Date: Tue, 23 Dec 2003 01:04:19 +0100 (CET) From: Barry Bouwsma <freebsd-misuser@remove-NOSPAM-to-reply.NOSPAM.dyndns.dk> To: Freebsd Current <current@FreeBSD.org> Subject: CMOS checksums (was: Re: SC520 and reboot ) Message-ID: <200312230004.hBN04Jo03608@NOSPAM.spam.NOSPAM.spam.NOSPAM.dyndns.dk> References: <23707.1071348202@critter.freebsd.dk> <20031214090456.Q7016@gamplex.bde.org>
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Bruce Evans <bde@zeta.org.au> wrote...
> On Sat, 13 Dec 2003, Poul-Henning Kamp wrote:
> > If you run adjkerntz -a it fiddles the CMOS RTC clock and possibly the
> > "century" byte I think. If your BIOS uses a checksum on the RTC and
> > adjkerntz doesn't know about it, your BIOS will think the contents is
> > trashed.
> Actually, adjkerntz -a uses the MI interface resettodr() to set the
> hardware clock, CMOS or otherwise. This has the same tiny chance of
This sounds like what my latest found motherboard is suffering from.
It has two problems affecting shutdowns:
1) Often, the CMOS checksum is claimed to be invalid at poweron, so my
BIOS settings are lost, but not always;
2) It appears to stop keeping time at poweroff, I think. When I boot
back up, ntpdate steps the time by an amount comparable to the time
I had it off to swap cards or whatnot.
I had to replace the on-board lithium battery, otherwise I'd lose CMOS
checksums every time.
Ideally I'd rather never powerdown, but I'm wondering if it's possible
for FreeBSD to ignore the CMOS clock -- never updating it, either with
resettodr() (in sys/kern/kern_time.c that I've found; haven't done a
rigorous search yet) or any other call that jerks around the CMOS time,
so I can avoid, hopefully, the checksum errors that pop up now and then.
Meaning my CMOS time would remain 2008 or 1986 or whatever it's set
itself to randomly, or 2003/2004 but losing a few minutes each poweroff,
while the system time would be set at boot (ntpdate/ntpd) and remain
accurate. There would be no correlation between the two, other than
that the CMOS time ticks so long as power is applied.
Is this possible, or am I going to break something, more than the
occasional CMOS checksum failures I get now? Seems like I'd comment
out any resettodr() calls I find, and if anything else adjusts the
CMOS clock, I'd have to find and comment it out too.
Comments?
The motherboard seems of vintage 1994-1997-ish, intended for Pentiums of
roughly 75-150MHz speed. It has other minor issues too, but seems to
work otherwise...
thanks
barry bouwsma
scrap computer collector
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