Moving from cap-exempt H1 to non-exempt H1

[pradeepkrishnan]

I am right now working for a university in a cap-exempt H1-B. I just started on my H1-B extension. I am planning to change jobs so I will be filing for a H1-B this April (2013). If my petition gets accepted, what would be my earliest start date on the new job would be? Will it be October 1st or can I work with the petition / receipt?

Thanks for you help.