These are instructions on how to jailbreak your iPhone 3GS or iPhone 4 on iOS 5 without updating the baseband using RedSn0w for Mac. You may want to do this to preserve an unlock from a lower baseband version.
Please note this jailbreak is tethered for every device but the old bootrom iPhone 3GS which means you will need to connect your device to the computer each time you reboot.
Create a folder on your desktop called Pwnage
Download RedSn0w 0.9.9b5 from here and place it in the Pwnage folder. Likewise, download the iOS5 firmware from here and place it in the Pwnage folder.
Extract the RedSn0w zip file by double clicking it.
Launch the redsn0w application from the redsn0w folder we just extracted.
Click to select Extras from the main menu.
Click to select Custom IPSW from the Extras menu.
Navigate to the Pwnage folder on your desktop and select the iOS 5 IPSW we downloaded then click Open.
RedSn0w will now begin building a custom IPSW for you.
You'll be notified once RedSn0w has completed building your IPSW. Click the OK button.
Click the Pwned DFU button from the Extras menu.
Plug your iPhone into the computer and make sure its OFF then click the Next button
RedSn0w will now guide you through the steps to get into DFU mode. You can find more help with DFU modehere
Hold down both the Home button and the Power button for 10 seconds.
Release the Power button and continue holding the Home button until RedSn0w detects the device.
RedSn0w will run the LimeRa1n exploit.
You'll then be notified that your iPhone is in Pwned DFU mode.
Launch iTunes by clicking its icon in your dock.
Select your device from the list on the left then under the Summary tab hold down the Option key and click theRestore button.
You will then be asked to select your IPSW for restore. Navigate to the Pwnage folder on your desktop and select the IPSW that begins with NO_BB then click the Open button.
iTunes will now restore and jailbreak your device using the Custom IPSW.