How to upgrade 3GS from 4.1 to 4.2.1?

Discussion in 'Jailbreaks and iOS Hacks' started by mklo, May 6, 2011.

  1. mklo
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    macrumors newbie

    Dec 8, 2010
    I have a 3GS with 4.1. I would like to got to 4.2.1. I downloaded the 4.2.1 firmware, when I hit shift-restore 4.2.1 itune gave me an error messaage. Can I use other software to upgrade? Thanks.
  2. eastercat
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    macrumors 68040


    Mar 3, 2008
    You need the blob for the ios. If you don't have it, you can only install the most current ios.

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