device not eligible

[nonquitt2000]

For those of you seeking to install an upgraded or a downgraded version of iOS, this is NOT a "restore". Under redsn0w you do NOT use the Custom IPSW tab.

I spent a frustrating week before I learned that you need to invoke the SHSH blobs tab in redsn0w, and find your stored blobs, then build a custom IPSW with the blobs imbedded. This is called "stitching" the blobs into the IPSW file.

My everlasting thanks to a participant named Jaxov whose posting on a forum somewhere clued me in to this. If you do not have your SHSH blobs stored either locally or on Cydia you are out of luck here. You will probably not be able to go from 6.xx to 5.xx or from 4.xx up to 5.xx in iTunes.

After creating a stitched IPSW file in redsn0w, you go the normal Pwned DFU route.

 

[Applejuiced]

Exactly.
And that's for the 3GS and iphone 4.
For the 4S even if you have shsh blobs you will not be able to downgrade on 6.0 to any lower firmware version.

 

[nonquitt2000]

Thank you

Thank you, Applejuiced, for your endorsement.

I apologize for not telling readers that yes, I was talking specifically the iPhone 3GS here. FYI: I upgraded from iOS 4.1 to 5.1.1 The baseband was (and still is) 5.16.05

I used the redsn0w version 0.9.14b2 to do this because it always accepted the 5.1.1 IPSW file.

A couple of peculiarities here: During the frustrating week, I noticed that every single download of the many 5.1.1 IPSW files ALWAYS came up exactly the same 9B206 build and exactly the same file size. There does not seem to be different versions for new boot rom, old boot rom, upgrade, downgrade, etc. etc. despite all the commentary out there.

My iPhone 3GS has apparently led a checkered life: the 3,4 and 5 digits of the serial number are 052 which suppposedly means this phone was built in December 2000. This is way before the supposed shift to the new boot rom, yet this phone now very definitely has the new boot rom. It made no difference in the end.

Also this phone has in the past been jailbroken and used to have Cydia on it, and also had at one time the dreaded iPad baseband.