While average power draw for a given task for mobile chips has stayed similar or declined over the last few years, peak draw has gone through the roof. It's quite plausible that the iPhone 5's SoC just never drew enough power at peak for this to be an issue.

Normally this sort of issue is solved with a capacitor network. It's actually common to get them removed during a "cost optimization" stage because the device will still appear to work. Just with grately reduced reliability.

Any capacitor network will need some power to stay charged waiting for use. If peaks are rare enough, they won't be a reasonable choice.

The root of the issue is that the internal resistance of the battery is too high to supply current under peak load to the device. Anyone creating an electronic device has to perform these calculations and design a power supply that is sufficient. Its basic electrical engineering.

For extremely short duration peaks up to a few microseconds capacitors are a great workaround. They are necessary for pretty much every digital integrated circuit. A billion transistors all switching at the same time on the rising edge of a clock cycle has a massive instantaneous current draw.

> Anyone creating an electronic device has to perform these calculations and design a power supply that is sufficient.

Yes. And it does look like a case of undersized batteries. If I had to guess, I'd say it was because of too strict product design specifications meeting a lower than expected quality in manufacturing.

CPU power peaks usually last for a (large) fraction of a millisecond or more, because that's how the OS scheduler works. Added to that, peaks may not happen for entire minutes or hours. Both of those work against the usefulness of large capacitor banks.

Apple (like other manufacturers) is continually looking for ways to improve performance, whether that be cpu speed or battery life, or other metric. I don't think this has anything special to do with a particular model, only when they decided to deploy this particular feature.

It's extremely suspicious this coincided with a massive battery recall that caused unexpected shutdowns.

I'm not sure if I follow you here, particularly the use of "extremely suspicious", which makes me think that you believe something underhanded is going on. If so, would you just come out and say it? Innuendo doesn't generally promote useful discussion, and it's even harder on an online forum. Was this something you were thinking about when you wrote your initial comment? If that's not the case, please forgive me. I assumed your initial comment was a legitimate question, and answered in good faith.

If they are related (and perhaps they are, I wasn't thinking about the recall when I wrote my comment), do you think it's unreasonable for engineers at Apple to try to prevent unexpected shutdowns? I would think it would be unreasonable not to, once they saw the impact it was having on user experience. And that's besides improving the battery. The amount of engineering that goes on with respect to power and performance management is incredible, and attacking these types of problems from multiple angles is expected, particularly when you're looking to eek out even more performance in something that's already been through years of optimization iterations.

To be explicit I think this was done to limit the scale of the recall. I think the design flaw exists in all the phones not just the subset they identified.

Apple knew the peak draw of their SoC (they designed it). And they knew the capabilities of the battery. Under sizing the battery is exactly what I would call a design flaw.

This certainly seems to be the case from my experience. Same thing they did for previous recalls on MacBooks.