Western Digital Caviar Black 2TB Hard Drive Review

Under the Hood

Like many other newer model drives, this HDD does not use attached cables to move data and power from the PCB to the drive (and vice versa). Rather it relies on perfect placement for the spindle power connections (the four hard points near the orange cable in the above picture) and a multi prong data port. This really is a nice step up from the old way of doing things as those old school cables were very delicate. To ensure proper alignment there are two small plastic alignment posts which have accompanying holes in the PCB. This is exactly how the 1TB did things, but the PCB of this drive is actually much larger than previous models.


Once we turned everything over we instantly realized why Western Digital had to go with a bigger PCB: it uses external and integrated cache, thus requiring additional chip. This drive ships with a massive 64MB of on-board cache and while we don’t think it will make much of a difference versus smaller cache sizes, it obviously had an impact on the PCB layout. The previous generation drive which we looked at had 32MB of cache integrated into its Marvel Controller chip; whereas we guess Marvel couldn’t cram 64MB onto its chips so to get the 64MB total cache Western Digital had to add the secondary 32MB chip to boost the specifications.

To be precise the chip used for the additional cache is a Hynix HY5DU121622DTP-D43 (please note that “f” in the above picture is really a 6) unit specified as 66 pin, lead free, 32MB DDR400 (3-3-3) memory.


It certainly is interesting to see that Western Digital has gone for a hybrid cache setup with half being integrated right onto the controller and the other half being a separate non-integrated chip. We have a sneaking suspicion that the controller will only use this secondary chip when its own on-board cache is full. This is only an educated guess as this would allow it to keep its efficiency from being degraded by having to call for data from the ram chip all the time (after all integrated cache is much faster).


As expected the dual processor which is the brains of this drive is very similar to the one we found on the previous generation 1TB model we reviewed. In this particular instance it is a Marvel 88i8945P-TFJ2 dual processor System On a Chip (SOC). As with all of Marvell’s chips very little is known about it. All we can tell you is our particular chip was made in 15th week of 2009 and this chip comes with what ARM refers to as “TCM” or Tightly Coupled Memory (or as it is commonly referred to as “On Die” memory).


Also as expected the Motor Controller on the WD 2TB Black is made by STMicroelectronics and is a SMOOTH L7251 3.1 controller chip. In a nutshell, if the Marvell is the “brain” of this setup then this chip is the Central Nervous System. It is responsible for governing nearly everything related to mechanical & electronic power functions of the drive. In many cases this is the chip which gets overstressed and dies or takes the power fluctuation (from a bad power supply) and burns out…etc. etc. More importantly this is why swapping out the PCB of many “dead” drives will resurrect them. All in all, it’s an important piece of silicone to say the least. It is also worth noting that this revision is much newer than the one we found on the 1TB as that was a 2.2 version and this one is a 3.1.