Upgrade AT&T Galaxy S3 i747 to Android 4.2.1 with Cyanogenmod 10.1 Custom ROM

No doubt that Samsung Galaxy S3 is one of the best selling device of the year. And due to its goodness & hardware capability, it is getting frequent software updates. In addition to that, Samsung has already rolled out Android 4.1.1 Jelly Bean update a week ago. Similar thing happened with the US variant of Galaxy S3 i9300 i.e, AT&T Galaxy S3 SGH-i747. They also have released an official update for the same.

But recently Google has pushed out Android 4.2 update for their Nexus devices. And Surely it will take some time for Samsung and AT&T to test the firmware and release it. But you don’t need to wait for the update to come out. Custom ROMs are always one step ahead of the official firmwares to provide latest Android experience for the users. And one of the best serving custom ROM is Cyanogenmod.

Cyanogenmod 10.1 based on Android 4.2 and having highly customizable features is now available for AT&T Galaxy S3. Thanks to XDA Recognized Themer itsmikeramsay for bringing out it to AT&T S3 users. The step by step guide given below will help you in updating your device to Android 4.2 via Cyanogenmod 10.1 custom ROM.

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Disclaimer: The given procedure is considered as risky and may cause damage to your phone. It is recommended that you should not follow it unless you are familiar with these things. Follow this article at your own risk. Neither We nor developers would be held liable for any damage caused to your device while attempting these steps.

This guide is intended only for AT&T Galaxy S3 SGH-i747. Dont implement it on any other device or variant of the same else it may result in permanent damage to your device.


  • Enable USB Debugging option in your phone.
  • Charge your device up to 75% battery level in order not to interrupt the installation procedure.
  • It is highly recommended to backup all your data from phone memory which includes contacts, messages (SMS/MMS), call logs, Internet APNs etc.
  • It is necessary to have Custom Recovery like Clockworkmod / TWRP installed in your phone for flashing Cyanogenmod 10.1 Custom ROM.

Procedure to Update AT&T Galaxy S3 SGH-i747 with Cyanogenmod 10.1 Custom ROM (Android 4.2.1):

  • Download Google Apps (Gmail, Maps, GTalk, Play Store etc.) from the link given below.
  1. Google Apps for Jelly Bean
  • After downloading ROM package & Google Apps, connect your phone to the PC. Enable mass storage mode to access SD card data & transfer both the files on the root directory of it.
  • Disconnect the phone from computer. Now boot into Clockworkmod recovery. To do so, switch off the phone completely. Press & hold Volume Up + Home Button + Power Key together until recovery mode appears (you can release power button after Samsung logo appears but keep holding other two until recovery mode shows up).
  • After getting into the recovery, make a nandroid backup of your current ROM so that it can be restored back in case of failure. To do so, Highlight backup and restore option in the recovery menu, select it & then choose backup to start the backup process.
  • Select wipe data/factory reset & subsequently wipe cache partition to wipe the data & caches respectively from the phone memory.
  • Now select install zip from sdcard & then on next screen select, choose zip from sdcard. It will show you the files & folders located on the SD card of your device. Navigate to the ROM file, select it using power button (unless youre using touch CWM) & confirm the installation by pressing on Yes. This should start installing the ROM.
  • From the main menu, select Wipe cache partition. After that, Go to “Advanced –> Wipe Dalvik Cache”.
  • For installing Google Apps, do the same steps as you’ve done for ROM.
  • After you finish flashing all the files, Selectreboot system nowto Restart the phone.

Note:If you want to restore back your previous ROM, you can do so by booting into the recovery mode. In recovery, selectBackup and Restoreoption & on next screen, selectrestore.Now choose the backup you like to restore (or the restore the backup you’ve made before flashing this ROM).

Great! Android 4.2.1 Jelly Bean based custom ROM Cyanogenmod 10.1 is now running & up on your AT&T Galaxy S3. Keep visiting official ROM development page for the latest updates.

Comments (9)
  1. udi April 7, 2013
    • Viraj SK April 7, 2013
      • udi April 8, 2013
        • udi April 8, 2013
  2. leon February 26, 2013
    • Viraj SK February 26, 2013
  3. Joe February 23, 2013
  4. HELP February 15, 2013

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