I installed the latest build of ESXi 5.5 on a new PE R630 today. The server has an I350 NDC, an Intel X540T2, and 2 Intel x520 DP 10GB DA/SFP+ NICs. The server came with the 2 X520 NICs pre-installed, and I added the x540T2 myself. ESXi sees the I350 NDC and the X540T2 that I added, but it does not see either one of the 2 X520 NICs. I updated the drivers for the X520 SPF+ 10GB NICs and ESXi STILL does not recognize them. I found a post that said to disable a BIOS setting Memory Mapped IO > 4GB, so I did that and it had no effect. Tomorrow I will see if there is a BIOS update for the system and/or firmware update for the NIC. In the meantime, if anyone has any suggestions I will be most grateful.