@AMIGA-FAN
You will usually get your questions answered on the ML, or at least an attempt will be made to locate the problem.
I don't know why newemubox.gz fails on your P4, but then I don't have a P4, so perhaps I wouldn't come across the problem at all. There may be an easy fix.
As for the serial device to use with emubox.gz, that's powercom.device. The amithlon1_com.device needs the newemubox.gz kernel as I believe it's part of the contrib3 update.