I have a KDJ11-SD (M7554-SD from a DECserver 550) that uses 27256 ROMs, and a KDJ11-DA (from a PDP-11/53) that uses 27128 ROMs. Someone emailed me the PDP-11/53 boot ROM hex files. They're numbered 261E5.hex and 262E5.hex. I burned these into a pair of 27128's and plugged them into the -DA board, and it runs great. If I plug these ROMs into the -SD, I get the slow "KDJ11-D/S 1.0" message that means that the powerup selftest can't even get off the starting line. I'm guessing it means a bad ROM checksum. This same board runs RT-11 and 2.11BSD great if I boot from the Andromeda UDC11 disk controller. I tried burning these hex files into 27256 ROMs several different ways, for example: first half second half ---------- ----------- firmware all zeros firmware all ones all ones firmware <- this emulates 27128, A14 replaces PGM all zeros firmware You can plug a 27256 into a 27128 socket if it has been burned like case 3, since a run-mode 27128 socket has PGM/A14 pulled high. The board will not be able to tell the difference. Can anyone tell me the magic key to getting the ROMs burned for the -SD? Maybe there is a jumper that tells the board to use 27128 ROMs, but I haven't figured that out. I've figured out all but three of the jumpers by now. -- Jonathan Engdahl Rockwell Automation Principal Research Engineer 24800 Tungsten Road Advanced Technology Euclid, OH 44117, USA Euclid Labs engdahl(a)cle.ab.com 216-266-6409