[Beowulf] Mobo battery life in constantly on systems?

[David Mathog]

The question: what is the expected motherboard battery lifetime in
systems that are continuously on?

Background:

The question arises because it was necesary to cycle the power today
on a couple of nodes by unplugging them and then plugging them 
back in again.  When one came back up the BIOS settings were gone.
That wasn't evident until a keyboard and monitor were plugged in.
Losing BIOS settings when power is removed is pretty much the
classic symptom of a dead motherboard battery.  

These nodes are now about 5 years old, and that is about the average
battery lifetime in PCs that are turned off every night.  However these
nodes have been on 99.99% of that time, so presumably the drain on the
battery should have been nil.  Shelf life for motherboard batteries is
typically about 10 years. There is no info on how old the batteries were
that went into these systems, but presumably Tyan goes through a lot of
batteries and these were probably fresh when installed.

So bottom line, is this just a freak event or would you expect the
other motherboard batteries to also die soon?

Thanks,

David Mathog
mathog at caltech.edu
Manager, Sequence Analysis Facility, Biology Division, Caltech