[ntp:questions] drift modeling question

Martin Burnicki martin.burnicki at meinberg.de
Mon Jul 21 14:35:47 UTC 2008

David Woolley wrote:
> Martin Burnicki wrote:
>> About which operating system(s) are you talking?
> For powered up timing, MS-DOS, its predecessors if they implemented a
> software clock at all, the MS-DOS Windows (3.0, 3.1, 95, 98, ME, 98SE),
> most, if not all of the NT Windows (NT 3.5, NT 4.0, Windows 2000,
> Windows XP, probably Windows 2003), Linux from start to 2.4, and mostly
> for 2.6, SCO OpenServer.......
> (The tick rate for MS-DOS family systems is a good clue to which timer
> they use.)

Yes of course. I'm familiar with those old DOS systems and timers.
>> The PC's standard RTC chip can certainly generate cyclic interrupts.
>> However, if a cyclic interrupt from the RTC or from another timer chip is
> But generally isn't used for that.  ISTR that some early PCs didn't have
> an RTC and had to be set when booted.

Yes, the PC/AT was the first IBM PC which had an RTC built-in by default. 

As mentioned in my other reply I just wanted you to be more specific.

>> used to drive the scheduler depends on the type and eventually on the
>> version of an operating system, isn't it?
> Divergence into alternative periodic sources on IBM PC type machines is
> very recent.


Martin Burnicki

Meinberg Funkuhren
Bad Pyrmont

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