Connectors & Jumpers

This is a Serial ATA hard drive, with native support for SATA 6.0 Gb/s. However, it is backward-compatible so you will have no problem using it with older SATA 3.0 Gb/s or SATA 1.5 Gb/s controllers.

The faster SATA 6.0 Gb/s interface is pretty pointless since this WD Caviar Green 2 TB hard drive boasts a maximum sustained internal (platter-to-buffer) transfer rate of 110 MB/s, which is not even close to saturating the SATA 3.0 Gb/s interface. However, it can help improve performance by doubling the throughput between the drive's large 64 MB buffer and the SATA controller.

Like all Serial ATA drives, it comes the standard SATA data (left) and power (right) connectors and is hot-pluggable. That means you can connect and disconnect this hard disk drive to your PC while it's still running. To the left of the SATA connectors is the jumper block.

From what we can tell, Western Digital ships some drives with a jumper and others without a jumper. Since our OEM unit did not come with one, it is likely that only retail drives come with the jumper.

According to Western Digital, jumpering pins 1 and 2 enables Spread Spectrum Clocking (SSC). Placing the jumper across pins 5 and 6 will force the drive to use the slower SATA 1.5Gbits/s (OPT1) transfer speed. This is only necessary for certain SATA controllers that do not properly implement the SATA 3.0 Gb/s speed negotiation, like the VIA VT8237 and VT8237R south bridge chips.

The most important jumper setting is the Adv Format jumper. On older operating systems like Windows XP, you must either use the WD Align software or place a jumper across pins 7 and 8. Otherwise, the drive will perform poorly due to sector misalignment. If you are using a newer operating system like Windows Vista or Windows 7, there is no need to do this.

Breather Holes

The Western Digital WD20EARX does not have any clearly-marked breather holes on the top plate.

The underside has two breather holes (see picture on the right) near the top of the drive. These holes must not be covered.

Breather holes allow condensation inside the hard drive to escape. They also equalize the hard drive's internal pressure with the ambient air pressure. The hard disk drive needs them to function properly, so please make sure you do not occlude the holes!

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