> Powering something off of any old USB port means it would have to fit within the 5V 500mA basic specification, which the Raspberry Pi 3 exceeded long ago.
Theoretically, devices like the iPhone have lower power consumption than that and loads of performance features like recording 4k 120fps video.
Of course, an iPhone costs much more than a RPi, and has much better economies of scale, so they’re not truly comparable.
> Theoretically, devices like the iPhone have lower power consumption than that and loads of performance features like recording 4k 120fps video.
iPhones use cutting edge (expensive) manufacturing processes for their chips.
They also have batteries inside to cover the power demands while doing intense work like recording 4K 120fps video.
I don't understand what point you're trying to make. The Raspberry Pi is not in the same class of device as an iPhone.
An iPhone will absolutely draw more than 2.5w under load.