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I've searched quite a bit for the answer to this question but there surprisingly isn't much information on it. I have an old system that only has USB 1.1 ports and I want to expand its storage by adding an external USB hard drive to it. But before I go and buy an external hard drive, I was wondering whether a USB 3.0 device will even work when plugged into a USB 1.1 port? I've seen some people saying a USB 1.1 device will not work when plugged into a USB 3 port because USB 3 ports aren't backwards compatible with 1.1, but is the reverse still true?

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    From my experience a HDD will operate at 2.0 with degraded speeds, and fails to register with a USB 1.1 due to power supply errors. Might be worth looking at the power ratings the USB ports on the PC give out. – DankyNanky Jul 31 '17 at 7:44
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    Have an intermediate USB3 hub with external power supply as a means to use the new stuff? – Hannu Jul 31 '17 at 7:55
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USB 1.x/2 define maximum power load as 500mA. USB 3 defines maximum power load as 900mA. Therefore you can risk being sort by up to 400mA when connecting a USB 3 hard disk to a USB 1.1 port.

If the power situation is okay, the connection should be working, since USB is, in theory, backward compatible.

To solve your problem> by an inexpensive PCI expansion card for USB 3 and get a lot more out of your drives. ~20$ for 4-7 ports. If you are planning on buying USB 3 expansion drives it should be in your price range :)

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    Unfortunately the device doesn't have any PCI expansion slots and is more along the lines of an embedded device so expanding the ports isn't an option. Since USB 1 and 2 have the same max power loads, a USB 3 hard drive that's labeled as compatible with USB 2 shouldn't have any power issues with USB 1 then right? – Generalkidd Jul 31 '17 at 8:42
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    Theoretically yes. – MadMrCrazy Jul 31 '17 at 9:14
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Yes, a USB 3.0 device must work in USB 1.1 environment, since USB 3.0 has a USB 2.0 wiring in parallel to USB 3, and USB2 falls back into Full-speed mode under USB 1.1 controller. However, given the dismal state of USB-IF certification program and brutal disregard of it among small manufacturers, the mileage might vary.

To avoid potential power limitations of USB 2.0 port, I would recommend to get a HDD storage based on SSD -solid-state drive. Modestly sized SSDs have a fairly reasonable power consumption (under 1 W), which is well within the 500 mA limit of a standard USB port.

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