How do you downgrade a 3G from iOS4 to 3.13?

Discussion in 'Jailbreaks and iOS Hacks' started by darngooddesign, Jul 14, 2010.

  1. darngooddesign macrumors G3

    Joined:
    Jul 4, 2007
    Location:
    Atlanta, GA
    #1
    It doesn't need to be jailbroken or anything. Co-worker's husband upgraded and now, obviously, finds his phone to be even slower. A link will be fine.

    Cheers
     
  2. thelatinist macrumors 603

    thelatinist

    Joined:
    Aug 15, 2009
    Location:
    Connecticut, USA
    #2
    Just put the phone in DFU mode and shift-restore to 3.1.3.
     
  3. esadb macrumors 65816

    esadb

    Joined:
    Nov 29, 2008
    #3
    also get recboot, to kick it out of DFU once done.

    Just did this procedure 20min ago...
     
  4. darngooddesign thread starter macrumors G3

    Joined:
    Jul 4, 2007
    Location:
    Atlanta, GA
    #4
    Thanks, didn't know if there was a lock against downgrading OSes, like apple not signing OSes prior to 3.13. On an aside, can you downgrade a 3GS from 4 to 3 the same way?

    Do you have to use recboot or can I just hard reboot (home + power) ?
     
  5. The General macrumors 601

    Joined:
    Jul 7, 2006
    #5
    you have to use recboot or firmware umbrella or irecover or something like that. it will not boot because 3.1.3 expects there to be an older modem firmware. you have to tell it not to care.
     
  6. thelatinist macrumors 603

    thelatinist

    Joined:
    Aug 15, 2009
    Location:
    Connecticut, USA
    #6
    The real problem is that the downgrade technically "fails" at the last step because it is unable to upgrade the baseband -- since you already have a newer version. As a result, it does not change a flag in the bootloader configuration that allows it to boot normally, rather than back into recovery mode.

    Fortunately, by the time you get this failure, the phone has already been completely restored. All these programs do is change the bootflag to allow you to boot the OS. It's harmless.
     
  7. Jethrotoe macrumors regular

    Joined:
    May 24, 2009
    Location:
    Somewhere over there.
    #7
    Thanks. I was looking for the actual reason for needing iRecovery (or similar). You explained it well.

    I am going to upgrade a 3G (3.13) to 4.0 (I know, I know) for a specific bluetooth function that I need for a specific set of BT headphones. The fallback seems to be pretty much foolproof so I'm going to try it. I bet you don't get your app specific data back though. I have to search some more on that.
    Thanks again.
     

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