T-Mobile was supposed to release Android OS 1.5 (originally code-named ‘Cupcake’) was supposed to be released the week of May 18th. However T-Mobile decided to delay the release.

Enter the Android community… Someone has found the downloadable version of Cupcake, signed and ready to install on the T-Mobile G1! And with a few simple steps, you can install it before the T-Mobile OTA (over-the-air) push.

Now, without any further ado – the following warning:

WARNING: T-Mobile does not support manual installations and will not assume responsibility for any device problems or failures that occur from following these instructions.

*NOTICE: This can be a risky procedure, and if you make a mistake and brick your phone: T-Mobile, the T-Mobile Forums, authors of this post (i.e. ME), or other subsequent discussions, nor any party, company, corporate entity, individual, or estate; living or dead, associated or otherwise connected with the above shall not be held liable for any damage you do to your device, others devices, your person, other people/living things, or property belonging to you any other entity in the known universe should you attempt to root your phone. You take full responsibility and liability for any action you choose to take to attempt to gain root access to your phone. Do this at your own risk.

  1. Go download the Android 1.5 ‘Cupcake’ release here.
  2. Rename the downloaded file from signed-kila-ota-148830.de6a94ca.zip to update.zip and place it at the root i.e the very top directory of your Micro SD card. (If you added the file to your microSD card by connecting the handset to your computer via USB [rather than using a dedicated microSD card reader], make sure to unmount it and disconnect the USB cable now.
  3. Turn off your G1 Make sure it is completely powered off. Now again turn it on by holding the Home+End keys until you see T-Mobile G1 logo.
  4. From the icon screen, open the keyboard and hit Alt+L.
  5. Press Alt+S to begin the update. Remember, the update needs to be in the root of the Micro SD card and needs to be named update.zip.
  6. Once it finishes, follow the onscreen instructions and press Home+Back to finish.
  7. G1 Phone will reboot a few times to flash different parts of the firmware.

If all went well, you should now be running Android Release 1.5 on your T-Mobile G1…!

And, yes.. I installed it using the above steps.. and it’s working great..!