The problem is the network performance, not the whole CPU one. It seems all okay w/o the HyperV R2 role. Still checking.
I would also look at updating to the latest network driver, I think it is now at 15.1.1, http://downloadcenter.intel.com/Detail_Desc.aspx?agr=Y&DwnldID=18388&lang=eng , also the firmware package for the S5520UR should also be updated to the latest package, which is now at 49.1 , http://downloadcenter.intel.com/Detail_Desc.aspx?agr=Y&DwnldID=19011&lang=eng. See if it helps.
Tried all the latest 15.1 and 15.2 drivers plus latest S5520UR package of course.
It might be Windows Datacenter edition vs. Ent. edition, but something in the Hyper Role makes the network card 80% slower.
Any ideas are welcome..
Check the following links:
http://support.microsoft.com/kb/2000977
http://support.microsoft.com/kb/975530
Not sure if it's related to your issue but you can give it a try.
I'll open a new thread as I have news about this issue
