[damien]

Are you sure? The article doesn't seem to say whether it's a hardware or software issue, and the iphone's hardware parts aren't exactly secret proprietary stuff... I mean the Galaxy S4 is supposed to have the better PowerVR GPU for example. I'm thinking the difference is in the software stack, I think you'd be surprised at how much code gets run between the time there's an input event and an app reacts to it on the screen.

Anyways, it'd be interesting to know if running Android on an iphone showed the same delays.

[mdwrigh2]

I mean, fundamentally it's both. Touch controllers and their firmware can add 15-45ms of latency based on their technology (hardware) and the quality of their filtering in the firmware (software). On the other side of the spectrum it's all about fill-rate, inherent latency in drawing pipeline, whether the input dispatching is phase locked with the display refresh, etc. etc. Again, some of this is software, some of it is hardware, but most of it is directly tied to the specific device. The actual input pipeline on Android, once you get out of the touch controller, is pretty negligible today (<1ms from touch controller interrupt until the application receives the input event).

[modeless]

The hardware that matters here is not the GPU. It's the touchscreen controller, the display controller, the associated firmware, and to a lesser extent the drivers for those. All either Apple proprietary or heavily customized.

[mdwrigh2]

The GPU can matter as well. On the Nexus 10, for example, the fill rate is pretty low compared to the screen size, so applications have to be very very careful not to exceed the limit or they'll end up adding frames of latency (which looks like touch or interaction latency).

But in general you're right, those are the components that contribute the large majority touch latency to a device.