Probably some of us already read about how the playstation3 firmware runs linux (the “OtherOS”)
Some insight:
1- it uses as bootloader a very minimal linux system that then loads the right kernel using the kexec call (yai!, after the gamecube the other ppc platform with kexec implemented is the playstation3…)
2- the instructions obviously are scarce and seems to point out that the provided loader has a nice script to install just one kind of distro (I’ll let the reader the exercise of guessing witch) and doesn’t seem to provide anything useful if you happen to prefer something else…
3- [update] you can access the busybox shell from kbuild and just install gentoo the usual way (suggested using recent ppc64 stage3 and then build a cell-sources kernel using the cell_defconfig)
The kboot is quite neat in itself: it has a great deal of features (like ssh or tftp) and uses pretty standard tools (busybox, linux, kexec-tools, dropbear) plus something specific (the ps3pf-utils).
I’ll add the ps3pf-utils once I have them mirrored on powerdeveloper and maybe adding an unofficial svn/git for it and libspe2 (since looks like they will be improved a lot in the next weeks and keeping track fo the patches is a bit easier this way)