To add a twopennyworth to the thread, I used a transient analysis program (a bit like Spice for those who are familiar) around 1970 to help in designing MOS integrated circuits. It was called TRIMOS, written in Fortran for the PDP10 and also run on a local university's ICL4130. I had a much-reduced version which I translated into Focal and ran (if that's the right word) on a PDP-8/I around 1971 which was OK for working out DC operating points. The same company had some layout tools again for MOS ICs called IIRC Lady Jane which ran on the 10. This fell into disuse when Calma brought out their DG Nova-based GDS1 system somewhere around 1973. I wouldn't want to go back though. Bob Adamson