Windows 8 and 8.1 Forums

USB 3.0 Adapter Fails to Enumerate But Works Anyway

  1. #1

    USB 3.0 Adapter Fails to Enumerate But Works Anyway

    I recently installed a USB 3.0-to-PCIe adapter card. Windows 8.1 64-bit (Update 1) recognized the adapter and installed its native USB 3.0 driver stack (a Renesas USB 3.0 eXtensible Host Controller and a USB Root Hub xHCI.)

    The adapter has two USB 3.0 ports that are occupied by bus-powered portable external hard drives. Both external hard drives are recognized by Windows and both drives are working properly.

    Every now and then and for no apparent reason, Device Manager reports that "The SuperSpeed link to the USB device keeps going to an error state Compliance." Nevertheless, both my external hard drives continue to work properly.

    According to this article from the Windows USB Core Team Blog [Problem Descriptions for USB Devices and Hubs in Device Manager] the message in Device Manager means that my USB 3.0 adapter card fails to enumerate successfully. That makes no sense because the USB 3.0 hub and its controller are in Device Manager with no problems and both attached portable hard drives work properly.

    The USB Core Team refers users to this article of possible solutions [What to Try When Your USB Device is an "Unknown Device"], none of which work or are even relevant.

    Since my USB 3.0 adapter works properly, I'm tempted to simply ignore the message in Device Manager. Has anyone diagnosed this issue and found a solution?

      My System SpecsSystem Spec

  2. #2

    The adapter has two USB 3.0 ports that are occupied by bus-powered portable external hard drives
    Both being bus powered is my first suspect and may be the problem here. Like most electronics, and especially electro-mechanical devices, their power demands vary greatly, depending on the task. If both drives just happen to hit peak demands at the same time, this may be momentarily causing issues.

    I note your second link addresses power. I think you should get a USB power adapter to power these drives. In the meantime, disconnect one and see if you have problems with one drive alone. If okay, swap drives and see what happens.

    You could ignore the error message, but I wouldn't, at least not until you know exactly what is actually causing it. Since your OS is, presumably, on an internal drive, critical data corruption is not likely. But you sure may lose some data on a drive if power or communication is disrupted during a write.
      My System SpecsSystem Spec

  3. #3

    Thanks very much for your helpful reply.

    My external drives are used only for backups and archival storage. I can't think of a time when they would be running together. In any case, the problem manifests even when both drives are idle.

    Sufficient power might be an issue. The USB 3 adapter card is connected to my power supply. It's a simple OEM power supply, 350 watts. Unfortunately there is no connector on either drive to attach external power. My backups run at night when the computer is idle, so it doesn't seem like they could cause excessive power draw. Then again, I'm nobody's hardware engineer.

    I think I might try a different USB 3 card.
      My System SpecsSystem Spec

  4. #4

    I can't think of a time when they would be running together. In any case, the problem manifests even when both drives are idle.
    The motors are still spinning, even when idle. Plus, when you are idle, Windows does housekeeping, including defragging and other drive functions.

    It's a simple OEM power supply, 350 watts.
    That is small by today's standards - and may especially be a problem if there have been other HW upgrades since new. Also, many OEM supplies are of lessor quality, with a poor and bell-curve efficiency rating - which means they get maximum efficiency only at one load level, then quickly drop off on either side from there. A quality supply has a "flat" efficiency rating, able to deliver efficient power at any expected load.

    You can buy USB power adapters.

    At the very least, connect the two drives to different pairs of USB ports.
      My System SpecsSystem Spec

  5. #5

    As it happens, I have a new power supply on order. Thanks again for your advice.
      My System SpecsSystem Spec

  6. #6

    That may very well fix your problem. Keep us posted.
      My System SpecsSystem Spec

USB 3.0 Adapter Fails to Enumerate But Works Anyway

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