iPhone 3GS restore question (hypothetical)

**de0s** · 05-28-2010 07:08 PM

I'm kind of new to the iPhone community, so I'm trying to learn some things. Maybe some of you can help me.

Consider the following scenario:
iPhone 3GS with fw 3.1.3, bb 05.12.01 and new bootloader.
Let's say the SHSH blobs are saved for 3.1.3 (saurik's server or locally).
Now, the iPhone is upgraded to the new fw 4.0 with, let's suppose, a new baseband (let's call it 06.xx.xx - as I don't know the baseband in the new OS4

)

I recently learned that you cannot restore with a custom fw on 3GS with new bootloader.

So now the questions:
1. Considering an iPhone 3GS (new bootloader) with fw 4.0 and the new hypothetical bb 06.xx.xx, would the user be able to downgrade the fw to 3.1.3 (for which it has saved SHSH)?
2. I'm assuming that in step 1 only an original ipsw can be used, thus with a 05.12.01 bb. Would the iPhone just update the fw and return an error when trying to update the bb? And from here there would be some hypothetical tool to get you out of it and help boot the phone normally?

Thanks in advance

**n1ckn4m3** · 05-28-2010 09:34 PM

Originally Posted by de0s

I recently learned that you cannot restore with a custom fw on 3GS with new bootloader.

That's not entirely correct. You cannot restore a custom FW on the 3GS in DFU mode -- but you can still restore a custom FW on a 3GS in restore mode.

1) Yes, if the SHSH was on file, they should be able to downgrade the FW only to 3.1.3.
2) Incorrect assumption, see above. You can use a modified firmware to restore without the baseband, but when downgrading, unless you have a prior baseband, there is no point in doing this. If your phone has a newer baseband, the restore will complete but will error out at the baseband flashing. Use iRecovery or iReb to reboot the phone and kick it out of recovery mode and you'll be back on the previous firmware with the newer baseband.

Did this answer everything?

**Olethros** · 05-28-2010 10:56 PM

Originally Posted by n1ckn4m3

That's not entirely correct. You cannot restore a custom FW on the 3GS in DFU mode -- but you can still restore a custom FW on a 3GS in restore mode

On a new bootrom 3GS custom (pwnagetool/xpwn) ipsw does not work. The only way to fix this is either to do a full restore with stock ipsw (and SHSH) or the last ditch method (remove LLB from an otherwise stock ipsw)