The article seems to confirm your recollection of a macrotized "master": > Each of the assembly source files contains a header stating This translation created

The article seems to confirm your recollection of a macrotized "master": > Each of the assembly source files contains a header stating This translation created 10-Feb-83 by Version 4.3 > Since the Instruction Set Architecture (ISA) of the early processors used in home and personal computers weren’t spectacularly different from one another, Microsoft was able to generate a substantial amount of the code for a port from the sources of a master implementation. (Alas, sorry, we’re unable to open-source the ISA translator.)