vQuicky

• VMware today reported of a known issue where a Windows 2012 virtual machine will fail to recognize a hot-added CPU.
• Windows device manager identifies hot-added cpus but will not use them as they will remain inaccessible.
• The virtual machine is running virtual machine hardware version 9
• Work around is to have the virtual machine hardware version set to 8.
• Unclear on if this is only affecting datacenter editions only?

inDepth

VMware today reported a bug in hot-adding and using virtual cpus for Windows 2012 virtual machines. Seems like the Windows servers can take cpus as they are shown in the device manager however they remain inaccessible by the OS. Reboots won’t fix it either. It also only occurs on virtual machine hardware version 9.

I am unclear if this is isolated to the Windows 2012 datacenter editions only.

There is no fix as of today however a work around is to set the virtual machine hardware version to 8 where it works just fine.

KB article