WD Caviar Back 750gb 250 OR 333/platter, Fact or Fiction

I've read a lot about the Caviar Black 750, and most of it goes like this:

"This drive, while it is the Caviar "Black" performance model, doesn't have as good performance as all the other "Black" Drive models. This is because this particular drive has 3 x 250GB platters, while the 1TB has 3 x 333GB platters and the 640GB has 3 x 320 GB platters."

However, on WD's web site it indicates that the difference is the number of heads (5 on the 750, and 6 on the 1tb), suggesting that both use the 333gb platters, w/ the 750 having one less head. I.E., the 3rd platter only has 1 head, instead of the normal 2 heads per platter (both sides).

Anyone have any hard facts on this one?


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Here's what I'm suggesting.....the wd7501aals may have the same platters/density as the 1TB drive, but it had one less read head, hence the lower storage.

HD tests by me on the 640 and the 750 (black caviar) come up about the same:

~ 115mb/s max
~85mb/s average
~12.5ms seek

The 750GB has slightly fewer sectors per track, but higher capacity, than the 640GB. It should be slightly slower (within 3%) in linear transfer transfers compared to the 640GB, but any difference in desktop application performance will be well within any testing application's margin of error.

Thxs Douglite, that makes sense. But I'm still curious about the 5 heads on the 750GB and 6 on the 1TB....very interesting.

Indeed, the 750GB has five heads. One side of one of the platters is not used (and is likely defective) This is a substantial cost cutting measure for the makers of drives, as it allows them to use platters with a defect on one side that they would otherwise have to scrap out. AMD uses a similar strategy with their three core Phenom (II) chips - they can sell a chip with a defective core as a three core chip rather than having to scrap out the entire die.

Yep, and if that's the case....one side defective, that means these are the 333gb platters, and therefore, the speed of the 750 should be the same as the 1TB hard drive....head for head, so to speak.......I'm not anal, just that soon I will have all three drives, and I'm just a curious George.