I call BS on tweaking and optimization regardless of optional command sets being disabled. If the drive could tweak and optimize without them, they wouldn't be optional. Don't forget how much AV we do on computers using non-AV drives. Clearly, AV can work (to a point) with any platter drive. Might an AV drive be better suited to the way TiVos write in long contiguous blocks, even though the AV command set is disabled? So far, I have found no proof of this, but haven't ruled it out. The only optimization I dare to suggest is the lifespan being extended due to PWL, on the AV drives that have it. The only thing I can't verify is if the PWL is independent from the optional modes (can't verify it makes the platter sweeps while not using the AV extensions). My SD channels are 3.89MB/s and my HD channels are 11.36MB/s on the better channels. Some are a fraction lower, but the only channels I have that are significantly lower are music channels, 0.38MB/s SD & 0.67MB/s HD. Your bandwidth calculations are off, and your interpretation of the WD specs and marketing materials seem off.