I built a cross-compiler on Intel for SPARC from the binutils and gcc sources, i.e. without using the Debian packages. If you check the debian-sparc archives I think my recipe's in there somewhere. (Otherwise ask me and I can probably find it and e-mail it to you tonight - in about 12 hours.) In general I found the bootstrapping process stopped with an error, but I could install bits by hand and then recontinue the process. Edmund