Has anybody heard of a 6502 assembler running under RSX-11M? And is there any documentation for it? <<<< I don't know for certain, but most of those early micros had cross-assemblers written in Fortran - and by programmers who worked hard on making the Fortran machine independent. If this applied to the 6502 then it probably could run on RSX. I don't see such listed on http://www.npsnet.com/danf/cbm/cross-development.html however and that has a LOT of 65xx cross-assemblers Further searching gives hints that MOS Technology did indeed have such a Fortran-based cross-assembler, but no evidence that anyone still possesses a copy. Andy