You might be right that it wasn't GCC specifically. I think I was running a free/low cost version of OS-9 68K for the Atari ST, and managed to get hold of a pro

You might be right that it wasn't GCC specifically. I think I was running a free/low cost version of OS-9 68K for the Atari ST, and managed to get hold of a proprietary C compiler for it. The combination of a "real" OS + C compiler made it possible to port the popular Unix text games of the time (empire, nethack, larn, etc). My point was more that the 68K home computers like Atari ST and the Amiga of the mid-to-late 1980s were powerful enough to "run emacs / C compilers", even if it wasn't the GNU stuff yet.