Looking at Table 1 on page 10 of the following document, I see that the 1.5TB and 2.0TB drives both have 4 platters and 8 heads, and identical data densities.

Barracuda LP Series SATA Product Manual:

http://www.seagate.com/staticfiles/supp ... 64361b.pdf

In fact the only difference in the specs is the number of guaranteed sectors.

Why wouldn't Seagate have used 3 platters and 6 heads for the 1.5TB drive?

I have considered the possibility that, for the same capacity, more platters means less cylinders, and therefore better average seek times, but this isn't reflected in the specs.

Surely this isn't a yield issue?

If the 1.5TB drive is indeed just a capacity-limited version of the 2TB model, then is it possible to enable the additional two heads via the serial port? I'm assuming that both heads need not be on the same platter.

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