MIPS doesn't require that you install a bootloader. The MIPS PROM handles the booting, but you need to install your kernel as a viable option.

First, install dvhtool, needed to copy the kernel to the SGI Volume Header.

# emerge dvhtool

Now copy over the kernel to the SGI Volume Header. By default dvhtool assumes that the SGI Volume Header is on /dev/sda. If this is not the case (for instance when IRIX is installed on /dev/sda and Gentoo/MIPS on /dev/sdb) you need to inform dvhtool about it using -d <device>.

# dvhtool --unix-to-vh <kernel name in /boot> <name you want to give in volume header>

If you want to see all available entries in the volume, use --print-volume-directory:

# dvhtool --print-volume-directory

To setup your system to boot Gentoo/MIPS you need to go tweak some settings in the MIPS PROM. We will describe this later on when the Gentoo installation has finished.

Now continue with Installing Necessary System Tools.