virtualbox.org

I can't explain it either as I lack the necessary knowledge. But it does work, the only problem is that performance seems far worse than when using the standard setting and only 8 cores. The errors thrown in the logs posted above say something about Hypervisor and failure. I am going back to 8 cores and default settings for virtualization to see if performance is restored.

Looking forward to see if anyone else has an idea on how to solve this.

I join the thread. More than 8 CPU cores can not work. 8 cores are efficient. I have Arch Linux.

Signed up just to post on this thread.

I also can't assign more than 8 cores to my server 2012 VM's. If I do, the VM will fail to boot with a fatal error(will post a log when I get back to work).

Also, VirtualBox can't see all 64 threads of the AMD 2990wx, just 32.

Spec:
2990wx, Windows 10 with the latest VirtualBox

Hello, it does work on my configuration which is a 12 cores x 2 threads each Xenon CPU only using default mode, as mentioned before. I could run 18 cores on that machine. I wander when or if this issue will ever be solved.

See ticket #17898: Can Not Assign More Than 8 Processors to Windows 10 Guest. Actually tying the ticket to the thread, and the thread to the ticket.