downloaded from openbsd
install78.img: disk image to be written to a usb, includes the file sets
miniroot78.img: same as above, but file sets are not included.
install78.iso: same as =.img, but suitable for cd/dvd. includes the file sets
cd78.iso: same as above, but file sets are not included
floppy78.img: supports old machines that lack other booting options