The CyanogenMod team has released their first CM10.1 M1 Snapshot ROM for the AT&T variant of Galaxy S3. Use this guide and you’ll learn how to successfully flash the custom ROM without problems.
CM 10.1 M1 ROM is based on the Android 4.2.1 Jelly Bean. It is a much more stable version than the Nightly. Such M builds should be released once per month and this is the first one which is based on the latest Jelly Bean OS. In order to make sure that you install this custom ROM successfully, you should first read the guidelines listed below:
use this tutorial only with the AT&T variant of Samsung Galaxy S3 model number I747. Don’t attempt to flash this custom ROM on any other phone.
use this guide only if you’re device is on unlocked bootloader, rooted and running a custom Recovery image.
Use the custom Recovery image and make sure that you create a full NANDROID backup of your current ROM. This will serve as a restore point for your device in case something goes wrong during the installation.
This guide should be completed by advanced Android users. Do not attempt to flash this ROM if you’re a novice and you don’t know what you’re doing.
Read the entire post and make sure that you don’t skip any steps that I have listed.
Charge the smartphone’s battery so that the device won’t power off during the installation.
Backup your most important files by moving them on to your computer or you can choose to simply place them on the internal SD card.
We cannot be blamed in case something goes wrong and your device is unable to boot normally after installing this custom ROM.
Don’t blame us in case you lose any important data files.
If your device is already running on a CM10.1 ROM then you can install the new build without the need of formatting the system partition. If you’re running a different ROM then you will have to wipe data and factory reset your phone.
If you cannot complete the installation of CyanogenMod OS then you can ask for more help in comments. Make sure to leave a detailed comment at the end of this post so that we can come up with a viable solution easier.
I think that these were all the guidelines you had to go over before moving to the next part of this post.
How to install CM10.1 M1 ROM on the AT&T Samsung Galaxy S3 I747:
Download the custom ROM from HERE. Save the file on your PC and don’t unzip its contents.
Get the Gapps for CM10.1 from HERE. This is the file that you have to flash in order to get all the Google based applications on your device. Save this file on your PC and don’t extract its contents.
Now, connect your SGS3 AT&T to your computer. Move the downloaded files and place them on its internal sdcard. Disconnect the device from PC when the files are copied successfully.
Power off the smartphone.
Boot it into CWM Recovery mode by pressing and holding at the same time the Volume Up, Home and Power buttons. Release the buttons when the ClockworkMod Recovery screen loads.
Optional Step: Select the ‘backup and restore’ option in order to create a full NANDROID backup of your current ROM. If you already have a backup then you can skip this step.
Now you need to select ‘wipe data/ factory reset’ and confirm this process. The contents from the /system partition will be removed while the contents of the Internal SDcard will be left unchanged.
Select ‘install zip from sdcard’ and then ‘choose zip from sdcard’. Find the CM10.1 M1 ROM and confirm that you wan to install it on your device.
Select once again ‘choose zip from sdcard’ and install the Gapps zip.
When both zip files have been successfully installed, you should return to the main recovery menu.
Select ‘reboot system now’.
The first boot process of this new ROM shouldn’t take more than 5 minutes to complete and you should wait until the welcoming screen of CyanogenMod 4.2.1 appears.
Test the new ROM and tell us in comments which are its best features.
These were all the steps you had to take. Now you can use this new ROM and remember that you can update it on a daily basis with new Nightly builds. Use the CyanogenMod Updates button under the ‘About phone’ menu.
NOTE: if the first boot process takes too long to complete, then you will have to power off the device by removing its battery. Re-insert the battery and then repeat the entire the tutorial starting with step 5. Make sure that you don’t skip any steps this time and you should also apply the step 7.
In case you cannot complete the install, then you can ask for our help in comments.