Dev-Team Released Baseband Downgrade for iPhone 3GS, 3G *Now u can use stock ipsw & GPS*

Redsn0w 0.9.14b1
Typically you’d have the 06.15 baseband if you unlock with ultrasn0w but updated your iPhone baseband past 05.13.04. With this new capability, you can now downgrade specifically from 06.15 to 05.13.04 (even if you never had 05.13.04 on that device before). This gives you the best of both worlds: ultrasn0w compatibility and a normal iPhone baseband with full GPS and the ability to use stock IPSWs again. 



***UPDATE 1***

Baseband Freedom

Happy 4th of July! Today’s release of redsn0w 0.9.14b2 improves the iPad baseband downgrade and should cover anyone who couldn’t downgrade with 0.9.14b1. This version covers 3 different types of NOR chips in the iPhone 3G and 3GS (the earlier version covered only the most prevalent NOR chip). We’ve also simplified the process and added logging to help diagnose any remaining stubborn iPhones.

The revised steps are:

1. Connect your iPhone in normal mode, then click “Jailbreak” after redsn0w identifies its model and BB version (you needn’t pre-select the IPSW anymore).
2. Choose the “Downgrade from iPad baseband” option (you needn’t worry about de-selecting Cydia anymore).
3. Do a controlled “slide to power off” shutdown of your phone and proceed through the normal DFU ramdisk steps.

Should the downgrade fail to take, feel free to leave the redsn0w log in the comments below. Use the “Extras->Even more->Backup” button to grab a copy of /var/mobile/Media/redsn0w_logs, then extract the log text file(s) from the zip and paste them into the comments (currently that log file is generated only during baseband downgrade runs).
NOTE: For those who are wondering if you can update your 3G or 3GS to 06.15 solely for the purposes of downgrading to 05.13.04, the answer is “yes” for 3G owners, and “maybe” for 3GS owners. The iPad baseband is not compatible with 3GS units manufactured week 34 of 2011 or later.If you have an iPhone3GS and if digits 3-5 of its Serial Number are 134 or later (xx134…), then you should NOT try to install the 06.15 baseband on your 3GS! It will brick your radio, preventing both the downgrade from working and normal iPhone software from using it as a phone!Be warned!
 

DFU IPSW

We’ve gotten a lot of feedback from users who can’t launch a DFU ramdisk because their iPhone home/power buttons are broken or intermittent. We’ve added a new redsn0w feature that lets you enter DFU mode as long as your phone is healthy enough to restore to a normal, everyday IPSW. You don’t need to be already jailbroken to use this method. 
In redsn0w, go to “Extras->Even More>DFU IPSW” and select an IPSW that is currently being signed for your device and that you’d normally be able to restore to without any hacks. redsn0w will create an “ENTER_DFU_” version of the IPSW that you can restore to just like any other IPSW, except that now you’ll be dumped into DFU mode towards the end of the restore (WARNING, your screen will remain completely black…the only way to even know its own is that iTunes and redsn0w will detect it!). The technique used by this feature is 3 years old but surprisingly still works today!

Download
redsn0w v0.9.14b2 Windows
redsn0w v0.9.14b2 OS X

Source

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0615 fun 
The iPhone Dev Team is happy to announce a baseband downgrade option in redsn0w for those who are using the iPad’s 06.15 baseband on the iPhone3G or iPhone3GS.

Redsn0w 0.9.14b1
Typically you’d have the 06.15 baseband if you unlock with ultrasn0w but updated your iPhone baseband past 05.13.04. With this new capability, you can now downgrade specifically from 06.15 to 05.13.04 (even if you never had 05.13.04 on that device before). This gives you the best of both worlds: ultrasn0w compatibility and a normal iPhone baseband with full GPS and the ability to use stock IPSWs again.
Here are the steps that will be used:

1. Use the “Extras->Select IPSW” button in redsn0w to tell it which firmware version you have installed (new-bootrom 3GS users can usually skip this step but it doesn’t hurt for them to do it too).
2. Do a controlled shutdown of your iPhone (“slide to power off”). This step is very important to avoid mount problems when the ramdisk is running!
3. Go back to the first screen and click “Jailbreak”. Enable the “Downgrade from iPad baseband” checkbox, disable Cydia if you already have it installed, and click Next proceed through the normal DFU ramdisk steps.

After the ramdisk gets launched and you see the running Pwnapple, you’ll eventually get to the “Flashing Baseband” step. THIS STEP TAKES A VERY LONG TIME to complete and there won’t be any feedback while its running. Please just let it be for the next 3-8 minutes! When the ramdisk has done its job it will reboot the phone on its own.

For those who are wondering if you can update your 3G or 3GS to 06.15 solely for the purposes of downgrading to 05.13.04, the answer is “yes” for 3G owners, and “maybe” for 3GS owners. The iPad baseband is not compatible with 3GS units manufactured week 34 of 2011 or later. If you have an iPhone3GS and if digits 3-5 of its Serial Number are 134 or later (xx134…), then you should NOT try to install the 06.15 baseband on your 3GS! It will brick your radio, preventing both the downgrade from working and normal iPhone software from using it as a phone!
Be warned!

Download
Mac
Window