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

Now that the iPad has been launched, the focus has shifted to jailbreaking the iOS 5.1, which will allow A4 iOS users to access Cydia.

Sn0wbreeze 2.9.2 offers a tethered jailbreak similar to the Redsn0w exploit and hence requires the device to be connected to the computer for a reboot to jailbroken state after installing any new updates. This will ensure the device continues to receive benefits of Cydia.

If you are the owner of an A4-run device (such as: iPhone 4, iPhone 3GS, iPad 1, iPod Touch) and can manage with the tethered status of the jailbreak, follow the guide to using Sn0wbreeze 2.9.2 to jailbreak iOS 5.1

Creating Custom Firmware Using Sn0wbreeze:

Step 1: Download a copy of the latest iOS 5.1 IPSW suitable for your device

Step 2: Download and launch latest version of the Sn0wbreeze software, currently version 2.9.3

Step 3: At the main screen, click the blue arrow in the bottom right hand corner to continue

Step 4: Sn0wbreeze will present the option to browse for the previously downloaded firmware file. Select "Browse" and navigate to the location of the iOS 5.1 IPSW file downloaded in Step 1

Step 5: If the firmware file is legitimate, Sn0wbreeze will confirm the file verification process and display a firmware message as well as the model of the attached device on a popup window

Step 6: Sn0wbreeze then offers the user with a number of options including Baseband Preservation Mode, Simple Mode and Expert Mode. If you plan to unlock an iPhone 4 or 3GS (old basebands only) then select Expert Mode followed by the blue continue arrow

Step 7: The next screen provides a number of options to cater for all usage types. If you are unsure about what each does and all you care about is a simple jailbreak and Cydia installation, then select "Build IPSW" and click the continue arrow

Step 8: Sn0wbreeze is a restore-based tool and will now create a custom-pwned iOS 5.1 firmware file. After completion, a confirmation dialog window appears signaling the successful completion of the process

Step 9: The next step involves putting the device in DFU mode by following on-screen instructions. When Sn0wbreeze detects DFU mode, the device's screen will go black and a confirmation prompt will appear

Step 10: The custom created firmware should now be loaded on the device. Open iTunes with the device still in DFU mode and click on the device name in the left hand side bar of iTunes. Hold down SHIFT and press the restore option in the window to bring up a directory search prompt. Find the custom-created IPSW and double click to select. The process will be same for any official iTunes-based restore and when completed, the device will be loaded with a pre-jailbroken firmware.

Booting the Device into a Tethered State Using iBooty

The current available jailbreak for iOS 5.1 using the Sn0wbreeze method is a tethered one, requiring a tethered boot in the event of any power cycles. In the event of your device powering down or rebooting, you will need to follow these steps every time...

Step 1: Launch the iBooty utility and choose the relevant device from the drop down list before hitting the "Start" option.

Step 2: Once the process starts, iBooty requires DFU mode to work, which can be achieved by following on-screen prompts

Step 3: iBooty will now boot the device into a tethered jailbreak state. When completed, it will present the user with a completion message. This ends the jailbreak process

Booting Semi-Tethered:

Additionally, you may want to try out a SemiTether package by BigBoss. Though, this tool is not largely tested on iOS 5.1 yet, some reports suggest it may work through iOS 5.1, allowing you to boot your device without a computer. But, it means without the luxury of launching Cydia or any of its tweaks/apps.

Users who wish to unlock their iPhone 4/iPhone 3GS for installing iOS 5.1, can do so using the UltraSn0w Fixer.

MUST READ: iOS 5.1 Untethered Jailbreak: New Status Update for iPhone 4S, iPad 2 and New iPad from Pod2g and Chpwn

MUST READ: Downgrade iOS 5.1 to iOS 5.0.1: Developer Unearths a Way for iPad 2 and iPhone 4S

MUST READ: iOS 5.1 Jailbreak: How to Unlock iPhone/iPad/iPod Touch Using Redsn0w 0.9.10b6