dcbz(and a few other cache instr.) is buggy on 8xx CPU:s. See http://ozlabs.org/pipermail/linuxppc-embedded/2005-January/000867.html for a litte more input or google.
This bug will cuase random craches or "hangs" if not used with care. There is an old patch floating around for 2.4 that will workaround the bug by doing instr. decoding in the TLB Error handler. Jocke
