On Sat, 5 Jun 2010 15:54:20 -0400, you wrote: OK, you tried playing nice -- so now play dirty! If you never found a way to make NULJOB (or whatever TOPS-10 has for an idle loop -- I've never been into the sources) identify itself to KLH10, why not hack up KLH10 to detect NULJOB itself? Well, this approach has various issues that have to be considered: 1. first of all, we do not know anything about PDP-10 machine code, so it would be quite difficult to pin down the exact instruction sequence that would tell us the OS is in its idle loop. And then there must be someone quite proficient in C language who should modify the emulator (i.e. not me). 2. I have some very faint memories about difficulties in tracking down the TOPS-10 idle loop (or it was TOPS-20?). That is it does not make something easily identifiable by just analyzing the actual instruction stream. I must have read something about this topic somewhere in the last three years... 3. Oh well, it would be nice to learn where is the culprit and how to rebuild a TOPS-10 monitor from scratch! :-) Now I've posted a request to alt.sys.pdp10. Let's see if someone will explain me what to do. Some misc bits: A nice post about the (dis)advantages of modifying either the emulator or the OS: http://groups.google.com/group/alt.sys.pdp10/msg/c1c8e09d247595ce A description of the special KLH10 idle device. At the end of the document there is also a brief explanation about where to put the needed monitor patches: http://www.avanthar.com/~healyzh/klh10/doc/dvhost.txt Bye, G.