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Date: Mon, 10 Jun 1996 18:00:51 -0600
From: Nate Williams <nate@sri.MT.net>
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To: Bruce Evans <bde@zeta.org.au>
Cc: current@freebsd.org, nate@sri.MT.net
Subject: Re: CLOCK stuff at bootup
In-Reply-To: <199606102355.JAA01251@godzilla.zeta.org.au>
References: <199606102355.JAA01251@godzilla.zeta.org.au>
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> >CLK_USE_I8254_CALIBRATION not specified - using default frequency
> >CLK_USE_I586_CALIBRATION not specified - using old calibration method
> >i586 clock: 0 Hz
> >CPU: Pentium (75.16-MHz 586-class CPU)
> >  Origin = "GenuineIntel"  Id = 0x524  Stepping=4
> >  Features=0x1bf<FPU,VME,DE,PSE,TSC,MSR,MCE,CX8>
> 
> >I'm assuming I'm supposed to define one or both of the above, but why?
> 
> Because defining one or both might work better.  Using sysctl to set the
> actual (current) value might work better still.

Umm, what am I supposed to set using sysctl?  I don't remember ever
seeing this kind of detail in old email.

> >How do I determine which one is the more accurate, since obviously the
> >i854 clock is not running at the same frequency as my Pentium chip. :)
> 
> The i8254 clock determines long term accuracy.  Run for a while and
> determine the drift and/or the time daemon adjustments.

How?

> Use sysctl to
> specify the i8254 clock frequency that minimizes the drift and/or the
> adjustments or accept the default from calibration or accept the fixed
> default.

How?

> The i586 clock determines intra-clock-interrupt times.  Specify the i586
> clock frequency that minimizes the jitter in getttimeofday().

How?