Though Stock firmwares are always more stable, the custom ROMs can provide you more flexibility in terms of features, performance and other customizations. Companies tend to freeze the OS updates once the device becomes old in terms of hardware or lag in market value.
The Samsung Galaxy S3 is one of the most popular and stylish smartphones from Samsung and there are still a huge number of users who look to have the latest android OS on their device. You can still update the device to Android 5.0.2 based CM 12 Lollipop. Though CynogenMod hasn’t released the Official CM12 build for SIII I9300 yet, there are a number of UnOfficial CM12 builds available for installation.
I have been using this build for almost 2 weeks and I can say it is close to a stable build. So for users who want to have the Lollipop flavor on their Samsung S3 GT- I9300, can follow this guide to flash it on their devices.
PreRequisites: (click here to know How to Root Galaxy S3 GT-I9300)
- Take a backup of your important data and settings using a custom recovery such as ClockworkMod(CWM) or TWRP to create a full image of the existing data. In case anything goes wrong then you restore your data.
- Enable USB Debugging Mode on your Galaxy S3 GT- I9300 by going to Settings > Developer Options
- Your Galaxy S3I9300 should be rooted with TWRM recovery installed. Click here for steps to install TWRP.
- The bootloader of the phone should be unlocked.
- Make sure that the battery of your phone is at least 60% charged before proceeding to the installation guide.
Steps: [Note: Please use TWRP 188.8.131.52 or above for flashing. The screenshots shown below are for reference only.]
- Download the CynogenMod CM12 custom ROM and Google Apps Package (GAPS) on your desktop PC. Make sure you are downloading the right files available for your device.
Links– CM12 UnOfficial Build for Galaxy SIII I9300 Download Link [Build Updated on 1-04-2015]
For Latest CM 12.1 build please visit the below link-
These are ZIP files and should be saved as it is on your PC.
- Connect your Galaxy S3 GT-I9300 device to the PC and copy the 2 ZIP files to the root folder of your SD card.
- Disconnect your device from the PC and switch it off in order to boot it in recovery mode.
- Turn ON the device by pressing and holding Volume Up + Home + Power keys at the same time.
- The Galaxy S3 GT-I9300 will boot in TWRP recovery mode. Go to Backup option and take a full backup of your phone so that you can recover it to last backup in case of any issues.
- Next Go the Wipe option and perform a full data wipe using the Factory Reset option.
- You can use the Volume keys to navigate between options
- Power button to select an option in the Recovery Mode
- Now in Wipe option, go to Advanced and select the Wipe Cache/Dalvik. (Wiping the Cache/Dalvik helps to avoid the boot loop issues)
- Now go back to the Main menu and select the Install option. Select the location as SD Card and select the CM12 build ZIP file from the location you had copied earlier. Start the installation.
- Now select the GAPS ZIP file and install it.
- After Installation, go back to main menu and Reboot the device.
- Your Galaxy S3 I9300 will reboot with Android 5.0.2 Lollipop. It may 4-5 mins approx for first time reboot. Enjoy Lollipop on your phone.
Screenshot- [This is a device dependent process so please be careful while performing the installation. Same steps can be used for other devices as well as long as you have the correct CynogenMod build file].
You can download the Official CynogenMod build version for your device from the following link-
Please refer to the following XDA forum for ChangeLogs/Updates/Details on the CM12 Galaxy SIII I9300 build file-
Please leave your comments and feedback.
I’ll keep updating the POST to include CM12 build updates as they come.
Thanks for checking out !