xCode 4.0.2 how to run for 3.x simulator

i downloaded xCode 4.0.2 (Build 4A2002a) on my mac, and i want to test my program on old iOS (like 3.1.3)

I try开发者_开发知识库 many options in sdk menu, but nothing work.

Is there any way to run old iphone simulator on new sdk

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No. I think Apple want to encourage developers to adopt new versions of iOS as quickly as possible, so they only go back as far as they think they need to. That seems to be 4.0 in the current downloads (as of June 2011).

To be fair, though, there is no substitute for testing on real hardware. Remember it's a simulator not an emulator. There are differences that you're not going to spot if you rely too heavily on the Simulator.