Once this is set, VMs seem to happily run on these older generations of CPUs. $ cat '/Library/Preferences/VMware Fusion/config' monitor.allowLegac圜PU = 'true' This file can simply be edited to set this value to true. There is a VMX config parameter, monitor.allowLegac圜PU, which can be set either directly within the VM’s VMX file, or as a system-wide default in VMware’s config file at /Library/Preferences/VMware Fusion/config. Luckily, this has been discussed already on VMware Fusion forums and the solution was quick at hand. I learned only of the system’s incompatibility to show me the above notification after I was attempted to start an existing macOS VM from my VM library.

Originally I discovered this issue the hard way when VMware Fusion 8.5 on my MacPro4,1 system (dual 6-core X5550 CPUs) advertised the 10.0 upgrade, and happily let me run the upgrade on this system without any mention of this CPU feature requirement.

Earlier versions had a more ambiguous dialog wording which didn’t explain the incompatible features, however it seems as though currently they seem to be providing more detailed info, mentioning the “unrestricted guest” capability.

Vmware fusion 11.5 pro