The iOS 9 beta currently includes the ability for developers to cut off older devices from being able to run an app. While iOS 9 will run on any device that is compatible with iOS 8, developers will now be able to restrict their apps only to devices equipped with a 64-bit processor. (A7 and above.)
In fact, with iOS 9, developers can choose to make their apps exclude any non-64 bit architecture. This means all iPod touch models, all iPhones before the iPhone 5s and all iPads before the iPad Air will not be able to install apps where developers have required 64-bit CPUs.
Developers who have complained in the past about supporting older hardware will appreciate this option as a way to simplify development and support for their apps. Any app that has this option enabled, will simply not show up in the App Store for users with older devices.
While iOS binaries can easily be built to support both 64-bit and non-64-bit platforms, developers have been facing a bit of a strain to support both platforms. The image above shows how GPU performance has increased dramatically in the last two generations of the A-series processor.
While this is a welcome feature to developers, users of older devices that can still run iOS 9 will be disappointed to learn their favorite app may no longer be available to them.