Xcode4.2 app generation supports older iOS devices

First, let's talk about the differences between armv6 and armv7:

What is armv7?
It's a new CPU architecture of iPhone. Make some apps run faster.

What does armv7 to do with me?
Here is a post by most_unique found on iphonecake.

Most apps today use fat binary which cracked on armv7 device will not work on armv6 device.

• Armv7: iphone4, iphone4s, iPad, ipad2, iPhone 3gs, iPod 3G
• Armv6 machines: iPhone 2g, iPhone 3G, iPod 1g, ipod2g

To run on an old machine, for example, iPhone 3G, armv6 must be supported.

By default, only armv7 is set for ubuntures in xcode 4.2.

Solution: Set ubuntures to armv6 armv7,

Before modification:

After modification:

In this way, the generated IPA installation package supports the old iOS devices.