[ntp:questions] Is 24PPM an Excessive Real-Time Clock Correction?
root at localhost.invalid
Thu Jul 12 13:13:23 UTC 2007
Per Hedeland wrote:
> Spoon wrote:
>> The HPET is supposed to replace all the other clocks I mentioned.
>> Some manufacturers do choose high-quality components when they implement
>> the HPET.
>> Intel south bridges have included an HPET for some time now. Perhaps
>> other manufacturers will follow their lead?
>> We agree that the situation right now is pathetic. I was saying that
>> maybe, just maybe, there is hope on the horizon?
> Well, the HPET, as specified by Intel and as far as I understand, is
> still just another set of timers/counters, isn't it?
I'm afraid you're probably right.
I thought a separate oscillator would be required when I read:
"Main Counter Tick Period: This read-only field indicates the period at
which the counter increments in femptoseconds (10^-15 seconds). A value
of 0 in this field is not permitted. The value in this field must be
less than or equal to 05F5E100h (10^8 femptoseconds = 100 nanoseconds).
The resolution must be in femptoseconds (rather than picoseconds) in
order to achieve a resolution of 50 ppm."
> Maybe designed to
> tick faster and have more bits than the others (though with 500 ppm I
> think 11 bits gives you all the *precision* you can get:-) - but the
> interesting part as far as NTP is concerned is the little box with
> "Clock Gen" inside it, which is not discussed in the spec beyond the two
> numbers you quoted, as far as I can see.
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