Motivation could be directly tied to available
HD channels which are quite limited at this time. As to any chipsets they would reside in the HD side box. Along with anything else required for HD specific to HD. The motivation for software upgrade would be maintaining customer base. Knowing they could sell far more boxes at $150.00 than $650.00 it makes logical sense to me to convert current units with future units having a pass through port. It would also be an excellent testing ground for the concept with minimal investment on the part of the receiver manufacturer.