Best answer by bcacciola
Acropolis 4.6 System Maximums:
4.5 (might be the same)
Also from the AHV release notes:
Important: As of NOS 4.1.1 and Acropolis base software 4.5, any VM with a vCPU setting that is greater than the actual physical number of CPU cores on the underlying host will not start. This condition also applies to existing VMs from the NOS version from which you are upgrading. To start these VMs, reduce the vCPU count to a value equal to or less than the number of actual physical cores.