It could have been located away from view on the other side of the motherboard, as is sometimes the case.
As for what the full intended purpose and potential capabilities of these secondary batteries are, I have no idea since that's not documented. I do know that it's for a whole lot more than an RTC, however.
As for what the full intended purpose and potential capabilities of these secondary batteries are, I have no idea since that's not documented. I do know that it's for a whole lot more than an RTC, however.