While searching for an answer, I found this question on SU what is the purpose of this 4 pin interface on sata hdds and why doesnt it exist on SSDs?

Well, on my Kingston HyperX SSD drive, they do exist.


So if Spread Spectrum Clocking and reduced power spin up is not needed, what would be the function of these four pins?

All of my search attempts show only a few variants that apply to 2.5" spinning platter drives depending on vendor and none for SSD, to include the attached SU question.

Any ideas?

2 Answers 2


The pins are manufacturer specific and used by both the manufacturer and data recovery experts to access the System Area of the drive. Sometimes those pins support a serial interface, in which case you can attach a 4 pin cable (power, ground, transmit, receive) and talk to the hard drive. Data Recovery hardware, such as a PC-3000, might use these pins to update/repair the firmware on drive, remove an ATA password, or modify/clear the G-list.

  • 2
    on some manufactures SSD they were calling these a "maintainance mode" or "Engineering mode" ocztechnologyforum.com/forum/… Another location they were discussing its use when flashing the firmware. One data sheet I saw long ago one of the 4 pin type was a compatability mode. I have never seen any really important things for standard operations. Asking kingston sounds like the thing to do.
    – Psycogeek
    Aug 22, 2013 at 6:58
  • @Psycogeek - would you consider posting this as an answer to be evaluated with the others? I like that there is an actual spelled out use, at least for OCZ.
    – Carl B
    Aug 23, 2013 at 1:32

Partial Answer

I emailed Kingston technical support to get their answer on the subject

Thanks for contacting Kingston technical support. For those 4 pins, basically they do not have any function. Only SATA connector and power connector of SSD will be connected and used.

I Pushed for more information and got this in reply

Thanks for your reply. Our apologies but they are intended for any use or purpose.

I will make note that in the footer from the email It had 下午 2:02 (下午/xiawu means afternoon in chinese) so this information has come from china and I believe the first point of contact team is trying to say is that the port is not intended for any use or purpose but have done so in poor English however this is an assumption.

Personal thoughts:

I suspect that they are for development/recovery use as I noticed on a picture of a stripped down OCZ Vertex 3 SSD they had 4 un-soldered points on the board in the same location as OP's SSD labeled vcc, tx, rx, gnd

  • VCC - Power supply pin
  • GND - Ground
  • TX - Transmission of data
  • RX - Receives data

Stripped OCZ SSD

Note: This SSD is using the same NAND controller SandForce 2281 as the drive shown by OP as per OCZ Vertex 3 tech specs

  • 6
    Sounds a lot like USB, No? VCC (+5v) d-(data -) d+(data+) and ground?
    – Carl B
    Aug 23, 2013 at 0:49
  • Yes USB is one of the most popular standards that would rely on this 4 connector style. That being said a SATA connector is just 2 data IO and 3 ground; really just a scaled version.
    – 50-3
    Aug 23, 2013 at 1:18
  • 3
    Looking at Psycogeek's comment on other answer, there is actually a function of shorting two pins to enable "Engineering mode". This is directly for the OCZ SSDs, so not sure if it relates to Kingston or any other SSD that have the 4 pins available.
    – Carl B
    Aug 23, 2013 at 4:22
  • Big if here but if the boards are the same and it's for data then it will most likely not be jumpers like the 1st ocz ssd mentioned by Psycogeek
    – 50-3
    Aug 23, 2013 at 4:46
  • 4
    The @50-3's answer (the second part) is correct, I only want to clarify that TX/RX lines are not USB, but rather a generic serial (UART) on TTL levels.
    – Jerzyna
    Sep 2, 2013 at 12:03

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