What the heck is the four pin adapter / connector for on the back of SATA drives

COLGeek

Cybernaut
Moderator

In addition to the possibility of beeing a MOLEX power connector (as pointed out by Twoboxer), you could also be looking at some jumper headers that some SATA drives have. Ther are usually used to force the device to work in SATA I vs. SATA II mode (compatibility mode).
 
In addition to having certain user configurable functions, certain combinations of jumpers can configure the drive for factory test mode.

For example, Seagate's SATA jumper pins have the following functions:

- 1.5Gbps limitation jumper
- Ground
- Rx (serial terminal input)
- Tx (serial terminal output)

Jumper Settings for WD SATA and EIDE Hard Drives:
http://www.wdc.com/wdproducts/library/other/2579-001037.pdf