This is the device in the iPhone and iPad that manages all the functions which require an antenna. The baseband processor has its own RAM and firmware in NOR flash, separate from the ARM core resources. The baseband is a resource to the OS. The Wi-Fi and Bluetooth are managed by the main CPU, although the baseband stores their MAC addresses in its NVRAM.
The iPhone's baseband processor is the S-Gold 2. The iPhone 3G, the iPhone 3GS and the iPad make use of the X-Gold 608 chip for this purpose. The iPhone 4 (iPhone3,1) and iPad 2 (iPad2,2) use the XMM 6180, while the iPhone 4 (iPhone3,3) uses the MDM6600 and the iPhone 4S uses the MDM6610. iPad (3rd generation) uses MDM9600. iPad (4th generation), iPad Air , iPad mini, iPad mini 2, iPad mini 3, iPhone 5, iPhone 5c and iPhone 5s use MDM9615 while iPad Air 2, iPad Pro (12.9-inch), iPad mini 4, iPhone 6, iPhone 6 Plus and iPhone SE use MDM9625. iPhone 6s, iPhone 6s Plus and iPad Pro (9.7-inch) use MDM9635.
This is the area in the baseband where the lock state is stored.
0x400--NCK token 0xA00--IMEI signature 0xB00--IMEI 0xC00--Locks table
PMB8876 S-Gold 2
PMB8878 X-Gold 608
XMM 6180 X-Gold 618
PMB9943 X-Gold 736