"N_Cook" wrote in message
news
On 11/01/2017 20:14, Benderthe.evilrobot wrote:

"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.

The clue for me , is progressively worsening internal clock timekeeping.
Incidently , hot soldering a tag, remove the power from the soldering iron
before soldering , while still hot

IME: The time and date data usually survives - but it surprises me every
once in a while.