Xiaomi has finally released a firmware update (V45) for his most popular smartphone, the Redmi 1S. The firmware can be downloaded from the link which is provided at the end of the article, or also can be upgraded via OTA.
Based on users reviews, Redmi 1S gets very hot (sometimes above 45C), particularly in warmer areas of India. So, the company has improved thermal control algorithm to better regulate temperature and keep it under 38C in normal usage conditions.
Some users from India had pointed out that background apps are sometimes getting killed more aggressively than they would expect (for example, music player stopping while user is playing a 3D game). The company has made a few significant improvements in how MIUI manages RAM on a 1GB device, which has resulted in noticeable improvements.
Xiaomi has also confirmed that the Redmi 1S comes with a 1.6 GHz Qualcomm Snapdragon 400 MSM8228 but some 3rd party apps report a MSM8226. The smartphone comes with a Lithium-ion Polymer (lithium polymer or li-poly) battery, not Li-ion battery.
You can read more about the problem and rectifications at Xiaomi Forum.