Clock drift on an iBook2

3 messages, 2 authors, 2001-07-17 · open the first message on its own page

Clock drift on an iBook2

From: Ethan Blanton <hidden>
Date: 2001-07-17 14:27:30

Hi,
I have a new iBook2 and I'm having *severe* clock drift problems -- on
the order of several seconds gained per minute.  I'd like to get this
taken care of, and it seems to be a linux problem as OSX appears to
have a stable clock.

I'm running BenH's 2.4.7-pre6 right now, but I also saw it on 2.4.6.

Is this a known problem?  If not, what can I do to help get this fixed?
Ethan

-- 
If I've told you once, I've told you once
And once is all that you needed.
		-- The Refreshments, "Carefree"

Re: Clock drift on an iBook2

From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Date: 2001-07-17 16:50:32

I have a new iBook2 and I'm having *severe* clock drift problems -- on
the order of several seconds gained per minute.  I'd like to get this
taken care of, and it seems to be a linux problem as OSX appears to
have a stable clock.

I'm running BenH's 2.4.7-pre6 right now, but I also saw it on 2.4.6.

Is this a known problem?  If not, what can I do to help get this fixed?
Ethan
Are you using MOL or do you experience this with nothing special running ?

Do you have the same issue if you disable powersave_nap (/proc/sys/
kernel/powersave_nap) ?

The TB is calibrated using the VIA, if we don't have a correct VIA frequency
or if the calibration routine is slightly off, that may also explain the
problem.

Ben.


** Sent via the linuxppc-dev mail list. See http://lists.linuxppc.org/

Re: Clock drift on an iBook2

From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Date: 2001-07-17 16:52:31

quoted
I have a new iBook2 and I'm having *severe* clock drift problems -- on
the order of several seconds gained per minute.  I'd like to get this
taken care of, and it seems to be a linux problem as OSX appears to
have a stable clock.

I'm running BenH's 2.4.7-pre6 right now, but I also saw it on 2.4.6.

Is this a known problem?  If not, what can I do to help get this fixed?
Ethan
Are you using MOL or do you experience this with nothing special running ?

Do you have the same issue if you disable powersave_nap (/proc/sys/
kernel/powersave_nap) ?

The TB is calibrated using the VIA, if we don't have a correct VIA frequency
or if the calibration routine is slightly off, that may also explain the
problem.
Something else you can try: in arch/ppc/kernel/pmac_time.c, comment
out the call to via_calibrate_decr() (and the return too) so that
we use the device-tree "timebase-frequency" instead, and tell us if
it makes any difference.

Ben.


** Sent via the linuxppc-dev mail list. See http://lists.linuxppc.org/
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