Last week, we reported that MuscleNerd was working on an update for Redsn0w that would allow the users of iPhone 4S, iPad 2, and The New iPad (A5 or A5X) users to downgrade their firmware if they had their SHSH blobs saved.
Now the big news is that the update has been released. iPhone 4S and iPad 2 users have the ability to downgrade as low as iOS 5.0.1. The new iPad users have the ability to downgrade as low as iOS 5.1. A4 users have been able to downgrade since the dawn of time due to a shiny bootrom exploit.
Originally Posted by Dev-Team
Jailbreakers with devices that pre-date the iPad2 will always be able to downgrade (with SHSH blobs) to previous firmware versions due to geohot’s limera1n exploit, which allows us to bypass the restrictions that Apple places on restores. But until now, that ability has been limited to those older devices (if you have an older device and don’t know how to do that, check the popular tutorial sites or ask in the comments below).
Starting with redsn0w version 0.9.11b1, those with newer devices (iPad2, iPad3, and iPhone4S) can join the downgrade fun too! In a radical departure from previous versions of redsn0w, it now directly supports restoring IPSWs to your device. The first use of this new feature implements a hack that allows A5 downgrades without a bootrom-level exploit.
The new version of RedSn0w allowing A5 iOS device users to join in on downgrading their firmware. MuscleNerd has said that the new downgrading process does not require a bootrom exploit. The latest version, dubbed Redsn0w 0.9.11b1 is compatible with Mac OS X and Windows. If you are running Redsn0w 0.9.11b1 in Windows, it is highly recommended that you run the software in administrator mode by right-clicking on the icon, followed by clicking, “Run As Administrator.”
The new feature that allows A5 iOS device users to downgrade their firmware can be found under Extras>Even More>Restore from the Redsn0w navigation menu.
To use this new feature to downgrade your A5 device, you must have your SHSH blobs saved. For example, if you wish to downgrade your iPhone 4S to iOS 5.0.1, you must have your iOS 5.0.1 SHSH blobs saved. Apple has stopped signing iOS 5.0.1. So if you have not saved them already, then you would not be able to save them now. Apple also has the ability to patch this downgrading method in a future firmware update. Thus, try to take advantage of this update, as long as you can.
Another warning for all those who use jailbreak tweaks is that the iPhone Dev-Team has announced that the new downgrade measure updates the iOS firmware before downgrading. Thus, it will update your baseband. For this reason, if you are relying on an unofficial iPhone unlock, do not use this new downgrade method until a workaround can be found. If you used the SAM technique (now patched by Apple) to unlock your iPhone, then you can use this new downgrading method without losing your unlock.
iPhone Dev-Team has also said that since the new version of Redsn0w is built with a ton of new code, they recommend using the more stable Redsn0w 0.9.10b8b unless you plan to be taking advantage of the new downgrading feature. This will give them some time to work out the bugs. There is no reason to run this new version of Redsn0w over your existing jailbreak because there are no improvements to the jailbreak in the latest version of Redsn0w.
If you are ready to finally have the freedom to downgrade your iPhone 4S, iPad 2, or The new iPad, then you should download this new Redsn0w release.