What is USB 3.0?

USB 3.0 is a new Universal Serial Bus specification that was released in November 2008. It promises wire speeds of 5Gbps, bi-directional communication, and better power management.

What is xHCI?

The eXtensible Host Controller Interface (xHCI) is the hardware on your PC that talks to USB 3.0 devices and legacy USB devices. The xHCI specification details can be found on Intel's website.

Wasn't USB 2.0 good enough? Why is USB 3.0 cool?

USB 3.0 is expected to be 10 times faster than USB 2.0. It's also more power efficient, which translates into longer laptop battery life. Since USB 3.0 packets are routed instead of broadcast, idle links can be automatically put into low power states without the help of an operating system. USB 3.0 also adds the concept of endpoint "streams", which are used to submit multiple SCSI commands and get better performance out of USB attached SCSI hard drives and flash drives.

What about all my old USB devices?

Older USB devices will still work when you plug them into a USB 3.0 port on an xHCI host controller. They will still operate at their original speeds.

Can I plug a USB 3.0 device into my old computer?

If you plug a USB 3.0 device into an EHCI host controller, it will work at USB 2.0 speeds. To get 5Gbps wire speed, you need an xHCI host controller.

USB 3.0 sounds pretty cool. When will Linux support it?

The Linux xHCI driver has been merged into 2.6.31. The git development tree for the driver can be found on kernel.org

Is there any mailing list for xhci driver related discussions?

You can subscribe to the linux-usb mailing list at http://www.linux-usb.org/mailing.html I'll also post updates on my blog.

I found a bug in the xHCI driver. What should I do?

Enable xHCI debugging in your kernel (CONFIG_USB_XHCI_HCD_DEBUGGING) and send your dmesg output to sarah.a.sharp@linux.intel.com. Please CC the Linux USB mailing list linux-usb@vger.kernel.org.

You didn't answer my question; where can I find more info?

See a longer blog post for more information.