Stupid question - physical differences between HDD sizes

[janspambox]

Hi,
sorry if this is a stupid n00b question, but I couldn't find the answer by searching and I'm curious.

Are there actual physical differences between e.g. a 1 TB HDD and a 2 TB HDD of the same kind, and if so, what are they? Different platter count? Or is it more of a deal "build the same thing, test them, the good ones become 2 TB and the bad ones get downgraded" (which is AFAIK done with GPU chips)? Or is it rather a "same thing, different price" where the additional capacity is simply disabled to provide a different price point, as e.g. with the Tesla (electric car) where a certain low-capacity battery is the same battery with a software lock that can be disabled for an additional price?

Kind regards,
Jan

[Doomer]

If the drives are from the same internal family then the difference is platters and heads count (and firmware, to accommodate physical difference)
However sometimes (not very often) 1TB drives could be downsized 2TB drives: either disabled heads or reduced data density, or both.