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Comment by sp332 | Hacker News Reader

There's a certain amount of lag I can get used to with Android. I noticed that upgrading from 4.1 to 4.2.2 didn't eliminate the lag, but it reduced it to being much more usable. I used a WP8 phone for a while, and I found that even though the swooshy animations can take a relatively long time to complete, it was so responsive in starting an animation that it was hard to go back to Android.

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According to this test WP8 isn't any better than Android. Well, specifically the Lumia 928 isn't any better than the Galaxy S4. Need to be specific about which device, since we're almost exclusively talking about hardware here (touch controller, GPU, and display controller) - the OS isn't doing much.

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.

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.

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.

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).

The test measures the "minimum response time", but I don't think that's the most useful measurement of responsiveness. After all, changing the software does make a difference in how "laggy" the phone seems.

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