[MonoTouch] Startup times: nib vs. nib-less [was Re: Can I show splash image within a second?]

[Shawn Hempel]

I was discussing this with a friend of mine and he pointed out that Apple
has made some big changes between iPhone versions in its handling of ARM
Thumb mode <http://en.wikipedia.org/wiki/ARM_architecture#Thumb>. Whether or
not that is the primary reason for the change in app startup performance
between the 2G and 3G is unclear - although it seems you could test that
theory by unchecking "Compile for Thumb" in XCode's build options and
re-testing on both platforms. With the 3GS, the instruction set was expanded
to include Thumb-2
<http://en.wikipedia.org/wiki/ARM_architecture#Thumb-2>which supports
limited floating point operations and is generally less
problematic than the old architecture for mixed Thumb/ARM instructions.
Building for "Optimized" in XCode produces a fat binary which will use
Thumb-1 for 2G and 3G phones and Thumb-2 for 3GS.

I have no idea how any of that translates to MT because I haven't looked at
the build switches it uses against the native code.

- Shawn


On Fri, Nov 27, 2009 at 7:02 PM, Rory Blyth <lists at rory.me> wrote:

> The fact that performance seems to be better on a 2G (and, as you probably
> saw, Ed feels the same way you do) is disturbing. Only because I have a 3G.
> If I didn't have a 3G, I'd think, "Well, this really sucks for people with
> those garbage 3G models."
>
> But I *do* have a 3G. So, instead, I think, "Drat."
>
>
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