Freebsd: Calcru Runtime went backwards.

Freebsd: Calcru Runtime went backwards.


This error can be triggered by several situations:

  1. the time on your bsd system changes unexpectedly, most likely due to syncing with a overloaded or incorrect Network Time Protocol (NTP) server.
  2. In virtual machines, the cpu units are set too high.
  3. Your processor has SpeedStep technology which dynamically changes cpu speed based on load.
  4. FreeBSD has multiple clocks, and chose the wrong one.

Any one of these solutions has been reported to fix the problem for various people. My recommendation is to try them one at a time.

Solution 1. overloaded or incorrect Network Time Protocol (NTP) server.

Edit the /etc/ntp.conf file to your preferred time server.



                server prefer






Solution 2. FreeBSD inside a VM

        Vmware wrote a paper about this issue

        If you are running bsd inside a virtual machine, change the cpu units to 100. On Proxmox virtualization software which I use and love, the default cpu unit is 1000.


Solution 3. CPU Speedstep technology

        Open the bios and disable any sort of speedstep technology

Solution 4. FreeBSD multiple clocks

        Your computer has two or more clocks, and FreeBSD has chosen to use the wrong one. (credit given at link)

FreeBSD chooses the clock with the highest Hz quality. To see what clocks are available enter this command:


                dmesg | grep Timecounter



On my particular system the “High Precision Event Timer” (HPET) was chosen. You can verify this by entering


                sysctl kern.timecounter.hardware



You can change it with this command


        sysctl kern.timecounter.hardware=TSC


About spuder
spuder is a "super computer" support engineer by day, and tinkerer / hobbyist by night.

One Response to Freebsd: Calcru Runtime went backwards.

  1. mcdiesel says:

    Thanks, solution 2 works on pfSense on proxmox.

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