I want to do a technical analysis on the big issue of iOS slowing down our phones every year.
Let's debunk some myths about iOS planned obsolescence.
1) every new iOS version gains a lot more features. This is why it slows down.
More features generally do not slow down an OS. Let me explain.
Think about a feature as a separate tool. It does one function. If I have many separate tools, why should that affect the performance of a completely unrelated tool, such as scrolling? It can be understandable that the new features are slow on older iOS devices, but existing, unchanged features should be just as fast as before.
Scrolling is the same from iOS 1 to now. It is an act of moving pixels from the left or right with some physics added as well. These calculations are the same, no matter how many features you have. iOS was smooth from iOS 1, not just smooth, it was PERFECTLY smooth no matter what. Think about it, Apple perfected scrolling on hardware hundreds of times *slower* than current iPhones.
Windows 8/10 is a fantastic argument of this.
Windows 8 and 10 has *far* more features than Windows 7. It added animations that simply weren't available in Windows 7. Yet, both OS are subjective *and* objectively faster than Windows 7. In fact, it is much faster subjectively than Windows 7. Oh and the animations? They are perfectly smooth running on an extremely underpowered Intel Atom CPU on a netbook. Windows managed to add a ton more features and animations while speeding up!
2) The new features take more resources on the phone, so it slows down.
Let's see why that's wrong. Say if the new features took up so much of the phone's resource that it caused the animations to lag. Let's assign an arbitrary number, say animations needs 80% of the CPU to be smooth, and the new features now take up 30% of the CPU, so now the animation can't get the full 80% of the CPU it needs to be smooth.
This cannot be true. To achieve iPhone's current battery life, the CPU of the phone must be kept at the lowest power state to conserve power during standby or idle times. This usually means keeping the CPU below 2-3% usage most of the time. Going to even 5% CPU utilization is a large bump to the power state that greatly reduces battery life. This is why iOS heavily limits what apps can do in the background because just a bit of background usage can be a huge battery drainer.
Therefore,
any features that take up background resources must be very, very small, otherwise there is a HUGE impact on the battery life. And this is why the argument new features take more CPU resources does not hold.
Now some arguments for planned obsolescence.
1) How is it possible that the exact same actions, such as scrolling, or other UI animations, starts to lag in a new iOS? When they introduced parallax in iOS 7, those are different animations, then there is a case on why it might lag on older devices that can't handle the blur and physics as well. But simple UI animations that have been around since iOS 1 should never lag. It is doing the same thing.
2) Say if the lags were actually because the code is so unoptimized that the hardware isn't powerful enough to support it, this means the CPU is being maxed out while doing these tasks. Then why isn't there a HUGE drop in battery life between smooth and laggy iOS versions?
3) How is it possible the keyboard lags on older iOS devices? The keyboard is an incredibly lightweight program. The most it does is some spell check. How is it possible that it takes a few seconds to load the keyboard and have the keys not keep up with my typing? Why? Because keyboard lag is extremely noticeable to the user, and it pushes them to buy new devices to return to the previous swift speed.
4) Have you ever used old iOS devices on old iOS versions? Check out the video of the iPhone 4S on iOS 5 vs iOS 8. Everything on iOS 5 shows up instantly, just as fast as the latest iPhones.
I have an iPad 3 on iOS 7. The speed is unbelievable. If iOS was not purposely slowed down on older devices, there is actually very little reason to upgrade iPads. While there are often very nice hardware improvements on the iPhone that's worth upgrading to, people would experience very few speed improvements over new iPhones because they were so fast to begin with. And honestly, it doesn't take much chip power to make UI's fast and smooth. Apple demonstrated UI animation perfection from iOS 1 on the original iPhone's absolutely pathetic hardware. There should be no reason an iPhone with a CPU over 100x faster cannot do perfectly smooth animations.