Power to the PCIe to SuperSpeed USB 3.0 Card?

It looks like there is a molex power connector on the PCIe to SuperSpeed USB 3.0 2-Port PCIe Card. Is it recommended to supply power to the card?

I have a WD1600U017-004 160GB Western Ditital Passport drive that uses bus power and it works fine. Is the Molex connection only required for USB 3.0???

I have a WD1600U017-004 160GB Western Ditital Passport drive that uses bus power and it works fine. Is the Molex connection only required for USB 3.0???

Hi Paul,

Yes, without the Molex connector, the card is able to provide enough power for some USB 2.0 devices (for example, a keyboard/mouse combo, or a USB graphics adapter) That WD drive probably has a relatively low power draw – good to know that works.

But we still recommend connecting the supplemental power – it’s hard to know how much power a USB 2.0 device will draw (in theory, up to 500mA, but in practice varies), and for USB 3.0, you’ve got up to 2x 900mA of draw.

Note that if your system has a 15-pin SATA power cable available, but no 4-pin molex, there are cheap cables available on Amazon (e.g. http://www.amazon.com/dp/B003AI272I/ ) to do that conversion.

Thanks for commenting on this thread - it’s an important question!


My company purchased the card for use with a Passport 1TB USB 3.0 drive. (WDBACX0010BBK-NESN) We got them in the mail Friday and they work fine. You suggested using an adapter to convert a SATA power cable to Molex, this would be possible if I had spare SATA power cables. I would suggest that you change your literature to make the limitations of this card very clear.

Needing power on a USB 3.0 PCIe card is not a limitation of “this” card, but a limitation of the PCIe bus. As I discovered, all reputable manufacturers (e.g., SIIG, StarTech, IOGear, LaCie, Buffalo) provide a power connector on their USB 3.0 PCIe cards. They are not usually necessary (especially for low power drives like the Passport), but it is a wise precaution if you have an extra power connector.

Hi, I’d like to use a bus powered USB-3.0 device with a PCIe board, but my mainboard only offers a slimline SATA connector (GND and 5V) - no additional LP4 (Molex) connectors available. Would your board work with just the 5V (12V from PCIe bus) and would your board ship with a corresponding cable?
Thank you very much in advance,

Hi Arend,

Thanks for asking ahead! Because there are a few different variations of the power cabling, we don’t currently include any SATA->LP4/Molex cabling in the box (although we’re looking at doing it for full-sized).

For your case (only a slimline SATA power connector is available), you’ll want to look for products like this: http://www.amazon.com/Cables-Unlimted…

Which breaks out the the 5V power pins from slimline SATA to a LP4/Molex which is compatible with this card.

Hope that helps. Let us know if you have any other questions!


We have a USB 3.0 PCIe card for a Dell R610. There are no SATA\Molex on the board to power the card. We are trying to use a Tandberg rdx QuickStor tape drive on it. It uses a 12v 1 amp and is self powered but we get a power exceeded message when we plug it in. What options do he have?

Hi Matt,

Thanks for posting your question, we’ll be happy to help. It’s unusual for a device to trigger over current messages on our PCI-e card, especially when it’s self powered. We haven’t seen an issue like this or USB 3.0 tape drives in the past so working in parallel with the Tape Drive manufacturer may be useful. USB 3.0 allows 900mA per port and a self powered device shouldn’t be pulling more than that.

Some things to try:
Make sure you are using a USB 3.0 cable, as a 2.0 cable will cause the system to negotiate down to the USB 2.0 spec and the OS will then expect 500mA, max.

You maybe able to use a splitter on your power connectors to get power to the card, but it’s not likely to stop the over current messages. The PCI-e bus is able to provide enough power to the card to cover the 900mA per port so I suspect the Tape Drive unit is pulling more than this ammount.

Can you say which operating system you have and which power supplies your Power Edge Servers have?

Thanks for the additional info, let me know what you find,

Plugable Technologies

We are running Windows 2008 STD SP2 64 Bit. We spoke with dell and the only available SATA plug is on the DVD drive…but they do not endorse splitting it.

Hi Matt,

Thanks for the additional detail. Can you check if you are using a USB 3.0 cable? Also verify that the 12V, 1Amp power is functioning. Can you verify with the manufacturer what the power draw of the Tape Drive should be with the power supply connected?

Can you test the PCI-e card with another USB 3.0 or 2.0 device? This way if you still get the over current message, we’ll focus on the card more than the peripheral device.

Let me know what you find out,

Plugable Technologies

Western Digital’s new USB3 card doesn’t take a power connector, it provides power from the PCIe bus. I’m guessing it uses a voltage regulator of some sort to convert 12 volts to 5.
Could you consider such a design to avoid the power cable in a future design, or do you consider it an inferior approach?
Also a product that’s needed but nobody offers on the market yet:
Combo PCIe card with both Firewire800 and USB 3.0 … could you please offer this?

Hi Sordna,

Thanks so much for the comment and feedback!

Actually, our card can also do without the supplemental power - it also does the 12V (PCI) to 5V (USB) conversion. Our expectation is on most motherboards, it will be able to power the 2 USB ports with about 1.4A @ 5V this way.

The supplemental power cable is just to make sure you can get to the full 1.8A that two USB 3.0 ports should theoretically be able to supply (although we’ve found few USB 3.0 devices that take advantage of the 900mA USB 3.0 calls for vs. the 500mA called for by USB 2.0).

And thanks for the Firewire 800/USB 3.0 suggestion. It’s all about what the chipsets support – and we’ll be on the lookout for that.


Awesome info! And you can bet on many customers on that combo card, it will help modernize a computer’s I/O in one fell swoop, I’ll be the first customer.

This discussion is excellent. Two questions, I want to add a USB 3.0 card to an HP ML 110 G5 Server, and the type of USB 3.0 card which does not require added power would be great. Would anyone know if their is such a card with Microsoft Server 2008 x64 bit drivers? I’d be happy to find an eSata 3 (6 GBs/sec) as well.

Next question: with a non-powered USB 3.0 card, will a typical USB 3.0 Flash drive work? I realize that a powered external USB 3.0 hard drive will work (thanks to this discussion thread).

Hi tom.milliner,

Thanks for your post regarding PCI-e USB3.0 card and your HP ML 110 G5 Server.

First, the good news… even though our PCI-e USB 3.0 card has a molex connector to connect to the power supply, we’ve never run across a case where it’s necessary. In fact, many people run without it connected.

Thumb drives are no problem. The reason for the external power to hardrives is that they are often designed to use more power than the USB spec allows so they come with an AC adapter (or a double headed cable) to draw from.

Thumbdrives are designed to work in a standard USB port, so there shouldn’t be any exceptions for USB 3.0.

Now for the (maybe) bad news…

From what I can tell there’s no PCI-e 1x slot in your target machine. I had a quick look the specs for the HP ML 110 G5 and it looks like there are two PCI-e X8 slots with X1 link but I’m not exactly sure if that’s compatible.

The only way to know for sure would be to try it, and if you do need to return it we make it easy to get a full refund from Amazon for 30 days.

As far as drivers go, there’s an installer package that should install the proper drivers for your version. Here’s the link to the drivers:


You can run the installer to see if it works before purchasing the card. If it does, then the drivers will work, it’s just a matter of the slot then.

I hope this helps,

I just purchased the USB 3.0 PCI-E / Express Card. Per the recomendations in this forum, I also purchased a molex-SATA adapter to supply power to this card. The card arrived but there is no spot to plug in a molex power plug.

So how do I provide the additional power I might need?

what happens if i provide both 4 pin molex and 15 pin power to same usb 3.0 pci card?

What about using a 15 pin low-profile SATA connection to power a card? Is this sufficient for a USB 3.0 PCI-E x1 that offers this connection rather than molex?? Regards.