The Q4 2005 numbers on Motorola's set-top box shipments demonstrate an accelerating penetration of HD among U.S. digital cable subscribers, although well over half of all new STBs continue to be SD.

In the last quarter, the firm shipped about 1.4 million digital STBs including 626,000 HD and 705,000 SD units. Slightly more than half (525,000) of the HD boxes came with built-in digital video recorders (DVR). Motorola doesn't make an SD box with a DVR (although others do).

The firm's HD STBs reportedly also work with SD analog. Therefore, there is some speculation that part of the HD DVR growth might be motivated by consumers who are simply more interested in using their STB digital recording capabilities to record SD than merely watching or recording HD. If so, this diversion-of-intended-purpose mentality would be analogous to some owners supposedly opting to use their new HD monitors to watch progressive-scan DVD movies rather than HD content, per se, via cable, DBS or terrestrial.

For all of 2005, Motorola shipped about 2.8 million HD STBs (2.2 million with DVRs). Its total STB shipment was 6.4 million units.