July 3, 2009 - Matthijs Haverink

Change Microcode in Xenserver/Everrun

Up until today I even didn’t know what Microcode or what it’s purpose was. After today I’ve learned a lot about it and would like to share it with you.

 “Microcode is a layer of lowest-level instructions involved in the implementation of machine code instructions in many computers and other processors” is the description from Wikipedia. I read more and normally the microcode is updated by using a BIOS upgrade or ROM Flash from your vendor (In my case Intel).

Why was I updating this? Because I was updating my Marathon Everrun version from 4.0.2 to 5.0.0 to add Level 3 Fault tolerance. And after the upgrade I couldn’t protect my machines with level 3 protection because of the out of date microcode. So my logical next step was to update my BIOS. After updating my bios through the linux tool provided by HP I rebooted the server and still got the error message. So my Microcode still hadn’t been updated.

After a long and hard search I found out that for Example ESX and some Linux versions update the microcode during the boot sequence by placing a microcode.dat file within the /etc/firmware folder on the root of the server. But of course this folder doesn’t exist on a XenServer (Would have been to easy). So I started looking for a microcode.dat and found it on the server directly in the root of the /etc folder. I renamed the file to microcode.dat.old en placed my microcode .dat (provided by Intel) in the root of the  /ETC folder.

Rebooted the server this did the trick. Good Luck

Virtual Infrastructure Citrix / everrun / marathon / microcode / xenserver /


  • Wouter Heije says:

    And of course in XenServer 5.5 you can find the microcode.dat in the right place eg. /etc/firmware folder 🙂

  • Erion Nako says:

    We are trying to install Marathon everun VM on top of a Citrix XenServer 5.5, and what we get from the level – 3 protection is:

    CPU version is not supported in Level-3.

    We open case to Marathon Support and described all to the support Team, which kindly respond one with one line:
    “Upgrade the BIOS of the machine”.

    If we face the same issue ( tomorrow we will try), is anybody helping us how to continue on that.

    We had not upgraded BIOS, but we tried the procedure of Wouter Heije July 3, 2009, under /etc/firmware this time as it is XS 5.5, but still the same.

    I will let you know if we succeed after the upgrade or not.


    Erion Nako