i have a very similar setup:
slackware 13.0 amd 64 dual core 1.9GHz
slackware 12.2 amd 32 single core
Host running virtual box 3.1.2, and idles at 7% average on both cores, but shot up to 90% while the VM is booting. Then back to 7%.
Guest idles (from top) at 2%
Maybe top reports it wrong that works natively but not virtually.
Last edited by tacorama; 12-31-2009 at 10:42 PM.
Reason: clarification of host idling