Tim:
> I've come across computers that foul up when powered up with
a dead
> CMOS battery. I get the impression that some BIOSs have parts of
> themselves powered only by the battery, and don't get anything from
> the main power supply.
Joe Zeff:
Well, of course. What do you think powers the CMOS when the
computer's off? However, the clock will start to run slow long enough
before the battery dies as a warning.
I was thinking in the other direction: That when mains power is
available, the main supply powers the CMOS instead of the battery, to
prolong its life.
It's a common enough circuit, in some devices. A diode from supply to
clock and memory circuits, a diode from back-up battery to the same
circuit, the greatest voltage drives everything.
By "foul up when powered up with a dead CMOS battery" I meant while
powered up (from the mains) and with a dead CMOS battery...
--
tim@localhost ~]$ uname -rsvp
Linux 3.15.10-201.fc20.i686 #1 SMP Wed Aug 27 21:33:30 UTC 2014 i686
All mail to my mailbox is automatically deleted, there is no point trying
to privately email me, I will only read messages posted to the public lists.
George Orwell's '1984' was supposed to be a warning against tyranny, not
a set of instructions for supposedly democratic governments.