[TriLUG] why does usb card on PCIe bus need extra power to detect a disk?

[Joseph Mack NA3T via TriLUG]

On Thu, 13 Dec 2018, Joseph Mack NA3T via TriLUG wrote:

> I have a machine with only a usb 2.0 hub. To get some usb 3.0 ports, I bought 
> a PCIe card with two external USB 3.0 ports (Orico PVU3-201IV1).

The webpage for the card said that with usb 3.0 I'd get 10x the speed of my usb 
2.0 setup. This sounded great to me. However I didn't look critically at this 
statement. Further looking found that a usb 3.0 hub operating on a PCIe bus gets 
about 2x the speed of a usb 2.0 hub. If I want full usb 3.0 speeds, I need a hub 
directly on the mobo. (I don't know what difference that makes. I assume the usb 
3.0 hub on the mobo is still talking to the PCIe bus.)

Joe

-- 
Joseph Mack NA3T EME(B,D), FM05lw North Carolina
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