I’ve been using Windows 8 Enterprise with Oracle VirtualBox on my MacBook Pro, which runs OS X Mavericks (10.9). Now that Windows 8.1 has been released, I decided to upgrade. I had read that the upgrade was fairly easy, and could be done through the Windows Store. This is not always the case – such as when you are running the Enterprise version.
If you are running the Enterprise version of Windows 8, you must install from DVD media, or a mounted .iso, or equivalent. I downloaded the iso file from MSDN and mounted it in OS X to install the upgrade. At this time, I came across an error I had never seen before:
“You can’t install Windows 8.1 because your processor doesn’t support CompareExchange128″.
Fortunately, this can be easily fixed. Open a Terminal Window and change directories to your VirtualBox.app directory. (This step may be unnecessary if your path is set up correctly.)
Next, at the command prompt, type:
vboxmanage setextradata [vmname] VBoxInternal/CPUM/CMPXCHG16B 1 <ENTER>
“[vmname]” should be the name of your VM, which in my case was “Windows 8 Enterprise”. Quotes are necessary if there are spaces in the name.
Restart your Windows 8 VM and try to install again!