This message was posted on behalf of Intel Corporation
Thanks for reaching out!
Could you please let us know the steps you took in order to enable this option? Also, is there any reason why you wanted the board to boot every 500ms?
Right now, let's try to reflash your board's BIOS and OS to see if that helps. Try to follow the steps in the following guides:
Let us know if you have issues flashing the BIOS and the OS.
I hope this information helps you,