How to Install Android 6.0 Marshmallow OctOS on AT&T Galaxy S3 I747

Guide on how to install Android 6.0 Marshmallow OctOS on AT&T Galaxy S3 I747 smartphone.

AT&T Galaxy S3 I747 Android 6.0 Marshmallow update is here, although not officially. This update is possible only through OctOS custom ROM. You can download the custom ROM file from the description and flash it on AT&T Galaxy S3 SGH-I747 through any custom recovery like TWRP or CWM.AT&T Galaxy S3 SGH-I747


To flash this ROM on your device your device need to be rooted and it should have a custom recovery TWRP (recommended) installed on it. Also make sure that you are aware of the fact that once you root your device your device warranty will void. In case any thing goes wrong during the process you may brick your device for which will not be responsible in any manner.

So, if agree with all this facts and willing to update your device then you can go ahead flash the ROM on your device by carefully following the description given below.

Preparing Your Phone

  • This instructions are strictly for AT&T Samsung Galaxy S3 SGH-I747, so do not try it on any other device or you may brick your device.
  • Device should be fully charged.
  • Install Samsung Galaxy S3 USB drivers on your computer.
  • Back up all the required data to some safe storage.
  • Make a Nandroid back up of the current ROM so that you can restore it when required.
  • Make sure the device bootloader is unlocked.
  • Root your device and install custom recovery on it if not done already.
  • Enable USB debugging mode of your device. Go to Settings > Developer options > USB debugging mode.USB Debugging

Install Android based OctOS Custom ROM

  1. Download Android 6.0 Marshmallow based OctOS for AT&T Galaxy S3 from here.
  2. Download the Google App’s for Android Marshmallow from here.
  3. Connect the device to computer and transfer both the files i.e ROM file and Google App’s file to your device root storage.
  4. Disconnect the device and turn it off completely.
  5. Reboot the device into Recovery mode, press and hold Volume Down + Home + Power key for few seconds.
  6. When in recovery mode tap on Wipe tab and select the options you like to wipe, given under it.
  7. Now, confirm the wipe action by swiping the button at the bottom of the screen.
  8. Now, return to main menu and tap on Install tab.
  9. Locate the ROM file stored on you device and select it.
  10. Swipe the button at the bottom to flash the ROM file on your device.
  11. In the same way flash the Google App’s on your device.
  12. Return to main menu and tap on Reboot.
  13. System will now reboot in normal mode.

That’s all you can now check the device Android version in Settings > About device > Android version.