This gives you best of both worlds, you update your iPhone 3GS to iOS 4.2.1 and since the baseband is preserved, you can unlock your iPhone 3GS using Ultrasn0w 1.2 without the need to update it’s baseband to 06.15.00, which has its risks.
iPhone Dev team has provided the following information on their blog about the unofficial PwnageTool bundle:
For those Mac users with an old-bootrom 3GS who really know what they’re doing, here’s a minimal 3GS 4.2.1 bundle that will get you to 4.2.1 without updating your baseband. Be sure to uncheck “Activate the iPhone” using Expert mode. To actually jailbreak after you’ve restored with the help of that bundle, please use redsn0w.
You can follow these steps to install the bundle:
Download the PwnageTool bundle from this link and extract the contents (iPhone2,1_4.2.1_8C148a.bundle ) of the zip file.
If you have downloaded PwnageTool, right click on the extracted PwnageTool app and select Show Package Contents from the menu.
Navigate to Contents/Resources/FirmwareBundles/.
Copy and paste the iPhone2,1_4.2.1_8C148a.bundle that your had extracted earlier into the FirmwareBundles folder.
That’s all. When you launch the PwnageTool, it will pick up the latest firmware bundle. You can then use it to upd
As always, let us know how it goes.
[via Dev Team’s blog]