On the 6ULL EVK board, there is one 256 MB QSPI Nor Flash device. To boot from the QSPI flash, the boot device switch (SW601) settings must be changed to OFF, OFF, OFF, OFF.
Additionally, the developer should adjust the BOOT_CFG settings for specified QSPI Nor Flash device, by exchanging the pull up/down resistors. See the main board schematic for more information