Slow Clock in guest OS on VMWare Server 1.x

When using VMware Server 1.x, I’ve encountered a few guest Virtual Machines, VMs, where the clocks do not advance correctly. What is especially frustrating about this is that frequently the clocks in the other guest VM’s on the same host are operating correctly. I’ve not yet determined what causes the inconsistency across the guest VM’s, but overtime, I’ve found a few tricks to work-around this issue.

Trick #1 — Host OS power management may be causing the host to update the clock incorrectly, tell the VMware server software the real clock speed of the cpus by modifying the config.ini.

Add the following entries and restart the vmware authorization server

  • host.cpukHz = “30000000″ (this example is for a 3 GHZ system)
  • host.noTSC = “TRUE”
  • ptsc.noTSC = “TRUE”

On windows the default location of the VMware config.ini is C:\Documents and Settings\All Users\Application Data\VMware\VMware Server

On Linux this file is in /etc/vmware/config

Trick #2 — set the VMware Tools Clock Synchronization to update more frequently by editing the .vmx file and adding

  • tools.syncTime = “TRUE”
  • tools.syncTime.period = “1″ (this is for a 1 second update)
  • timeTracker.periodicStats=”True”
  • timeTracker.statsIntercal=”10″

A word of caution, If you use Trick #2 and later you attempt to convert the VMWare Server VM to ESX , then you may have to comment out or remove these items

  • tools.syncTime.period
  • timeTracker.periodicStats
  • timeTracker.statsIntercal

from the .vmx file. At least one version of VMWare converter did not create a VM that I could use in ESX, until I had removed those items prior to running the converter.


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  • John the Pirate – Arrr!

    Good post, I like your writing style! I’ve added to my feed reader, and will be reading your posts from now on. Just a quick question – did you design your header image yourself, or have it done professionally? If you had it done by a professional, who was it?

  • david

    Hi John,
    Thanks for the kind remarks.
    The images were the default ones from the wordpress theme. I’ve now switched my theme to PrimePress.

  • Nick

    Awesome post, I’ve been pulling my hair out over time drift in my Ubuntu VMs. Normally time isn’t an important thing for most of what I do, but I run my MythTV backend in a VM and after upgrading to an i7 processor, my clock was drifting causing me to not record my shows on time. Option 2 was the ticket for me. Thanks a million.

  • AdminIMGE

    This issue was such a pain for me that I wanted to post our solution because I didn’t find it during days of searches the past week or so.

    In my case we are running VMWare Server 2.02 on Windows Server 2003 R2 Standard. The Host is also Windows Server 2003 R2 Standard. I had the VMware Tools installed and set to sync the time. I did everything imaginable that I found on various internet sites. We still had horrendous drift, although it had shrunk from 15 minutes or more down to the 3 or 4 minute range.

    Finally in the vmware.log I found this entry (resides in the folder as the .vmx file): “Your host system does not guarantee synchronized TSCs across different CPUs, so please set the /usepmtimer option in your Windows Boot.ini file to ensure that timekeeping is reliable. See Microsoft KB… for details and Microsoft KB… for additional information.”

    Cause: This problem occurs when the computer has the AMD Cool’n'Quiet technology (AMD dual cores) enabled in the BIOS or some Intel multi core processors. Multi core or multiprocessor systems may encounter Time Stamp Counter (TSC) drift when the time between different cores is not synchronized. The operating systems which use TSC as a timekeeping resource may experience the issue. Newer operating systems typically do not use the TSC by default if other timers are available in the system which can be used as a timekeeping source. Other available timers include the PM_Timer and the High Precision Event Timer (HPET). Resolution: To resolve this problem check with the hardware vendor to see if a new driver/firmware update is available to fix the issue.

    Note The driver installation may add the /usepmtimer switch in the Boot.ini file.

    Once this (/usepmtimer switch) was done the clock was dead on time.