VirtualBox not maxing out CPU?

Super-PI doesn't max my C2D either, highest I get is low 70%'s... check it with Prime95 or IBT (with coretemp running to show core load)
 
I wonder if something has changed. I recall running Folding@Home inside a VirtualBox VM a while back and that quite happily maxed my CPUs. Perhaps they have limited the amount it can use to prevent the host system from being bogged down?
 
Ah...I need to set the number of CPUs to 2 in the virtual box settings...

I thought that Virtualbox would spread the load automatically if I put 1 CPU.

I have the option to select up to 4 CPUs i think (probably due to hyperthreading)...should I....or do I leave it at 2?

When I select 2 CPUs it uses a maximum of 50%...and compilation takes 1 min 55 seconds....when I select 4 it goes up to about 90% sometimes and takes 2 mins 12 seconds...

....no idea why its slower...
 
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Nevermind you've answered yourself.

That said, some works loads will be slower with HT on. Some server distributors specifically advise that it be turned off, as the overhead isn't worth it. Its very specific to what you're doing though.
 
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