iOS 5: iPhone Basebands and Unlocks
HITB 2012: MuscleNerd Explains Evolution of iPhone Baseband and Unlocks [VIDEO] IBTimes

The iPhone Dev-Team have once again stepped up to rescue the jailbreak users from the dead-lock situation with Apple's new software update - iOS 5.1. This time the semi-tethered version of the Redsn0w tool brings some respite for users to break free of the restrictions with jailbroken devices while trying to update iOS 5.1. The devices supported with this tool include iPhone, iPad and iPod Touch with the exception of iPhone 4S and iPad 2.

It should be noted that the jailbreak is tethered, requiring you to connect your device to a computer whenever a reboot is required to register jailbreak changes, if you switch off your device or install a new update. The 'SemiTether' patch eases the tethered scenario by allowing devices to boot without connecting to a PC or Mac, although features are extremely limited, thus it needs to be booted tethered in order to support complete functionality.

Although, this is not as exciting as a full-fledged untethered jailbreak, it still gets the job done and unlocks support for new features as well as apps for the new update. The user however, needs to note a few key points before running the procedure:

  • This jailbreak does not support iPad 2 or iPhone 4S.
  • If you unlock with GEVEY or Ultrasn0w, do not update to the stock iOS 5.1 firmware. Skip to the latter part of this guide for more info.
  • If you are uncomfortable with constantly connecting and rebooting on tethered jailbreaks, wait for an untethered version or downgrade to iOS 5.0.1/4.x.

How to jailbreak iOS 5.1 using Redsn0w

Step 1: Download the latest version of iTunes (10.6)

Step 2: Open iTunes, and back up data on your device.

Step 3: Upgrade your firmware to iOS 5.1. [download links]

Step 4: Download the latest version of Redsn0w (Windows/Mac)

Step 5: Start Redsn0w, hit "Jailbreak" then "Install Cydia". Follow the onscreen steps to put your device into DFU mode.

Step 6: Now we enter the process where you will need to repeat it, every time your device is switched off. This is called tethered boot. Launch Redsn0w, choose "Extras", then hit "Just Boot" in order to boot your device tethered.

Booting Semi-Tethered (Optional)

The "SemiTether" patch is a cross/hybrid between tethered and untethered - allowing you to boot your device without a computer, but with limited, so you'll need to boot tethered through Redsn0w in order to enjoy full-fledged functionality. The download is free, and available over at the BigBoss repo: http://thebigboss.org/semitether.

Here are a few things to keep in mind before you unlock your device:

  • If you use the GEVEY SIM interposer or Ultrasn0w to unlock your iPhone, you will need to create a custom .iPSW, in order to preserve your baseband.
  • In Redsn0w, select "Extras", then "Custom IPSW", locate your iOS 5.1 file, and let Redsn0w work its magic.
  • Then enter pwned DFU mode (Extras > Pwned DFU) and restore to your custom firmware via iTunes. After that, you'll be able to unlock with GEVEY, Ultrasn0w fixer, or Ultrasn0w (when it is available).

Watch the Full Video Tutorial below:

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