Geekbench Founder: iPhone Battery Health Does Impact CPU Performance

When an iPhone ages, we expect its battery performance to decrease – that is something that is generally accepted about all smartphones, tablets or anything else that uses batteries that are rechargeable.

The more a battery is charged and discharged, the shorter it lasts on a single charge. What we might not always expect, however, is for an iPhone’s old battery to impact CPU performance. That does, however, appear to be the case after a report last week suggested that an iPhone 6s with an old battery could see improved performance when that battery is replaced.

This, and a lengthy Reddit thread with a mind boggling number of comments, got Geekbench founder John Poole wondering and he has since posted on the subject. With some users noting that Geekbench scores were reduced when using an older battery and then that they increased following that battery’s replacement, it was clear something was amiss.

While Apple acknowledged that there was a battery issue with the iPhone 6s to the point of releasing a software update to address it by dynamically changing the maximum speed of the CPU depending on the amount of battery power left, this has the effect of potentially leaving users with devices that performed sub-optimally, often without their knowledge as to why. This, as Poole points out, could see users replacing devices sooner than required because their iPhones were deemed to be exhibiting performance issues.

If the performance drop is due to the “sudden shutdown” fix, users will experience reduced performance without notification. Users expect either full performance, or reduced performance with a notification that their phone is in low-power mode. This fix creates a third, unexpected state. While this state is created to mask a deficiency in battery power, users may believe that the slow down is due to CPU performance, instead of battery performance, which is triggering an Apple introduced CPU slow-down. This fix will also cause users to think, “my phone is slow so I should replace it” not, “my phone is slow so I should replace its battery”. This will likely feed into the “planned obsolecense” narritive.

As that last line eludes, plenty of people already believe that Apple cripples older devices on purpose in order to get users to upgrade sooner than they normally would. This news will be music to their ears and will surely only go to strengthen that belief.

Also relating to this finding is developer Guilherme Rambo’s discovery of the “powerd” process introduced in iOS 10.2.1, which controls the performance of the CPU, and is most likely what is responsible for reducing it in cases where degraded battery performance is detected.
(Source: https://www.geekbench.com/blog/2017/12/iphone-performance-and-battery-age/, https://twitter.com/_inside/status/942847979991523328[Twitter])