Per PCN 0506 Altera® performed a die substitution from Sharp flash die to Intel flash die. The EPC4, EPC8, & EPC16 devices with Intel flash die are indicated by the letter C in the last character of the date code.
As indicated in the PCN functionality differences exist requiring changes in the programming support. Quartus® II software version 5.1 and later is required to program the Intel Flash EPC4, EPC8, & EPC16 devices. The same programming file can also be used for the Sharp flash devices.
Table 1 of PCN 0506 covers affected devices by the die substitution. Please see table 2 of the PCN 0506 that covers the functionality differences.
For more information, please refer to the Altera White Paper Using the Intel Flash Memory-Based EPC4, EPC8 & EPC16 Devices (PDF) and the Enhanced Configuration Devices (EPC4, EPC8 & EPC16) Data Sheet (PDF).