The new NOR chip which is mass produced by Intel/Numonyx has the model of either 36MY1EH or 36MY1EF , it's not compatible with iPad baseband 06.15.00,it's same type of chip used on iPhone 4.
You can check this by looking at your iPhone 3GS serial number :
The 3rd,4th and 5th digital of the serial number represent the week and year the logic board was produced.
3rd digit : year .
4th and 5th digits : week
For example , if your number is : xx129xxxxxxxxxxx so your logic board was produced in year 2011,week 29th - not compatible with iPad baseband .
Or use iPhone tools like idetector By: snowbreeze whitesatan iRt iphoneYeta ichecker By:chevli etc.
100% Safe procedure Before proceed Update iPad baseband 6.15 better to dismantle PHone & check Ic value.
NOT Safe new NOR Radio IC Value 36MY1EH or 36MY1EF
NOT safe Numonyx NOR 36MY1EF same NOR ic Of iphone4 image sample HERE
NOT Safe 36MY1EH No image
Safe NOR Radio IC 36MY1(EE) and spansion TesteD By:NAVSTER
EE & SPANSION
TNx to iRT family and NAVSTER for INFO.HAPPY Unlocking.