How Many USB Controllers Are in the Late 2014 Mac Mini? I am transferring a lot of data to a large number of iPads from a Mac Mini, over USB. I am finding that the late 2014 Mac Mini is significantly faster at completing the transfer than the Mid 2011 model.

If it's relevant - I'm connecting to iPad 2s.

I think I can rule out any CPU / Ram differences.

Have Apple added more USB controllers to the new Mac minis?
My understanding is that the old models had 2 controllers, is it possible that the 2014 model has 4?
The 2011 Mac Mini only have USB2 ports. 
Since 2012, the Mac Minis have USB3 ports. 

That probably the reason. 

Also, there is only one physical USB controller the Mac Minis ref1,ref2, that never changed (note: On the 2014 Mac mini, it's integrated in the processor ref,ref)