Lidt google:
The 24-pin main ATX motherboard modular cable is definitely different between the two series.
These two Series are made by different OEMs. The AX Series use Seasonic as the OEM and the RM Series use Chicony Power Technology as the OEM. The PSU's modular interface pin-out assignment doesn't adhere to any particular standard except for the OEM's own standard.
Et område, der vist kunne bruge lidt standardisering...