Jason Wright and Mark Kettenis have spent much of their time at the c2k6 hackathon finishing up support for UltraSparc III processors on the OpenBSD/sparc64 architecture. A number of months ago Henric Jungheim put in several weeks of effort reverse engineering support for the UltraSparc III, then OpenBSD creator Theo de Raadt [interview] put more time into cleaning up the diff and comitting much of it to the source tree. Halfway through the hackathon, Jason and Mark have taken what was not-quite functional code and have it successfully booting into multi-user mode. A couple of years ago there was an unsuccessful attempt to obtain documentation for this processor from Sun [story], so this current effort has had to use the FreeBSD and Linux UltraSparc III implementations as references. Theo explained, "Sun released CPU docs, but that's useless. It is kind of like trying to fix a car engine with the owner's manual. The rest of the hardware is not documented."
Jason points out that not only does OpenBSD run on the UltraSparc III processor, but it is also "self hosting". In other words, it is possible to build an UltraSparc III kernel on an UltraSparc III, and then reboot to that new kernel. This is important, Jason explains, because GCC is very memory and CPU intensive, "it really hits a server hard". He goes on to add that for this reason all the different OpenBSD architectures are built on their own architecture, and that this policy often catches bugs that could otherwise be missed.