Well, foo, the one from TUHS has the same symptom: random re-starts. Looks like I'm going to have to actually debug this. I guess the first step is to work out how the re-start is happening; I suspect it's not a trap (I'll check, but I think Mini-Unix catches them all). My best guess is a jump to 0 (somehow); if so, that should be easy to catch. Then the next thing is to try and work out where/how/why that is happening. Following a suggestion of Warner Losh, I think there's a good idea on how to make progress, which is to mount the Mini-unix pack under V6 (running on a simulator); that's rock-solid - and the V6 tool-chain can be used to build Mini-Unix binaries. And here I thought it was going to be easy to convert Mini-unix to run on an -11/03. Well, it still might - if I can get Mini-Unix to run reliably! Noel