IOS Color band question

In this thread

:
http://forum.unity3d.com/threads/115263-Banding-on-the-iPhone?highlight=color+banding

somebody says that "Posted: 12:15 PM 4 Weeks Ago
Besides this, using a 32bit frame buffer will help with other color banding issues, for example when using anti aliasing "

I just want to know where the "32bit frame buffer " is?

Xcode ?or Unity3D Pro ?

Thats a checkbox in your ios playersettings