i386/104867: Clock running at 2x speed of wall clock

[Jeffrey Brower]

Wow!  I wish I could have found you back in 2006!  This sounds like the
perfect solution as my clock was in solid error and the problem was never
transient.

I still have that board so I might pull it down just to prove this, but I
think you have a solution for my problem here.  I hope it helps someone
correct their computer clock.  Thanks for replying!

--  Jeff
 

-----Original Message-----
From: Bruce Evans [mailto:brde at optusnet.com.au] 
Sent: Saturday, May 10, 2008 6:58 AM
To: Jeffrey Brower
Cc: freebsd-i386 at freebsd.org
Subject: Re: i386/104867: Clock running at 2x speed of wall clock

On Sat, 10 May 2008, Jeffrey Brower wrote:

> I verified that the timecounter was indeed i8254 after I recompiled 
> with that option and it still ran double time.

With the i8254 and precisely double time, just type in the correct
(doubled) freqency to "sysctl machdep.i8254_freq=..."  With the APCI-fast
timecounter, first fix the bug that the corresponding sysctl is read-only.

> Everything I tried failed - even NTP gave up because it was constantly 
> slewing.  No one could solve it and I never got an answer so I ended 
> up

NTP can't reasonably handle a 2x error in the clock frequency.  Nor can
fixing a 2x error work if the error is transient.

Bruce