Installing ESXi 7.0 on a host with unsupported X5600 series CPU

  VMware _vSphere

Disclaimer : The method described in this article is not officially supported by VMware. Also, applying this method to your servers can lead to unwanted harmful consequences in the future.


VMware announced Vsphere 7.0 on March 10, 2020, which everyone was eagerly awaiting. Since the features that come with the new version and the differences with the previous version are a completely different topic, I will not mention them here.

Before enter this topic, let’s remind ESXi CPU requirements and restrictions for those who do not know:

  • ESXi 7.0 requires a host with at least two CPU cores.
  • ESXi 7.0 does not support the following CPU family models.      
      • Intel Family 6, Model = 2C (Westmere-EP)      
      • Intel Family 6, Model = 2F (Westmere-EX)

You can visit to see the detailed VMware compability guide list.



When installing ESXi 7.0 on a host with an X 5600 series CPU, you will encounter the following error:

ESXi 7.0 Unsupported CPU error




As you can see, the installation screen does not offer you any other option except for F9 (Back) and F11 (Reboot). At this point, you need to reboot the server by pressing F11.






ACU Code263 Warning




After server restarts, the following screen is displayed at the beginning of ESXi installation. At this point, you need press Shift + O (letter O, not number zero 0 ) together.






Shift+O allowLegacyCPU=true




You should add following parameter then press Enter allowLegacyCPU=true







ESXi 7.0 Continue to installation




In the later stages of the installation, instead of an error screen, the warning screen will be displayed with the Enter (Continue) option.







ESXi 7.0 installation completed




As you can see in the screenshot, ESXi 7.0 installation has been completed on the HP Proliant DL380 G7 server with Intel Xeon X5660 CPU without any problems.








After restarting the server, I never had to enter the same parameter again on the ESXi start screen. However, in my researches on the internet, I found that some users who do not usually use an HP server wrote that they had to enter the parameter with “Shift + O” at each boot. Whatever server you use, I think it’s worth trying your luck.