<Even if you don't intend to use PROMs in your final device, I'd certainly <recommend you build a few PROMS which make the processor do rudimentary <things and perhaps which make the DMAC do the same things. You then have <simple tools with which to troubleshoot your memory interfaces. that can be helpful. I just use the CPU executing junk FF/00 or whatever else the bus lets it see, <After reading about the problems you're having, I think I'll fetch the 124 <LA out onto the patio as well. I troubleshoot 90% of my s100 problems with a good logic probe and a DVM. The rare case I've dragged out the scope it was handy but usually because I missed something stupid. The recent NS* bring up required the logic probe, its where I spotted a missing Mwrite/ (jumper smeared off the cpu board). With rare exception and all if a board doesn't work scoping it may or may not help. just follow the logic with a logic probe as likely it's a chip or socket failure. The reason is the board worked, was sold working and if it were good it should still work. The exception is when you have bus incompatability problems and a scope will not help unless your going to alter the board to make it work assuming it was not also broken. Allison