Messages in this thread |  | | From | (Andreas Koppenhoefer) | Subject | Re: time warps, I despair | Date | 04 Nov 1996 12:33:44 +0100 |
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>>>>> "IM" == Ingo Molnar <mingo@pc5829.hil.siemens.at> writes: In article <Pine.LNX.3.93.961101175301.3565B-100000@pc5829.hil.siemens.at> Ingo Molnar <mingo@pc5829.hil.siemens.at> writes:
IM> On Thu, 31 Oct 1996, Ulrich Windl wrote: IM> >> So what's the effect? From time to time the clock offset jumps for >> some amount always less or equal to what's worth one tick (i.e. >> offset jumps around from -5ms to 5ms when synchronized). [...] IM> IM> this could be caused by a 'lost jiffy'. Lost jiffy is a timer hardware IM> interrupt that misses us completely. Under normal hardware circumstances IM> (no APM, etc.), this is only possible if there is a cli()/sti() pair that IM> lasts for more than 10 millisec. IM> IM> You can totally eliminate the Pentium stuff by turning APM support on in IM> the kernel (or commenting out the last few lines in time.c), thus the PIC IM> timer is used as high precision timing offset source.
Sorry, but I think this is NOT only pentium related - It might be a more general problem!
Ulrich's graphs show spike interval of 10-12 minutes if I read these graphs correctly. On my system I can see a similar spike interval of about 120 minutes.
My system is a i486-DX2/66 running on a ASUS-SP3G motherboard with xntpd-3.4z and linux 2.0.14. I see this anomaly for about two years now (since kernel 1.1.3x or so). Time source is a cheap DCF77 receiver on a serial port. Before you ask: There are no processes which runs every even hour like cron or so.
- - Andreas
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