I agree you should logically understand the code you write....

however..... he asked for a compiler not an assembler and chances are if you are used to new compilers features you take for granted may be completely broken in the old compilers or non existant.

so better to have it on hand from the get go so you can test incrementally as you go along rather than developing the whole program essentially on paper to find out it won't work without a rewrite.

Also I said retro64 earlier when it is acutally Retro68 and apparently its being used to build the Browsy App for system 6. https://github.com/clehner/Browsy