The first custom ROM based on the latest Android version compatible for the AT&T Samsung Galaxy S3 is now available - the CyanogenMod 13.

To install the CM13 ROM, users should satisfy several requirements first such as ensuring that they have the correct model for the smartphone. According to Team Android post, the CyanogenMod 13 ROM update is only compatible with the AT&T Samsung Galaxy S3 with model number SGH-I747.

To easily verify the smartphone's model number, AT&T subscribers only need to go to Settings > About Phone > Model Number.

Another essential requirement to secure before installing a custom ROM in the AT&T Samsung Galaxy S3 is a reliable recovery tool. This will ensure that all the data and settings found on the handset device will have a proper backup before the installation process.

Team Android warned the readers that installing a custom ROM such as the CyanogenMod13 based on Android 6.0 Marshmallow update could wipe clean the mobile device. Thus, recovery tools such as ClockWorkMod Recovery or CWM and the TeamWin Recovery Project or TWRP are advised to be used by Android experts.

It is also necessary that the smartphone has at least 85% battery level to avoid interruptions when the installation is ongoing. Another thing to consider before installing the CyanogenMod13 Android 6.0 Marshmallow ROM is that using a custom firmware automatically voids the warranties available for the smartphone.

Those who have fully decided to use the CM13 custom ROM to update to Android 6.0 Marshmallow will need to download the CyanogenMod 13 custom ROM as well as the Google Apps (GApps) zip files. After doing so, connect the AT&T Samsung Galaxy S3 to the PC and save both the files into the root directory of the phone or the SD card.

Turn off the AT&T Samsung Galaxy S3 and then disconnect it from the PC. Go into the Recovery Mode by pressing the Volume Up, Home and Power buttons.

Once in the Recovery mode, S3 users need to delete the smartphone's memory by choosing the "wipe cache partition." Return to the recovery screen and select "install zip from SD card." Choose the CyanogenMod 13 ROM saved in the SD for the update process to commence.

After installing the custom firmware, AT&T Samsung Galaxy S3 users should restart the device through simply tapping "reboot system now" option from the recovery screen.

The AT&T Samsung Galaxy S3 became available in the market on July 2012. At launch, it is pre-installed with Android 4.0 Ice Cream Sandwich OS. Currently, it is only officially upgradable using the Android 4.1.1 Jelly Bean, GSM Arena noted.

Below is a review from Phone Dog for the AT&T Samsung Galaxy S3, posted on Youtube :