Before you get carried away with trying to use a serial cable to power a motor, read this:
What gage wire to use:
http://www.cnczone.com/forums/showthread.php?t=17350 http://www.cnczone.com/forums/showth...480#post136480
JUST BECAUSE A PIN/WIRE IS RATED FOR WHATEVER AMPS IT IS RATED AT, THAT DOESN"T MEAN YOU RUN IT AT THAT VALUE!!!