numa config option

Hi,

Since 3.4, there is this 'Enable numa' checkbox.
I am a bit confused as to what implications enabling this has?

Does it mean 'this host system is numa, therefore make use of CPU pinning, restrict memory to come from the used Core's CPU node, etc. to optimize the guest's performance' ?
Or is it rather some sort of emulation / pass through thing like 'This node should behave as if its architecture were numa'?

And what does it mean when moving VMs between nodes with different architectures?

One of my nodes is an older dual socket intel xeon system that is not numa and the other two are dual socket Opteron 6300 that are numa.

Thanks,

Martin