While Apple normally tries to extend the software love as far back as it can, there’s inevitably some devices that miss out.
Here’s the full i OS 9-friendly list: i Phones: i Phone 4S, i Phone 5, i Phone 5C, i Phone 5S, i Phone 6, i Phone 6 Plus, i Phone 6S, i Phone 6S Plusi Pads: i Pad 2, i Pad 3rd gen, i Pad 4th gen, i Pad Air, i Pad mini, i Pad mini 2, i Pad mini 3, i Pad mini 4i Pods: i Pod touch 5th gen Devices that miss out include the i Phone 4, but amazingly the i Pad 2 is still in the mix.
This method is definitely the easiest, but it could take a long time.
On major launch days like today, Apple's servers can become overwhelmed by the number of users attempting to update their devices.
The tricky bit is that the GPU is much more powerful than the i Pad 2 and i Phone 4S (mainly so it could drive the extra pixels), but the CPU is more or less the same — a 1GHz dual-core based on the ARM A9 design.
In fact, it’s the first version of Apple’s operating system made available for the public to try before its launch.Make sure you are connected to Wi-Fi and running the latest version of i OS -- i OS 8.4.1.Then head to Settings, select General, followed by Software Update and click the Download and Install button.In the past, battery problems have occured immediately after new software releases are common.They normally settle down after subsequent updates, or after a hard reset, but it might be worth waiting a few days before updating if you want to be careful.