Short-circuiting the USB port causes BSOD?

11
2013-08
  • Alvin Wong

    Here comes a computer at school, running XP.

    A classmate actually use a USB Flash Drive which is designed badly that every time you insert it to a USB port there is a high chance of short-circuiting the USB port.

    Well, short-circuiting the USB port isn't very big deal. The most it will do is trigger the current overload protection, and Windows will pop up a bubble telling you the USB port has been overloaded (can't find an image of it). Not kidding, I've actually tried this a few times when getting 5V from it.

    However, when my classmate insert her badly-designed USB Flash Drive (and of course short-circuiting the port), Windows BSOD and reboot.

    My question is: How could this actually causes a BSOD and reboot the computer? Shouldn't current motherboards/PSUs have enough current protection to handle short-circuit events? How could this kind of hardware exceptions trigger a "software exception"? Is that only an extreme rare case happening only to that computer?

    Because I frequently need to get 5V from the USB port to power circuits that is possible to exist a wiring error short-circuiting the power source, I need to make sure that the current protection will work on my own computer so that even if there exists an error, it won't crash my computer and make me lose all opened documents and webpages. Till now the most serious situation I've met on my computer is the Windows bubble notice, but after I saw the school's computer BSOD-ing, I am quite worried of whether it is safe to use the USB port to power my hobbyist electronic hardware.

    • Answers
  • sourcejedi

    Anything that happens to hardware could cause a software exception... if your software is buggy. (And/or if your hardware is buggy :). I'd suggest not trying to mix general computer use with powering experimental circuits.

    I used to use cheap mains-powered multi-adaptors. They included a 9V-battery-style connector that was very easy to attach crocodile clips to. (Failing that, there were also power jacks that looked a little like headphone jacks).

    [That said, many modern programs will perform autosave. Modern productivity apps should do it. Firefox does it every 15 seconds (!). And modern FS's don't wet themselves on power failures. So you might not be risking too much in that respect].

  • danielcg

    I think the problem here lies more with the USB device than anything else. So what if it's BSODing when you short connectors out? I would actually expect that to happen.


    • Related Question

    How to tell if my USB ports are 1.1 or 2.0 for different OSes?
  • dwj

    In the same vein as this question, how do you determine what speed the USB ports are on your machine with different OSes installed?

    • Windows XP
    • Windows Vista
    • Windows 7
    • Mac OS X
    • Linux (Ubuntu)
    • etc.

    • Related Answers
  • Community

    On Linux

    • USB 2.0 will use the ehci_hcd module
    • USB 1.x will use either ohci_hcd or uhci_hcd modules.

    You can find out which module is being used by lspci -v or lshw.

    Perhaps a better method (if you're interested in particular ports/devices) is to use "lsusb -t"

  • slhck

    The way I check for Windows is Start → Run → devmgmt.msc → Universal Serial Bus controllers -> (expand).

    • If there's one that says "Enhanced Host Controller" then it has 2.0.
    • If they're all "Universal Host Controller" assume 1.1.

    At least that's how it looks in Windows Vista, Server 2008 and XP for me. Windows 2000 Pro says something like USB 2.0 root.

  • slhck

    On OSX, you can go launch System Profiler and look for USB. If you have a High-Speed bus, that means USB 2.0.

    enter image description here

    Also, the speed is shown, here it's 480 Mb/sec, indicating USB 2.0

    enter image description here

    Also this may help:

    $ ioreg -k IOUserClientClass | grep UserClientClass | grep USBDeviceUserClient | head -1 | sed -e 's/.* = //'
"IOUSBDeviceUserClientV2"
  • Mark Thalman

    On Mac OS X it depends on the hardware, not the software. If you are running a fairly modern Mac, then you have USB 2.0. All Intel Macs and the last couple of generations of PowerPC machines have USB 2.0. I had a first generation aluminum PowerBook 17" that I bought 5.5 years ago. That machine had USB 2.0, so unless you get a really old machine it will probably have USB 2.0.