SBCL on MIPS still mostly works. It seems, with a little encouragement, to be able to build itself, at least to the point when my hardware dies:
I/O error: dev 08:02, sector 136384 I/O error: dev 08:02, sector 136456 I/O error: dev 08:02, sector 136376etc. So I am now engaged on backend refactoring, having actually RTFCVSM to find out how to branch... which is lucky, because these changes are tricky to synchronize across six architectures, so I'm glad I don't have to.