MDM6610

The Qualcomm MDM6610 is the baseband chip used in the iPhone 4S.

Baseband Firmware
The firmware for the baseband chip comes in Trek-X.X.XX.Release.bbfw files (with X being the version). The BBFW file is just a renamed standard ZIP archive and contains a couple of .mbn files which are all digitally signed with a certificate from Qualcomm. Qualcomm's Senior Engineer Shital Mehta is involved with the programming of the firmware. The amss.mbn file is an ELF file:

Mac OS X file command output
file Trek-1.0.11.Release/amss.mbn /Trek-1.0.11.Release/amss.mbn: ELF 32-bit LSB executable, ARM, version 1, statically linked, corrupted section header size

iPhone 4S
1.0.11   5.0          (Build 9A334) 1.0.12   5.0.1 beta   (Build 9A402) 1.0.13   5.0.1 beta 2 (Build 9A404) 5.0.1       (Build 9A405) 1.0.14   5.0.1        (Build 9A406) 1.2.01-1 5.1 beta     (Build 9B5117b) 1.4.00   5.1 beta 2   (Build 9B5127c) 1.5.04   5.1 beta 3   (Build 9B5141a) 2.0.10   5.1          (Build 9B179) 2.0.12   5.1.1        (Build 9B206) 2.8.01   6.0 beta     (Build 10A5316k) 2.8.04   6.0 beta 2   (Build 10A5336d) 2.8.07   6.0 beta 3   (Build 10A5355d) 3.0.00   6.0 beta 4   (Build 10A5376e) 3.0.04   6.0GM        (Build 10A403) 6.0         (Build 10A403) 6.0.1       (Build 10A523) 6.1 beta    (Build 10B5095f) 6.1 beta 2  (Build 10B5105c) 6.1 beta 3  (Build 10B5117b) 6.1 beta 4  (Build 10B5126b) 6.1 beta 5  (Build 10B142) 3.4.01   6.1          (Build 10B142) 6.1.1 beta  (Build 10B311) 3.4.02   6.1.1        (Build 10B145) 6.1.2       (Build 10B146) 3.4.03   6.1.3 beta 2 (Build 10B318) 6.1.3       (Build 10B329) 4.3.01   7.0 beta     (Build 11A4372q) 7.0 beta 2  (Build 11A4400f) 4.4.00   7.0 beta 3   (Build 11A4414e) 4.4.03   7.0 beta 4   (Build 11A4435d) 7.0 beta 5  (Build 11A4449a) 7.0 beta 6  (Build 11A4449d) 5.0.00   7.0GM        (Build 11A465) 7.0         (Build 11A465) 7.0.2       (Build 11A501) 5.0.02   7.0.3        (Build 11B511) 7.0.4       (Build 11B554a) 7.0.6       (Build 11B651) 5.1.00   7.1 beta     (Build 11D5099e) 7.1 beta 2  (Build 11D5115d) 7.1 beta 3  (Build 11D5127c) 7.1 beta 4  (Build 11D5134c) 7.1 beta 5  (Build 11D5145e) 5.2.00   7.1          (Build 11D167) 7.1.1       (Build 11D201) 7.1.2       (Build 11D257) 5.2.01   8.0 beta     (Build 12A4265u) 5.3.01   8.0 beta 2   (Build 12A4297e) 5.3.02   8.0 beta 3   (Build 12A4318c) 8.0 beta 4  (Build 12A4331d) 8.0 beta 5  (Build 12A4345d) 5.4.00   8.0GM        (Build 12A365) 8.0         (Build 12A365) 8.0.1       (Build 12A402) 8.0.2       (Build 12A405) 5.3.02   8.1 beta     (Build 12B401) 5.4.00   8.1 beta 2   (Build 12B407) 8.1         (Build 12B411) 8.1.1 beta  (Build 12B432) 8.1.1       (Build 12B435) 8.1.2       (Build 12B440) 8.1.3       (Build 12B466) 8.2 beta    (Build 12D436) 8.2 beta 2  (Build 12D445d) 8.2 beta 3  (Build 12D5452a) 8.2 beta 4  (Build 12D5461b) 8.2 beta 5  (Build 12D5480a) 8.2         (Build 12D508) 5.3.02   8.3 beta     (Build 12F5027d) 8.3 beta 2  (Build 12F5037c) 8.3 beta 3  (Build 12F5047f) 5.4.00   8.3 beta 4   (Build 12F61) 8.3         (Build 12F70) 5.3.02   8.4 beta     (Build 12H4074d) 8.4 beta 2  (Build 12H4086d) 8.4 beta 3  (Build 12H4098c) 5.3.03   8.4 beta 4   (Build 12H4125a) 5.5.00   8.4          (Build 12H143) 8.4.1 beta  (Build 12H304) 8.4.1 beta 2 (Build 12H308) 8.4.1       (Build 12H321) 5.3.02   9.0 beta     (Build 13A4254v) 5.3.03   9.0 beta 2   (Build 13A4280e) 9.0 beta 3  (Build 13A4293g) 5.3.04   9.0 beta 4   (Build 13A4305g) 9.0 beta 5  (Build 13A4325c) 9.0GM       (Build 13A340) 9.0         (Build 13A344) 6.0.00   9.0.1        (Build 13A404) 9.0.2       (Build 13A452) 5.3.04   9.1 beta     (Build 13B5110e) 9.1 beta 2  (Build 13B5119e) 6.0.00   9.1 beta 3   (Build 13B5130b) 9.1 beta 4  (Build 13B136) 9.1 beta 5  (Build 13B137) 9.1         (Build 13B143) 5.3.03   9.2 beta     (Build 13C5055d) 9.2 beta 2  (Build 13C5060d) 6.0.00   9.2 beta 3   (Build 13C71) 9.2 beta 4  (Build 13C75) 9.2         (Build 13C75) 9.2.1 beta  (Build 13D11) 9.2.1 beta 2 (Build 13D14) 9.2.1       (Build 13D15) 5.3.04   9.3 beta     (Build 13E5181d) 9.3 beta 1.1 (Build 13E5181f) 9.3 beta 2  (Build 13E5191d) 9.3 beta 3  (Build 13E5200d) 9.3 beta 4  (Build 13E5214d) 6.0.00   9.3 beta 5   (Build 13E5225a) 9.3 beta 6  (Build 13E5231a) 9.3 beta 7  (Build 13E5233a) 9.3         (Build 13E233) 9.3         (Build 13E237) 9.3.1       (Build 13E238)

External Resources

 * Reverse-engineering a Qualcomm baseband - Video
 * Reverse-engineering a Qualcomm baseband - Slides