[Libreboot] I can not boot using USB with iso non-UEFI,

[Wellton Costa de Oliveira]

Hi, how are you?
I can not boot using USB with iso non-UEFI, eg
debian-live or gNewSense 4 (which I use).
when I use debian jessie
or trisquel he conegue find the boot via USB. someone could help me with
that?
att.