I have a Nortel 6/16 which on power down retains its memory for a about 30 min. On power up the memory is still there but for the time showing a default Jan/01 etc. I see one 5.5 1F cap.on the mother board and one 5.5 1F cap in the cartridge. Which one is for power out info retention and what is the other one for? What backsup the time clock?