Dave Plowman (News) wrote:
In article ,
Paul wrote:
A few systems won't start if that battery is flat. That's
when you'll begin to care about it. None of my systems here
have exhibited that behavior (as just about every computer
here has run the CR2032 battery flat at some point).

I suppose it depend on spec. If you have more than one HD, the CMOS won't
remember which one to boot from. But doesn't exactly take long to reset
the date and time, and tell it which one is needed.


The symptoms are suggestive the BIOS POST is stopping well before
it gets to sniffing hard drives or anything else.

I don't have a good theory as to why a flat battery should
stop a BIOS. One of my systems here, will say something
like "Press F1 to enter BIOS" when a bad checksum on the
CMOS (from the flat battery) is detected, and the user
then loads up the settings as desired. And the settings
stay there for that session, as long as +5VSB is present.
Once you switch off at the back, the next time mains power
is applied, you're back to the "F1 prompt".

On the small number of affected systems, there is no
opportunity to press F1, because the BIOS has stopped
the POST at that point. It's a black screen early in POST.

The people who suffer these, don't usually have any equipment
to be offering clues as to what's up. Like a Port 80 card output,
a check of the RESET signal to see if it's a Power_Good type
issue, or whatever.

Paul