Info from the official Supermicro website:
AOC-UG-i4 is a high performance 4-port Supermicro Universal I/O (UIO) Gigabit Ethernet LAN card based on the Intel® 82571EB Gigabit Ethernet Controller. It interfaces with Supermicro UIO motherboard through a PCI Express UIO slot to maximize the I/O bandwidth. The dedicated input/output connections of the PCI-e ensure priority performance on each port without bus-sharing. The AOC-UG-i4 improves performance especially in multi-processor systems by balancing network loads across multiple CPU and processing cores.Key Features:

• Dual Intel® 82571EB Dual-port Ethernet Controllers
• PCI-E x8 Connector
• Four RJ45 Jacks
• Intel® I/O Acceleration Technology (I/OAT)
• Jumbo Frame Support for up to 9KB Packets
• Wake-on-LAN (WOL) Support (Port A only)
• Intel® PROSet Utility for Windows Device Manager