Clock drift on an iBook2

Benjamin Herrenschmidt benh at
Wed Jul 18 02:52:31 EST 2001

>>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?
>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

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.


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