An update to the PS3 system software was released on 18 October 2011. If you update your PS3 system, the system software version will be 3.73 and the following features will be updated. In order to download PS3 system software version 3.73, you will need a minimum 186MB of free space on either the PS3 Hard Disk Drive (System Update) or on removable storage media (PC Update).
Main features in system software update version 3.73
- Playback quality during use of some PlayStation 3 format software has been improved.
- Depending on the software title, you may not be able to play without first updating the PS3 system software.
- Do not perform updates using any data other than the official update data provided by Sony Computer Entertainment over a network or on disc media, and do not perform updates by methods other than those described in the product documentation or in this site. If an update is performed using data from another source, by another method, or with a PS3 system that has been altered or modified in any way, the PS3 system may not operate properly and may not be able to install the official update data. Any of these actions may void the PS3 system warranty and affect your ability to obtain warranty services and repair services from Sony Computer Entertainment.
Source: PS3 (UK)