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?
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 :)
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.