note davies IIRC, some of the old 68xx processors had undefined opcodes. Most of these were effectively NOP, but at least one sent the processor into a mad series of loops,and could be stopped only by powering the machine down. I always heard it called "HCF", standing for "Halt and Catch Fire". I never saw it for myself, but it had its fifteen minutes of fame.<br><br> Regards,<br><br> John Davies 129726 129804