Windows 7: A question about two different molex connectors on USB 3.0 cards

Hey all,

I have two USB 3.0 PCIe cards, one with a small molex connector, and one with a larger one. The card with the larger Molex connector works with my external WD MyPassport drive without issue, but the smaller connector card can't quite mount with the drive.

I've ensured that both are properly secured in the same slot, and they both use the exact same drivers, but the little card remains stubborn. I'm wondering if it has to do with the smaller connector, which can't power a larger device like a desktop external hard drive.

For a visual reference, I'm attaching pictures of both cards to the thread, with the connector of each card circled. The little card is on the left, and the big card is on the right.

Hopefully someone can shed some light on this and explain what difference, if any, the two different connectors make concerning the cards' performance.

The connectors supply the same voltage, assuming they both have all four wires. Your PSU will determine the amperage, should they be on different sets of wires with different amperage supplied to different sets.

Some connectors will only use one pair of wires. (One pair is 12V, the other 5V.) If the connector you're having trouble with only has one pair of wires that would be the problem. If not...?

In the attached picture (ignore the SATA power connecter) you can see that the two sizes of Molex connectors are actually wired in parallel.

Thanks for your prompt and helpful reply profdlp! I really appreciate your help.

OK, so I should check my PSU cords to find out whether or not the 5V is connected to the 12V, or if it is connected to the PSU separately? If it is connected separately - it has its own set of wires - then it would only be providing 5V, instead of 12V if it were sharing a connection with the 12V hookup, right?

I thought of something else you may want to check. If the WD MyPassport uses two USB connections it may be that the card you're having trouble with is only powering one of them.

The WD only uses one USB cord, but it does have its own AC adapter. The card only powers 2 USB ports, as the pictures show.

My previous (followup) reply crossed yours in the mail.

First, I would make sure that the smaller connector from the PSU uses all four wires. If there is a Y-Adapter anywhere inline make sure it uses all four wires, too. I've seen some fan connectors which only needed the 5V or the 12V and didn't have both.
There is a pinout diagram of what each wire does here: http://en.wikipedia.org/wiki/Molex

Turning to the Power Supply question, you'll notice that the wires coming out are in separate bundles. Some PSUs run everything off of one big rail, meaning the total power is shared among all the connectors as needed. Other (Multi-Rail) units split the total power into chunks. For example, there might be two 50W rails instead of one 100W rail. The reason I mention this is that it's possible that the PSU you have doesn't pump a lot of juice into the Molex connectors, since they're used mainly for lower power devices these days, and instead saves the heavy duty power for the special connectors for your graphics cards, etc.

In that case, the drive is getting enough juice for the motor to spin the platters.

I'd look in Control Panel>>Device Manager and find the USB card, then check in the "Advanced" area and see what sort of bandwidth is being allocated. If you can increase it, try that.

Thanks a bunch for the detailed response pofdlp! The Wikipedia link was also helpful.

All right, I'll check my PSU. I'm away from home right now, but I'll check it tomorrow and get back to you on the state of its connections. If it helps any, I know it is a Corsair 750W, so I hope it does have enough juice!

I do have an ATI Radeon 5800 HD 1GB graphics card, so that may be hogging all the power, but again, I won't know for sure until I check it myself. I might also take some pictures of the computer interior and post them for clarification.

You are correct about the WD getting enough power: it does spin up, but one of three things happen:

1.) The drive does not mount; Windows doesn't "see it" at all.

2.) The drive attempts to mount but fails, with the Windows notification area message: "The device has malfunctioned."

3.) The drive does mount, but it appears as unformatted (it's formatted NTFS) and when I try to access its contents from My Computer, Explorer locks up until I either restart it or pull the plug on the drive.

These symptoms lead me to believe that the drive is connected to the card properly, but somehow the signal is lost. I thought it might be because there just isn't enough power for the USB 3.0 hookup. I can attach the drive to my computer's USB 2.0 ports without issue.

Thanks for the Device Manager tip to increase bandwidth; I'll give that a shot tomorrow and post back with my results.

Great recap of your situation! You'd be surprised how often that kind of info needs to be dragged out of people over a series of fifteen posts.

To summarize a response to your latest:

1) You should have all the power you need with that PSU, no matter what rail kerjiggery they are using.

2) Does the drive have a hardwired USB cable or is it removable? Is it a USB 3.0 drive? If so, are you using a USB 3.0 cable?

3) Do you have another computer you could try the questionable card in? If it won't work there either, you may just have a dud USB card.

4) Does any other USB device work on the iffy card?

Good luck!

Oh no problem, I can give you all the info you need; you're talking to a forum veteran here!

Well that's a relief; I'm glad that I "got the power" - pun intended!

Yes to all your questions in your second point: the drive is USB 3.0 compatible, the cable can be removed, although only a USB 3.0 connector can be used to attach to the drive's port, and I'm using the cable that came with it, which is of course also 3.0. For more info, here's the link to my exact model, 3TB size: My Book Essential

Sadly, my only other computer is a laptop, so it wouldn't work, or I would certainly test it!

You know, I can't answer that last question, since I haven't tried plugging any USB 2.0 devices into the fussy card, and the only 3.0 gadget I have is the WD.

I can find out more tomorrow when I get home, as I can try the card with a 2.0 device and see what happens!

Thanks again for your time and patience in helping me solve this matter.