This part is a kind of semiconductor called 82559ER.
Function of this product has Fast Ethernet PCI Controller.
Manufacturers : Intel
Image and pinout :
Some of the text within the PDF file :
82559ER Fast Ethernet PCI Controller Networking Silicon Datasheet Product Features s s Optimum Integration for Lowest Cost Solution Integrated IEEE 802.3 10BASE-T and 100BASE-TX compatible PHY Glueless 32-bit PCI master interface 128 Kbyte Flash interface Thin BGA 15mm2 package ACPI and PCI Power Management Power management event on “interesting” packets and link status change support Test Access Port Available in extended temperature version Extended temperature range: -25 C to +85 C case temperature s High Performance Networking Functions Chained memory structure similar to the 82559,82558, 82557, and 82596 Improved dynamic transmit chaining with multiple priorities transmit queues Full Duplex support at both 10 and 100 Mbps IEEE [ ... ]