Hi Daniel,
1) Confirm current Mellanox OFED Driver installed supports the Window version, Connectx-2 HCA card with a valid FW. (RN of Winof).
2) Download the Performance Tuning Guide from our website (mellanox.com) and validate BIOS & OS tuning for maximum performance.
3) From our community site, follow document:
HowTo Configure RSS on ConnectX-3 Pro for Windows 2012 server DOC-2312
Also applicable in your environment.
Sophie.