PRAM abttery board for the 550MHz, 667MHz, 800MHz, 867MHz and 1GHz models of Titanium PowerBook G4. This board has an integral rechargeable power cell and is used to store perameter ram settings such as date, time and speaker volume.
A dead PRAM battery will cause these settings to be lost when the PowerBook is not connected to the mains and the main battery is removed. In extreme cases it can prevent the PowerBook from starting at all.