This part is a kind of semiconductor called JMS539.

Function of this product has SuperSpeed USB to SATA II 3.0G Bridge.

Manufacturers : JMicron

Image and pinout :

Some of the text within the PDF file :

JMicron/JMS539 JMS539 SuperSpeed USB to SATA II 3.0G Bridge Description The JMS539 is a bridge controller, which translates the communication protocol between SATA II 3.0G and SuperSpeed USB commands. The integrated 60MIPS 8051, SATA II, Hi-Speed USB and SuperSpeed USB technology enable users to perform SuperSpeed USB to SATA II 3.0G, applications in a signal chip. In this chip, the Hi-Speed/SuperSpeed USB controller supports the USB Mass Storage Class Bulk-Only Transport Specification. Features • Complies with Gen2i/Gen2m of Serial ATA II Electrical Specification 2.6 • Supports SATA II Asynchronous Signal Recovery (Hot Plug) feature • Complies with USB 3.0 Specification, USB Mass Storage Class, Bulk-Only Transport Specification • Supports USB Super-Speed/High-Speed/Full-Speed Op [ ... ]

JMS539 PDF Datasheet Download