One major focus area for this release is to optimize the OS to run faster and consume less memory. An astonishing 30% of the entire engineering budget has been devoted to optimization. That shows, and of special interest is that apps written using Windows 8.1 app model and XAML stack consistently runs 30% faster than apps written using the Windows Phone 8 Silverlight app model. It also consumes significantly less memory. So this will enable programmers to write apps that gives an even better experience on low-end devices like the
Nokia Lumia 520.