iPhoto: A Case Study in Why More CPU Performance is Important In our section on iPhoto we mentioned just how frustratingly slow the app can be when attempting to use many of its editing tools.
In profiling the app it becomes abundantly clear why it's slow. Despite iPhoto being largely visual, it's extremely CPU bound. For whatever reason, simply having iPhoto open is enough to eat up an entire CPU core. Perhaps this is why Apple forbids the application from running on a first generation iPad, with only one CPU core
Use virtually any of the editing tools and you'll see 50 - 95% utilization of the remaining, unused core. The screenshot below is what I saw during use of the saturation brush:
The problem is not only are the two A9s not fast enough to deal with the needs of iPhoto, but anything that needs to get done in the background while you're using iPhoto is going to suffer as well. This is most obvious when you look at how long it takes for UI
elements within iPhoto to respond when you're editing them. It's very rare that we see an application behave like this on iOS, even Infinity Blade only uses a single core most of the time, but iPhoto is a real exception. I have to admit, I owe NVIDIA an apology here. While I still believe that quad-cores are mostly unnecessary for current smartphone/tablet workloads, iPhoto is a very tangible example of where Apple could have benefitted from having four CPU cores on A5X.
Even an increase in CPU frequency would have helped. In this case, Apple had much bigger fish to fry: figuring out how to drive all 3.1M pixels on the Retina Display.