Xbox 360's backwards compatibility

So around about E3 time, we ran this story. As you can see from the update on it, the report was

bogus.

Well now comes some more news on the subject. Since the consoles don't share a common chipset, Xbox titles will have to be run in emulation. Some engineer types have said that getting XBox titles running on 360 is impossible. Microsoft themselves have simply said that top games will run. Microsoft's word is that five to twenty titles will run on launch day.