This mainly applies to 970 chipset mainboards, so your mileage may vary.

Symptom, no USB 3 , or Network, or USB 2 using Ubutnu 14.04 (actually from 12.04 up) 64 bit editions. As this is a kernel problem this should affect most 64 bit linux distros, not just Ubuntu.

There seems to be a problem with all recent 64 bit linux distros and 970 chipset mainboards.

There are 3 options.

1) Use a 32 bit distro.

2) In your BIOS enable IOMMU. This will fix your network and USB 2. You probably wont have USB 3 though 🙁

3) Enable IOMMU in BIOS and add iommu=soft to your grub config. This gets rid of the stream of warnings you get at boot with IOMMU enabled in BIOS. USBB 3 should work too.

sudo nano /etc/default/grub

Change the line

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"

to:

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash iommu=soft"

Then do

sudo update-grub

and reboot.

This should make the USB 2 and 3 work as well as networking.

Let me know what chipsets/mainboards this helped you with.

[updated]
Changed option 3 as noted by Anthony Barnett. Many hanks for the feedback Anthony.
[/updated]

BaDboD