version 5.4 - amd64
  dhcp net0
  kernel -n img http://static.netboot.me/memdisk-iso iso
  initrd -n img http://ftp3.usa.openbsd.org/pub/OpenBSD/5.4/amd64/cd54.iso
  boot img

Version 5.6 - i386
 dhcp net0
  kernel -n img http://static.netboot.me/memdisk-iso iso
  initrd -n img http://ftp3.usa.openbsd.org/pub/OpenBSD/5.6/i386/cd56.iso
  boot img