Your iPhone is about to become a lot slower as Apple flips the switch to dim the performance of its older phones to make you buy the new model that is just about to be released. At least that is what the conspiracy theorists would have you believe. Is there any truth in this? Does Apple make your iPhone slower when new ones are released? Yes, but not by flipping a switch.

This is not a deliberate act by Apple, it is just inevitable that iPhones, and iPads too, slow down over time. One of the causes of the slowdown problem is that every year Apple releases a new version of iOS. This year we will have iOS 8, last year it was iOS 7, and iOS 6 was the year before that.

Each new version of iOS adds a lot of new features to the phone and these require extra storage space, extra processing power, extra memory to run and so on. This means that with each new version of iOS installed on your phone, the hardware is having to do more work. New phones have faster hardware and this balances the extra work required by the new version of iOS, which means that they don't slow down, but existing phones are just having to work harder and harder.

This year iOS 8 will be released and it will run on the iPhone 4S and later, but you have to remember that the iPhone 4S was never designed to run iOS 8 and it shipped with iOS 5 which had far fewer features and required less processing power and memory to run. It is unlikely to run as fast on old hardware as the iOS it came with.

If you performed a backup of the iPhone 4S on the day you got it, and then restored it today, it would run as fast as it did back then.

Of course it is nice to have the latest version of iOS running on your iPhone, but before you upgrade you should be aware that it will slow down your device because of the extra work running all those great new features. Do you want features or speed? The only way you can have both is by buying a new iPhone because the new hardware is much more powerful than previous generations of the iPhone.

Another cause of the 'iPhone slow' problem is increasingly complex apps. As developers pack more features into apps, they become larger and require more memory and processing power to run. You can see this most clearly with arcade action games that push the device to its limit. Modern games require more processing power than older ones.

The final reason why the iPhone slows down is because of all the junk that fills up the system. You cannot see it, but you will have seen a similar thing on your computer where the disk accumulates temporary files, software that wasn't completely uninstalled and left behind files and settings, and so on. File clutter builds up over time and slows down the system - on phones as on computers.

Apple does not need to flip a switch to slow down old iPhones and prompt users to buy the latest one, because iOS updates, larger more complex apps, and filing system junk will see to that.