4.8 "Alternate system clock has died" error

John Baldwin jhb at freebsd.org
Sat Nov 19 03:16:04 GMT 2005

On Friday 18 November 2005 10:05 pm, Charles Sprickman wrote:
> Hello,
> I tried this query on -stable, hoping someone here can help me further
> understand and troubleshoot this.
> Reference:
> http://thread.gmane.org/gmane.os.freebsd.stable/32837
> In short, top, ps report 0% CPU on all processes as of a few weeks ago.
> "systat -vmstat" hands out the "Alternate system clock has died" error.
> Box is running 4.8-p24 and has been up 425 days.  Nothing out of the
> ordinary except for the above symptoms.  In searching the various
> lists/newsgroups, it seems that the other folks with this problem have
> fixed it in various ways:
> -early 4.x users referenced a PR that was committed before 4.8
> -some 5.3 users reported this with unknown resolution/cause
> -sending init a HUP was suggested (tried it, no luck)
> -setting kern.timecounter.method: 1 (tried it, no luck)
> -one user seemed to actually have a dead timer

Actually, there was a patch that was committed in 5.4 and 6.0 for this issue.  
You can see the diff here:


That patch would probably backport to 4.x fairly easily.

> The -stable poster had a warning that if the RTC is bad, the machine
> likely won't come back up if I boot it.  That has me very worried as this
> box is very important (mail server).

If it's a software glitch such as the ones fixed in the patch above, your box 
will come up after a reboot without a problem.

> Can anyone help me determine if this is a hardware problem?  If it is, I
> really need to stretch the budget and dig up some new hardware to
> transplant everything into.

That is not very easy to tell.  It's doubtful that it is a hardware problem, 
but if it is, it would require a new motherboard to fix as the RTC is part of 
the southbridge which is rather firmly attached to your motherboard. :)

John Baldwin <jhb at FreeBSD.org>  <><  http://www.FreeBSD.org/~jhb/
"Power Users Use the Power to Serve"  =  http://www.FreeBSD.org

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