I have a case which has some front panel USB 2.0 sockets and the usual 2.0 connector. It also has a front panel USB 3.1 Gen 1 socket with a separate 3.1 Gen 1 cord.
My motherboard, however, which is an ASUS WS C422 SAGE/10G only has 3.1 connectors. The front panel USB connector is labeled U31G2_E3 and has a 20-pin USB 3.1 Gen 2 female socket. The motherboard documentation says nothing about backwards compatibility.
The motherboard also has a USB 3.1 Gen 1 header. Documentation that came with the motherboard says that is DOES have backwards compatibility with 2.0. Currently, I have the 3.1 Gen 1 cord from the front of the case plugged into this header.
So, the question is... how do I get the USB 2.0 in the front of the case connected to the motherboard? I seem to have two options:
(1) Find some kind of adapter that will allow me to plug the USB 2.0 cord into the 3.1 Gen 2 header. This assumes that 3.1/2 is backwards compatible with USB 2.0 and that such an adapter exists.
(2) Unplug the 3.1/1 cord from the front of the case from the 3.1/1 header on the motherboard, plug in a 3.1/1 "module" (mentioned in motherboard manual) whatever that is, and that module will provide both a 3.1 and a 2.0 header on it maybe? I have not seen what this module looks like so I don't know.
Just so we are clear, on the left is what i have coming from the front panel, on the right is a 3.2 g1 motherboard header:
2 Answers
Your right photo is U31G2_E3 (#10 in the manual). Then there's also the U31G1_12 (#14 in the manual).
Option 1) Turns out that you can't do what you want to do; apparently it's an ASUS proprietary connector. So #10 cannot be used with a USB 2.0 front header. If your case does not have that connector and its corresponding front panel, you could buy one from ASUS. I think it's this one: (sorry for the German link, did not find it in US). If you use that front panel, you can connect USB 2.0 devices to it.
Option 2) What you could to is to use #14 with a cable adapter to use it with your existing USB 2.0 front panel. That would then be this cable (again, sorry for the German link)
Option 1+2) There exists the following adapter cable () which, from the looks of it, would turn #10 into a #14, but according to the product description it does not allow you to use USB 2.0 front panels. I believe that this is only due to the fact because the pins don't match in number, but after adapting this with the adapter mentioned above (chaining two adapters) it might work (no guarantees! could even fry your board, you know, 2020 is a really bad year).
(1) Find some kind of adapter that will allow me to plug the USB 2.0 cord into the 3.1 Gen 2 header. This assumes that 3.1/2 is backwards compatible with USB 2.0 and that such an adapter exists.
Yes, it should definitely be compatible as the cable literally goes straight to the USB Type-A ports, and you know those are compatible – you can always connect a 2.0 device to a 3.0/3.1 port and the other way around. As mentioned by others in the comments, USB 3.x only adds some extra pins to type-A ports, but it changes nothing about how the existing "2.0" pins behave.
So indeed there are adapters available, both for connecting a 2.0 panel to a 3.0 or 3.1 motherboard, and the other way around.
(2) Unplug the 3.1/1 cord from the front of the case from the 3.1/1 header on the motherboard, plug in a 3.1/1 "module" (mentioned in motherboard manual) whatever that is, and that module will provide both a 3.1 and a 2.0 header on it maybe? I have not seen what this module looks like so I don't know.
This "module" sounds very much like a basic PCI-Express card with an additional USB 3.x controller on it. (Those often have direct ports on the back but also a 3.x header for front panel as well.) It is not motherboard-specific, just a standard PCIe device, and you can find plenty of those as well.
