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February 26, 2020

Transient USB Phantom Devices Suggest Power Insufficiency

OK, then. I’ve been dealing with an interesting USB issue lately. Happens on my laptops when I plug certain devices in. The general flow of symptoms is:

1. Plug in Device.
2. USB device added tone sounds
3. 1-2 seconds later, USB device removed tone sounds
4. Device does not show up in Explorer (or Device Manager)

Just for grins, I started watching inside Explorer while this was going down. And indeed, right after steps 1-2, a device would show up under This PC very briefly. It would disappear as soon as step 3 occurred (USB device removed tone sounds).

Troubleshooting USB Phantoms

Next I did some data gathering. I noticed that this phenomenon happens only with unpowered USB devices. That is, it does not occur if I plug in a storage device in a SATA drive caddy, no matter how big or small the drive involved might be. For unpowered devices — I’m talking about mSATA or M.2 SSDs in USB 3.0 or USB-C unpowered drive enclosures (see featured photo at head of this story). I tried both mSATA and M.2/NVMe devices at capacities of 250 GB, 500 GB, and 1.0 TB, and obtained consistent results independent of channel type (USB 3.0, 3.1, 3.2/Thunderbolt and USB-C of the same kind).

What Makes USB Devices “Go Phantom?”

I’ve run into this kind of behavior before, most recently when trying to plug an 8 TB HDD into a dual-drive ThermalTake caddy alongside a 4 TB drive. That caddy worked fine with 2×4 TB drives, but as soon as I plugged in 1×8 TB and 1x4TB, it dropped off-line. Turns out it’s a power problem. If the USB channel can’t deliver the amount of power that the drive needs to work properly, it will remove itself from the USB connection, thereby rendering it inaccessible.

What happens with my unpowered USB SSD drive enclosures is pretty similar, but the cut-off capacity is lower. If I plug in an enclosure with 250 GB drive, it works fine. If I plug in an enclosure with a 500 GB drive, sometimes it works and sometimes it doesn’t. If that device has the USB channel to itself, it will usually work. If I plug in a 1 TB drive (doesn’t matter if it’s USB 3.0, 3.1, or 3.2 or USB-C) it doesn’t work, period. I hasten to add that this is on my laptop PCs, which are mostly Lenovos (one Microsoft Surface Pro 3 does likewise). On my desktop PCs, as long as the higher-capacity drives have the USB channel to themselves (and don’t have to share power with other devices) they work just fine.

Thus, my best guess is that the USB ports on the laptops have a power threshold that, when exceeded, causes the USB channel to shut itself down. On devices that may be powered by battery, this kind of policy makes sense. But it also means if you want to take an SSD in a drive enclosure on the road, if you need one with capacity of 500 GB or greater, you’ll want to find one with external power to make sure it doesn’t “go phantom” on you after you plug it in. I’d imagine you’re doing this because you want to use the device, so hopefully this information will be useful to those ponder such hardware choices.

Author: Ed Tittel

Ed Tittel is a 30-plus-year computer industry veteran. He’s a Princeton and multiple University of Texas graduate who’s worked in IT since 1981 when he started his first programming job. Over the past three decades he’s also worked as a manager, technical evangelist, consultant, trainer, and an expert witness. See his professional bio for all the details.

One Response “Transient USB Phantom Devices Suggest Power Insufficiency”

  1. CountMike
    February 5, 2020 at 14:30

    It’s better to use USB cable with 2 male ends, you get twice the power that’s otherwise limited to every USB port.

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