virtualbox.org

I am running WIN 10 on El Capitan on a Mac Pro 12-core. With only 1 processor selected in the settings, in runs reasonably fast, however any CPU number higher than 2 the speed slows to a crawl.

I'm sure there's an explanation for this, and I'm not complaining about the speed with 1 processor, but it would be nice to take advantage of some of the power of the machine I have.

Thoughts?

My guess is, once you exceed 2 cores the overhead of running more than 2 cores catches up and surpasses any advantage. It seems more than 2 cores on a 4 core CPU has similar performance issues. At least on OSX hosts.