[ECOS] how to use redboot to boot pc

[niky]

Hi,

    I make redboot

    ecosconfig new pc redboot
    ecosconfig tree
    make

    There is just redboot.elf in install/bin
    I copy the file to floppy

    dd conv=sync if=redboot.elf of=/dev/fd0H1440

    and then I use the floppy to boot pc
    but it fail.    
    There is no prompt "RedBoot>" .
    How can I do ?
    Thank for your help.