iOS 9's split-screen feature will only work properly on the iPad Air 2, because it's only one in the existing lineup with hardware capable of supporting it.9to5mac and developer Hamza Sood, however, found proof in OS X El Capitan that Apple's releasing a new iPad mini, and that it will also be capable of supporting split-screen apps. They found a resource file from within the upcoming platform's Safari browser that clearly states that an iPad mini will get "half screen" capability, as you can see below the fold.
http://www.engadget.com/2015/08/12/i...ew-el-capitan/