SOLVED: Time Clock Stops in FreeBSD 9.0 guest running under ESXi 5.0

Adam Strohl adams-freebsd at
Fri Aug 3 07:46:14 UTC 2012

Just a heads up on the original issue, which is FreeBSD's timer/clock 
stopping under ESXi 5.0 and some later versions of VMware Workstation.

I've gotten a few direct messages that this thread ranks high on Google 
but people are missing the solution.  A few months ago I found this 
forum posting (I believe this was linked in this thread already) 

The long and short of it is that changing the kern.timecounter sysctl 
value to ACPI-fast or (ACPI-safe if you're not running 9.x yet) fixes 
the hanging issue so far for us.

To temporarily enable it under 9.x:
sysctl kern.timecounter.hardware=ACPI-fast

Pre 9.x (which doesn't have the ACPI-fast mode):
sysctl kern.timecounter.hardware=ACPI-safe

To make this persist across reboots and be enabled by default add this 
line to your /etc/sysctl.conf

Under 9.x:

Pre 9.x:

Hope this helps anyone running across this issue.

Adam Strohl

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