According to the official document of SDK from Apple, the iPhone SDK does not support the MAC compower with a PPC cpu.

That means I can't develop iPhone application by my powerbook. Sign. It makes me to think whether I need purchase a new MBP even MBA. Surely another choice is to run a Hackint0sh on an X86 box.

The good news is coming today from iPhond unoffical SDK's mailing list. Someone found he can just move Aspen.platform to /Developer/Platforms to work around that. How excite to me, so I just do it tonight. Compile a sample project and run it on iPhone Simulator. It works well. Only exist issue I know is there is no "Cocoa Touch" in new project list.