David J Taylor wrote:
John Allen wrote:
[]
I found references to possibly using a different HAL (Hardware
Abstraction Layer). I then did what was probably not wise, which was
to change from "ACPI Uniprocessor PC" to "Advanced Configuration and
Power Interface (ACPI) PC". I also set the BIOS option "FSB Spread
Spectrum" to "disabled".
I would have though that "spread spectrum" (implying a continually
changing random frequency) was definitely something to avoid for accurate
timekeeping! As you say, changing the HAL is not something to be
undertaken lightly.
I wonder if you could check just the effects of the spread-spectrum being
enabled or not?
David,
Yes, I have checked with and without FSB Spread Spectrum with both HALs.
My observations for the 4 combinations are:
Motherboard: A7N8X-X (nForce2) Windows XP SP 2
HAL: "ACPI Uniprocessor PC" (with APIC, halaacpi.dll):
1) FSB Spread Spectrum = 0.50% : system clock unstable, NTP did not synchronise
2) FSB Spread Spectrum = disabled : system clock unstable, NTP did not
synchronise
HAL: "Advanced Configuration and Power Interface (ACPI) PC" (no APIC,
Halacpi.dll)
3) FSB Spread Spectrum = 0.50% : system clock stable, NTP synchronised
4) FSB Spread Spectrum = disabled : system clock stable, NTP synchronised
It's a bit anecdotal, but it seems that FSB Spread Spectrum may not make a big
difference. However, I'm still running (3), I'll have to check its behaviour
over a longer period.
It should be mentioned that according to the Microsoft KB article
http://support.microsoft.com/?kbid=821893
there is a quite fundamental difference between the two DLLs:
- Halaapic.dll: uses the Real Time Clock (RTC) to generate clock interrupts
- Halacpi.dll: uses the 8254 Programmable Interval Timer (PIT) to generate clock
interrupts
John
--
John Allen
Bofferdange, Luxembourg
allen{at}vo{dot}lu
http://www.homepages.lu/allen
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