Imagination’s chart for the Series 7XT GPU puts a hypothetical 12-core design in the same general performance neighborhood as an Nvidia GeForce GT 730M, a low-end discrete GPU that’s a bit slower than the stuff Apple is shipping in its high-end MacBook Pros. Our own graphics benchmarks place it a bit higher than that, but as some of you have pointed out, iOS may have a small advantage in some of these tests because of differences between the mobile OpenGL ES API in iOS and the standard OpenGL API used in OS X.
He also mentions the probable cause for the lack of an L3 cache.
Quite frankly, I’m a bit surprised it’s as fast as it is in benchmarks, because it doesn’t feel that fast — many animations which are as smooth as silk on the iPad Air 2, stutter on the Pro. Apple obviously needs to further optimise iOS for the new screen size and resolution.