These files are for booting NetBSD 4.0 onto an x86 machine and then attaching your mips cobalt and netbooting it for an automatic install. These were originally grabbed from (unmodified since) http://www.batlande.de/cobalt/ as per http://mail-index.netbsd.org/port-cobalt/2008/04/01/msg000082.html

For more instruction relative to these, you may also see http://www.dayid.org/os/netbsd/doc/NetBSD-on-Cobalt.txt