Amazon Kindle Fire HD 7″ is a great tablet with 7″ display. It runs on the Dual-core 1.2 GHz Cortex-A9, PowerVR SGX540 GPU. It also has 1 GB of RAM. The camera is a bit disappointing with 1.3 Megapixels. Kindle Fire HD ran on the Android 4.0 OS at the time of its release.
Android 4.0 was released more than 3 years ago and it is a very old OS. You can upgrade the Kindle Fire 7″ to Android 5.1 via the CM 12.1 custom ROM. Interested users can follow the guide given below.