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From: John Hay <jhay@mikom.csir.co.za>
Message-Id: <199510191319.PAA27646@zibbi.mikom.csir.co.za>
Subject: Re: clock running faster?
To: bde@zeta.org.au (Bruce Evans)
Date: Thu, 19 Oct 1995 15:19:05 +0200 (SAT)
Cc: freebsd-current@FreeBSD.ORG (FreeBSD-current)
In-Reply-To: <199510191251.WAA16201@godzilla.zeta.org.au> from "Bruce Evans" at Oct 19, 95 10:51:40 pm
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> 
> >Yesterday I rebooted my current machine (90M Pentium) with a new kernel. The
> >previous kernel was build on the 13th. Now suddenly the clock gains almost
> >30 second in an hour. Previously the clock was very stable. I have even
> >rebooted and it still does it.
> 
> >Has anybody seen something like this? I see there were changes made to
> >i386/isa/clock.c and kern/kern_clock.c.
> 
> The changes have the effect of making the Pentium clock the reference.
> Apparently your 8254 clock's frequency is closer to its nominal value
> (1193182 Hz) than your Pentium clock's frequency is to its measured
> value (pentium_mhz = N MHz where N is as reported at boot time).  The
> measurement and use of N depends on N being an integer for accuracy.
> Apparently the measured value is too small by a factor of 90/90.75.
> 
Those measurements made on kernel startup does not seem stable. Here is a
grep in my /var/log/messages file.

  Oct 18 18:39:57 angel /kernel: CPU: 86-MHz Pentium 735\90 or 815\100
	(Pentium-class CPU)
  Oct 18 18:42:11 angel /kernel: CPU: 87-MHz Pentium 735\90 or 815\100
	(Pentium-class CPU)
  Oct 19 11:53:40 angel /kernel: CPU: 83-MHz Pentium 735\90 or 815\100
	(Pentium-class CPU)
  Oct 19 11:57:18 angel /kernel: CPU: 85-MHz Pentium 735\90 or 815\100
	(Pentium-class CPU)
  Oct 19 11:59:33 angel /kernel: CPU: 89-MHz Pentium 735\90 or 815\100
	(Pentium-class CPU)

John
-- 
John Hay -- John.Hay@csir.co.za