2.3.2. Non-Volatile Memory
Non-volatile memory retains its contents when the power switches off, making it a good choice for storing information that the system must retrieve after a system power cycle. Non-volatile memory commonly stores processor boot-code, persistent application settings, and Intel FPGA configuration data. Although non-volatile memory has the advantage of retaining its data when you remove the power, it is much slower to write compared with volatile memory, and often has more complex writing and erasing procedures. Non-volatile memory is also usually only guaranteed to be erasable a given number of times, after which it may fail.
Examples of non-volatile memory include all types of flash, EPROM, and EEPROM. Intel recommends you to store Intel FPGA bitstreams and Nios® V program images in a non-volatile memory, and use serial flash as the boot device for Nios® V processors.