Originally Posted by Matt D

Some, or all?


Didn't have to get all new apps when the iPad 2 and iPhone 4S went dual-core with the "Apple A5", or when the iPad 3 gained a quad-core GPU with the "Apple A5X".

Some apps did get updated (for free) to take proper advantage of the improved CPU and/or GPU, but there was no general "everything needs to be updated". I don't know how much of it is handled by iOS itself being updated to handled the increased core count.