conclusion the grub of both debian32 bit and fedora 32 bit can boot openbsd 6.2 amd64 boots easily .
the details is http://openbsd-akita.blogspot.jp/2017/10/macpro-2006-runs-openbsd.html the movies of fedora's one is https://www.youtube.com/watch?v=lqK9LIcHiQg but my taste is debian.
