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I would like to buy an internal flash card reader. There are now loads of USB 3 reader, however I still have an USB 2 system. Would it be possible to connect the new reader to the old USB port on the motherboard?

I understand that I will not be able to take advantage of having the faster reader with the old motherboard, but I am planning an upgrade next year and I would like to avoid having to upgrade the card reader as well...

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Most flash card readers seem to top off around 20MB/second, which is well below USB3 and below USB2 speeds. Why not get a USB2 reader and avoid all possible problems ? – Hennes Nov 16 '12 at 11:35
@Hennes, I am mostly tempted by the USB 3 port that you usually also get on these internal card readers. It would be quite handy because my case doesn't have one of these (and I don't want to change the case in foreseeable future) – Grzenio Nov 16 '12 at 11:54
@Grzenio - If the card reader requires a USB 3.0 header you are out of luck. Why don't you just add a USB 3.0 PCI-E card? – Ramhound Nov 16 '12 at 12:14
@Ramhound, that is what I will probably end up doing. I was hoping though that it would just work slower on an existing USB 2 port. – Grzenio Nov 16 '12 at 12:21
@Ramhound It should be possible to connect a USB3 device to a USB2 header with the appropriate converter cable. From the controller's point of view, this is the same as connecting an external USB2 device to an external USB3 port (i.e. reduced speed ['Hi-Speed', as opposed to 'SuperSpeed'] mode), and should work if the USB3 peripheral is backwards compatible (as many are). – Bob Nov 17 '12 at 5:50
up vote 3 down vote accepted

From what I've seen the internal headers are different - notably the USB 3.0 plug completely lacks the 'filled' in pin of the USB 2.0 connector, and incompatible, as far as physical design goes - its twice the size for one thing. The best option would be to get a cheap USB 3.0 pci-ecard and to use that I'd guess.

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USB 3.0

As compared to

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You forgot to mention its twice as big :-) – Ramhound Nov 16 '12 at 12:13
added. Missed it cause it was too obvious – Journeyman Geek Nov 16 '12 at 12:31

In theory, USB3 should be backwards compatible. This is always true where the host is USB3 and the peripheral is USB2, but not always true the other way around - it depends on the peripheral. Some of them just have a limited speed, while others (notably the ones with higher power requirements) may not work at all. A card reader should be fine, but it's impossible to say for sure without someone having tried it.

While the external USB ports are backwards compatible, the motherboard headers are not and you will need a USB2 to USB3 header converter cable (e.g. this or this) to connect it. Whether the device actually works or not cannot be determined without testing (or a thorough specs sheet). It would also be a good idea to make sure your motherboard has a free USB(2 or 3) header available.

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USB ports being compatible is one thing (power requirements for USB3.0 devices aside), however there is no point attempting connect the wrong header to the wrong cable. The pin layouts vary, and you risk damaging your motherboard and/or USB device.

I would just purchase a USB2.0 port which is designed for the motherboard header, rather than trying to force a square peg into a round hole.

Or as someone else suggested- and this is your best option as it will give you USB3.0 functionality- you should buy a USB3.0 PCI add-on card.

I bought one myself recently, and they are very affordable.

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