[ntp:questions] drift modeling question
unruh-spam at physics.ubc.ca
Fri Jul 18 21:59:03 UTC 2008
David Woolley <david at ex.djwhome.demon.co.uk.invalid> writes:
>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
>> 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.
>> 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
There is the rtc, and then there is the timer chip on the PC board. I
thought that they were very different. The RTC is the on board real time
clock powered by a battery on the cmos. The timer interrups are a divisor
of the main bus clock that drives the computer bus I believe. I thought we
were talking about the rtc, not the bus clock. ( int 8 not int 0)
More information about the questions