> 65536 ticks per hour would be approx 18.2hz, which definitely can't be
> true. Timekeeping accuracy does not depend on the actual value of the
> oscillator frequency, but of course it depends how precisely the
> oscillator frequency matches the agreed standard frequency, and on it's
> stability. The el. cheapo oscillator story sounds more feasible. I believe
> the clock kept in the CMOS RAM uses a different time base, so in theory it
> would be possible to regularly syncronize the 'DOS clock' to the CMOS
> clock, which already happens when a computer is rebooted, so the
> motherboard manufacturers are reasoning 'we're saving money, and software
> can fix it, so lets do it'.
The current time code for most systems with cycle counters is permanently
computing the number of cycle counter cycles p
> I scanned some PI mainboards and a PII board for the crystal oscillators,
> and all of them have a crystal on which at least the digits "14.3" are
> written, some of them "14.318", and an Intel TX-based socket 7 motherboard
> even has the full "14.31818" written on its oscillator. We can calculate
> that a clock of 14.30000Mhz instead of 14.31818Mhz would result in the
> clock lagging approx. 1.8 minutes per day. If the '14.3' crystals can
> range from 14.25..14.35 Mhz, then te clock error can be, in extremes -6.8
> minutes to +3.2 minutes per day. So your story of el. cheapo oscillators
> could be true for compaq (and for some of my boards). Maybe compaq figured
> computers would be switched on at the beginning of each workday, and that
> a time difference of less than 2.5 minute per workay in extreme cases
> would be sufficiently precise. For a computer that reboots (crashes) every
> 3 hours, the maximum time difference would always be less than a minute!
> (?)
Crystals deliver the frequency within a few ppm of the specified frequency.
The frequency also is temperature dependant; the next step to higher
accuracy is keeping the oscilator at constant frequency.
Ralf
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