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I've been working on my new PC build with the GA-Z77X-UD5H-WB WIFI motherboard. This board comes with a wifi/bluetooth card that goes into a PCIe x1 slot... but the card also wants to be connected to the motherboard through an internal USB cable:

internal usb cable

to a motherboard USB2 header. This would be fine and dandy but this motherboard only has two USB2 headers and they're already occupied by my case front panel USB pin blocks. However, there are at least two USB3.0 headers free on the motherboard; can I just connect this internal cable to a USB3 header?

USB 3.0 and USB2.0 header

Pictured: USB3.0 header (middle, light blue), USB2 header (right, blue) (not my motherboard)

Looking at pinouts and discussions online, it seems like it could work if I connect the USB2 pin block to the first 9 pins of the USB3.0 header, though I'm afraid of frying the wireless card, motherboard, or both. Some sites even say that the USB3.0 motherboard header isn't standard, and can vary in pinout depending on manufacturer! Can anyone shed some light on this?

P.S. If I can't do this, then is there a way to 'split' my existing USB2 motherboad headers?

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up vote 2 down vote accepted

On page 33 of the motherboard's manual you can find the pinouts for both USB2 and USB3. They are not compatible. And even if they were compatible the physical connectors are not - the spacing between pins is different.

There are 2 "sockets" in each connector, so if you really, really want to connect USB2 cable into a USB3 socket you have to match pins manually:

  • USB2 Power (5V) to USB3 VBUS
  • USB2 USB DX- (or DY- for second socket) to USB3 D1- (or D2- for second socket)
  • USB2 USB DX+ (or DY+ for second socket) to USB3 D1+ (or D2+ for second socket)
  • USB2 GND to USB3 GND

This is a dangerous procedure so if you don't know what you're doing just buy a separate controller and use that.

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Thanks for the clarification. The cable is in a single plastic 9 pin block, so I can't move individual pins around, and it looks like I wouldn't want to anyway! – Aphex Dec 19 '12 at 0:47

You could add an internal usb hub - nzxt makes a pretty nice one called the iu01 that breaks out one into 6 headers and 2 normal usb ports and would work perfectly here.

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I ended up ordering this, thanks! – Aphex Dec 19 '12 at 0:46

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