Samsung S3 (I9300) Marshmallow




Previous to update Galaxy S3 I9300 to Android 6 CM13 requirements:
Back up important data on your Samsung Galaxy S3 I9300 as a full clean during flashing is required.
Settings> Developer Options> USB Debugging: USB debugging option on the enabling device.
Samsung Galaxy S3 I9300 must be rooted, unlocked and installed with a recovery tool TWRP or CWM like.
The device must be charged at least 60% power.
Note: This tutorial focuses on the Samsung Galaxy S3 I9300; Please do not try this guide on other Android and Samsung device..

How To Update Galaxy S3 I9300 Android 6.0 CM13 Marshmallow:

necessary files: download custom firmware 6.0 per night for Galaxy S3 I9300 Android CyanogenMod 13 and save it to your computer. Do not remove the content.
Connect the Galaxy S3 to your computer via a USB cable and copy the zip file to the phone’s SD card.
Disconnect the USB cable and turn off the Galaxy S3.
Boot into recovery mode by pressing and holding the volume buttons up + Home + Power together.
Perform a Nandroid backup of your current operating system: Backup> Backup and Restore ClockworkMod recovery.
Clean data Task: from the CWM recovery menu, select restore wipe data / factory and confirm the process. Then go to delete cache partition and wipe the Dalvik cache.
From the recovery menu, select install zip from sdcard followed by choose zip from sdcard. Look for the CM13 Android 6.0 custom firmware marshmallow and confirm the flashing process.
Back to main recovery menu and restart the Samsung Galaxy S3 I9300 in the new custom ROM. The first boot may take a few minutes.