I copied a voltage table from an OC kernel for Samsung Galaxy SL i9003 on xda developers, this phone as well used OMAP 3630 processor. Frequency used the voltage value listed below can enjoy a stable overclock.
CPUfreq >>>>>>> Voltage used

120 MHz >>>>>>> 840000
300 MHz >>>>>>> 1000000
600 MHz >>>>>>> 1162500
800 MHz >>>>>>> 1300000
1000 MHz >>>>>>> 1350000
1100 MHz >>>>>>> 1370000
1200 MHz >>>>>>> 1380000
1300 MHz >>>>>>> 1455000
1350 MHz >>>>>>> 1485000
1380 MHz >>>>>>> 1500000

I am now having one more concern, apart from overclock, is this possible to underclock to 120 Mhz to save battery?
Does N9 have the CPU governor to force the phone stay on lowest frequency when stand by ?

Xda thread: http://forum.xda-developers.com/showpost.php?p=24802553&postcount=1385

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