IBM CMX58886CX - Manual (Page 36)

28 CMX58886CX cpuModule BDM-610000050 Rev A
Battery
Pin 9 of the multi-function connector is the connection for an external backup battery. This battery is used by
the cpuModule when system power is removed in order to preserve the date and time in the real time clock.
Connecting a battery is only required to maintain time when power is completely removed from the cpuModule.
A battery is not required for board operation.
WARNING The optional RTC battery input connector (CN13) should be left unconnected if the
multi-function connector (CN5) has a battery connected to pin 9.