What's happening to my USB ports and how do I make it stop?
September 9, 2013 9:00 PM   Subscribe

My computer's rear panel USB ports periodically stop working -- even after replacing the motherboard. I'm at the limits of my diagnostic abilities here. Has anyone ever seen anything like this?

Apologies for the length, but I want to make sure I list everything I've tried already.

My current PC is one I built myself maybe a year ago. Windows 7, i5-2500K, Radeon 7850 GPU. It's been working fine since I put it together, except that very occasionally it would give the "unrecognized USB device" warning for no apparent reason. But over the last few weeks, it's suddenly started doing this thing where the rear panel USB ports will apparently shut down. The LEDs on my mouse flicker erratically for a few seconds before turning off, and the keyboard/mouse stop responding, but otherwise the machine keeps running as normal. Sometimes re-plugging things into different ports gets them working again; more commonly, I have to put it in standby using the power button and wake it up again. At first this was happening maybe every few days, and now it's more like hourly. I've scoured the Windows error logs and haven't found any log messages that coincide with it. And I've swapped out the keyboard and mouse to confirm that one of them isn't somehow triggering the problem.

Since it was still flaky when running Ubuntu, I figured it had to be a hardware problem, and since the USB ports are physically mounted on the motherboard, it seemed like the obvious culprit. So I went ahead and replaced the motherboard with a new one (a different model from the same manufacturer, ASRock) and reinstalled Windows for good measure. But the exact same thing keeps happening! If anything it's even worse now.

My only other theory is a bad PSU, but my voltmeter shows the USB power supply as a steady 5.01V even when the ports are nonfunctional. And except for the peripherals, the machine is rock solid and stable under heavy load, which doesn't make sense if there's a power supply problem. In any case, if this guess turns out to be wrong too, I'd rather not keep spending money replacing one component after another with no idea what's wrong. Has anyone seen anything like this before?
posted by teraflop to Computers & Internet (9 answers total) 1 user marked this as a favorite
I had a similar problem once, and the culprit was USB autosuspend in Linux: to save power, the computer would autosuspend my USB devices. And to save even more power, it wouldn't bother to start them back up again until I unplugged and reinserted the USB connectors. It was supposed to start them back up again upon mouse movement, etc., but it was quite obstinate in that respect, and disabling that so-called feature in the kernel was the only way to solve it. So that might be it, though I have no idea how one would disable it in Windows. (Nor, to my knowledge, did that same computer have the same problem in Windows.)
posted by matlock expressway at 9:28 PM on September 9, 2013

Sounds more likely that you've never installed the proper USB drivers for the northbridge/southbridge pair on either of your motherboards...
posted by thewalrus at 10:55 PM on September 9, 2013

Several folks in this Microsoft link fixed their issues by following the advice in this post titled "Windows 7 and Vista USB Fix By bmerdinian."
posted by LuckySeven~ at 10:56 PM on September 9, 2013

This is going to sound kooky, but several "wise old greybeard who worked on DEC mainframes" types have told me that this type of thing is usually a grounding issue... and i think they're actually usually right.

What you want is a good, proper connection between the port shield for the motherboard, the case, and the back of the power supply to the case. Ever wonder what those little "fingers" on the case that contact the back of the power supply are for? yep. I once had this problem go away when i swapped a power supply, then swapped back and that area of paint on the PSU case was now scratched.

I've noticed that every, every OEM system i've ever seen had a solid connection at both of those points. And i've never had this problem with a prebuilt machine even if it was an absolute hunk of shit emachines or something that was rife with other problems.

I've had this problem with at least 2 home built systems, and one of them i can remember never had the port shield on the mobo. The other one i became convinced it was a software problem and tried everything. Latest chipset drivers, chipset drivers from the mobo manufacturers website, older drivers, nuke and reinstall windows, and a lot more. I never tracked that shit down.

It wasn't until after i was using that system that i remember back to the "use the force!" of the grounding thing though. So yea, make sure that port shield is totally snapped in snug. And that the fingers on it are fully contacting the USB shell, and that the fingers on the PSU surround are really on the power supply and not just rubbing against paint.

I might be completely crazy here though.
posted by emptythought at 3:37 AM on September 10, 2013 [6 favorites]

Response by poster: Thanks for the suggestions everyone. I guess I was stuck thinking of this as a hardware problem and didn't stop to consider drivers. I've installed everything that came with the motherboard, turned off USB selective suspend, and turned off the "Allow the computer to turn off this device to save power" option on all 4 of the USB hubs listed in Device Manager. Unfortunately, that didn't fix it.

emptythought: you might be on to something there. The port shield is about as snug as I can get it, but there's still a tiny gap between it and the ports. When I have a chance this evening I'll see if I can get it properly grounded.
posted by teraflop at 9:44 AM on September 10, 2013

When you changed motherboards, did you do a fresh install of Windows? If not, you probably carried over a driver problem from the old motherboard.

It may also be a problem with one of the devices. Have you tried a different keyboard/mouse combo to see if one of them is somehow affecting the ports?
posted by cnc at 11:10 AM on September 10, 2013

Response by poster: cnc: yep, as I mentioned, I've already reinstalled Windows and tried with a different keyboard and mouse. I don't have any other usb devices plugged in.
posted by teraflop at 3:58 PM on September 10, 2013

Sorry about that last post. My reading comprehension today isn't great.

How about trying the front panel ports for a while? If it happens with the front panel ports, it's less likely to be grounding and more likely to be a bad controller. If your case doesn't have front panel ports, I imagine you could pick up a 3.5" front panel with ports for not too much money (Monoprice?)
posted by cnc at 5:07 PM on September 10, 2013

Response by poster: As it turns out, this was actually two separate problems. Fixing the USB chipset drivers caused my keyboard to start working reliably, but not the mouse. And I had thought the mouse was working on other computers, but after repeated testing, I realized it wasn't working reliably — if I used it for long enough, it would start failing the same way. So after swapping out the mouse, everything's good as new. Thanks for all the suggestions.
posted by teraflop at 10:46 PM on October 10, 2013

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