The original Digi 13-slot chassis (the one with the big ribbon cable) is not supported because the cards need to be installed in reverse order (right to left) and the TDM flex cable needs to make a severe bend that would compromise its integrity.Pro Tools|HD Incompatible Models S/N = NB055300B1 or lowerPro Tools|HD Compatible Models, the S/N begins with NB0600100C