This emulation mode attempts to emulate a Cobalt Cube. It is possible to install NetBSD/cobalt and run that in the emulator.
The following instructions will let you install NetBSD/cobalt onto a disk image:
dd if=/dev/zero of=nbsd_cobalt.img bs=1024 count=1 seek=2700000
ftp://ftp.netbsd.org/pub/NetBSD/NetBSD-7.1.2/cobalt/binary/kernel/netbsd-GENERIC.gz ftp://ftp.netbsd.org/pub/NetBSD/NetBSD-7.1.2/iso/NetBSD-7.1.2-cobalt.iso
gxemul -x -E cobalt -d nbsd_cobalt.img -d bd:NetBSD-7.1.2-cobalt.iso -j cobalt/binary/kernel/netbsd-RAMDISKand proceed like you would do if you were installing NetBSD on a real Cobalt. Install onto wd0, choose "Use entire disk" when doing the MBR partitioning, and choose to install from CD-ROM device "wd1d".
You should now be able to boot NetBSD/cobalt like this:
gxemul -x -E cobalt -d nbsd_cobalt.img netbsd-GENERIC.gz
Known issues: The clock may go too fast inside the emulator.