"Peabody" wrote in message
...
The standard instructions for changing out a desktop CMOS battery say you
should turn everything off and unplug the power cord. But I wonder if
guys
who do this kind of stuff for a living don't hot swap the batteries with
the
power on, or at least leave the power cord plugged in so the always-on 5V
supply provide power to the CMOS. That should prevent losing the contents
of
the CMOS memory, including the TOD and the BIOS settings.

There doesn't seem to be any logic to hot swapping a CMOS battery - many
motherboards have a jumper header to discharge the smoothing caps on the RTC
rail - it holds for at least a few minutes with the battery out.

Usually you don't even know it needs replacing till boot up reports a CMOS
checksum error - then I just fit a new battery and load optimum defaults.
There's only a couple of values I need to set manually.