: Known issue"
Tony Swash
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Things like Geekbench may not produce a useful metric in this situation.

What Apple has done is introduce a throttling system used in very specific and episodic situations where iPhones with older partially worn out batteries encounter peak system utilisation (a relatively rare event) which without the episodic throttling could cause the iPhone to suddenly shut down due to lack of power. Once the peak usage passes the throttling is turned off. Most of the time the throttling isn't implemented because most of the time older iPhones with worn out batteries are not being used at full system capacity. Obviously the more worn out a battery is the more like it is likely to encounter an event that requires throttling but even a very worn out battery is highly unlikely to require permanent throttling.

This episodic throttling will almost always show up in benchmarking exercises as benchmarking software is intended to test the maximum system performance and will thus almost certainly trigger precisely the circumstances which trigger the throttling. The benchmarking software does not replicate normal everyday usage.

Edited 2017-12-22 13:28 UTC

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