This PDP10 simulator that is ;) I'm hacking on the simh ( http://simh.trailing-edge.com/ ) and have the pdp10 module compiled and running a-ok. Also looking at the PDP10 Software kit ( http://old-pdp-10.trailing-edge.com/ ) but I'm rather clueless where to even begin. Everything in the TOPS-10 table are *.tap tapes, one is tagged "BOOTABLE". I d/l that, attach it to TU0 and boot TU0. Nothing happens but when I stop the sim it reports: Simulation stopped, PC: 000000 (000000000011) Another one marked TOPS-10 7.03 KS Bootable tape I just tried, with similar results. Any hints on where to start exploring or should I just give this up as hopelessly impossible w/o a wall of orange books and years of experience?? Thanks Chuck cswiger(a)widomaker.com