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Date:	Tue, 12 Sep 2006 20:04:38 -0700
From:	Peter Skye <pskye@peterskye.com >
Reply-To:	scoug-programming@scoug.com
To:	scoug-programming@scoug.com
Subject:	SCOUG-Programming: Ouch! SysSleep(), NTP, cpu clock

Content Type: text/plain

> Hi Peter,

Well hi there Nathan,

> . . . every day that it would add about 30 seconds to the RTC.
> I found it to be a problem with the motherboard.

Yes, that makes sense since iirc the oscillator is on the motherboard.

> I replaced the motherboard with a newer one and have never had that problem again.
> I think it loses a second now every couple of days with the newer motherboard.

The oscillator frequency is, among other things, temperature sensitive.
I have to synchronize to an accurate external clock such as NTP does.

> I also have a program that I wrote that reads nist.time.gov every hour.

I use OS2NTPD because it constantly updates the RTC using a software
phase-locked loop. Essentially, your RTC is always correct since the
updates are done as soon as the RTC is off by more than 1/2 cycle.

> The OS/2 API has DosSleep(xx) where xx is milliseconds.
> It uses the hi-res timer and not the RTC.

Thanks for this info. I think I remember that the Intel architecture
contains some on-chip counter/timers (3 of them maybe?) and perhaps one
of them is how DosSleep() is implemented. DosSleep() using the hi-res
timer is consistent with my observations about the inconsistencies of
the sleep function and the RTC.

Thanks again,

- Peter

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