[miro]

I'd have thought that with flash memory these days it's not necessary to have a battery for storing some settings. But that's why I speculated about older devices, before flash so to speak. An internal clock is certainly something that needs a battery, since that is not static, it has to run.

My two canon camera has flash eeprom en backup battery. there are 3 different type of memory and they all have purpose.
1. Flash for big chunk of data/ boot SW. 
2.eeprom for logging and settings data
3. sram or so called CMOS  / RTC RAM for volatile data - think about RTC - real time clock/ date, logging and telemetry data
So far this 3 blocks are  common for all brands.  The SW architecture is what make difference.