Both are antiques, but even the long obselete F84 is a better chip than the C54 - it should be fairly easy to port a C54 program to the F84, or even better a modern replacement for the 84.
Problems arise with the subs addressing ... as the Stack is only 2 level deep, programmer used nice tricks ... and when porting to a wider PC chip ... bits truncature ( I suppose ) used are no more truncated ...
so addressing becomes false ...
from there to fine running, no one found the right way ... to that day ...