Update iPhone 4 or iPhone 3GS using RedSn0w. The latest version of RedSn0w is capable of upgrading an iPhone 4 or iPhone 3GS to a newer version of iOS including iOS 6 without upgrading its baseband. This feature of RedSn0w is super useful for those who have to unlock their iPhone so that it could be used on other carriers. Follow the steps below to install a newer version of iOS on your iPhone while preserving its baseband.
Things you need for the process:
Step 1. After you have downloaded the RedSn0w for Mac or Windows and the iOS IPSW file, extract and launch RedSn0w. Windows users should open it in Admin mode.
Step 2. Click on the ‘Extras’ button and then on ‘Even More’.
Step 3. Click on the ‘Restore’ button from the menu and then click on the IPSW button. From the window that opens, select the iOS version file you have downloaded from the web and click the ‘Open’ button.
Step 4. From the prompt menu click on Yes button. Now RedSn0w will work on the firmware file you have selected. This should take less than a minute.
Step 5. Now RedSn0w will ask you to put your device in Pwned DFU mode. Select OK then connect the iOS device to your computer and turn it off.
Step 6. After device is turned off, click on the Next button. Now RedSn0w will tell you how you can put your device in DFU mode. Follow the on-screen instructions. After you have placed it in DFU mode RedSn0w will start injecting Limera1n exploit and other other stuff. This should take 1-2 minutes or less.
Step 7. After RedSn0w is finished doing its work, your device will reboot and will be running the new iOS version with the same baseband it had before.
That’s it! Enjoy.