( 3GS )Difference Between Old Bootrom and New Bootrom

Finding the Bootrom version is very easy as it is included in the serial number and model number of your iPhone.

• Serial Number: If the second character of the model number of your iPhone 3GS is “B”, Such (MG/MB) then it is uses the old bootrom. If it is “C”, like as (MC) then it runs on the newer bootrom.
• Model Number: The third digit of the serial number of your iPhone indicates the year it was released in (9 for 2009). While the fourth and fifth are dedicated to the week it was made in. Any iPhone made on or after Week 45 of 2009 runs on the new bootrom.