backup and capacitor for short term memory storage. The battery only kicks in when the capacitor is discharged. The capacitor will hold the info in the memory for about a week and then it draws off the battery. The drain is miniscule. But when you turn the car on, the capacitor charges up quickly via the power terminal on the EPROM socket. So once you set your parameters, disconnect your laptop and you are ready to go. No burning chips - that's archaic.
