This part is a kind of semiconductor called JMC251.

Function of this product has PCI Express to Gigabit Ethernet & Card Reader Host Controller.

Manufacturers : JMicron

Image and pinout :

Some of the text within the PDF file :

JMC251 JMC251 PCI Express to Gigabit Ethernet & Card Reader Host Controller Overview The JMC251 is a single-chip PCI-Express Gigabit Ethernet combo Card Reader Host controller. The Gigabit Ethernet function is compliant to IEEE 802.3 Media Access Controller, and IEEE 802.3u 1000BASE-T/100BASE-TX/10BASE-T. The MAC supports IPV4, IPV6, TCP, UDP checksum, segmentation task-offload, priority encoding and IEEE802.1Q VLAN features. It also supports Receive Side Scaling (RSS) to balance the loading for received data processing across multiple CPUs. The Ethernet function supports remote wakeup (including AMD Magic Packet™ and Microsoft® Wake-up frame) in both ACPI and APM (Advanced Power Management). The Card Reader Host provides one set of 4-in-1 Combo Memory Card Reader Mechanism, and suppor [ ... ]

JMC251 PDF Datasheet Download