The EEPROM on the Cyclone® II FPGA Starter Development Kit is connected to the USB FIFO IC (FT245BM) through the "EECS", "EESK" and "EEDATA" pins for customizing the USB VID, PID, Serial Number, Product Description Strings and Power Descriptor value of the USB FIFO IC for OEM applications.
The EEPROM is optional, because when no EEPROM (or a blank or invalid EEPROM) is attached to the USB FIFO IC, the USB FIFO IC no longer gives a serial number as part of its USB descriptor.
This EEPROM is also used on the Altera® Embedded Systems Development Kit, Cyclone III Edition.