First of all a Playstation Bios image is a piece of code/software. It controls many of the basic functions of the system. It is also the Bios you are dealing with when you start the Playstation without a PlayStation disk or if you listen to a music CD. Most freeware PlayStation emulators require a Playstation Bios Image to work. Commercial Emulators including the deceased ones use their own code embedded into the emulator it's self, this can be a drawback of these emulators as the code does not work as well as the original Bios code and can cause Incompatibility with some of the games. However I will come onto commercial Emulators later. It is important to note that the Bios were written by Sony and is subject to Copyright!