True. But if the SIMH code has breakpoint support, GDB can use that as a "hardware breakpoint". Not all that interesting, perhaps, unless you're putting breakpoints in ROM. More interesting is watchpoint support, which some SIMH targets have, and GDB supports. I haven't tried to do a minimal BFD/opcodes implementation for a platform that doesn't yet have one. PDP-10 perhaps (unless Lars did one years ago?). One wonders if non-power-of-two wordlengths add complication, as they do in recent GCC. I don't know if the SIMH execution and control frameworks make it convenient to hook up the GDB remote stub protocol. A stop to the SIMH console would want to be turned into a GDB remote interaction instead, and break signals from GDB would have to be recognized while SIMH is running the emulated machine. paul