On Tue, 2004-05-04 at 00:59, Carlos E. R. wrote:
> The Monday 2004-04-19 at 18:28 -0700, John Sowden wrote:
> 
> > I am concerned though, as to why this happened.  In addition, is this
> > something that I will have to do periodically?
> 
> No - unless it gets screwed. Yes, every time you manually reset the
> clock. Don't remove the adjtime file for a clock trim.
> 
> Long explanation:
> 
>   http://susefaq.sourceforge.net/howto/time.html
> 
> and/or
> 
> > >         http://lists.suse.com/archive/suse-linux-e/2003-Nov/0001.html
> 
> as Gar kindly said :-)
> 
> -- 
> Cheers,
>        Carlos Robinson
I haven't been following this thread closely and assuming xntp is being
used to synchronise the clocks. I've installed a new motherboard and I
am seeing clock drift possibly because of a low battery, though ACPI is
not reporting anything. I've had to edit crontab "crontab -e -u root"
and insert the following line to keep my clock synched.
* * * * *       /usr/sbin/ntptimeset -S 1 -s >/dev/null 2>&1
Regards
Sid.

-- 
Sid Boyce .... Hamradio G3VBV and keen Flyer
Linux Only Shop.

* Anders Johansson [05-04-04 01:26]:

That runs once a minute. Is it really as bad as that? That can't be good. How much does a CMOS battery cost these days?

BestBuy us$6.95 -- Patrick Shanahan Registered Linux User #207535 http://wahoo.no-ip.org @ http://counter.li.org HOG # US1244711

The Tuesday 2004-05-04 at 07:16 +0100, Sid Boyce wrote:

I haven't been following this thread closely and assuming xntp is being used to synchronise the clocks. I've installed a new motherboard and I am seeing clock drift possibly because of a low battery,

If you had read my article O:-), you would know that while the system is up and running the CMOS clock is not used for anything in linux: thus a low battery has no effect at all; after boot, that is. If that drift is while running, and you have 9.0, read this: http://portal.suse.com/sdb/en/2003/10/pohletz_desktop_90.html If the drift is only at boot time, delete /etc/adjtime

though ACPI is not reporting anything. I've had to edit crontab "crontab -e -u root" and insert the following line to keep my clock synched. * * * * * /usr/sbin/ntptimeset -S 1 -s >/dev/null 2>&1

Every minute! that's not the solution. -- Cheers, Carlos Robinson

The Tuesday 2004-05-04 at 21:56 +0200, Anders Johansson wrote:

The RTC (real time clock) is on the CMOS chip and powered by its battery, as far as I understand.

Correct.

Also, from what I can tell, the CMOS clock is accessed quite frequently as part of the timer interrupt.

No, it is not accessed at all, for many reasons. One, it is a very slow access. Two, the CPU maintains its own clock, and doesn't need it. Linux does not access it at all, except during the boot sequence. Windows accesses it every time you change the hour in the system, to keep both synchronized. Read my howto, it is documented there, and my sources for so saying.

I'm not exactly sure what effect a low or dead battery will have on those, but it can't be good

Nothing at all after boot, while the system is running. And some (or all) of those chips are also powered from the board 5 Vcc while powered up. -- Cheers, Carlos Robinson

The Tuesday 2004-05-04 at 22:43 +0200, Anders Johansson wrote:

...

No, it is not accessed at all, for many reasons. One, it is a very slow access. Two, the CPU maintains its own clock, and doesn't need it.

/usr/src/linux/arch/i386/kernel/time.c

do_timer_interrupt()

It is accessed, around once every 11 minutes it seems, though I'm not entirely certain under what circumstances STA_UNSYNC is set, I didn't trace it that deeply.

Huh? Ah, Well; it can be periodically updated, on certain circumstances: /* * If we have an externally synchronized Linux clock, then update * CMOS clock accordingly every ~11 minutes. Set_rtc_mmss() has to be * called as close as possible to 500 ms before the new second starts. */ That may be of use when the kernel got synchronized by ntpd, for example.

In any case, /dev/rtc has many uses in a running system, even if not by the kernel itself

Of course it has :-)

...

Read my howto, it is documented there, and my sources for so saying.

I only read one source.

I never read only one source for any writeup :-)

...

And some (or all) of those chips are also powered from the board 5 Vcc while powered up.

OK, that is interesting. Then maybe this debate is entirely pointless :)

-- Cheers, Carlos Robinson

The Friday 2004-04-30 at 13:35 +0200, Robert Rozman wrote:

What do you mean to repeat adjustment at boot. Should I run : "hwclock --systohc" and remove /etc/adjtime

on every boot ?

No, read again:

...

"rm /etc/adjtime" (all w/o quotes)

so time adjusting scripts don't think that the clock was slow or fast, and repeat the adjustment automatically on boot.

If you do not remove /etc/adjtime the boot script will try to adjust the clock the next time you but, and do it badly, because the clock was manaully reset last time. -- Cheers, Carlos Robinson