How is the iPhone 5 armv7s processor different from its predecessors?

Question

The iPhone 5 is the first Apple device with armv7s processors.

Is the instruction set identical?

What about backwards compatibility? Will the iPhone 5 be able to run apps compiled for the armv6 and armv7 architectures?

Answer 1

AnandTech has an analysis of the new CPU: http://www.anandtech.com/show/6292/iphone-5-a6-not-a15-custom-core

The main difference is apparently that ARMv7s has VFPv4 support (but you should read the full article, it's very thorough).

The cpu is backwards compatible, it will be able to execute apps compiled for both ARMv6 and ARMv7.

Answer 2

This may not be a different processor at all. They may have just started compiling everything for a new mode that has a different ABI. In the Linux world they're doing a similar transition with the move to hard-float (arm7hf).